can't keep my 91 xlt running
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can't keep my 91 xlt running
I'm new here, but have been reading some post over last few month's that have been helpfull. So being convinced allot of people here share good advise I've decided to come onboard. this post will be longer than typical so i may give as much detail as i can, in hope of getting my issue rsolved.
the truck: 1991 F-150 xlt 4x4, 5.8 w/ auto overdrive, all the beeps and whisle's available back then. never had a problem with this truck "UNTILL" I parked it for 15 month's, Started it up (only requiring a new battery) hopped in and blew the brake lines on first application. Figured if that was the worst to happen I got off easy for the length of time she sat. repaired and off I went for 5 months when smoke and odor fill the cab. Apon removing the kick panel it was obvious by the discoloration and smell of the ecm that the problem was found. fortunately wires and harness had not been affected. replaced with a yard unit from 92 bronco 5.8 auto. wouldn't run untill cap, rotor, plugs, wires, TFI, and about half the relays were replaced. Off and running again...for 2 month's. Anywhere between 4 and 12 miles (over winter) she would just shut down. had full power to everything but wouldn't run till she sat for 5 to 10 minutes. then the same routine would continue. hooked up a fuel pressure guage with extend hose so I could monitor in cab while driving, and fluctuations were between 6 and 38 pounds, replaced the pressure regulator and problem pursisted but now it would maintain 33 to 38 and then suddenly drop to zero. i had heard ford pumps when going bad will shut down after they get warm, and work again when they cool. So the pump got replaced. Now I have steady fuel delivery, but the truck won't stay running under load. I've since taken evry electrical component (related to the engine ignition) off one at a time and had tested at the local Azone. All have come back with a green light. can't figure this thing out. Through frustration i finnally allowed a freind tow it to his mechanic to have it diagnosed so i may perform the repair. he's had it a month and hasn't been able to identify anything but a guess. he's pretty much told me the same things i advised him of when he recieved it. with the exception of telling me the ecm is the wrong one for the truck, but he flashed it and it seems to be running better but he doesn't advise trusting it. Now i've read on here that flashing that ecm isn't even an option. "it can't be done". The truck is tired and with high mileage does have some smoke from weak rings. I don't know the numbers on compression, but have a hard time believing that after sitting for a couple months the next time you start it you're compression is gone. I meen the motor can't wear worse if it's not used, so if that wasn't a proble before why would it be now. so right now at at a point of changing out the ecm again. one has been offered to me(free. I like free) but it's out of a 93. will this work with my 91 and what are the critical concerns? Obviously same motor and trans, 4x4 what about cruise trans cooler, A/C etc.. I keep hearing different things.
Again sorry for the long post, but i'd rather get it on now (history always helps) instead of allot of back and forth delaying what's already been looked into. future post will be shorter.
the truck: 1991 F-150 xlt 4x4, 5.8 w/ auto overdrive, all the beeps and whisle's available back then. never had a problem with this truck "UNTILL" I parked it for 15 month's, Started it up (only requiring a new battery) hopped in and blew the brake lines on first application. Figured if that was the worst to happen I got off easy for the length of time she sat. repaired and off I went for 5 months when smoke and odor fill the cab. Apon removing the kick panel it was obvious by the discoloration and smell of the ecm that the problem was found. fortunately wires and harness had not been affected. replaced with a yard unit from 92 bronco 5.8 auto. wouldn't run untill cap, rotor, plugs, wires, TFI, and about half the relays were replaced. Off and running again...for 2 month's. Anywhere between 4 and 12 miles (over winter) she would just shut down. had full power to everything but wouldn't run till she sat for 5 to 10 minutes. then the same routine would continue. hooked up a fuel pressure guage with extend hose so I could monitor in cab while driving, and fluctuations were between 6 and 38 pounds, replaced the pressure regulator and problem pursisted but now it would maintain 33 to 38 and then suddenly drop to zero. i had heard ford pumps when going bad will shut down after they get warm, and work again when they cool. So the pump got replaced. Now I have steady fuel delivery, but the truck won't stay running under load. I've since taken evry electrical component (related to the engine ignition) off one at a time and had tested at the local Azone. All have come back with a green light. can't figure this thing out. Through frustration i finnally allowed a freind tow it to his mechanic to have it diagnosed so i may perform the repair. he's had it a month and hasn't been able to identify anything but a guess. he's pretty much told me the same things i advised him of when he recieved it. with the exception of telling me the ecm is the wrong one for the truck, but he flashed it and it seems to be running better but he doesn't advise trusting it. Now i've read on here that flashing that ecm isn't even an option. "it can't be done". The truck is tired and with high mileage does have some smoke from weak rings. I don't know the numbers on compression, but have a hard time believing that after sitting for a couple months the next time you start it you're compression is gone. I meen the motor can't wear worse if it's not used, so if that wasn't a proble before why would it be now. so right now at at a point of changing out the ecm again. one has been offered to me(free. I like free) but it's out of a 93. will this work with my 91 and what are the critical concerns? Obviously same motor and trans, 4x4 what about cruise trans cooler, A/C etc.. I keep hearing different things.
Again sorry for the long post, but i'd rather get it on now (history always helps) instead of allot of back and forth delaying what's already been looked into. future post will be shorter.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Couple of observations,
A component that over heats and quits working only to work again once cooled will likely test as "good" at your local auto parts.
And no, a motor that sits for long periods of time doesn't "wear" but rings tend to stick in the ring groves and vales tend to get sticky in the guides along with lifters tending to collapse. However running the motor to bring it up to running temp, then shutting it down allowing it to cool a few cycles usually frees it up if and when that occurs.
As far as the EEC, I do know that my '94 for instance has one of 9 possible EEC's in it for that model/year/motor/tranny/options according to the book. Only way to get the right one is the numbers off the sticker on the EEC itself. Replacement with just any computer won't help especially when "trouble shooting" so make sure you have the right one in it.
A component that over heats and quits working only to work again once cooled will likely test as "good" at your local auto parts.
And no, a motor that sits for long periods of time doesn't "wear" but rings tend to stick in the ring groves and vales tend to get sticky in the guides along with lifters tending to collapse. However running the motor to bring it up to running temp, then shutting it down allowing it to cool a few cycles usually frees it up if and when that occurs.
As far as the EEC, I do know that my '94 for instance has one of 9 possible EEC's in it for that model/year/motor/tranny/options according to the book. Only way to get the right one is the numbers off the sticker on the EEC itself. Replacement with just any computer won't help especially when "trouble shooting" so make sure you have the right one in it.
