Fuel Delivery Issue

[TexNeck]

I will give that a shot.

Yes, I nearly fell over when I saw the cost, what a bunch of criminals.

Would you agree that the truck should run fine with the race plug in the fuel rail if that solenoid/pressure controller was working properly?

A friend of mine is trying to tell me it NEEDS the pressure relief plug, and I feel that it’s just there for extreme pressure spikes, aka, rarely bypasses fuel.

Race plug is fine the common rail system can handle the pressure of a single CP3.

I’ve got one I still need to put in my fuel rail.

If you were running dual CP3 I’d say you need to reconsider.

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[AMFC]

Well, I guess it’s time for an update.

Still no progress.

Replaced the CP3 regulator twice, tested resistance between the wiring harnesses to and from the PCM.

My truck shows 8702.3 desired rail pressure at all times, runs and drives at 12.5-13.1k no matter how much throttle is given.

I would like to do an injector return flow test, however, I’m still wondering why I would make 29k psi rail pressure with the race plug installed.

If I was bypassing fuel at an injector or feed tube, how would it maintain 29k with a rail plug?

And WHY am I getting 29k nonstop if the relief is capped?

I’m about ready to just pull the trigger on a PCM or new injectors and feed tubes just to eliminate possibilities.

ANY recommendations will be much appreciated.

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[RATLIN'HP]

I would of changed them filters that only have 1000 miles on them first.

I'd still change them now unless I missed something skimming this, and you already have.

Also get a fuel sample maybe.

A load of bad fuel and plugged filters could cause this I'd think.

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[AMFC]

I’ll do that.

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[AMFC]

Whelp, 0 mile fuel filters and 0 changes.

The cartridge filter wasn’t even slightly discolored or contaminated.

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[cumminsdieselfreak]

Whelp, 0 mile fuel filters and 0 changes.

The cartridge filter wasn’t even slightly discolored or contaminated.

So just to be clear, you replaced the FCA on the CP3 with a new one, correct?

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[AMFC]

Yes, twice actually, all of the symptoms led me to believe the replacement was faulty since the pump is making good pressure, it just seems as it’s not being regulated... however, my desired rail pressure is at 8702.3 all the time. I don’t know if that’s a “limp mode” default or what, but the only time it changes is at startup, builds to 22k and then goes right back to 8702. Maybe lasts 3-5 seconds. The truck is just running at 12-13k, not increasing or decreasing with throttle input.

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[cumminsdieselfreak]

Yes, twice actually, all of the symptoms led me to believe the replacement was faulty since the pump is making good pressure, it just seems as it’s not being regulated... however, my desired rail pressure is at 8702.3 all the time. I don’t know if that’s a “limp mode” default or what, but the only time it changes is at startup, builds to 22k and then goes right back to 8702. Maybe lasts 3-5 seconds. The truck is just running at 12-13k, not increasing or decreasing with throttle input.

Did they replace the rail pressure sensor? A bad one will cause a loss of power/erractic engine behavior. I can get you a Genuine Cummins one at a discount. Shoot me a PM or email if you'd like to try that.

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[AMFC]

That was replaced also.

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[cumminsdieselfreak]

That was replaced also.

Wow, idk then. Everything points to a bad FCA but with replacing it twice idk. It's rare but you could have a short in the wiring for the FCA plug.


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