94 Cummins troubleshooting - lacks power and stalls
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94 Cummins troubleshooting - lacks power and stalls
94 Ram 3500 12v Cummins 2wd auto
Just bought this truck and could use some help sorting out some issues. It starts right up and idles fine, all the gauges work, transmission shifts smooth, but it's severely lacking power and won't go above 45 or so. Could be missing 4th gear/overdrive, but I can't tell. It has absolutely no power on hills, even struggles going up a somewhat steep driveway from a stop. It had the following OBD1 trouble codes:
42 - Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles (for some reason code 42 was in there twice?)
24 - Throttle Position sensor signal outside acceptable range
47 - Charging system voltage too low
53 - Internal PCM failure (but why do the gauges work?)
Here's what I've tried so far:
-Siphoned out the old diesel and put in fresh (it was sitting a long time)
-New TPS
-New fuel shutoff solenoid (should have done the relay at the same time, oops). When I pulled off the old FSS and bumped the ignition, it didn't move. When I put on the new one, it definitely moved, but I didn't take note of whether it held position
-Took it for a test drive and it kinda seemed to have slightly more power but not much. At one point after giving moderate throttle and letting off, it died and started back up on its own. Then I attempted a hill and had the throttle pinned going 20mph, let off the throttle to pull off the road it totally died.
That's where I'm at currently, could really use guidance on next steps. Planning on doing the FSS relay next. And to complicate things there are wiring shenanigans that don't look right, there's an external voltage regulator with the blue wire in a 3-way splice with the dark green/orange wire, which I think goes to the ASD or PCM? And a blue/yellow wire that was snipped and rerouted to ground on the chassy? Oh and the 120A alternator fuse is gone and it's just directly wired, which seems dangerous. I'm assuming someone did all this to bypass a potentially failed PCM?
Any input is appreciated, thanks for reading.
Just bought this truck and could use some help sorting out some issues. It starts right up and idles fine, all the gauges work, transmission shifts smooth, but it's severely lacking power and won't go above 45 or so. Could be missing 4th gear/overdrive, but I can't tell. It has absolutely no power on hills, even struggles going up a somewhat steep driveway from a stop. It had the following OBD1 trouble codes:
42 - Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles (for some reason code 42 was in there twice?)
24 - Throttle Position sensor signal outside acceptable range
47 - Charging system voltage too low
53 - Internal PCM failure (but why do the gauges work?)
Here's what I've tried so far:
-Siphoned out the old diesel and put in fresh (it was sitting a long time)
-New TPS
-New fuel shutoff solenoid (should have done the relay at the same time, oops). When I pulled off the old FSS and bumped the ignition, it didn't move. When I put on the new one, it definitely moved, but I didn't take note of whether it held position
-Took it for a test drive and it kinda seemed to have slightly more power but not much. At one point after giving moderate throttle and letting off, it died and started back up on its own. Then I attempted a hill and had the throttle pinned going 20mph, let off the throttle to pull off the road it totally died.
That's where I'm at currently, could really use guidance on next steps. Planning on doing the FSS relay next. And to complicate things there are wiring shenanigans that don't look right, there's an external voltage regulator with the blue wire in a 3-way splice with the dark green/orange wire, which I think goes to the ASD or PCM? And a blue/yellow wire that was snipped and rerouted to ground on the chassy? Oh and the 120A alternator fuse is gone and it's just directly wired, which seems dangerous. I'm assuming someone did all this to bypass a potentially failed PCM?
Any input is appreciated, thanks for reading.
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Joined: Sep 2012
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From: Europe
Good ol' mechanical 12 valve engine, needs electrics just for shut-off solenoid and starter to run.
Start by doing basic maintenance; fuel filter and air filter, check valve lash. Check turbo shaft for excessive play. Is the exhaust stock? There's a cat from the factory, after the turbo, that might be clogged.
Mechanical lift pump might be weak, check the fuel pressure.
Is the engine stock?
Start by doing basic maintenance; fuel filter and air filter, check valve lash. Check turbo shaft for excessive play. Is the exhaust stock? There's a cat from the factory, after the turbo, that might be clogged.
Mechanical lift pump might be weak, check the fuel pressure.
Is the engine stock?
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Update: turns out slime in the fuel causes problems! Siphoning out the old fuel wasn't nearly enough. There was a huge glob of crap blocking the lift pump screen, that's when I learned about the fuel heater and pre-filter, which was ripped and packed full of slime. Deleted the heater, added some Power Service tank cleaner and biocide, and have been running fuel through, cleaning the new pre-filter about 15 times and replacing the main fuel filter a few times. Running better, cruises up hills no problem but still doesn't have lockup/overdrive
