TPS Throttle Position Sensor Code

TPS Code Thomas School Bus With an Mercedes MBE 900 Diesel Engine 

The driver called us up on the radio and said he had no throttle. The bus he was driving was 10 minutes out of town. The bus was a Thomas HDX Pusher with a Mercedes MBE 900 diesel engine. The TPS which needs to send a signal to the engine ECU or in Mercedes terms it's called an MCM (Motor Control Module). This was not happening so some diagnostics were in order.

Without a throttle position signal to the MCM shifting and engine power goes crazy. Engine RPM will decrease and the transmission (Allison 3000 series automatic) will not shift properly. The 5 volt signal to the CPC (common powertrain controller) from the throttle position sensor will not happen. The CPC is the interface between the chassis controls and the engine / transmission. In other words it communicates the signals to the MCM.

After finding a proper wiring schematic and checking the circuits we traced the problem down to the TPS itself which as you saw in the video is mounted on the right side of the throttle pedal. It was a funny occurrence because we swapped throttle position sensor units with another bus with out any change. But...the problem was not with the TPS but the wiring to the throttle position sensor connector.

It was hanging by a thread and caused an intermittent throttle signal with a big voltage drop. This causes a bigger challenge for the mechanic doing the troubleshooting. Wiring is tricky at times but the only difference is the time involved to find the fault. So guess what...next time we have a pusher bus with no throttle that connector will be one of the first places to check.

The TPS wiring and switch is on the Thomas Bus (OEM) side so we can't blame the Mercedes diesel powering this piece of equipment. In conclusion it might have been the operator's boot that hit the connector wiring while going into full throttle. It's a hunch but it could very well happen. If you have time leave a comment or a question.

I don't get to questions right away but always check back periodically. Thanks for reading this post and I hope it helped you out. Remember that a diesel engine control module needs to be told what to do. It must have a signal from a sensor before it allows the diesel engine or transmission to operate. It's great technology if you don't get mad at it and lose patience. Work with it and get the experience..... you will not regret the knowledge that you accumulate over time.

Mercedes MBE 900 Diesel Engine Emissions and Engine Codes

EGR - Exhaust Gas Recirculation Maintenance

I want to share some observations and solutions with emissions and engine codes we have been experiencing with the Mercedes MBE 900 diesel engines in our bus fleet. We have a dozen of these engines 2007 - 2008 emission controlled and they are all off warranty so this has allowed us to learn by "doing" with the various emission and engine codes that normally occur. The time we have spent troubleshooting these various problems has taught us a lot and we have adapted to the typical problems that happen with this model engine.

The EGR Cooler above had to be replaced due to a leakage problem. With a coolant leak they will eventually plug up with a sludge build up if it does not get attended to. If the EGR cooler is not leaking and has a soot build up it will require removal and a hot tank cleaning at your local radiator repair shop.

They are not cheap to replace however if they leak you'll experience coolant loss and engine code problems because of the soot wet mess that will develop inside the cooler exhaust core. This will cause poor exhaust gas flow and reduce engine power. The EGR cooler exhaust gases flow to the EGR valve which mixes the cooled gases with the charge air intake reducing NOx (oxides of nitrogen) creating reduced emissions out of the tail pipe.

Charge Air Cooler Failure Mercedes Code 2631

The charge air cooler to the left split open right at the core on the engine side. This problem was hard to detect because of the noise going on when the engine is running.

The reason we found it was because of a pressure check on the cooler itself. There was a 2631 Mercedes engine code which is a "turbo boost performance" issue.

Mercedes has a procedure for troubleshooting this code and it's quite involved. You have to check the boost pressure sensor for soot build up then using the software check the EGR operation along with the intake throttle valve etc. Any part of the engine that isn't allowing full flow including the air intake and boost side will produce the 2631 code.

In this case we have blown charge air cooler causing a big drop in boost pressure. The good part is we found a problem the down side is it's located 10 days away in Memphis. This bus is down until then. NOTE: We used a regulator to pressure test this cooler at 30 psi and made plugs that can be clamped at both ends.

Mercedes Diesel Engine "low doser fuel pressure" Code

The doser code activated because the fuel pressure supply in the system was too low and this caused the regeneration process to fail.

The "doser" system shoots a mist of diesel fuel down stream to cause the regeneration operation to activate at the DPF (diesel particulate filter).

No regen operation meant the DPF was going to build up soot and ash to the point where the engine would eventually shut down. This is serious since the engine control unit is programmed to protect the engine and will not allow it to run when the emission parameters are out of the ball park.

The Mercedes power service literature is very good for troubleshooting information. This test shows how to measure the return fuel going back to the tank. At idle the lines are hooked directly to the secondary fuel filter return and a tee fitting is hooked into the overflow valve.

There are 2 fuel regulators one for the doser fuel side and one for the high pressure injection side (unit pumps). If there is too much fuel returning back to the tank the fuel pressure reading drops.

The fuel pump is a positive flow gear pump that is engine driven. Fuel pressure must get up to at least 65 psi to supply the doser system (does the exhaust regen operation) and the unit pumps which provides the high pressure fuel to the injectors.

Once we changed the 2 valves in the fuel return lines "overflow valve" and "doser fuel pressure regulator valve" the exhaust regen started working again and the engine power improved drastically. So it was a win - win in this case.

If you're interested in viewing more blog posts photos and videos check out mechanicshub.com and look for "blogs". I'm posting under the name "schoolbusmechanic"

International DT 466E In-Frame Repair

The International diesel engine project is at the head installation stage. We had the head sent to a machine shop and inspected. The valves were touched up and the head was checked for cracks since the failure was an overheating condition. If you're going through all this work it makes sense to take every step necessary to prevent a come-back.

With the head installed the injectors come next. They are hydraulic electronic unit injectors that run on high pressure oil controlled by the electrical signals from the engine ECU. The valve rocker arms are then torqued down and the valves are set at .025 inches.One thing to note with DT 466E engines is the diesel mechanic needs to make sure the engine oil pressure is up to specs because it is responsible for engine starting. If you have low oil pressure for whatever reason you will experience a hard starting or no start condition. We have since returned this bus into service and it's running nicely. The total cost of the in-frame was much less a complete rebuild on a non wet cylinder diesel engine. The fact that everything can be performed in-frame saves a LOT of time and money. One of the disadvantages of running an engine with removable cylinders is they are not part of the block and can move against the sealing o-rings around the liners. If a Mechanic has to rebuild a DT 466 diesel engine once in it's lifetime after hundreds of thousands of miles, I would say that engine definitely paid for itself.

International DT466 Diesel Engine Rebuild Cylinder Liner Seals

International DT466 Diesel Engine Rebuild Update
The next step after removing the head is pulling out the pistons. Once the rod caps are removed they can be pushed up through the cylinder liner and out. Light tapping with a wood drift works as well. The cylinder numbers will be stamped on the connecting rod caps. If there was a thick build up of carbon at the top of the liner, that needs to be removed for the piston rings to pass by easily.

The liners are going to be replaced anyways so you don't need to be gentle removing them. You need a liner puller for this job because of the o-ring seals that have been press fit against the engine block for many years, they require a good pull to jar them loose. (for those of you who have never used a liner puller) The 2 short feet rest on top of the block while the long arms hook onto the bottom edge of the liner. A socket and wrench is used on the top nut and the liner is easily wound out of the block.

Having removable liners for the DT 466 E Diesel Engines makes the in-frame a very cost effective process. We paid around 1500.00 for the "Works Kit" from the International dealer. That's a cheap rebuild! There is no engine removal and that saves a ton of  labor.

Once the liners are removed it's time to do the cleanup on the block deck and engine liner bores. While you're doing this keep an eye out for anything unusual like wear on the block surface or cracks in the casting etc. DT 466 Diesel Engines are bullet proof so the chances are slim to none there will be a problem.

Here's the bad liner or should I say the bad o-ring. We had a full crankcase of sludge, with a gravity feed from the block coolant supply. So the first thing to check if you are losing a lot of coolant is pull the dipstick and check for a sludge build up in the oil.

The new liners have been upgraded with only one o-ring compared to the original 2 seen here. This is the only disadvantage of  running wet liners but this type of failure is not overly common, especially with this engine having under 100,000 miles.

If you are a Mechanic you want to make sure to check on recent Technical Service Bulletins on these DT Diesel Engines . We found one that brought our attention to the new style liner seal and to use a vegetable oil to lubricate the seals. They also need to have retention hold downs after installation to keep them seated in the block.

Diesel EngineTurbochargers Need TLC

Cummins C Model Diesel Engine Turbocharger

The turbo on a diesel engine is an amazing piece of equipment that puts out thousands of rpms and gives us the boost we need to get into that perfect torque curve we need to power up a grade. You will know right away when the turbocharger is faulty. Without that charge air flowing into the intake the ratio between air and fuel will go south and heavy plumes of exhaust will pump out of your tail pipe getting some unexpected onlookers staring you down along with a huge loss of power.

This Holset Model pictured here comes with  a waste gate (the round housing top left). A boost line is connected to a diaphragm and when the pressure hits a pre-calibrated level the excess boost pressure is exhausted out at around 20 psi or higher. The compressor wheel seen here as well is driven by the exhaust turbine wheel on the opposite side, so it's a self driven unit.

This is pure genius and gives the engine the extra air intake volume to keep up with the fuel injection system. Both the compressor and turbine wheels should be checked periodically for wear on the shaft and if there is any scuffing on the turbo housing caused the blades making contact. You don't want one of these guys blowing up and debris getting into the intake.

School Bus Engine Rebuild Video Cat 3116

Here's a video I put together going through the steps to rebuilding and installing a Cat 3116 Diesel engine in a pusher school bus. It's a big job and you can see it happen in a matter of minutes. It's much easier to assemble the transmission to the engine and use the trans jack for support and hydraulic hoist on the front end.

The whole works rolls right into the frame. Thankfully Thomas Bus allows the rear end frame to be removed. The Cat 3116 is a fussy engine to set up and you MUST have the Cat tool kit. There is no way to set up the timing, synchronization & fuel setting without the kit.

The valve train is the only weak spot on these engines, when they get too hot (in this case) the exhaust valve let loose requiring the major repair including a new cylinder head. Too avoid this keep the engine temperature down and check valve adjustment every 30,000 to 40,000 km (18-24,000 Miles). Enjoy the video....Please Leave a Comment


School Bus Mechanic Pictures..Exclusive! by jelletse

Diesel Engine Overheating School Bus Pusher

The diesel engine on a school bus pusher is a strange design with a transversely mounted radiator. Operators love these units because are very quiet (engine in the rear) with a stubby driveshaft. Low occurrences of driveline vibration and hearing yourself think is a bonus.

One thing that does cause problems is the hydraulic fan drive system that runs the engine cooling fan. The steering pump driven off the compressor runs the fan hydraulic motor as well. For those who find this confusing, the engine fan assy. is attached to the hydraulic motor shaft. Since the motor is driven by the steering pump it is labelled as a motor.

If you find you have stiff steering and the engine is overheating as well, you might want to look at the hydraulic steering pump. Check the hydraulic filter and magnet that resides inside the oil reservoir. If there is anything metallic then you're on the right track.

Older fan drives have a control manifold that has a electric solenoid that is triggered by an engine coolant temperature sensor. once the 200 degree (approx.) engine temperature is reached then the flow control opens the gates to full flow directed to the hydraulic fan drive motor. There is no need to worry about a fan belt on these rigs.

Newer pusher school buses have a 2 stage steering pump with sensors and manifold that controls the engine fan with a module bolted to the side of the frame. One stage of the hydraulic pump runs the steering and the other stage runs the engine fan. You also need the software to hookup to the fan control module to check out the entire system for proper flow and other parameters.

School buses have come a long way from the old belt drive and incredibly noisy gear box system that were popular in the early 90s. I think I've just dated myself, OK now you know I'm a child of the 60s... Hooray for Bob Dylan and the Chevy 283 cu. in. engine.

Valve Adjustment On A DT466E International Diesel Engine

DIESEL MECHANIC - How To Adjust Valves On An International DT 466E Diesel Engine

The DT 466E diesel engine is the electronic version of the former DT 466. This an engine we diesel mechanics all know and love since they are virtually almost bulletproof with a fantastic performance record. With emissions standards here to stay International has followed the other engine manufacturers and engineered electronic injection into their design.

The hardest part about working on these diesel engines is getting to the components, especially the valves if it's time for adjustment. The air to air piping has to be removed as well as the doghouse cover from inside the cab followed by the electronic control unit. These steps are required just to be able to reach the valve cover bolts.

Remove the multi-pin connectors at the ECU [electronic control unit] with a 1/4 inch drive ratchet. Remove the round connector going into the valve cover housing.

Remove the 4 bolts holding ECU to the support bracket using a 10 mm socket. Remove ECU and take care it's an expensive component!

Remove ECU support bracket, there is a larger fastener below bolted to the block and 4 valve cover studs at the top side where you have to remove four retaining nuts.

Push the ECU harness connector into the valve cover housing as it will stay with the injector wiring when removing cover.

Remove valve cover, the weight has increased drastically compared to the original non-electronic engines because of the integrated intake manifold that is now part of the valve cover.

Rotate engine until TDC [top dead center] is achieved. There is a notch on the serpentine belt pulley behind the vibration dampner. An arrow and the letters TDC has been cast right into the front cover. Once lined up, the engine valves will be on #1 TDC compression or exhaust stroke.

An easy way to tell is if #1 cylinder valves are both loose and #6 cylinder valves have no clearance, then you know you are on #1 compression stroke. Note: There are 12 valves in total #1 valve being at the front while #12 valve is the last valve at the rear of of the cylinder head.

So if I say adjust #4 valve you just count from the front of the head, the first valve being #1. This makes it easier to explain which valves to adjust.

On #1 TDC compression stroke adjust adjust valves #1 #2 #3 #6 #7 #10 . The valve clearance for both intake and exhaust is .025 in. preferably with the engine cold but that's not overly crucial.

Rotate engine 360 degrees the engine is now on #6 TDC compression stroke. Adjust #4 #5 #8 #9 #11 #12 valves.

Once you have all the valves adjusted you reverse the disassembly procedure and torque the valve cover bolts to 13 ft. lbs. and the 1/4 drive wiring harness connectors at the ECU to 35 in. lbs. The valve cover gasket is reusable but still inspect it for damage or indications of wear.

I hope this helps you out when it's time to adjust valves on your DT 466E Diesel Engine.

Diesel Mechanic

How To Set Valves & Injectors - Cat 3116 Diesel Engine

Diesel Mechanic Tips:

Today I am going to show you how to adjust the valves and injectors on a Caterpillar 3116 Diesel Engine. The injectors are mechanical and are checked and adjusted manually using the appropriate Caterpillar tune-up tools.

Here are the tools needed to perform the valve and injector adjustment:

Caterpillar Part #'s

*Dial Indicator # 1U-8869

*Contact Point # 9U-7274

*Feeler Guage # 123-4941

*16mm/18mm Drop Wrench # 128-8824

* Timing Guage Block # 9U-7269

Magnetic Base # 123-4940

Setting the valves and injectors is a preventive maintenance operation and should be done on a regular basis. Once you get through one setting it's a cakewalk the second time around. Below is the dataplate that tells you the timing specification for setting injectors.

The dial indicator has to be pre-set so it reads 62.00 mm when placed on the timing guage block as shown below. These tools come with the complete Caterpillar tune-up kit with detailed instructions included.



The first thing to do is rotate the engine over until # 6 cylinder valve rockers are rocking. Watch # 6 valve rockers as you are rotating the engine, keep turning the engine until the exhaust valve closes and the intake valve JUST starts to open. Stop there, # 1 cylinder is now on the Compression Stroke and ready for valve adjustment as well as the other designated injectors and valves.

*Adjust 3-5-6 injectors to timing spec. / in this case 65.74 mm / + or - .020 mm

*Adjust 1-2-4 intake valves .015 in.

*Adjust 1-3-5 exhaust valves .025 in.

Rotate engine over 360 degrees and adjust the other remaining valves and injectors. # 6 cylinder is now on compression stroke since #1 and # 6 pistons are always at TDC [top dead center]together.

*Adjust 1-2-4 injectors

*Adjust 3-5-6 intake valves

*Adjust 2-4-6 exhaust valves

As you can see from the above picture the magnetic dial indicator holder sits on top of the injector. The dial indicator measures the distance from the top of the injector to the machined body surface at the bottom which must be set correctly. This dimension effects injection timing and can be adjusted at the injector rocker arm set screw.

I hope this post helps out all you Cat 3116 owners. The valve and injector adjustment is probably the most crucial as adjustment can change with normal wear and tear as your diesel engine racks up the mileage.

That's all for now, thanks for visiting and be sure to check back for more Diesel Mechanic Tips.

Mercedes MBE 900 Diesel Engine - Changing Thermostats

MBE 900 Diesel Engine Specs:

Configuration: inline 6

Displacement: 7.2 Liters
(439 cu in)

Bore: 4.17 in (106 mm)

Stroke: 5.35 in (136 mm)

Weight: 1,362 lbs (618 kg)

Electronics: DDEC® VI

Compression Ratio: 18:1

The local Mercedes dealer recommended to replace thermostats and coolant every two years on the MBE 900. Coolant breaks down over time and becomes acidic chowing down on gaskets and engine parts. On a conventional and pusher bus this is an easy operation. Three bolts and upper rad hose is all it takes to get to the thermostats.

The two thermostats come with a split o-ring that fits around the edge of the stat and nestles nicely into the bore of the thermostat housing. Below is a short video of a Mercedes MBE 900 diesel engine idling in a pusher bus. These engines come with  EGR and DPF (Diesel Particulate Filter) systems to control emissions. Check out how the emissions are controlled using these components Right Here.

Cummins ISB Troubleshooting Coolant In The Lubricating Oil

The Cummins ISB diesel engine is one of my favorites in the fleet, simply because it's easy to work on and really does not cause a lot of problems in the long run. Every Mechanic knows that easy accessibility is key to a smooth repair and these models are great to work on even if the back 2 cylinders are under the firewall on a school bus.

However no diesel is perfect so follow me through this quick troubleshooting procedure if you experience coolant in the lubricating oil.

1. The first thing to check is the lubricating oil cooler. The engine oil is cooled by way of the coolant running through a sealed core inside the housing. If it develops a leak you're stuck with coolant getting in the oil. The coolant core can be tested and replaced.

2. The next possibility is the air compressor cylinder head is cracked, has a defective casting (porous) or the head gasket is defective. This is an overlooked cause, the cooling system from the engine is connected to the compressor running through the compressor cyl. head.

3. If  your cummins isb engine came with an aftercooler it can be pressure tested to see if there is any problems with the inner core leaking.

4. The engine cylinder head is the next possibility with a leaking core or defective expansion plugs. The head must be checked out with a pressure test and magniflux test to find any leaks or cracks.

5. Last but not least is the worst case scenario, the cylinder block. If it's cracked or porous you may  be looking for a replacement block or reman (remanufactured) engine.

These are mechanic tips that you can use to get you started finding the cause of coolant in your engine oil.

CHECK OUT ALL MY PREVIOUS POSTS ON THE CUMMINS ISB ENGINE

Diesel Engine Troubleshooting GM 6.5

When it comes to diesel engine troubleshooting you're opening up a really big can of worms. There are so many models and designs that you would need several years of study to know everything about them. However I have seen so many of the same failures in non-fuel injected areas of a diesel engine that it's always a good practice to check the simple things first.

If you start at the fuel tank (The Source) think about the problem and if lack of fuel is related to the symptoms. Is the engine hunting and sounding like Grandma's old wringer washer? If the flow of fuel is interrupted by a restriction or a gaping hole in the suction line then you will get this type of symptom.

If you're getting plumes of black smoke then there's too much fuel that could be caused by a bad injector. With today's electronic engines if you don't have a laptop, all I can say is Good Luck. If you have a bad sensor somewhere you gotta have a computer hooked up to find it.

I know it's tougher and more expensive to run a diesel these days but it's all for the good of helping sustain a healthy environment, I'm all for that but the frustration is accelerated sometimes when a problem isn't poking you in the eye telling you directly what's going on with a diesel engine performance problem.

Troubleshooting: GM 6.5 Diesel Engine.

We had a 2001 GM One Ton Van with our 6.5 diesel engine making a strange noise. It was very loud right after start-up but would quiet down a fair bit 3 minutes or so into the morning warm up.

It was a thumping sound coming out of the intake side through the air cleaner. That made it obvious we were looking at a possible intake valve problem. A couple of us put our inquisitive minds together and guessed it could be a valve lifter. The lifters are hydraulic and can be noisy at first start up.

The only drag about changing lifters on a 6.5 is you have to pull the heads. You can add some time since we're working on a van body. You can see the defective lifter below. It got misaligned somehow and caused the intake valve it was operating to not close properly and turn that cylinder into a compressor.

It's highly advisable to send the heads out for a magniflux treatment which checks the head for cracks. Both of these heads had hairline cracks around the combustion chamber so the only option was to get 2 new ones. One of our local machine shops Valley Speed supplied the heads and did the testing. This isn't the first time we've had trouble with the 6.5 models.

They tend to crack in the block as well from high heat and loads. We've had a couple of long blocks and a rebuild go out the door in the past year. We bought half a dozen of these 1 ton vans in early 2000. They gave us ten years of service so it's worth the time and money to fix'em up.

Modern Diesel Technology: Diesel Engines

Cummins ISC Diesel Engine Fuel In Oil Repair.

The Cummins ISC Diesel Engine is a great performer, we have several in our fleet and they are a very durable diesel engine. As with any engine there are failures and in this case we experienced the oil level increasing to an over full condition. One test that told us it was fuel in the oil was the oil sample analysis. We took a sample and the guys at BTA in Kamloops faxed over a report to let us know it was in fact diesel fuel.

Another tell tale red flag was the oil pressure was dropping below normal along with a splatter of oil on the rear engine compartment door. The viscosity decreased making the oil thinner causing these conditions. We actually went through this repair before and the symptoms were exactly the same (that's what happens when you have a fleet with the same drive train).



The CAPS Fuel Pump has to be replaced to repair this condition since it provides the high pressure fuel and injection delivery. It runs directly off the accessory gear and is about the same size as a 2 cylinder air compressor. The fuel lines and accessories have to be removed along with the pump accessory drive gear. The first thing to do after this repair is change the engine oil and get rid of that thinned out engine oil.

DT 466 Diesel Engine - engine oil pressure problem

We had a DT 466 Diesel Engine that could not build up engine oil pressure, especially in the cold weather. It is a 1998 International Thomas School Bus.

The electronic model requires high pressure engine oil supplied by a separate oil pump that feeds the electric over hydraulic operated injectors.

The engine ECU controls injection by sending an electrical signal to each injector solenoid at the specific time required.

This happens VERY QUICKLY. The problem we were having? no oil pressure was being supplied by the engine oil pump that in turn supplied the high pressure hydraulic unit injector oil pump.

So we stripped down the front end and replaced the oil pump and the pressure regulator (some scoring evident). We knew that since it came on the hook without any oil pressure if the engine fired up after the fix we obviously solved the problem.

CLICK ON PHOTOS TO ENLARGE

Oil Pump Pressure Regulator fits into the block oil gallery behind the front cover.
Pressure Regulator Disassembled (the body had some obvious scoring) If it was stuck open this would cause a no oil pressure problem. The nice thing about the electronic DT466 is the engine will not start without oil pressure...
Front cover disassembled. Oil pump is driven off the crankshaft, a very reliable drive system!


Ta Da! Once reassembled the DT466 Diesel Engine we know and love came back to life!I hope this post on diesel engine repairing and troubleshooting the DT466 has helped you....
PLEASE COMMENT! I LOVE THE FEEDBACK...

Cummins Diesel Engine Drive Gears

If you were to remove the front cover off of any diesel engine you will come across a series of drive gears. No belts or chains here, you're looking at the timing gears that make this diesel engine run. Each gear is timed to each other with specially placed marks that must be lined up during assembly.

Enlarge this picture by clicking on it and you should see the timing marks on the crank and cam gears. They look like center punch marks one on the crank and two marks on the camshaft.

The crankshaft and camshaft gears are driven together to provide proper valve and piston timing for combustion to occur. Fuel injection timing on the Cummins C Model diesel engine (pictured here) is accomplished by inserting a pin into the injection pump drive gear (top right).

The pump in turn has a pin in the side of it's housing that has to be removed, flipped around & aligned into the injection pump shaft setting it for injection on #1 cylinder.

The oil pump is also driven off of the crank gear and idler gear. The air compressor is located lower right without it's drive gear installed.

Diesel Engine Mechanic Tips

Here are some diesel engine mechanic tips I've learned over the years. I want to keep them basic so anyone can follow them. Keeping things simple and following these tips will pay off in the long run. If you are thinking you don't have time just think about the consequences if you neglect these basic areas on your diesel engine.

1. Always keep the intake air clean with proper filtration and check the inlet piping and hoses for deterioration.
   
2. Make sure fuel filters are replaced consistently according to manufacturer's specs. (probably the most overlooked mechanical solution)
   
3. Adjust the engine valves at least once a year or depending on how much mileage accumulated.
   
4. Check the coolant for proper protection and replace every 2 years to prevent deterioration. Coolant breaks down and becomes acidic eating away at gaskets and castings.
   
5. Check turbocharger and exhaust system for leaks to prevent power loss. Check the turbo shaft for wear or any indication of contact with the housing.
   
6. Make sure charge air cooler does not have any leaks to prevent power loss. Turbo boost drops substantially with any core leakage in the cooler.
   
7. Check fuel lines for looseness or damage to prevent air entering the fuel system. Air in the fuel causes hard start & no power problems.
   
8. Replace coolant thermostats every 2 years. A thermostat that is stuck open or closed causes overheating or cold running conditions.
9. Load test your batteries every fall to give you an indication of their state of charge. Being prepared before winter starts is a good habit to get into.
10. Check your block heater as well, which goes without saying how vital it can be when you are on the road and parked far away from any mechanical assistance.
    

I hope these basic Mechanic Information Tips have helped you. I have seen a lot of preventable break downs because one or more of these checks have not been made. It's preventive maintenance that should be followed to save you headaches down the road.

Diesel Engine Repairing & Troubleshooting.

One of my favorite tools for diesel engine troubleshooting and repairing is a digital heat sensor.

You can compare the block temperature to the coolant gauge reading, check for an engine miss, confirm any type of heat sensor that's sending a signal.

Case in point: I had a Cummins ISC (electronic) diesel engine that was not heating up properly. So the first thing you want to do is get the story first hand from the operator.

Questions like: How long until it DOES heat up or when did it START to develop?

In this case the operator stated the problem started when the cold weather showed up. So the first thing to do is a scenario with the bus (2000 Thomas Saf-t-liner school bus). So I went for a road test and the first thing I noticed was the engine was heating up very slowly.












I used the digital heat sensor and confirmed the coolant gauge was correct and the engine was running at 170 degrees after a 1/2 hour road trip.

From experience I know that the engine fan locks on with these engine models so I tested both the coolant sensor and charge air sensor.

They have a 3 to 3.5 ohms reading. No ohms means a failed sensor (open circuit).


These sensors determine when the engine fan should come on full which is usually around 200 degrees, in this case the fan came on full right from a cold start up.

Since both sensors were good I replaced the control module which cured the problem(located below the engine fan on the frame). Parts aren't readily available for this module and rebuilding it isn't worth the downtime.












When you have a fleet of school buses there is an advantage to numerous buses having the same specs.

The troubles usually happen more than once and history will help with diesel engine troubleshooting and repairing.

Diesel Engine Troubleshooting

Today's diesel engine troubleshooting procedures have changed since the introduction to computers and higher fuel emission standards.

A laptop is a necessity and software is rampant among all the major diesel engine manufacturers. There is still things you can do to overcome the electronic learning curve a lot of technicians have trouble with.

If I were to think of the best advice to give someone embarking on a diesel engine troubleshooting scenario, it would be one thing.
That one thing is "always check the source".

Don't go to the injectors or valves unless you hear a noise of some sort. If there's mechanical noise coming from the crankcase then you're going to pull the valve cover and inspect the top end. Then you need to drain the oil and pull the oil pan looking for scored cylinders or tidbits/chunks of metal.

For a no start always check the fuel tank. This sounds so easy but it's happened caused embarassing moments. The tank gets overlooked and parts get replaced for no reason because of a cracked or rubbed through fuel line coming out of the tank.

Start at the pressure side [after the second fuel filter or fuel pump] of the fuel system and start cracking lines open. If you've got fuel keep going forward if not go backwards checking for fuel.

If the engine runs and craps out after a minute or so check for air in the system caused by a cracked or rubbed through fuel line. Run the fuel line into a bucket of fuel and see if that makes a difference. If so, start going backwards from there. Hook up a clear line to the return fuel line and check for air that way.

This isn't the technical way of diesel engine troubleshooting but it has worked for me many times finding some really goofy problems that are easily resolved. So check the simple things first and don't get too wrapped up in the high tech side of the engine until you're sure you've covered these basics.

How To Become A Mechanic-What Does It Take?

If you are interested in how to become a mechanic there are different avenues you can take. There is online training, vocational training [at a community college] or if you have experience already and want to get certified then you can challenge the trade qualification exam. If you want to specialize you may want to locate diesel tech schools that provide specific diesel mechanic training.

What's The Best Choice?
In my opinion the college route[if you're just beginning] is the best which gets into the meat of the trade with qualified instructors and pre-planned intruction modules that will give you the experience and confidence to work in any shop as an apprentice. In my part of the world for the "commercial transport" trade you start out with a 10 month pre-apprenticeship that gives you the basics and preps you for the "real world" truck shop atmosphere. Once completed it's up to you to sell yourself and get hired on as an apprentice. In some cases you may start out as a "Mechanic's Helper" which isn't a bad start. A lot of shops want qualified personnel since time is money and don't have a lot of time to train.

Mechanic Duties.
Depending in what area of the Mechanic field you want to work in, Mechanic Duties will vary. Generally speaking you must be ready to diagnose and repair everything related to the machine you're assigned to.

You will deal with Engines, steering, suspensions, transmissions, differentials, electrical and air system problems. After Tech School training is over you'll be released into reality and if you work in a retail repair shop get ready to hustle. Time is money as they say and customers can be demanding [you can't blame them with shop rates constantly increasing]. Fleet jobs are less demanding since there are hourly drivers and spare units available, but the work quality still has to be commendable.

As an apprentice you're supposed to be working with a Journeyman but you may find yourself on your own and using your instincts more often than not.


Mechanic Shortage?
On the other hand there is beginning to be a shortage of mechanics to replace seasoned old salts like me when it's time to hang up the tools. The first thing a lot of employers will look for is someone with a good attitude and aptitude to get the job done with some direction from an experienced lead hand.

Apprenticeship Timeline
A 1st year apprentice in Canada will start off at 60% of the journeyman mechanic's wage. This goes up every year after until certification is attained. Each year [for 4 years] you have to go for 6 weeks training and pass a written exam. The final year requires an 8 week course since you'll be writing a trade qualification and interstate/interprovincial exam.

Tools Required
Mechanic's Tools you'll need is the basic hand tools both standard and metric wrenches with 3/8 and 1/2 inch drive air tools. Don't go overboard, you'll buy more tools as needed.

Does The Trade Pay?
Wages are very competitive with other trades since it's getting harder for employers to find qualified people.
Journeyman mechanics can make anywhere from $20.00 to $35.00 per hour depending where your located and what kind of equipment you're working on.

Side Note:
In 1980 I worked up North making a Journeyman rate of $10.00/hr and the shop rate was $29.00/hr. [times have changed!]

That's a basic over view on how to become a mechanic. I can tell you it's the total package full of challenges that takes patience, intuition, strength & above all experience to over come and I highly recommend it to anyone who loves diesel engine repairing/troubleshooting and working on a variety of different mechanical systems.

Avoiding Cummins Engine Repairs With Regular Tune-ups.

We recently had a Cummins Diesel Engine with a power complaint. One adjustment that gets overlooked is valve adjustment. This particular engine gained substantial power after adjusting the valves which required an average of 1/4 of a turn to meet specs. So this simple tune-up procedure should never be overlooked and must be carried out on regular basis.

The following is a valve adjustment on a Cummins ISB Diesel Engine: Valve adjustment on a Cummins Engine Repair is the final step. Engine position is very important because the intake and exhaust valves must be in the closed position.

Rotate the engine clockwise [looking from the front] until #6 cylinder rocker arms are both rocking. When you're on the correct stroke the exhaust valve will be moving into the closed position, then once it closes keep rotating the engine until the intake valve JUST starts to open. You are now on #1 Compression Stroke & ready to adjust 1/2 of the engine valves.

Note: The crossheads pictured here on top of the valve stems [#5 & #6 Cyl] are located with the elongated contact surface towards the exhaust manifold. The Rocker arms are held down on aluminum cradles with one retaining bolt and torqued to 27 ft. lbs.

Cummins 24 Valve Turbo Diesel Valve Adjustment Specs.

With the Engine on #1 Compression Stroke.

*Adjust #1 #2 #4 Intake Valves to .010 inch.

*Adjust #1 #3 #5 Exhaust Valves to .020 inch.

*Rotate Engine One Full Turn. #1 Cylinder Valves will rock like #6 did previously positioning the engine on #6 Compression Stroke.

*Adjust #3 #5 #6 Intake Valves.

*Adjust #2 #4 #6 Exhaust Valves.

I hope this mechanic information has helped you: It's not hard to adjust valves on a Cummins 24 Valve Turbo Diesel once you get the hang of it. All you have to know is how to position the engine correctly, the valve settings and some basic tools. That's it for now on Cummins Engine Repair.




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