1990 foxbody 5.0 fuel system.

General karthief said:

Thread 'Cranks OK, but No Start Checklist for Fuel Injected Mustangs'

May 22, 2006

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995

A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work your way down. Jumping around will possibly cause you to miss just what you need to see to find and fix the problem. Don’t skip any steps because the next step depends on the last step working correctly.

Revised 26-Jul-2017 to add fuse link diagram.

All text applies to...

• jrichker
• Replies: 93
• Forum: Fox 5.0 Mustang Tech

#4 deals with the fuel pump issues but honestly start at the top and work each step to find the issue.
Who checked your ECU out?

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Mustang5L5 said:

Which wire did you apply power to? The fuel pump relay works by the ECU closing a ground (wire 97). Wire 366 should always have power from the inertia switch.

Here's the wiring diagram below and what to check

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AeroCoupe said:

Slow down and read what Mustang5L5 wrote...which wire at the relay did you apply 12V+ to? My guess is going to be pink/black wire if none of the wires at the relay have 12V+. If this is the case then you need to start with the orange/light blue wire which is powering the latching side of the relay visa fusible link at the starter relay on the driver inner fender. This should have 12V+ at all times regardless of the ignition switch position.

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