6.0 Ambulance No Start Hot?

Aaron · November 14, 2013

Got a head scratch-er here fellows.

6.0 ambulance. JASPER REMAN engine. Customer reports an intermittent no start hot.

I have a P2291, P0528 and a P0620 in continuous memory.

Hot IPR is 24%, wide open throttle IPR is 59%.

With oil temp at 195 or higher, IPR ramps to ~30 percent and truck fires up. Every time.

Air check reveals nothing.

I've not yet been able to get this thing to no-start, but I'm hesitant here, since I do have a 2291 and it is an ambulance.

A local dealership has shotgunned an IPR at it, and apparently the concern persists.

I'm scratching my head on this one.

The only thing I came up with and this is a LONG shot, but what if the ICP was feeding faulty info to the PCM? Will the ICP reading of less than 500 PSI cause a no-start, even if the actual pressure is over 500psi? I know when the ICP is open circuit it will substitute values and start anyway, but I can't recall or find documentation that says if the ICP bias is incorrect if the vehicle will actually not start.

Any ideas guys?

Thanks!

mchan68 · November 14, 2013

If it's a Jasper engine, does it come will all the usual updated '05+ parts (dummy plugs and STC etc.)? Failing that, if you can't duplicate the concern, it's a shot in the dark. Not sure it helps much, but I vaguely recall having a '10 E-Series in for a no-start hot and it turned out to be the HPOP outlet two bolts had backed off to where both were hand loose.

Bruce Amacker · November 14, 2013

Yes, if the ICPV is too high KOEO the PCM decides it doesn't need to command the IPR up and the truck won't start. I posted screen caps of this here a few years ago, and no DTC's were set. I'm not sure if this answers your question or not.....

Jasper "generally" puts all updates in their engines.

:grin:

Keith Browning · November 14, 2013

I have had biased ICP sensors cause a no start in the past. Some display odd data that you can see and a few did not nor did they leave a code. Considering the nature of the symptom and the application an ICP IS THE LEAST INTRUSIVE and cheapest thing to try if diagnostics lead you nowhere.

Aaron · November 14, 2013

I'd really like to recreate the concern, but if I can't I don't want to shotgun parts at it either.

Do you remember where those screen caps are Bruce?

Keith Browning · November 14, 2013

I found three with that title in the gallery in Bruce's album.

lmorris · November 14, 2013

Just to add, if the PCM sees less than 500 PSI it will not activate the injectors.

Keith Browning · November 14, 2013

Just to add, if the PCM sees less than 500 PSI it will not activate the injectors.

That is the problem possibly with this concern. If the sensor is biased high, the PCM could be seeing 500+ but in reality the actual pressure could be far less and in theory not enough to inject fuel or enough fuel to start. Most of the engines I came across with biased-high ICP sensors also exhibited a surging idle and or heavy surging while driving.

What screws with a lot of tech's heads is that KOEO voltage may read in the proper range therefore there seems to be nothing wrong with it. But once pressure is applied the sensor begins to read incorrectly. Once you have seen this scenario it sticks with you and you will recognize the symptoms when you see them. I agree with Aaron in that "shot-gunning" a part at it is not necessarily the most attractive approach and I too would love for him to be able to duplicate the concern... with that said, I repeat my suggestion that if all other proper diagnosis has been performed TRY a new sensor and harness pigtail. Yes, it is a guess BUT in this instance it should be considered an educated and reasonable guess worthy of attempting.

ktmlew · November 14, 2013

I would scope the crank sensor.

Bruce Amacker · November 14, 2013

http://www.forddoctorsdts.com/gallery/image/280-no-icp/

I'm still struggling with posting pictures in the forum. I can see the pic but I can't find the link to post it....

Note 0rpm, high ICP/CIPV, no DTC's and it was a no start. Unplug the ICP and it started, replace ICP and it was fine. It happened in class, oddly enough.

lmorris · November 14, 2013

Just to add, if the PCM sees less than 500 PSI it will not activate the injectors.

I am leaning more towards the sensor being biased low and reading lower than 500 PSI when the pressure is actually higher, with the PCM ramping IPR up to 85% it should be over 3000 PSI at this point, but the PCM sees below 500 PSI. At this point the PCM sets the P2291 and will not give the FICM any signal to turn them on electrically.