Starts with starting fluid, but will not start with fuel pump manually turned on?

Tiny
VIPERKING75
  • MEMBER
  • 1992 FORD F-250
  • 5.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Vehicle was sitting for 5 years, replaced both front and rear fuel pumps, not getting ground at relay from ECM, during crank. Vehicle will start with starting fluid, but won't start with fuel pump manually turned on, where can I look to find what's causing ECM to not provide ground?
Wednesday, February 26th, 2025 AT 7:35 PM

13 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,584 POSTS
This can be because of bad ignition module even though is has spark or I have seen a bad MAP sensor not tell the computer the engine has vacuum which will not turn the fuel pumps on. Have you run the codes to see if any are stored?

https://www.2carpros.com/articles/ford-lincoln-mercury-obd1-1995-and-earlier-diagnostic-trouble-code-definition-and-retrieval

Here is the locations of the map sensor which I would try swapping out. Check out the images (below). Please let us know what happens.
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Friday, February 28th, 2025 AT 6:23 PM
Tiny
VIPERKING75
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  • 55 POSTS
No codes are pulling up, I've replaced the fuel filter and pressure regulator as well, and Noid test confirmed I've got injector pulse. I'm having trouble understanding why it's not starting even with the fuel pump manually jumped at the relay though.
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Friday, February 28th, 2025 AT 8:15 PM
Tiny
KEN L
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That is a good sign, did you check the inertia switch? Did you check fuse O in the under-hood fuse panel? Here are the wiring diagrams so you can see how the fuel system works. Check out the images (below). Please let us know what happens.
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Saturday, March 1st, 2025 AT 10:46 AM
Tiny
VIPERKING75
  • MEMBER
  • 55 POSTS
Yes, inertia switch, tank selection switch, relay and fuse are all working correctly, my fuel pressure Guage isn't working properly though so I can't tell exactly how much pressure there is when the pump is forced on, it shows 0 but the test port sprays out at a decent rate when valve core is depressed.
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Saturday, March 1st, 2025 AT 11:26 AM
Tiny
KEN L
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The fuel pressure gauge shows 0? This would be the problem then.
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Sunday, March 2nd, 2025 AT 10:26 AM
Tiny
VIPERKING75
  • MEMBER
  • 55 POSTS
It's a faulty gauge, it isn't depressing the core of the test port, I can assure that there is much more than 0 PSI.
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Sunday, March 2nd, 2025 AT 11:11 AM
Tiny
KEN L
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Did you swap out or check the vacuum line to the MAP sensor?
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Monday, March 3rd, 2025 AT 10:26 AM
Tiny
VIPERKING75
  • MEMBER
  • 55 POSTS
Vacuum line is fine, replaced MAP, still won't start.
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Tuesday, March 4th, 2025 AT 12:47 PM
Tiny
KEN L
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Hmm, so no codes, the engine has spark, and fuel pressure and all the fuses are good. let check the power and ground for the PCM and if okay I would replace the ignition module and then the PCM with a rebuilt unit. Please use this guide below to help check the power and ground. Please use the wiring diagrams above.

https://www.2carpros.com/articles/how-to-check-wiring

Please go over this guide and get back to us.
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Wednesday, March 5th, 2025 AT 8:44 AM
Tiny
VIPERKING75
  • MEMBER
  • 55 POSTS
I may have found the issue, I found a mouse nest under the intake, there's a chance the injector wires for half the engine have been chewed up, I will check and update after I get the intake removed.
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Thursday, March 6th, 2025 AT 8:37 AM
Tiny
KEN L
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Good find! I can't tell you how many times rodents cause these kinds of problems.
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Friday, March 7th, 2025 AT 8:55 AM
Tiny
VIPERKING75
  • MEMBER
  • 55 POSTS
No damage to any of the wires, however I did find that almost all of the injectors were completely clogged, flushed out the fuel rails and ordered new ones. Will update if it works.
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Saturday, March 15th, 2025 AT 9:15 AM
Tiny
KEN L
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Yep, bad tanks of fuel can clog the fuel injectors, have a good weekend, happy wrenching!
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Saturday, March 15th, 2025 AT 10:33 AM

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