Sunday, May 21, 2006

Cummins Diesel Engine - Will Not Start

Cummins Diesel Engine

Here are a few tips and checks you can make when your Cummins Diesel Engine will not start.
Don't feel insulted with some of these checks because the simplest steps have been overlooked many times.
The rule of thumb is Check The Simple Things First!

  1. When your Diesel engine cranks but will not start - No smoke from exhaust
  2. Is there fuel in the supply tank? Always check the source on your diesel engine
  3. Check electric or manual fuel shut-off.
  4. Is the air intake or exhaust plugged?
  5. Note: Remember, a diesel engine needs air and fuel to run
  6. Fuel filter plugged / seperator full of water?-drain as required.
  7. Your diesel engine injection pump not getting fuel or fuel is aerated. Check fuel flow or bleed fuel system.
  8. Check inlet restriction to fuel transfer pump
  9. Inspect lift pump operation. Remove outlet line and crank over engine
  10. Worn or malfunctioning injection pump
  11. Internal pump timing incorrect
  12. Engine camshaft out of time

My experience with diesel engines has taught me to start from the source and work my way to the injectors.

Check the filters to see if they are still full of fuel, if not you've got a diesel engine that has run out of fuel - a no brainer. I went on a service call once and found out that the operator had filled the tank with gasoline, anything can happen!

Otherwise you have an obvious failure that you have to sink your teeth into. Replace fuel filters if the mileage or hours are excessive.

Check fuel lines from the tank to the primary filter [Fuel/Water Seperator]

Tip: I use a remote fuel container and slip the suction line before or after the primary filter. If diesel engine performance improves you know you have to start checking for faults back to the tank. This procedure bypasses the fuel tank and lines up to that point which tells you if the problem exists in those areas i.e. restriction or split/cracked fuel line or bad pick-up tube in the tank.

Pull output line off of the lift pump on the side of the block and crank engine over and check for fuel output.

Prime fuel system with primer pump and bleed the injection pump, once primed crack injection lines at the injection pump and observe for fuel output.

In most cases you will find a problem up to this point, if not check injection pump timing or check to see if the camshaft gear is actually driving the injection pump. These failures are not common at all.

I hope these tips help you troubleshoot your Cummins Diesel Engine.


Anonymous said...

how to replace cylinder liners

John Whelan said...

The Cat 3116 diesel use dry pressed cylinder liners. If there is a scored liner the engine has to be stripped down to the block and sent to a machine shop where the block is bored out and an oversize liner sleeve is pressed in to bring the bore back to standard.

jim said...

1999 thomas built school bus with 5.9 cummins. Wont bust off untill spining over several times. once does it runs fine but turn it off and and restart just spins over. replace electric pumpcause old one was bad. wont to check code to see maybe have ijection pump codes in memory but dont have software to do it. have hookup for lab top that plugs in but not software. got good pressure to injection pump from lift pump. 11 psi and goes down to almost zero when cranking. What you think maybe injection pump? how do you get the code manual out of the bus?? to see maybe whats going on?? any help i appreicate it

John Whelan said...

If you changed the fuel pump is it energizing properly? It should prime the system quick enough for normal starting. I'm wondering if the press drop to 0 is normal? Did you buy the pump at a Cummins dealer? Could you ask them the pump specs?