Rascle

I'll make this as short and as plain as possible. First off im a old school mechanic,,if it has fire and fuel itll run, and if one or the other is missing, i knew how to fix it.
Now to the meat of the situation..I have a 1988 F150 with a 302 EFI. It was running perfecty untill one day i shut it off to get fuel. Only way i could get it started after that was with starting fluid, and once it started it would restart all day long on its own.
Things have progressed after 3 visits to differant mechanics shops. Now it will only start with starting fluid no matter how many time you try and start it, also it doesnt have hardly the power to pull itself now. Theres a humming coming either from fuel line or return regulator or somthing now.
Pumps in both tanks are good an have plenty of fuel in them. Have changed the fuel filter,crank sensor,air temp sensor, throttle position sensor, cleaned throttle body,has new cap, rotor, wires and plugs. Injectors show good,fuel pressure is up around 40.
Ive read on this problem untill my eyes are about to bleed and have checked or had checked all that has been suggested on differant site.
This truck is definately worth saving as body and interrior is in emaculate condition, im just at a loss as to what to do or have done next.
Any and all help is appreciated,,Thank you

wde3477

Have you checked the timing, if for nothing else, just to eliminate this possibility? If you're not familiar with this era, the SPOUT connector needs to be pulled first in order to get an accurate timing reading.


How strong is your spark? Nice and bluish-white, or puny and yellowish-orange?


As this happened after you got fuel, any possibility of bad gas? Also, your vintage should have a low pressure pump in the tanks, and a high pressure pump along the driver-side frame rail, about under the driver seat unless its already been converted to just high-pressure pumps in the tank.


Good luck, and keep us posted.

Chris_1

iTrader: (1)

I'm a little old school too. The 3 still apply, spark fuel and timing.
Most common things to go wrong with spark is the electronic pickup in the distributor. It replaced points but does the exact same thing. You'll see it hidden under the metal plate under the cap. Bitch to change, easier to swap the distributor (cause you have to pull it anyway).
Fuel pressure - Hearing a pump run or having fuel at the fuel rail is not good enough. You need to check the fuel pressure - with a fuel gauge pressure gauge-. You can have 20 psi at the schrader valve on the rail, it'll shoot gas 10' in the air but it won't run the truck. For your truck you need a bare minimum of 30 psi, and it should be closer to 45 psi.
Some of your symptoms sound a bit like pressure issues.
Once you have sufficient pressure, the injectors have to open. Which is controlled by the computer, which bases it's actions on the input it gets from sensors. A big one is the throttle position sensor. I see you changed it, but did you dial it in ? If your signal wire output is much below .9 volts dc, the computer won't open the injectors.
Only way to properly check the signal is actually getting to the injectors is with an LED test light.
Other thing will be timing, but for that to change drastically without moving the distributor, you'd have to have skipped a tooth on the timing chain. For that to happen you would have to have a LOT of slack in the chain - which you probably already know how to check for.
Start with a fuel pressure gauge and checking spark. That should tell you a lot.

Rascle

the spark is a hot blue snapping spark..i have drained both tanks and have added new fuel,also timing was my first thought, i did the timing myself at first, bringing #1 up to tdc and checking, also had the the first mechanic check and set.it still has the factory rail pump in it, checked out ok what the shops said.

jkenprice1

A friend of mine had the same problem. He finally sold the truck because nobody could fifind the problem. I hope you figure it out. I'd like to know the solution.

Chris_1

iTrader: (1)

10 degrees Before TDC, the little bump on the distributor shaft should be exactly at the pickup in the distributor.
If you assume the timing is good and you have a real good spark it would seem like fuel is the problem.

wde3477

Hmmm, just tossing these out to get a better understanding -
1) when the truck does run, does it sound like its idling fine?
2) does the truck sound any different when turning over than it did before these problems - more labored, different cadence, etc.?
3) did you or any of the mechanics check for any codes?
4) have you tried unhooking the battery for 20 minutes or so to reset the computer? You would want to do this after any code-checks.


One suggestion to see if it makes a difference - before you roll the key to Start, roll it just to On a few times and let the fuel pump time-out each time (about 2 seconds). Had a problem where mine would be difficult to start if it sat for any amount of time - this multiple key roll got me by. Never did figure out what it was, was assuming there was a stuck check valve somewhere or a failed fuel pressure regulator allowing the fuel to drain back.


Your comment about having hardly the power to pull suggests there may be a second problem lurking (or maybe not) - a plugged cat converter or other exhaust restriction COULD be part of this?


At any rate, this is certainly not the basic easy-button problem...

Rascle

wde3477 -- 1)when you first start the truck it idles fine around 800rpm,once you touch the gas the idle jumps up to around 1400rpm
2) no the truck sounds like it always has, good power turning over
3) As far as i know they have, i tryed the "key on" code thing where you use a jumper to get flashing codes,but it didnt work for me
4) yes i unhooked the battery over night, didnt make any differance.

truecountry

I just had the same problem sort of the selector valve on frame has a filter in it and it was so bad the valves had stuck
I replaced the selector and runs like new now

Rascle

truecountry; id seen this under the truck but didnt know what it was nor did anyone ever tell me ,, ill check it out asap and see what its gona take to get it replaced.. thanks for the fresh thought/imput,im about at my wits end