I replaced the fuel pump, fuel pump relay and the oil pressure sending unit. but when i turn the key to on i still dont hear a priming hum and the check engine light doesnt blink or turn on. i can get it to hum only by jumping the pump from the battery. any ideas?

 

Check all the connections to your ECU. The CEL light should be on when the key is in RUN but the engine is off. If all connections look good, find an ECU to swap in there to see if yours is bad. Check all wiring between relay and ECU also. If the relay works, and there's no CEL, it's definitely an ECU issue

 

I've been doing a lot of fuel pump research on here and most people are saying there is a fuel pump fuse the the inner fender wall next to the battery. You might want to check that as well.

 

checked the fuse its good. is there any way to fix an ecm or do they need to be replaced? cus ive already spent a lot more than i expected fixing this problem. would a used ecm be a good idea?

 

If the pump runs by sticking 12v directly to it, then it's not the pump.

Where are you putting the 12v to in order to get it to run?

Just because you replaced the relay doesn't mean the relay is good - alot of times brand new electrical parts are bad.

Did you check the relay connector to make sure it's not fried anywhere causing an issue? I have had a bad fp relay connector in the past.

Test the relay connection - make a small jumper and connect it in the relay connector (replacing the relay in effect) to see if the connector is good.

The ECM has nothing to do with the operation of the fuel pump other than the initial 2sec priming function. After the prime, the fuel pump runs off the Oil Pressure Sending Unit - a bad ECM will not disable the fuel pump operation, just the 2 sec prime function - so your wasting your time with a different ECM at this point. You need to recheck the relay and the OPSU connections.

 

i connected the 12v to the fuel pump connecter on the rear end by the tank. that works. i jumped the orange wire to the gray wire on the relay connector using a paperclip nothing happens

 

OK - try jumping at the OPSU - it will have 3 wires, unplug the connector and jump the orange with the red and see if the pump runs - that will tell you if the wiring forward of the gas tank connector is good or bad.

If it runs that way, then I'd suspect the relay, or the wiring to the relay.

 

that didnt work either

 

If the fuse by the battery is not blown, and you reconnected the fuel pump wiring at the tank, and jumped the orange and red wires at the OPSU, and it didn't run ... BUT it runs when you connect 12v at the tank connector, then sounds like bad wire between front of car and the connector at the tank. Try checking continuity between the OPSU wire and the connector at the tank.

 

what would explain the check engine light never coming on?

 

I've never seen a SES light for any fuel pump related issues. When my fuel pump died on my 1990, there was no warning, no SES light, no nothing - I was cruisin at 70mph one minute, the next I was coasting into a gas station with a 3/4 tank of gas - it just died. Even after I rigged a spare pump inline and limped the car 2 hours back home, I never got an SES light, and the rigged pump wasn't providing 1/2 the gas the car needed to run correctly - I was lucky to even get the car up to 45mph to limp home. These TBI computers have a very limited "brain", and they really don't do much other than storing fuel and spark tables, and read a few inputs like O2 and TPS.

 

No, there's no function in the ECM to tell if the fuel pump is bad or not. I don't even think there is on OBDII. However, if the CEL light doesn't blink then stay solid when the engine is off, but ign is in RUN, there is a problem somewhere between the CEL light and the ECU (ECU included). If you're not getting any fuel pump prime (like you stated initially) then I would suspect something with the ECU. The fuel pump could be running as you crank the engine (and you wouldn't hear it), but if the ECU isn't telling the injectors to fire, your car wont start. Get the relay to fire off the fuel pump with the oil pressure sensor jumped, then look to fixing the ECU problem.

I don't condone stealing from junkyards, but ECUs are moderately small. Not to mention, they're at most $40, especially if they 'look' mangled or broken (Find some broken circuit boards in a car or on the ground and toss them in the service hole of the ECU). Personally, I'd rather be wrong in this case, but if you can get an ECU for cheap (or free), and with some sort of short term return policy (many larger parts yards do this), then why not give it a shot.

 

Sounds rediculious but my SES light was on so long it burned out, lol. Check that... But it does sound like your ecu may be bad, it's rare, but possible. Pick one up from pick ur part (preferably a wrecked car because you know the last thing it did was run and crash, lol) Throw that in and see what happens. Obviously if the problem persists with the other ecu, you might wanna check your fuel pump ground and check and make sure the pins on the main fuel pump harness didn't push out or bend to the side.

 

okay i checked the voltage of the orange wire at the f/p relay, its reading .1 surely thats not good. what do i do now?