unusual fuel problem

[91phoenix]

Help please. Car won't start or starts and runs rough with high idle. It just started doing it a week ago. I have done most of the tests posted in the sticky. The odd part is that when i turn the key to "on" the fuel pump do not shut off after a couple seconds but continues to run. I can hear what sounds and feels like fuel flowing at a high rate through the fuel return line. I have replaced the fuel pressure regulator in the belief that it was the problem but no luck. If I turn the pressure up to 50 or 60 psi on the meter mounted at the shrader valve the sound stops. What the @%^^&*(&^$* is going on? This is on a 91 GT 5.0 with HCI, exhaust, etc., etc.

 

[bill302]

fuel pump relay located under the seat may be defective (stuck open)...welcome to :SNSign:

 

[91phoenix]

already tried switching fuel pump relay. could there be a short or elec problem causing fuel pump to to run continuously? why not starting? when i can start it seems to have a miss and af gauge shows very rich

 

[HISSIN50]

Ensure the fuel pump jumper isnt grounded on the self test connector. If it is, the pump runs non-stop with the key on.

 

[91phoenix]

best way to test?

 

[bill302]

best way to test, with key off check for continuity with a multimeter between the fuel pump test point in pic below and a engine or body ground then test to the computer test ground on the connector itself if you get continuity you have a short you will have to look for it...you might want to check for shorted wires under the carpet too.


picture copied from jrichker post in this thread http://forums.stangnet.com/showthread.php?t=717552&highlight=fuel+pump+test

 

[91phoenix]

finally had a chance to test. i get resistance at all points so no short. why is fuel pumping right back out the return line and fuel pump not shutting off? problem began suddenly w/out warning. fpr replaced, if i set fuel pressure crazy high (60 psi) i don't hear fuel flowing back through return line and car will start but runs reallllllllllllyyyyyyyyyyyy rich (black smoke out the tail pipes) what now?

 

[Boss91GT-SC]

I had a very similiar problem with my 2.3. Turns out the fuel pump was drawing too much current and blowing relays. Pump never shut off and car ran like crap if it ran at all. Had to replace the fuel pump.

 

[96SVTpilot]

I had a very similiar problem with my 2.3. Turns out the fuel pump was drawing too much current and blowing relays. Pump never shut off and car ran like crap if it ran at all. Had to replace the fuel pump.

+1, pull that pump and check it before something nasty happens.

 

[91phoenix]

ok ran to summit and picked up new pump. same problem. i'm guessing something electrical but can't find any shorts. tried to pull codes w/out success so far. hope to get a different scan tool later this week. any ideas about what to look for?

 

[Boss91GT-SC]

After you replaced the pump did you have a new relay? I needed one after the new pump went in.

 

[91phoenix]

swapped out relay. no change.