code reader just sits on 000 when i try to run the KOEO test.

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1986 4wd Ranger XLT 2.9L.

Hard to say, I don't use code readers, I check them manually at the diagnostic connector either using a meter, test light, or check engine light (if equipped). Don't want reliance on another device. Not getting any codes at all, need to go through the diagnostic connector wiring (check continuity), everything checks out I would most certainly suspect that the computer has failed since it's mal-functioning. Hard to diagnose problems like this over the net, though. I have an 88 auto computer lying around, might take a few small modifications, but would eliminate the EGR system at least if you have an auto trans.

Does the truck run???

Yea I think it's the computer that is fubar. It is what turns that relay on. Chances are the transistor that switches the output to the relay is toast. So as long as there is power going into the computer, it will flow right back out to the pump relay.

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(Formerly)
FireRanger
2003 Edge 4.0 4wd

How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide

Has anyone come up with an answer?

I have a 1986 Ford Ranger with the same problem.
I have changed everything even the computer to no avail.

Anyone have any idea?

Thank You

jrbsr

even fuel pump relay? computer is what ultimately controls the fuel pump operation. remove the FP relay and check for connunity on the ground that switches on the relay when key off to ground. good connunity, either someone has grounded the self test wire (anything weird going on at the diagnostics connector??) or there may be a short to that wire. IMHO the system runs 100% all of the time when the engine is running, it's a return style system, what pressure is "excessive" at the fuel regulator is returned back to the tank. it if runs OK and you can't narrow it down, it's really no big deal on the pumps.

With wire is that?

wiring colors might be different, i'm a big advocate of getting the EVTM specific to your truck, but here below is how the fuel pump circuit works. pin #8 at the ecm here is fuel pump monitor (22, 8, 1, 60 are pins into the computer), not all rangers had that (pin #8, this maybe 88+(?)). I cut this up out of a autozone diagram to only show the stuff that pertains to fuel pump operation for a basic understanding of the circuit..

Thank You !