My cousin just got and 87 4 Runner and he is trying to get it running. the problem is that the fuel pump looses power about 2 seconds after its started, after it dies you can turn the key off and restart it and after 2 seconds it will die again. we hooked a test light to the power wire going the the fuel pump and its like the power just shuts off to the fuel pump. we tryed a different air flow meter and it didn`t change anything. do the fuel pump relays go bad ?.

Any help is appreciated.

 

IF they go bad, they usually stay dead... I would have suggested changing the AFM, but you've already tried that. Search (google) for 4crawler "fuel pump" - he's got a diagnostic page that's pretty good.

 

Is there a fuel pump relay? Check that to make sure it's ok. Does the ECU send the signal for the fuel pump? If so you might want to look at that. Shoot, you might even try just resetting the comp first (pull the EFI fuse).

Those are just some ideas.. Sorry I can't be more specific but i don't have my books close by and I haven't had to work on my fuel system yet.

 

I have done a couple fuel pumps on my 92 runner but I don't know if it would be the same as yours, but there should be voltage for about 2 seconds like its doing and then once the vehicle starts the voltage should be constant. I just cant remember if the voltage ran on one wire for both start up and pre-start or if there was 2 wires that merged together down my the tank, either way it sounds like a relay problem. Good luck!

 

Check your circuit opening relay. This relay powers your fuel pump. There are two coils to this relay which close a set of contacts to operate the fuel pump. When the key is turned to the start position, the first coil closes the contact to operate the fuel pump. Once the engine is running the second coil is energized by a signal from the Volume Airflow Sensor. This is the coil that now keeps the contacts closed while your engine is running.

I think what is happening in your situation is that the first coil is operating normally, allowing you to start the engine. The second coil is either not working, or not getting the signal to keep the engine running.

here is a link to diagnose this relay...
http://personal.utulsa.edu/~nathan-b...38circuito.pdf

 

There is a fuel pump relay, and thats what we think it is.

 

....I forgot to mention the Circuit Opening Relay sits just above the ECM behing the passenger side kick panel.

 

Yeah, thats the one that were thinking is bad.

 

You may be able to just bypass it....bend the contacts over. Mine corroded from moisture...bent the contacts over and it works. Worth a shot.

 

I have the same exact problem. I am being told it is probably the EFI relay. I will be replacing that this weekend, and will update you with the results.