Monday, February 19, 2007

Cummins ISC Electronic Diesel Engine- cranks over but will not run.

Cummins ISC Diesel Engines need to be analyzed using a laptop computer with Cummins Insite software.

Sometimes however you can troubleshoot a no run problem the good old fashioned way by looking listening and using common sense.

The fuel transfer pump mounted on the left rear of the engine is a vane type unit driven by an electric motor.

The first clue was the transfer pump motor was not running at all with the ignition key on, it will charge up the system every time you hit the ignition key with a very distinctive motor noise at high rpms.

So since the golden rule with electrical problems is to check the source I went to the battery and checked the multiple fuses that supply power to the engine ECU [electronic control unit]

I found 3 fuses had blown indicating a possible short or high amp draw. The first thing to do was hook up a jumper wire [with an inline breaker in case there was a short]

Once hooked up the fuel transfer pump started working but sounded very sickly! It was enough to limp the School Bus back to the shop.

Since the main problem was a overly high draw from a faulty fuel
pump motor, replacing the fuel transfer pump was our next step.

The fuel pump must be installed as a unit [do not just change pump and motor] and will not seal properly on the old housing. You are guaranteed to have a fuel leak once you start it up.

How do I know? because I tried it as a shortcut and instantly had a fuel leak between the housing and fuel pump/electric motor.

There is very little room to move in this Thomas pusher since it is a rear engine unit. Remove power steering lines and rear radiator frame brace to gain access to the pump housing fuel lines and mounting bolts.

Test the pump by cycling it a few times with the ignition switch.

Fuel filter replacement is recommended, we pre-fill the primary filter and install the secondary filter dry which allows incoming fuel to be pre-filtered instead of being poured out of a fuel container, this avoids contamination.

The new fuel transfer pump will do all the work priming the system.

Just listening to the uncharacteristic sound of the fuel transfer pump led us to this rather easy diagnosis. It's a gimme that doesn't happen too often.

The main tip here is to always check the source first when troubleshooting a problem. Electronic diesel engines like this Cummins ISC model still run off a 12 volt battery so things have not changed too much from a few decades ago!

School Bus Mechanic on my "Squidoo" Lens

1 comment :

Jim said...

Hey here's the problem,2002 Bluebird 5.9 ISB has a hard time starting seem like it is loosing prime.
To elimate things I completely changed the suction (from tank to transfer pump )replaced the transfer pump as well I then tested it and it passes the pressure tests
I then did a vacum test on the primary canister fuel filter housing it also passed
............I am leaning towards a bad vp 44 pump but it has not set any codes. any ideas?
Jim