Cummins ISB 5.9 Cranks but no fire-ECM power.

[glamisorbust]

99 Holiday Rambler Endeavor 37CDS4 with Cummins 5.9 and Allison 3060. 180k miles. Just did a lot of major repairs including the following:
-Cylinder head rebuilt, including new OEM sensors and cam sensor.
-Rebuilt VP44 injection pump.
-New cooling fan from source RV, and bearing.
-All new belts, hoses, thermostat etc.
-Refurbished cummins ECM.
-New OEM Bosch injectors.
-Billet aluminum tappet cover(better seal than OEM).

Here is the issue: The coach was running when parked, but leaking water from the water pump and small leak from head gasket aging out. The gasket on the tappet cover had a bad leak too. So I decided to pull the head and have it rebuilt, clean it all up and put everything back together.

It will crank but not fire. Got a breakout box from cummins to verify the VP44 is in good working condition. It fired right using that tool. The stock ECM ended up failing somewhere after I took everything apart. No idea why. Maybe because it was covered in oil.

I have tried 5 different ECM's including the OEM one, and only one out of those fired it up. But the tune was wrong, making it undriveable. So I got a $2000 OEM refurbished one from cummins. It has been programmed properly, but this thing still fails to fire off.

I don't think I'm getting good power to the ECM, due to the lift pump also not activating. I have a suspicion the ignition key has something to do with it but haven't checked that yet. The step also doesn't come back in like it used to when you turn the ignition on. Is this most likely a bad ignition switch, relay or something else? The RV has been down for over 4 months now and I need to get it back running.

One more thing: The ignition crank works about 50% of the time, so I wired in a push button switch near the engine in an outside bay. Makes it where I don't get stranded if the engine doesn't crank.

Any help or ideas are greatly appreciated. Thank you.

[Bruce_Brown]

Thanks for the update.

[Whaler]

Fuel quality is critical but especially critical for the VP 44 injection pump. It doesn't take too much bad fuel to overheat the electronics on a VP44 so I was informed by some rebuild specialist. Maintaining quality fuel during storage is the key element to prevent problems as is the proper lift pressure. There are several threads on rv.net to get info concerning fuel quality.

[glamisorbust]

Update: I got my coach back from Freightliner on Saturday. It runs great as it always did. Cost me $5200 to have the VP44 replaced.

[glamisorbust]

Ok guys, I have found the problem. The last resort was towing this RV to freightliner, since I purchased the remanufactured OEM cummins ECM through them. Had it towed Monday 12/7 and I got a call from them a few hours after they received it.

The VP44 injection pump is no good. I purchased my remanufactured unit through Thoroughbred diesel. It did fire on a breakout box(cummins tool to make sure fuel injection pump is working properly). I went through 3 computers, one of them fired the engine up but ran poorly, no throttle pedal. Freightliner seems to think one of those ECM's that was programmed incorrectly fried the electronics on the VP44. There is a sensor on the pump telling it when to release fuel to each cylinder. That is not working. Pump needs to be replaced.

I am having them put on a remanufactured OEM cummins VP44 injection pump. Hopefully this will be the last of the problems. I will update again after I get the coach back from Freightliner. Thanks for all the replies, it definitely helped.

[wolfe10]

MrWizard wrote:
I had a 95 Safari with the Cummins 5.9
And had to replace the injector pump, mine was the old mechanical style, lift pumps provide the volume of fuel from the tank, but the injection pump supplies the pressure needed turn that fuel into vapor when sprayed into the cylinder, I think you lack fuel, not enough going into the cylinder to properly combust,
My insufficient knowledge says the spray goes in to meet the hot compressed intake air already in the chamber, meaning lots of pressure is need from the injector pump, my memory might be faulty, need to hear from Wolf or other more knowledge diesel person

Very good. A slightly different way of looking at it:

The temperature needed for combustion (to cause an explosion when diesel is injected) is straight from the IDEAL GAS LAW. PV=nRT. With the diesel's high compression, high temperatures are reached as those molecules are made to live in 1/17 to 1/20 of their "normal" space.

And, rather than wanting high intake air temperatures, diesels are equipped with a CAC (Charge Air Cooler) as cool air is denser (more molecules per cylinder full). Then they "squeeze" those molecules to raise the temperature for combustion.

And, yup, most use a turbo to force even more molecules of air (oxygen is the important part) into the intake and cylinder.

[alvie_h]

I would loosen injector pipe and crank engine 45 seconds if no fuel comes out of pipe you have fuel pump issues.

[MrWizard]

I had a 95 Safari with the Cummins 5.9
And had to replace the injector pump, mine was the old mechanical style, lift pumps provide the volume of fuel from the tank, but the injection pump supplies the pressure needed turn that fuel into vapor when sprayed into the cylinder, I think you lack fuel, not enough going into the cylinder to properly combust,
My insufficient knowledge says the spray goes in to meet the hot compressed intake air already in the chamber, meaning lots of pressure is need from the injector pump, my memory might be faulty, need to hear from Wolf or other more knowledge diesel person

[Stim]

I would double check/clean all battery connections.
Also check to see if you missed connecting a ground wire back to the engine.
Could even try a jumper cable from frame to engine temporarily.
My best unfamiliar with unit guesses.

[oldave]

You have found that 12v can back feed at times making diagnoses difficult.
The fact that your step is not responding properly implies there may be some
kind of problem in the ignition circuit. Add to that the key start works only
about 50% of the time makes it look even more like something in the ignition
circuit.
I would try repairing the step and hope that will repair your no start
problem too.
Ignition switches are relatively cheap you could try replacing it.
I think you can reach up behind the ign switch to make sure the wires are not
loose

It doesn't seem likely 5 different ECMs would all be defective.

I just read a thread on IRV2 where a poster had the same issue
A new ignition sw fixed his.

https://www.irv2.com/forums/f115/ignition-switch-516512.html

[robatthelake]

Is there a fuel shutoff solenoid? If so is it working? Try switching it manually!

[tropical36]

glamisorbust wrote:
We just checked all 5 fuses in the battery box, going right into the main wiring harness. All fuses are good, verified with test light. However, some of the fuse holders have power at both sides, without a fuse installed. Maybe the ECM is back feeding those lines with power?

The suggested fusible links look to be part of the wiring and not actual fuses. Not sure you're aware of that and just so you know.

[glamisorbust]

My brother and I spent about half of the day trying to diagnose the problem. I'm pretty sure at this point we know we have a bad ECM. There is definitely constant power there, and the switched ignition works as it should.

We got a wiring schematic from Freightliner south carolina, and traced out all the wires. The lift pump still has no power, indicating the ECM isn't letting the pump run. I have put a battery directly on the lift pump to see if it would fire. With 15 PSI the engine doesn't even try to fire. Just cranks.

[glamisorbust]

We just checked all 5 fuses in the battery box, going right into the main wiring harness. All fuses are good, verified with test light. However, some of the fuse holders have power at both sides, without a fuse installed. Maybe the ECM is back feeding those lines with power?

[carringb]

Check the ignition-source fusible-links. Sometime during all the work, something probably grounded out blowing the fusible link. I have no idea where they would be on your coach however. On a truck, they'd be near the starting batteries.