(original post...start of thread)
1990 F150 fuel delivery problem
Group: alt.trucks.ford Date: Sat, Oct 11, 2003, 10:14am (CDT-2) From: snipped-for-privacy@bitrealm.com (Brent Olson)
The truck cranks fine, so I got out the meter. With the key on but not started, I began checking for ignition voltage, all the while the fuel pump is running. I have a dual tank longbed f150 with the 6-cylinder and
5spd manual transmission. The fuel pump runs when either on the front or rear tank, but obiously switches to the other pump when I change tanks. I tried to start it a few times after unplugging/plugging various wires to no avail. After about 5 minutes and reading the manual, I hear the fuel pump finally turn off. I jump in the truck and it starts right up. If I turn it off now, then back to the on position, the pump runs for less than a second, and turns off, like its supposed to do in the first place and will start right away.
Question: what could cause this? It can't be BOTH fuel pumps, can it?
Re: 1990 F150 fuel delivery problem...pressure regulator...
== == Marsh Monster seemed to be concerned enough to answer the cry for help after reading all the weird diagnosis proceedures given..... to put forth this........
check yer fuel pressure regulator pinch off the return hose....on the tank side of the regulator when it acts up again. see what happens
marshmonster ..................................................................... ................................................................... During a recent episode of alt.trucks.ford we here snipped-for-privacy@nospam.com (Bob) flub his lines and improvise with......
What would you think will happen? Maybe ruin his fuel pump by running the pressure so high?
Bob ..................................................................... ..................................................................... which prompted ole Nubbs to quit stirring the pot of shroom juice that was simmering..... long enough to enlighten BOB with this......................
B.O.B. what do YOU think would happen?
Not very familiar with fuel systems are you there BOB ???????
BOB.......yer homework assignment is......
To write a 3 paragraph post that outlines in detail, the operation of an injector fuel system. Somewhere in those 3 paragraphs.......see if you can't explain why the fuel pump only runs for a few seconds when the ignition key is cycled to the "Run" postition.
yes BOB.....you may use GOOGLE as a research tool......just be sure to give credit for the resource material.....and be sure to give Marsh Monster credit for initiating the research papers topic for you.......
TO BRENT...... pinch off the return hose to see if the symptomj changes.
Nubbs McFarkle ~thinks BOB should have at least contributed to the thread with a diagnostic proceedure for the symptom~ . . Okay marshy (no your sock puppet didn't fool anyone.) The reason that the pump only runs for a couple of seconds when the key is turned on is because that's how long the PCM is programmed to turn it on if it doesn't see a signal from the PIP sensor. It doesn't know or care what the fuel system pressure is. That's why when you deadhead the system aka pinch the return hose off, the fuel pressure at the pump can and will go as high as 120PSI. If you haven/t already figured it out that is very hard on the pump... worse even then running them out of fuel. That's also a very good reason for people to change fuel filters regularly, a plugged filter will also cause the pressure at the pump to skyrocket.