Lincoln Navigator Low Power video question

*raises hand* Mr. Danner? I've got a question!



At around 21 minutes in, you're talking about fuel pressure bleed down testing in relation to mechanical and electronic returnless systems. The mechanical system diagnosis is (obviously) pretty straight forward, but you state that there are additional checks needed if it's an electronic system?

I ask because I looked at a Focus recently that had a long crank time symptom. I used the fuel pump bidirectional test to test pump output and bleed down rate, and came up with this:



I felt this was fairly conclusive. Fuel trims were positive, so no leaking injectors, and no fuel leaking into the pressure sensor vacuum hose. I'm unsure what else in the electronic system would account for rapid pressure loss. Thanks!

i wonder that to!

The additional tests I mentioned were not related to the bleed down issue but the low pressure issue.
For low pressure on electronic returnless systems that use a variable speed pump, you also need to consider the following:
Fuel rail pressure sensor operation
Fuel pump driver module and related wiring
PCM command to FPDM




Sorry Tyler, didn't know it was you. I'm pretty sure you already knew this. Sorry for the confusion.

ScannerDanner wrote: Sorry Tyler, didn't know it was you. I'm pretty sure you already knew this. Sorry for the confusion.

:lol: No problem! Apologies for the misunderstanding, just wanted to make sure I wasn't selling pumps and not diagnosing it all the way. :silly: