EFI fuel pump doesn't shut off. No fire.

WSM29 · Mar 22, 2016

So I had a fuel leak a few weeks ago and finally getting around to fixing it. I swapped out the mustang fuel rail for the explorer rail. The issue I have now is the fuel pump used to shut off after it primed. Now it seems sluggish and will not shut off. Engine still cranks and gives me one quick cough when I first turn the key and then nothing. I have a feeling it's because it's not getting the correct fuel pressure. I had a BBK guage on the mustang rail and was able to adjust the pressure as well. I am blind tonight but will get a cheapo guage to test fuel pressure. Is my pump done? It's only about a year old, in tank WH Pump. Any suggestions? Thanks!

WSM29 · Mar 22, 2016

Did some looking on the mustang forums. Looks like it may be the computer. Anyone have this issue? Any way to test it without buying a new computer?

browngr5 · Mar 22, 2016

What ecm?
Is the harness wired for manual or automatic.
The wrong wiring configuration will damage the ecm.

Do you have a chip plugged into the ecm?
your chip may have a corrupt tune. Remove the chip to see if the fuel pump shuts

browngr5 · Mar 22, 2016

Check your efi harness ground on the back of the intake.

EFI Guy · Mar 22, 2016

If you don't have a chip in it then the next thing to look at is the PCM. Crack it open and look at the 3 capacitors circled in yellow. Check them for swelling or any signs of leakage / corrosion. They die from old age but it's pretty easy to fix.

WSM29 · Mar 23, 2016

The mustang forums said some guys were able to tell a bad ECU by disconnecting the negative battery cable over night and trying again in the morning. I do believe I have something in the ECU bad. I let it sit without the negative connected and this morning it was acting all kinds of crazy. I turned the key to on and instead of the fuel pump coming on there was a lot of fast clicking in the engine bay. Electrical Clicking. I turned the key off and on a few times and got the pump to turn on a few times, but it continued to run and not shut off. Never tried to start it this morning.

No chip, just stock computer. Remans at the parts store are like $175. EFI GUY, I will take it apart today and look. Are you saying I can repair the old one? Thanks!

WSM29 · Mar 23, 2016

Well, that far left component you circled looks like the bottom leg is blown. What now??

EFI Guy · Mar 23, 2016

If you are comfortable with soldering just replace all 3 capacitors. If not, I replace all 3 with higher rated components for $35 plus shipping.

WSM29 · Mar 23, 2016

EFI Guy said:
If you are comfortable with soldering just replace all 3 capacitors. If not, I replace all 3 with higher rated components for $35 plus shipping.

What's your timeframe Sir? I have to move shortly due to a unexpected change of orders. I could get it in the mail to you today.

EFI Guy · Mar 23, 2016

I can usually fix them the same day I receive them.

WSM29 · Mar 23, 2016

PM sent. Thanks again.

chuzie · Mar 23, 2016

No codes on the PCM? Do you get a CEL before engine start? PCM going bad, though not unheard of, is less likely even for those Mustang computers.

On the mustang system, when power is removed from the EEC circuit, the fuel pump runs continuously. Have you tried playing with the relays? You could have one getting stuck in limbo and fluttering between on and off.

Steve83 · Mar 23, 2016

Capacitor plague affects all electrolytic capacitors of that era.

laserfish · Mar 24, 2016

Just had to replace mine on a full size bronco. Two symptoms were fuel pump would not shut off and no CEL when key on engine off. Replaced EEC and both symptoms cured and it runs again.

WSM29 · Mar 24, 2016

That left capacitor was blown. You can kinda tell from the pics I posted. I am now trying to figure out if I have a short that caused it. I have a 20 amp fuse that wants to blow every once in while in the RJM harness. It's one of the 4 in the fuse panel that's attached to the harness.

Steve83 · Mar 25, 2016

You need to KNOW what each fuse is for.

welndmn · May 26, 2017

Well crap, I'm getting this same issue.
My cap's were leaking, and one had a broken leg, but the truck was running, just poorly
I replaced all the caps, and now my pump just primes and it does not start

What was your issue?
Were there places you suggest for computer repair?

Steve83 · May 26, 2017

welndmn said:
...pump just primes and it does not start

There may be electrolyte residue still on the PC board causing that symptom. It might even have gotten under the potting layer. But that's the classic symptom of capacitor plague in '84-93 Ford truck EECs.

welndmn said:
Were there places you suggest for computer repair?

EFI Guy said:
I can usually fix them the same day I receive them.

EFI fuel pump doesn't shut off. No fire.

WSM29

Sr. Member

WSM29

Sr. Member

browngr5

Full Member

browngr5

Full Member

EFI Guy

TheEFIguy@gmail

WSM29

Sr. Member

WSM29

Sr. Member

EFI Guy

TheEFIguy@gmail

WSM29

Sr. Member

EFI Guy

TheEFIguy@gmail

WSM29

Sr. Member

chuzie

Bronco Guru

Steve83

Bronco Guru

laserfish

Jr. Member

WSM29

Sr. Member

Steve83

Bronco Guru

welndmn

Bronco Guru

Steve83

Bronco Guru

Similar threads