Well while driving home from work one day my bronco abruptly decided to stop running. After having it towed home , I found that it was not getting fuel, and when I turned the key i could not hear the fuel pump kicking in. So I bought a fuel pump assembly, dropped the tank and, installed it. Sure enough the old fuel pump was junk. Now with the working fuel pump in tank I turn the key and i still don't hear it kick in, So i replace the relay, and check the inertia switch ,they too seem to be fine. I was wondering if you could perhaps shed some light on my situation.

-THX

 

I just replaced my sending unit assy in my 88 and the fuel gauge doesn't work, so maybe you have a faulty sending unit. Have you taken a tester to see if you are getting volatage to the wire harness on the tank?

 

also make sure the new relay isn't bad cause I did the same thing..installed new pump and new relays. Truck wouldn't run, then I replaced the new fuel pump relay with the older one and it ran.....and it was the correct relay too. Its just simple things like that sometimes that get you.

 

I might be a bit **** , but you say you don't hear the fuel pump, but does it deliver fuel? My original (factory) fuel pump did make an audible noise, but the replacement is quiet enough that I can no longer hear it....

In my '95 there is some circuitry that determines if the fuel pump is good or not -- what it does it turns on power for a few seconds, then turns it off if something is not right. You need to remove the connector from the fuel pump and check to see if it gets power at all.

 

Yes it does deliver fuel when i bring 12vdc back from the battery, but not when it is used in the orignial fuel pump circuit.The old pump was bad, so something caused the system to be this messed up. Could it be the ECM? and if so is there a way to bypass the computer, or test it out?

-thx

 

The way to bypass the computer and most of the related circuitry is to simply direct wire +12VDC from the ignition switch to the emergency shutoff switch's outgoing connector. If it works that way, re-connect it before the shutoff switch since you might need that in case of a mishap.

There is at least one, but maybe 2 relays in the engine compartment that could be bad, and you may have blown a fuse or a bad connection. In essence, you need to verify the wiring, relays connection, etc., until you find the problem. Simple electrical troubleshooting i's not particularly difficult, but it can tedious and time consuming. If the ECM is cheap enough you can just replace it, but if it's expensive, I'd verify everything else first.

 

Try changing the EEC relay. It's in with the fuel pump relay. Factory colors are green for the fuel pump and brown for the EEC relay. You can't interchange the two factory ones due to differences in the plugs but the replacements from Autozone, Advance, etc are the same and work on either side. So if you buy it to replace the fuel pump relay and it doesn't work, put the fuel pump relay back and change the EEC relay instead. I went thru the whole mess the same way and after I changed the EEC relay everything worked fine.

 

check the ground wires at the battery terminal

 

Not sure about the 89 but the 86 has two pumps. One in the tank and one in the frame under the driverside door. This is the one most often heard when turnging the key to the run position. If the tank pump works it will push fuel to the secondary pump (under driver side door). If the secondary pump is not functioning then you still will not get the pressure you need at the fuel rails. What is your fuel pressure at the rails? Should be above 32psi.