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- Joined
- Feb 23, 2011
- Messages
- 128
- Vehicle Year
- 1991
- Engine
- 4.0 V6
- Transmission
- Automatic
Hey everyone my son just bought his first vehicle a "non-running" 91 Ranger 4.0. We got it running within a few minutes of getting it home but only on Ether. After some TS and identifying a bad pump, replaced that and the fuel filter, it got a bit better, next the fuel pressure regulator may or may not have been bad but that got replaced too (good pressure but instantly lost pressure when turning ignition off). Then when checking compression we pulled some wire ends off and a few of the plugs were sparking through the insulation so new set of plugs and wires. (looks like a pretty new coil pack already).
It currently will only start with a shot or two of ether, but then stays running after that (rough though). It stumbles when revving it and will die if the pedal is hit too quickly. The IAC seems to be good, TPS seems to be good (have proper voltage and the signal moves up to 10.6 volts ish wide open. Power is 11.6), MAF hasnt been cleared good yet, but haven't probed it while running to be sure.
CPS is good.
The PCM gets too hot to touch while ignition is on but truck not running and upon inspection looks like both ground bolts on the actual board have a bit of heat damage but nothing else looks out of ordinary. I checked all the pins on the plug and attached a pdf with the readouts. Only found 1 pin different than the schematic that I had: Pin 49 is an orange wire reading 12 volts. The only orange wire I could find on the other wiring diagrams is for the fuel sender/fuel pump gauge and is a ground wire so red flag there, but I cant find a route where the Orange wire on the tank connects to the orange wire on the PCM plug (potentially not the same run/ wire) They do not have continuity, but that could just be a broken cable if they are supposed to be the same wire.
The fuel relay doesn't kick on most of the time and other times it kicks on but doesn't turn off while connected normally. If I jumper the test wire in the EEC plug the relay kicks on and stays on normally. I have 36psi at the rail and all the injectors seemed to be ok.
The alternator was also getting hot while the ignition was on, so that's been unplugged, further indicating a potential wiring problem.
Specs:1991 Ranger 4.0L Automatic 2WD
Compression:
3: 170 4: 170
2: 180 5: 180
1: 180 6: 200
To recap:
Can anyone confirm what pin 49 is on the F17F-ACA PCM?
Thanks for any ideas, I want to confirm something is bad before throwing more parts at it!
It currently will only start with a shot or two of ether, but then stays running after that (rough though). It stumbles when revving it and will die if the pedal is hit too quickly. The IAC seems to be good, TPS seems to be good (have proper voltage and the signal moves up to 10.6 volts ish wide open. Power is 11.6), MAF hasnt been cleared good yet, but haven't probed it while running to be sure.
CPS is good.
The PCM gets too hot to touch while ignition is on but truck not running and upon inspection looks like both ground bolts on the actual board have a bit of heat damage but nothing else looks out of ordinary. I checked all the pins on the plug and attached a pdf with the readouts. Only found 1 pin different than the schematic that I had: Pin 49 is an orange wire reading 12 volts. The only orange wire I could find on the other wiring diagrams is for the fuel sender/fuel pump gauge and is a ground wire so red flag there, but I cant find a route where the Orange wire on the tank connects to the orange wire on the PCM plug (potentially not the same run/ wire) They do not have continuity, but that could just be a broken cable if they are supposed to be the same wire.
The fuel relay doesn't kick on most of the time and other times it kicks on but doesn't turn off while connected normally. If I jumper the test wire in the EEC plug the relay kicks on and stays on normally. I have 36psi at the rail and all the injectors seemed to be ok.
The alternator was also getting hot while the ignition was on, so that's been unplugged, further indicating a potential wiring problem.
Specs:1991 Ranger 4.0L Automatic 2WD
Compression:
3: 170 4: 170
2: 180 5: 180
1: 180 6: 200
To recap:
- Only starts with Ether (once warm if I turn it off and immediately try to restart I can coax it by pumping throttle just the right way to restart)
- Idle seems a bit high
- Stumbles and struggles to rev
- Will die if floored from idle
- PCM gets hot while ignition is on and motor not running.
- Fuel relay will kick on sometimes (I'm ok bypassing that till the other problems are fixed incase the relay actually is bad)
- The front most relay (WOT I think) randomly cycles a lot while the ignition is on
- Pin 49 (potentially a ground) has 12 volts while ignition is on)
- The "diagnosis" doesn't seem to work, the check engine light is just always on even when jumping the EEC plug to make it flash the codes.
Can anyone confirm what pin 49 is on the F17F-ACA PCM?
Thanks for any ideas, I want to confirm something is bad before throwing more parts at it!
