Key On Engine Off... Fuel Pressure?

[keybrdcowboy1]

Can't seem to find this answer anywhere..... I currently have a crank but no start situation... Slowly working through the checklist (thanks jrichker). Is there supposed to be fuel pressure when you turn the ignition on but the engine is off? I can hear the fuel pump whine and start up, but I get nothing on the fuel pressure gauge....

And for a secondary question, is it possible to for the fuel pump to still whine and sound fine but it is actually bad and not working correctly?

Thanks for any help!

 

[jrichker]

A fuel pump may run but not make pressure or enough pressure to run the engine.

Check fuel pressure:
The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.
Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.
Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.
Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.
Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

Fuel pump pressure test
Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.

Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.

 

[keybrdcowboy1]

jrichker, thanks for your help..... Finally got around to getting these tests done. There was no fuel in the vacuum line from the FPR... of course the car hasn't been running for several months so I don't know if that might have something to do with it. It won't start so I was unable to see what the pressure was at idle...

I did the fuel pump test and I only saw 5 psi when cycling the ignition on. I could hear the pump kick on but like I said, got barely anything on the fuel pressure gauge.... Based on that, is it a good idea to go ahead and get a new pump? The one that is in there is original, so it's probably not a bad idea either way.....

 

[mikestang63]

could be a clogged sock, filter or line restriction. Do the easy and cheap things first. Replace the filter and remove the line fom the connector on the lower pasenger side coming from the tank and blow some compressed air through the line if possible.

 

[JD1964]

In the tank there's a rubber hose that connects the pump to the sending unit assembly. This hose can rupture, mine did. Common problem with todays fuel additives. Also, check the plastic fuel return line near the passenger front suspension. Make sure it didn't get kinked.

 

[keybrdcowboy1]

Finally got around to replacing the fuel pump...it was the hose that connects the fuel pump to the fuel rails. It was broken and leaking...pump is probably fine but might as well replace the 28 year old pump while I'm there. Attached is a picture of the hose. Looks a little worse after I twisted it to get it off but it was definitely bad. Thanks to everyone for their help in diagnosing!

 

[JD1964]

That's what mine looked too. Again, check the return lines too at lower front part of engine block. If they get kinked, the pressure side of the system gets subjected to full pump pressure since the bypass from the regulator can't get freely back to the tank.