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2017 F-550 Ongoing No-Start P2291

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mchan68

By mchan68
in 6.7L Power Stroke® Diesel Engines

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mchan68

mchan68

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Hi guys. I have an interesting, yet frustrating one here. A 2017 F-550 tow truck. Unit has about 125,000 kms (78,000 miles) with high hours. Complaint is a no-start with P2291 set. I have managed to determine the cause to be the low pressure pump not delivering fuel. My first dig at this, I managed to pinpoint the cause to a faulty FPDM (by swapping a known good one from another 2018 F-550). The truck went back into service without further issue for about two to weeks. The second time, same thing happened. This time I disconnected to connector on top of the fuel pump (C3127) to check for B+ at pin #4 with the fuel pump commanded ON. This checked good. Reconnected the fuel pump connector and the truck fired up! After several successful restart attempts I sent it on its way. Well, one week later it's back with the same symptom. Check for B+ again at C3127, this time I get only 9 volts. Command the fuel pump ON and it gets back up to B+ voltage and guess what? It starts again! This time, I tried wiggle checking the harness at the fuel pump connector and around, unable to get this truck to react or quit. Drove it around and life is good again. I just got a call again, from the customer informing me it won't start yet again! Just looking through the wiring diagram, I see that fuel pump control involves only the PCM, the BCM, the non-serviceable relay in the BJB, the FPDM (already replaced) and finally the fuel pump (in-tank). Is there anything else I should be checking? I should also mention in each of all instances, the truck was shut off and would not restart. It never just died on them. I'm at a loss at this point.

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cbriggs

cbriggs

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Based on the nature of how its acting it sure sounds like the contacts in the relay are going bad. Might be worth connecting a testing breakout to the circuit somewhere so it could be tested during the failure without disturbing anything. You could also use it to power fuel pump manually and see if that makes it run. You would think it should set fuel pump primary circuit codes if it was high resistance or open.

We just had a similar concern on a 2019 e350 rental motorhome. PCM would randomly go offline. It has been at 3 dealers, twice concern went away during testing, once got a pcm, and then ended up at our store. This time it was fully dead. Load testing pcm powers revealed only 2 volts at one of the pcm powers. Touching BJB made concern come and go. Ended up having a broken internal shunt in the bjb.

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cbriggs

cbriggs

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Just a thought Mike, when it won't start does it fire and stall, or not fire at all? If the LPFP fails to run at key on they will usually fire a bit, or run for a few seconds and then die.

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mchan68

mchan68

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10 hours ago, cbriggs said:

Just a thought Mike, when it won't start does it fire and stall, or not fire at all? If the LPFP fails to run at key on they will usually fire a bit, or run for a few seconds and then die.

It fails to start at all. No stalling, sputtering or running rough, just fail to restart. But once you active command fuel pump ON (get the fuel pump running), it starts and restarts right way with further issue until.....

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