91 f-150 won't start

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#11

02-29-2016 | 10:37 AM

Alanah_Rae

Senior Member

Joined: Jul 2015

Posts: 338

From: Brooklyn, USA

Quote:

Originally Posted by hanky

When you first turn the key on, the ECA (computer) provides the ground for the fuel pump relay to run for 1-2 seconds. Unless it sees an RPM signal the fuel pump should stop. It could be the fuel pump relay is sticking or the computer is still providing the ground , which it should not. Try removing the fuel pump relay and see if the fuel pump stops, then try reinstalling the relay . If it doesn't run anymore, the relay is probably sticking closed. If it continues to run , need to confirm the fuel pump relay is still getting the ground whether from the computer or some other way. Check the diagnostic plug for corrosion because there is a terminal in that plug that when grounded with the key on will cause the fuel pump to run.

Great info. Thanks for sharing. Its really helpful !!

#12

03-01-2016 | 12:26 PM

greasemark

Senior Member

Joined: May 2011

Posts: 717

From: Colorado, near Denver

Ive seen it before. These processors were rated to last about 10000 hrs from new. That around 10 years of age at about 10000miles/year. Ive never seen a problem with the input/output buffers or even the actual processor.
Where these pcm's broke down was in the power section; the voltage dividers/regulators were the problem.
Glad you got it done!

#13

10-28-2021 | 09:46 PM

Listlesswizard

Junior Member

Joined: Oct 2021

Posts: 1

Quote:

Originally Posted by Skoglunc

Thank you for all the input. It ended up being bad caps on the ecm. Pulled the ECM and found two popped capacitors and the third was only attached with one leg. Pulled them off and put new ones in and now she runs.

Where was the ecm located?