Intermittent failure to fuel? Ideas?

fnordmorph · **Posted:** Thu Jul 30, 2015 1:44 am

I'm having trouble with my newly resurrected '05 CRD with 111k miles, GDE stage 2, GDE TCM, EGR delete, Suncoast, Provent, other mods as listed. Wondered if anyone (Geordi? Papaindigo? GMCTD? Anyone else?) could speculate as to why it behaves as follows:

Starts easy. Idles smooth. Press accelerator to floor, RPM creeps up to 1500 or maybe 2000 if I'm lucky. Let off, press it again, same thing. Let off, press it again, might get to 2500. Let off, press again, runs like it should (squeals tires and pulls hard to as fast as I want to go on the highway). Acts like it's not getting the message that it should be injecting more fuel, then acts normally. Sometimes a tiny puff of smoke when letting off accelerator. Behavior always there when started cold, seems less prevalent as it warms up. Replaced accelerator pedal, same result. Samco turbo hoses seem fine. MAP sensor clean. Timing belt just done and timing corrected. Valve cover was off before that and rockers were good. No leaks. No warning lights. No DTC's. Fuel priming pump firm.

Thoughts?

olypopper · **Posted:** Thu Jul 30, 2015 2:31 am

Have you watched rail pressure?

Auberon · **Posted:** Thu Jul 30, 2015 7:21 am

Not trying to be too basic but how old is the fuel filter?
Is Provent system closed or open to atmosphere?
It's important it remain a closed CCV system not elephant hose.
Any more happened to help you solve it?

flash7210 · **Posted:** Thu Jul 30, 2015 8:50 am

Thoroughly check the low pressure side of the fuel system from the tank through the filter and to the CP3. Make sure there are no flow restrictions and that there is no air in fuel.

Other than that, It could be a intermittent circuit problem like I had with my fuel rail pressure sensor. But that should throw a code.

fnordmorph · **Posted:** Thu Jul 30, 2015 11:40 am

Will do the fuel filter and check everything from tank to fuel head, see if that gets me anywhere.

Not sure how to check the rail pressure (Torque Pro and OBDLink MX?)

flash7210 · **Posted:** Thu Jul 30, 2015 11:47 am

TorquePro is a good tool and will allow you to somewhat monitor fuel rail pressure. The readings you do get can help diagnose the problem.
And don't forget to scan for codes again.

fnordmorph · **Posted:** Mon Sep 26, 2016 2:27 pm

Apologies for resurrecting this old thread, but I'll risk it since its about the same problem. My 05 CRD Liberty now has in-tank fuel pump, new fuel filter, tank full of fresh diesel. I still get the same behavior, worse when cold but sometimes happens warm too: press accelerator to floor, get minimal increase in RPM, do this several times and finally it will kick in and run normally. I have more info now from OBD Link; the accelerator pedal position is reading 90+% with the pedal down, the MAF appears to increase as expected with engine speed. When I'm getting the 'no go' condition fuel rail pressure is not coming up very well; getting maybe 12 kpsi. When its running right I'm getting close to 20kpsi at full throttle. Boost is tracking pretty much as expected, goes up to close to 20psi when running right and pulling hard, maybe 5psi when its in this 'I ain't gonna' condition. I'm slogging through the 40 pages of hits on a search for 'fuel rail pressure', but if anyone has an idea of what is likely to be wrong here, I'd love to hear it.

flash7210 · **Posted:** Mon Sep 26, 2016 2:42 pm

Rail pressures can vary depending on your ECM tune. But most will be close to the same at idle and WOT.
Here is mine:
Idle = 4500 - 5500 psi
Cruise at 65mph = 15000 - 17000 psi
Hard acceleration = 21000 - 25000 psi

Are you getting any codes?
Any fault in the hight pressure fuel system should produce a trouble code.

fnordmorph · **Posted:** Mon Sep 26, 2016 2:58 pm

No codes

Tune is GDE stage II (for the upgraded '07 type turbo)

I think fuel rail pressures are OK when it is running right; accelerates well (much better than when stock), but they don't want to come up when it's in this no-go state.

I'm looking at what I can find about the fuel rail solenoid... seems like it or its wiring might cause this kind of problem, but what I'm reading makes me think it should be a lot worse when it isn't working right... :-/

flash7210 · **Posted:** Mon Sep 26, 2016 3:46 pm

If the fuel rail solenoid had failed, it would not allow pressure to build in the rail and the engine will not run. Go ahead and unplug it while idling. The engine should stop immediately.

The fuel pressure sensor is mid way on the rail. If it were giving a false high reading, this would cause drivability problems but should throw a code.

The fuel quantity solenoid (MPROP) is on the cp3 injection pump. It regulates how much fuel goes up to the rail and how much gets sent out the return line.

Find each part and its wiring connector.
With the engine running at idle, shake and wiggle each connector. If the engine stumbles, sputters, or dies, its a wiring problem.

When I was having fuel rail problems, I installed a auto meter fuel rail pressure gauge. It has been a good tool for diagnosing problems. But it is electronic and ties directly to the pressure sensor. So if there is an electrical problem or bad sensor it wont work right.

Intermittent failure to fuel? Ideas?

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