diagnose bad fuel pump

hello, i have a 1995 tacoma with the 3.4l v6. while going down the highway at 65 the truck began stumbling, got off the exit as it began to lose power and finally died. it restarted after about 5 minutes and made it home and will not start back up. i have good spark, new air filter, throttle body looks clean, engine cranks fine, battery is new (2 months old) charging at 14.3 at idle. i pulled the fuel filter as a starting point and while the filter is off i had someone turn the key to run, then to start and got no fuel out of the line. i am assuming a bad fuel pump at this point, correct? any help would be appreciated

 

Not familiar with early model tacomas, but the newer models (up to 2004) have a circuit opening relay that can go bad.
You can also use the test port to run power to the fuel pump without all the noise from the truck trying to start and see if the pump is trying to operate.

 

It will have a circuit open relay. It should have B-W, W-B, G-Y, W-R and blue wire going to it. sometimes its right under steering column with wire loom.

 

The blue wire is the power feed to fuel pump.

 

the fuel pump is only energized when the starter is in use or the motor is running.

 

so if i crank the engine while the fuel filter is disconnected, I should get fuel coming out of the tank side line, correct?. if not then either the relay or the pump is bad?

 

There may be a fuse or you're out of gas as other possibilities.

I'm not sure where the starter relay is, but if you remove it then turn the key to START the fuel pump should still run. By doing this it might be easier to hear any sound from the pump without the engine cranking.

 

Go to Autozone and rent their fuel pressure testing kit. Test fuel pressure and report back. No need to be guessing at things.

 

i am new to toyota's, so testing the fuel pressure involes taking off the front engine cover to gain access to the banjo bolts on the rail? there does not seem to be a test port. and if so do i need to buy any extra adapters while at autozone?

 

The correct tester kit will contain the banjo bolt with test port. You don't technically have to remove the front cover to get at it. It does make it a lot easier though. The front top cover comes off easily.

 

thank you for the info. i am getting a test kit kit and will report back tonight.

 

If you find the relay i was mentioning above. You can test with a test light if pump is getting power to blue wire. Or you can jump power to it to see if pump runs

 

i tested the fuel pressure and got zero. i pulled the circuit opening relay and did the continuity test from the field service manual. st to e1 was good, +B to FC no continuity, +B to FP no continuity. according to the field service manual +B to FC should have continuity. i then tested the relay by applying 12v to it and got continuity from +B to FP. question is, what does FC stand for (fan control?) and would no continuity there cause the fuel pump to not work?

 

Maybe FC is Fuel Control. That is the terminal for the solenoid part of the relay.

Did you test continuity across +B and FP by applying 12V to +B and FC?

Was there infinite resistance across +B and FC? What I'm getting at is the continuity setting on a meter might say no continuity if there is just a little resistance. Did you check on the ohmmeter setting?

 

Can't help ya much on what FC is. Outta town away from my PC. It should say in front of manual what it stands for.

 

If the above is true, it is pointless to check for pressure on a pump that is not running, also removing the starter relay will prevent the pump from running while "starting" (key position) until a sufficient crank sensor signal is seen by the ECM (crankshaft rotation).

"FC" is a terminal on the ECM. The ECM enables the pump by grounding the COR coil (via FC) based on inputs from the starter relay or the crank position sensors. Also note that the EFI and COR relay contacts are in series. Both need to be closed for pump to run.
Schematic and theory of operation below.

 

i went and got a new relay and performed the diagnostic test on it and got the same results as the one i removed. i tapped into the blue wire (FP) with 12v and could not hear the pump running nor saw any fuel coming out of the line (i removed the fuel filter again). i guess its time to replace the pump and see if that works? thank you all for the help given so far.

 

well i pulled the pump and ran leads directly to the battery and it works fine. the strainer was a little dirty but not bad. i am back to the circuit opening relay. in my downloaded field service manual, it states to check for continuity from st to e1, and from +b to fc. i have no continuity from +b to fc, but the new relay also has no continuity from +b to fc. the efi relay checked out good. does anyone else have an FSM they could check? in mine it is found on page eg-147

 

Are using the fsm thays one complete pdf?
Manual or automatic?

 

nevermind. i found the problem and it is the previous owner. these are pictures of the sending unit connector