How to diagnose a bad fuel pump or FPR. - added

[turbovanman²]

First off, hook up a pressure guage to the shrader valve or tee in at the rubber line-engine cool and engine off.

Start the car and note fuel pressure, it should be around 50 or a bit less, unhook the vacuum line to the reg and it should go up to 55 psi. Now shut the car off and watch the fuel gauge, the pressure should stay. If not, pinch the pressure line-if it drops, you have a bad FPR or leaking injectors, if it holds, the check valve the in fuel pump is bad and the pump should be replaced.

Make sure the key is off, jump 12 volts to the coil + terminal, a fused jumper wire is best but a piece of wire will work just fine.

Now, you should be reading around 55 psi, now squeeze the return line, the pressure should jump to around 90-100 psi. If not, the pump is no good. You can check the FPR if you have a vacuum pump if not, the above test works.

These tests assume you have no leaks and a clean/newish fuel filter thats not plugged up.

If you have an amp clamp and a lab scope, you can check the brushs by looking at the waveform pattern, it should look like a nice sine wave.

[JeremyL]

Thanks, this just reminded me that I need to pick up a pressure gauge & check mine out soon. I've been through a couple pumps in the last year & a half and even now I've got a strange stumble every once in a while & an erratic idle at times. Guess it's a good thing I haven't been driving lately.

[Capt'n Dave]

That's a big +1 Simon on what you are saying,i have tried it myself,and that is the way it is

[turbovanman²]

Sorry guys, brain farting, fixed it. You clamp the pressure line to isolate pump check valve.

Cleaned up, thanks TurboDave and Vigo for straigtening me out,