My 90' 302 needs your help! Fuel problems...
08-26-2014, 05:34 PM
#1
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My 90' 302 needs your help! Fuel problems...
Hi, I recently acquired a 1990 f150 lariat. With an EFI 302, dual tanks, and 5 speed. It had been sitting and not well taken care of and barely managed to get it home. I am trying to get it running well to sell it and pay off my student loans...
When I got it, the main problem is that it would start, and run (very rough) untill it got hot and dropped the idle. Then it would start to miss and stumble over itself untill it died. If I gave it a ton of throttle, I could manage to keep it alive, but it would backfire out of the intake and shake like crazy. After it got past this stage, it would idle okay, but have a huge miss/hesitation if I gave it throttle quickly. Check engine light is on...
Here's where I'm at:
I've changed the oil, air filter, spark plugs, wires, cap and rotor. Drained the gas, changed fuel filter, refilled with shell and seafoam. Flushed cooling system and refilled. Cut off the rusted out exhaust behind the cats and changed O2 sensor. I replaced the distributor mounted ignition control module and fuel pump relay.
After all this, I've improved the running condition by a ton, but it's still got big issues.
The truck starts and idles for a minute or two, then starts stumbling. The fuel pump relay clicks randomly when this is happening. I give it gas to keep it running and then it gets over it, and starts idling okay again. Or it'll die then I can restart and it will then idle fine. At this point, I can rev the engine by slowly increasing throttle, but if I step on it, or just open the throttle quickly, it has a huge miss. Rpm will start to climb for a split second then drop and barely recover to idle...
I've gone through all the ideas that I had, and haven't fixed the problem. My last thought is that the electronic engine control computer is the problem, but I'm not sure. I've tried pulling codes, but the fuel pump relay will start clicking, and the pump will run sporadically while I try to read the codes and it causes the light to freak out.
Somebody has got to know what's going on, any ideas?
Thanks for reading!
When I got it, the main problem is that it would start, and run (very rough) untill it got hot and dropped the idle. Then it would start to miss and stumble over itself untill it died. If I gave it a ton of throttle, I could manage to keep it alive, but it would backfire out of the intake and shake like crazy. After it got past this stage, it would idle okay, but have a huge miss/hesitation if I gave it throttle quickly. Check engine light is on...
Here's where I'm at:
I've changed the oil, air filter, spark plugs, wires, cap and rotor. Drained the gas, changed fuel filter, refilled with shell and seafoam. Flushed cooling system and refilled. Cut off the rusted out exhaust behind the cats and changed O2 sensor. I replaced the distributor mounted ignition control module and fuel pump relay.
After all this, I've improved the running condition by a ton, but it's still got big issues.
The truck starts and idles for a minute or two, then starts stumbling. The fuel pump relay clicks randomly when this is happening. I give it gas to keep it running and then it gets over it, and starts idling okay again. Or it'll die then I can restart and it will then idle fine. At this point, I can rev the engine by slowly increasing throttle, but if I step on it, or just open the throttle quickly, it has a huge miss. Rpm will start to climb for a split second then drop and barely recover to idle...
I've gone through all the ideas that I had, and haven't fixed the problem. My last thought is that the electronic engine control computer is the problem, but I'm not sure. I've tried pulling codes, but the fuel pump relay will start clicking, and the pump will run sporadically while I try to read the codes and it causes the light to freak out.
Somebody has got to know what's going on, any ideas?
Thanks for reading!
08-29-2014, 05:07 PM
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I hooked a fuel pressure gauge on it and turn the key to run. It primes but the gauge barely moved. Then fired it up and the gauge slowly moves up to 32psi. It help there for a minute or two, then when the engine started stumbling the pressure rose again to 39. The truck died and pressure held there.
So I believe the regulator is good.
Something is causing the truck to cut off its own gas supply. Maybe?
Computer?
Thanks again!
So I believe the regulator is good.
Something is causing the truck to cut off its own gas supply. Maybe?
Computer?
Thanks again!
08-29-2014, 05:27 PM
#5
Senior Member
You should have full pressure without having to crank the engine. Sounds like you have some gunk in your fuel lines from sitting.