86 Ford Ranger fuel pump problems?
I went to work one day and it drove good and I came back after to go home but it didn't fire up. It cracked but didn't start. After a lot of work me and my father are out of ideas we replaced the EEC power relay and the Fuel pump relay after doing some digging on the internet. We had to settle at jumping the fuel pump relay (yellow to orange/blue) to get it to run. I currently have it temperately fixed with a toggle switch jumping those wires. It works… Until I can figure this out. Any ideas on what may be the problem? I was thinking that maybe I got a bad relay from the parts store but I'm a novice mechanic so I thought I would ask here.
wiring diagram (fuel pump relay is on left side):
Make sure the inertia switch… Fuel pump cutoff switch… Is not tripped or has bad wiring connections or the pump will not run properly… See link below.
The red wire going to the pump relay should have power coming from a branch splice /red wire coming from the EEC relay that also powers the injectors, EGR and a couple PCM terminals… Test that wire and if no power, then check the wiring back from there. Since the engine runs, I suspect that the EEC is working and the branch connection is good so the problem would lie between that and the pump relay if no power. The tan/lt green wire from the pump relay serves as the ground for the relay solenoid and goes back to the PCM terminal 22… The PCM controls the ground path for the relay… Switches on or off… So if that circuit is bad, the relay won't energize… No ground path. Check that wiring back to the PCM terminal 22 for continuity or the PCM terminal for damage/poor connection… Possibly a bad PCM although it might/should fail a self test… Check engine light on. If the pump relay red wire has power, then for testing purposes, run a jumper ground wire to the tan/lt green wire terminal on the relay to see if the relay closes and allows the pump to turn on… Key on… If so, then check the tan/lt green wiring or PCM for issues.
Just for your information in doing tests…
The wiring circuit for the pump and relays also has a series of fusible links in the wiring which may be fried and stopping the flow of power although I suspect other issues not related to fusible link problems.
Locate and test the wiring before and after any fusible links for power with ignition key on… If there's power on one side of the link but not after it, then the link wire is fried inside and should be replaced with an equivalent section of same gauge link or inline fuse holder with appropriate size fuse. Look for visible signs of the fusible link wire melting or bad/broken connections.
Fusible link wire looks like regular wire but internally, it is 4 gauge sizes smaller to serve as a slow burn fuse of sorts to prevent a wire harness from burning up due to a short. Fusible link wire is usually attached to the normal wiring of a circuit with large plastic but connector… Parts stores sell it in various gauge sizes marked on the old link sheathing in gauge size or ohm ratings. Or you can determine what proper size to use by the wiring it protects… If the wiring is 18 gauge, then use 22 gauge fusible link. Most are only several inches long and you can use regular but connectors to splice in a new section… Seal the ends with silicone or use shrink wrap style but connectors or SW tubing/tape to seal the connection from moisture.
Check the circuit wiring for any damage or bare wires touching metal before installing the new fusible link… Or install an inline fuse holder in place of the fusible link wire with the same size fuse for the circuit as the one in the fuse box… I.e… If the fuel pump circuit fuse is 15 amp, then use a 15 amp fuse in the inline fuse holder.
Related info…
"There's an inertia switch by the passenger's toes, under the carpet. Push its reset button fully. If that doesn't work, see if one of its two pins has power, while still connected. Backprobe the wires; if both have power, the inertia switch is good. When checking for that power, know that it is only present for about two seconds each time you turn the key to Run, from Off.
If one pin has power, disconnect it, and use a paper clip to jump the two pins on the removed connector. Should run then."
http://www.therangerstation.com/forums/showthread.php?t=113473
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