TheSamba.com :: View topic - 1988 Ford F-150. fuel pumps won't come on

Tue Feb 28, 2012 8:03 pm

howdy yall. i've tried everything i can do, even on the ford forums, but no help yet, so i figured, why not try here.

so anyhoo, I have an 88' f-150 super cab (2 door with the tiny backseat), 302 5 speed manual and i can't get the fuel pumps to come on. first a little background:

i bought it about 5 years ago. when i got it, it didn't run. The PO had taken all of the wires off the solenoid for some reason. so after wiring it all back up, it still wouldn't start. we took a crap shoot in the dark and just decided to replace the computer from one in the junkyard (computer was from a f150 with automatic trans (diffent computer)), but it cranked up, and ran. then a few weeks later it started to die when running. if i hit the gas it would die, but it would idle then die. after a few minutes of cranking it would start up, idle for about 3 to 4 minutes then die again when i checked fuel pressure there was none. if i tried to crank it a few times, and checked pressure again, a little gas would dribble out (low pressure). got tired of messin with it, and it sat for about 4 years, till i recently decided to tackle it again.

So now of course it still won't start. the fuel pumps aren't comming on. i replaced both relays and the computer with a reman one from advance auto (the correct one this time, lol). still nothing. if i pull the fuel pump relay out, and jump the two fat wires, the pumps come on, and when i check pressure at the fuel rail, gas shoots out. i tried to start it witht he jumper wire on to keep the fuel pumps on, and still nothing (injectors aren't firing). if i spray starting fluid in the throttle body, it will start up and run for a few seconds smoothly till the starting fluid runs out. if i keep spraying a bit of fluid while its runs, it'll keep running till i stop. the ECC relay is getting power from the ignition, and both fat wires are hot with ignition on, and only one hot with ignition off. with the ignition on the fuel pump relay is getting power fromt he little wires, and only the yellow (always hot power wire) is getting power, and the other fat wire going to the pumps isn't geting power.

so form what i can tell the computer isn't allowing the injectors to fire or the pumps to operate. any ideas? i'm at such a loss. thanks

-Mike

Tue Feb 28, 2012 8:05 pm

HIT IT WITH AN AXE!

Tue Feb 28, 2012 8:28 pm

don't think i haven't thought of that already :lol: . i never really was a fan of fords, but its a really nice truck and got a really good deal on it ($300). clean interior, body has no dents, only a few scratches, 5 speed manual, chrome push bumper, chrome bed rails, and only 93K miles.

if all else fails, i can always just take everything off, and slap a carb and intake on there. so it'll be running one way or another. but i would really prefer to keep it fuel injected as it will still need to pass emisions, and isn't exempt till 2013, and i want to have it running within the next month or so.

Tue Feb 28, 2012 8:37 pm

fuel pumps are probably bad..

Tue Feb 28, 2012 8:46 pm

:lol:

Tue Feb 28, 2012 8:46 pm

BugMan114 wrote:

if i pull the fuel pump relay out, and jump the two fat wires, the pumps come on, and when i check pressure at the fuel rail, gas shoots out.

i basically bypassed the relay, and the fuel pumps came on. this model has two fuel pumps, a low pressure pump in the tank (put out around 4-6 PSI), and a high pressure on the frame rail (around 45 PSI). both came on when the relay was bypassed.

Tue Feb 28, 2012 9:18 pm

check the fuel pump inertia switch. All fords have them in that era. It's a reset button somewhere that will turn the pumps back on. This will usually trip after hitting a larg pothole, abrupt stops or any other severe jarring motion. I'm guessing at the passenger kick panel under the glove box area.

Check the tank selection switch. An open at this juncture will not allow a pump to be chosen to direct fluid flow..

Tue Feb 28, 2012 10:01 pm

Hummmmm this problem sound's very similar to what the guy in the stall was working on 4 months ago at the dealer :-k I remember he had to call the ford hotline I think it was the computer, try taking that one back and see if you can exchange it. check all of the lines to make sure you are getting voltage maybe a rat chewed threw some wire's while it sat. Did you check the socket's in the power distribution box?

The computer controls the fuel pump through the fuel pump relay. To prime the system the computer turns the pump on for 1-3 seconds when you initially turn the key and then continously when it senses 400 rpm at the crank. The pump runs all the time the engine is running 400 rpm or more and maintains narrow band of fuel pressure to the fuel injectors at all times.

Also unplug the ECU look at the connecter and look at all of the pin's and the one's on the ECU. Did your truck sit that long with gas in it if so drain it out and get new gas in there.

also check what chazz was telling you about

Tue Feb 28, 2012 11:17 pm

chazz79 wrote: check the fuel pump inertia switch. All fords have them in that era. It's a reset button somewhere that will turn the pumps back on. This will usually trip after hitting a larg pothole, abrupt stops or any other severe jarring motion. I'm guessing at the passenger kick panel under the glove box area.

Check the tank selection switch. An open at this juncture will not allow a pump to be chosen to direct fluid flow..

^ditto!

Wed Feb 29, 2012 12:13 pm

chazz79 wrote: check the fuel pump inertia switch. All fords have them in that era. It's a reset button somewhere that will turn the pumps back on. This will usually trip after hitting a larg pothole, abrupt stops or any other severe jarring motion. I'm guessing at the passenger kick panel under the glove box area.

Check the tank selection switch. An open at this juncture will not allow a pump to be chosen to direct fluid flow..

X3 Ive delt with that before.

Wed Feb 29, 2012 3:59 pm

already changed the gas. also checked the inertia switch, all good. i'll try swapping out the computer. man, I wish new ones were available. :lol:

Wed Feb 29, 2012 6:18 pm

I have an 89 F-350 that acted the same way. It turned out to be the fuel pump relay connections. They were green and crusty. Cleaned the plug and it started but I went and got a new relay since it was corroded inside.
Tim

Wed Feb 29, 2012 7:24 pm

I believe terminal 86 is supplied ground when the engine is cranking. Check for ground at the relay pin that corresponds with pin 86 on the fuel pump relay. If this is happening then a computor is not necessary.

As long as I've been in this carreer path a computor has only fixed the problem 1% of the time it's replaced. Usually it's just wiping your butt with a 200.00 guess.

Get the distributor module tested. I've heard of those keeping the fuel relay off.

Wed Feb 29, 2012 7:47 pm

Wish i has a manual here with wiring diagrams :?

Wed Feb 29, 2012 8:27 pm

bugger101 wrote: Wish i has a manual here with wiring diagrams :?

http://www.google.com/search?q=1988+ford+f150+wiri...mp;bih=566 :)

Wed Feb 29, 2012 8:28 pm

http://www.ford-trucks.com/forums/index.php
Might find wiring diagram here.