hey, im new to this thing, and i just wanted to ask a question.

ive got a 91 F-150, with a 302 V8. about two weeks ago, it would not start, so i thought back and it hadnt had a tune up in about two years. so i changed the oil, the plugs, the wires, cap, rotor, and fuel filter just for safe keeping. then it still would not fire, just kept cranking and cranking. the next day, i sprayed starting fluid into the throttle body and it finally started. for about the next week, it started but i had to let it warm up because it would run fine, then the check engine light would come on, it would run rough, and bog down and die. and now it wont start at all without some starting fluid. the fuel pump comes on when i turn the key to on, and its getting fuel so far as i can tell.

i cannot figure out why this thing is still not running right. could anyone help me out here?

by the way, i have an idea of what may be wrong, just no way to test it. im thinking that maybe the fuel pump is going out because when i turn the key over, it turns on, but runs for a lot longer than it has when i have done that in the past. no one i can find will check the computer for free for me, so i do not know the code it is giving me when it runs rough.

help please!! this is my only way to get around.

 

first off do a search on here, there is a way to check your codes yourself on that era truck.

2nd sounds like you are on the right track, get a fuel pressure guage and hook it up to the valve see what kind of pressure you are getting. my bet is that you barely get enough to start with then drops off as the pump cant keep up.

 

You don't need anyone to check codes for you you can do it yourself with a paper clip.

How to run a self test> http://www.fordfuelinjection.com/?p=13

You need to check the fuel pressure, need a special gauge that connects to the valve on the fuel rail (looks like a valve stem on a tire, just bigger)

Fuel pump should run for a couple of seconds then stop when the key is turned to "run", its a "timed" thing. Computer runs the pump for a couple of seconds then stops until the key is turned off then on again then cycles again, or when the computer receives a signal the motor spinning and has started, then it remains on all the time, its not a build up to a set amount of pressure and stop kinda deal.

 

thanks....but the thing is. when its running im getting fuel pressure. by the way, what is the pressure supposed to be?

i had 40 on it when i tested the fuel pressure.

 

For the 302 (5.0)
32-35 PSI at Idle.
about 40-42 PSI at WOT.
about 45 PSI engine off and pin #6 of the self-test connector grounded with the key on or with the engine running and the vacuum line removed from the Fuel Pressure Regulator (FPR).

 

thanks to you all.

still having problems with it. my fuel pump was staying on as i said before, so i tried replacing the fuel pump relay thinking that could be failing out on me, but its still giving me crap. and i have no idea what could be happening.

ill be driving, and all of the sudden, dead. out of nowhere. and i cant figure out why this is happening. i know that i got my oil changed the day before this happened, but it ran fine and i drove around on it the same day as the oil change, but the next day. FAIL! and now its still giving me crap. i cant figure out why its doing this, and this is my DD, so i need to get this fixed, or im gonna have to do the unthinkable, and get rid of it.

can anyone else think of any other reason why my truck committed this mutiny on me out of nowhere?

 

If the fuel pumps are running and the engine is not with the key on and they stop when you turn the key off then I would say you have a bad PCM Computer.

 

sounds like you need a new computer.

 

AHHHHH...does anyone know where i can get one? or would it not be worth it?

 

I give $30.00 to $50.00 at salvage yards for them.
Just get the numbers off yours before you go.
They can also be orders at auto part stores for about $150.00 or so.

 

but my other question. would it be worth it?

 

only you can answer that.

i just put 100 buck starter in a 500 buck car.

was it worth it?

 

good answer. ill see what i can do.

and btw- by get the numbers. what do you mean?

 

disconnect battery, remove old computer, write down numbers on the tag, go to junk yard.

cpu (computer) is below brake master cylinder, remove harness, remove bolt, unbolt back of inner fender, remove cpu.

 

thank you.