Ok I have and 89 fox 5.0 was running fine.i think I jumped to many times went out to start car fuel pump not priming. Charged battery changed fuel pump relay nothing. Multi meter at inertia switch shows 4 volts at 1 side only. checked volts at fuel injectors is 4 volts. Fuel pump relay did smell burnt before I changed it forgot to mention. 2 points at the eec relay are at 12 volts.i have read over and over again the same postes that get re posted. Going to swap ecu with another extra my friend has. How do I bypass the fuel pump relay to see if the pump will run? Any suggestions what to check next? Pictures would be great
89 foxbody fuel pump not priming
- Thread starter Dubsantana
- Start date
I will caution you on swapping computers for two reasons, one it introduces unknown issues that may exist with that computer, and/or you may corrupt a good computer if a problem somewhere else cooked something in the original computer.
Best thing I think to do is send the original computer to the EcUExchange and get it checked out, not expensive.
Best thing I think to do is send the original computer to the EcUExchange and get it checked out, not expensive.
When you turn the key to the on position the pump is supposed to prime for about 3 seconds. If not then you can ground the tan / light green wire at the test connector under the hood. If the pump runs then it is good.
It is PIN 22 that triggers the relay. PIN 19 is conformation that the fuel pump relay is putting out 12V to the fuel pump.
Diagrams courtesy of Tmoss & Stang&2birds
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Diagrams courtesy of Tmoss & Stang&2birds
94-95 Mustang wiring diagrams
Mustang FAQ - Wiring & Engine Info
Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
If you pull the fuel pump relay and put a jumper wire across the two larger gauge wires in the connector the fuel pump will run all the time when connected - no cycling. It will prove out if your pump and power wiring is working.
Ok when I jumped from relay pump primes and has plenty of psi on guage..I was doing testing on both relays fuel pump and eec relay.on both had one wire with 4 volts changed eec relay cause I had an extra and all had 12volts after.but still will not prime when key turned. I can't feel or here any relay click and now getting 12 volts on 1 wire to inertia switch. I followed the easydiagnosticauto.com some I'm guessing ground signal from computer? Or I was reading maybe pip sensor
Most likely the ECU needs to be repaired.
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