Who's Good At Diagnosing Newer Stuff? Update! It runs!

azblackhemi

Old Man with a Hat
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My 1948 Desoto that sits on a 2001 Ram 2500 chassis won't start. It cranks but won't fire. It has a stock 5.9 fuel injected motor. It is getting spark but it's an erratic spark. I've replaced the coil, crank position sensor, distributor pickup and rotor with no improvement. Don't know what part to throw at it next. The check engine light along with the ABS, and airbag lights are on and have been since I bought it although there are no codes coming up. It is getting fuel. Any ideas?
 
Do you have a way to test fuel pressure
I don't. It is getting fuel though. Seems to me the intermittent spark is the problem. When I crank it it will give me maybe 3 sparks then a second or two with no spark then a couple spark then no spark etc. I'm wondering why it doesn't at least start and run bad since there is some spark and fuel.
 
With out a scanner its tough to say could be crank sensor been awhile since ive worked on one dont remember what the ohm reading on them is might be able to Google it
 
I believe the camshaft position sensor is in yhe distributor could ohm test or replace
 
Blow fuse? Fuel pressure at 55 psi . Ohm testing wires might be a brake in the wires trying to think it been 10 years since ive worked on one. I highly doubt its a timing chain
 
Do you have a key fob? Could it be arming a factory alarm? They'll crank/fire for a moment, then die.
 
I assume it's using the truck computer and relays, the ASD relay controls the fuel pump relay and power to the coil. Check to see if your loosing power at the coil. I will check out a couple things and get you some more trouble shooting
 
A 48 DeSoto that rides worse than a 48 Desoto.
I've got a rotted 4×4 1/2 ton here you can have. It will soften the ride and have that squishy GM flex frame ride.
Won't start is a good reason to pull it the body off that junk driveline and frame, and build it proper.
Sorry but that chassis is worse that the original could ever be.
 
I would hard reset the injection computer. Remove the positive battery terminal, hold it against negative battery terminal for up to 30 seconds.... don’t worry, no spark. Nothing touching hot pos terminal. If no luck there, leave battery disconnected overnight. All things point towards computer. You’ve covered your bases. Fuel pressure, weak spark (ECU), cam and crank sensors. Only thing besides computer would be low compression or there’s a flux capacitor under the timing cover.
Hard reset computer... if no luck grab another from junkyard or car-part.com, install, and you’re back in biz
 
I tend to agree that it’s likely the PCM that’s bad. “Check engine” is set by the PCM. The codes that caused the light to set are stored in the PCM. No codes and light on mean PCM is “confused”.
 
We have a winner!!! Thank you Chad! I did what you suggested and held the positive cable against the negative, re hooked it up and viola! It runs. I now know just a little bit more about this new fangled computer technology! Thanks to all for your suggestions.
 
We have a winner!!! Thank you Chad! I did what you suggested and held the positive cable against the negative, re hooked it up and viola! It runs. I now know just a little bit more about this new fangled computer technology! Thanks to all for your suggestions.
You’re welcome! This trick also works on pre 96 OBD1 computers as well. Most people only have obd2 scanners and that’s a trick that can also be used on pre 96 OBD1 stuff. Glad it fixed it. If you have any other diagnosing type stuff (or anyone for that matter) feel free to PM me. I’ve seen some weird stuff and the odd stuff I always try to really remember. Hot weather can mess with the sensor inputs and computers tend to act funky. Take care
 
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