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Fuel issues

DNeid

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#1
Howdy yall, first time poster,

2018 fiesta se sedan, just got done with a timing belt install (timing slipped while driving, internals are miraculously good) after everything was buttoned back up, fuel pump wouldn't prime, I KNOW it worked beforehand, as it was something I was testing when diagnosing what eventually became my timing issue.

Here's what I know, fuel pump works, wiring from relay to fuel pump is good (hot wired the fuel pump relay while starting engine, and it ran for several minutes no issues) relay is good, ignition (the act of turning the key and getting power to the car) works. But when I turn the ignition on, and while starting I'm showing precisely 2.4v at the relay. I've rotated the 30a fuel system fuse and that checks out good as well.

Any ideas? It's 2am and I'm freaking stumped.


****UPDATE***

After running the engine for a little, my camshaft actuators are both throwing codes, my AC clutch won't engage, and I'm still having to jump the fuel relay to get it to run. This sounds like a particular harness or module that's dead or not working.
 
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#2
I would re-check anything you removed, unplugged/plugged, moved or bumped. Also check for good grounds. Sounds like an electronic circuit without a proper ground or loose connection/wire.

Are you showing 2.4V at the BATT terminal for the relay or at the signal feed to actuate the relay? Relays dont require a full 12V to actuate.

If its a harness issue, it only takes 1 strand in a wire to read continuity, however a wire will not be able to carry the "full load" if needed. You can test a wires true working capability by wiring a headlamp bulb in series (briefly). If the headlight illuminates, the circuit is healthy.
 

Handy Andy

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#3
You need to recheck the wiring at the FUEL PUMP harness - that connector - the color of the wires off of it.

Why?

Fiestas came with two types of Fuel pumps, one that sets pressure inside the unit - self-contained, while another uses a Fuel Pressure Driver Module - a regulator in a unit back at the Body Control Module or in the Harness to the tank.

Which one?

That depends on the Flex/Fuel and or ST line and or Engine and displacement (Eco boost or Sigma) all these combine into a required separate regulation for Fuel delivery or jsut use an integrated unit..

You find that out easily enough by looking at your Wire harness wire colors used...

See below...
1693747742978.png

You mentioned 2.4V at the pump - so that tells me you may have the Driver Module, and it needs help or needs to be found and rechecked and it's harness reseated.

One pump had a bolted ground, while another sent both pump wires back to this module to have the voltage changed as the speed - load / pressures was required
 
OP
D

DNeid

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Thread Starter #4
Are you showing 2.4V at the BATT terminal for the relay or at the signal feed to actuate the relay? Relays dont require a full 12V to actuate.
I'm seeing the 2.4 volts at the signal feed side, I've even tried swapping around the other relays in that box to see if it was just a bad relay, but none of the relays I put in there actuate under the voltage supplied. I'd be willing to bet this is a ground issue, when I removed the starter to lock the flywheel, I didn't take the whole unit out, I let it rest under the intake and on top of the oil filter, so I'd be willing to bet I buggered up a harness or a ground in there.

As far as the fuel pump issues identified by Handy Andy, I know once the fuel system gets power through my relay bypass, it primes, runs, and controls fuel as expected, so I'm almost certain this is an issue with the ECU to the fusebox, or a bad ground or signal wire that i buggered up somewhere.
 

Handy Andy

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#5
Keep us posted on this...

Good luck, - its never fun.

Just so you know, the "Ground wire" for that Fuel pump is by the same harness ground bond point at the Driver Seat - it's not in it, it's back behind , a bolt on the side that drop into the seats center pan in the Seats bolts front rail that holds the seat rails close to the seat-belt bolt on the side of the pan - but towards the front on the front seat bolt rail towards the door panel.

You should be able to DVM Ohmic check that ground and see if its bad - that ground point though is a bit tricky to get at for you need to really lift the seat up to pull that carpet to get at that angle needed to get at the bolt this fuel pump grounds to.
 
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