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Open Roads Forum  >  Class A Motorhomes  >  General Topics

 > Cummins ISB 5.9 Cranks but no fire-ECM power.

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oldave

Tx

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Posted: 12/01/20 08:37am Link  |  Quote  |  Print  |  Notify Moderator

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

* This post was edited 12/01/20 11:45am by oldave *

Stim

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Posted: 12/02/20 05:41pm Link  |  Quote  |  Print  |  Notify Moderator

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.

MrWizard

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Posted: 12/03/20 04:57pm Link  |  Quote  |  Print  |  Notify Moderator

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


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alvie h

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Posted: 12/03/20 06:17pm Link  |  Quote  |  Print  |  Notify Moderator

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

wolfe10

Texas

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Posted: 12/03/20 06:56pm Link  |  Quote  |  Print  |  Notify Moderator

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.


Brett Wolfe
Ex: 2003 Alpine 38'FDDS
Ex: 1997 Safari 35'
Ex: 1993 Foretravel U240

Diesel RV Club:http://www.dieselrvclub.org/

glamisorbust

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Posted: 12/10/20 07:26am Link  |  Quote  |  Print  |  Notify Moderator

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.

glamisorbust

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Posted: 12/15/20 08:04am Link  |  Quote  |  Print  |  Notify Moderator

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.

Whaler

IN, USA

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Posted: 12/16/20 07:44am Link  |  Quote  |  Print  |  Notify Moderator

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.





Bruce Brown

Northern NY

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Posted: 12/16/20 11:33am Link  |  Quote  |  Print  |  Notify Moderator

Thanks for the update.


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Bruce & Jill Brown
2008 Kountry Star Pusher 3910


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