Runability issues and no fuel pressure port on 1985 5.0 fuel rail?
#1
Runability issues and no fuel pressure port on 1985 5.0 fuel rail?
This is my first post on here, folks, good to be here. If possible, I need your help with something. I just got a 1985 f150 with a 5.0L EFI engine (EEC IV and all that) AOD trans, and 1 fuel tank. This truck is having some runability issues such as stalling at first start, erratic idle, surging at idle and low speed, poor throttle response, and general part throttle loss of power under load and no load. This truck is one of the first EFI models apparently, as it only had the canister filter and the two pump setup - in tank booster and on frame high pressure. Having said all that, here's some of the things I've done. The former owner changed the tank and both pumps, and I've changed the canister fuel filter, did an upper intake cleaning, checked all vacuum lines (20" vac at idle), replaced a dead TFI module, cleaned and checked the EGR valve, cleaned and checked the IAC assembly, changed the plugs, cap, rotor, and wires (tune up), re set base timing to 10 deg BTDC, checked ohm and volt spec on the IAT, Coolant temp sensor, checked volt and scale on the TPS, and checked function on the knock sensor. Have you noticed that I haven't mentioned the fuel pressure yet? Well, I haven't been able to find a service port on this fuel rail. I have looked over the entire rail (even under the plenum) and there is no shrader port that I can find anywhere. Am I imagining this or has anyone else even heard of a 5.0 with no service port? Anyways, after all that checking, it is better, but only marginally. Being as I seem to be unable to check the pressure, on a whim I tried removing the vacuum from the regulator, which, if it was bad I assume, shouldn't have made any difference. Well, taking that vacuum line off made a HUGE difference. Idle smoothed out, power came back, part throttle response came back load or not, idle quality and power overall massive improvements, cold and hot. The only code I retrieved from the KOEO and KOER that even makes any relation to runability was 41, (the other codes were 31, 34, 77, and 25) and I assumed that was a bad O2 sensor, as my book lists that as no switching and too lean. Could the fuel pressure regulator be bad and cause insufficient fuel pressure? Would it be bad to continue running it like this with the vacuum disconnected? Could a single wire O2 sensor be causing the fuel pressure regulator to be malfunctioning to this degree, or am I just forcing fuel past the injectors and overriding the fuel curve enabled by the computer? Any ideas would be helpful, I seem to be at a standstill. Thanks in advance.
#2
You are correct, you have one of the first fuel injected trucks, and in the beginning they did not have a fuel rail test port. If you want to test the pressure you have to pull one of the lines off and rig a t in place.
The regulator is not controlled by the computer, only vacuum. It keeps the pressure around 39 psi, unless you are pulling a hill, which lowers the vacuum, which raises the fuel pressure.
I would check the fuel pressure. If it's in spec, I would get the fuel injectors cleaned.
The regulator is not controlled by the computer, only vacuum. It keeps the pressure around 39 psi, unless you are pulling a hill, which lowers the vacuum, which raises the fuel pressure.
I would check the fuel pressure. If it's in spec, I would get the fuel injectors cleaned.
#3
#4
During test drives with the FP regulator vac line hooked up, it did pop back through the intake on occasion under load, as well as the whole loss of power and seemingly erratic timing. With the regulator vac line unhooked (should be full pump pressure) , no more intake backfires (lean mixture?) and no more power issues. In addition, after heating and cooling repeatedly, cold starts are now 100% first time starts with correct hi idle - slow idle transitions.
Today I got a 87/88 5.8L fuel rail assembly from a friend of mine, I'll be installing it tomorrow. Hopefully, the width difference doesn't make too much of a difference.
Today I got a 87/88 5.8L fuel rail assembly from a friend of mine, I'll be installing it tomorrow. Hopefully, the width difference doesn't make too much of a difference.
#5
During test drives with the FP regulator vac line hooked up, it did pop back through the intake on occasion under load, as well as the whole loss of power and seemingly erratic timing. With the regulator vac line unhooked (should be full pump pressure) , no more intake backfires (lean mixture?) and no more power issues. In addition, after heating and cooling repeatedly, cold starts are now 100% first time starts with correct hi idle - slow idle transitions.
Today I got a 87/88 5.8L fuel rail assembly from a friend of mine, I'll be installing it tomorrow. Hopefully, the width difference doesn't make too much of a difference.
Today I got a 87/88 5.8L fuel rail assembly from a friend of mine, I'll be installing it tomorrow. Hopefully, the width difference doesn't make too much of a difference.
#6
#7
Yeah, missed the date on the other, and there was a final answer, but I get lucky half the time on the unanswered threads.
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