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Discussion Starter · #1 ·
Hello All! I have found good advice before on this forum, and I return with a real stumper. I have a 94 Ram 5.9 that simply will not stay running. Over a month ago, I put a fuel pump in it. It ran fine after I found it had a bad fuel pump ground wire and that was replaced. Now the truck starts and idles fine, reaches operating temp, will run for about 10 mins then idles really rough, backfires alot, misses/lopes and eventually dies. Truck has a new dist cap/rotor, wires/plugs (less than 600 miles), new coil, new crank sensor (long story), O2 sensor. Had a Mopar friend come with a scanner to help...all the sensors seem fine, timing is good, no codes, dist doesnt have excessive play, etc etc. Still having the same prob. Unplugged the PCM to check for corrosion (& potentially faulty pcm), plugged back it and symptoms continued immediately. He is baffled, but says the only things possible could be a PCM or a wiring issue. Any advice or suggestions would be super helpful and greatly appreciated. I do apologize for the long post (just wanted to cover all the bases).
 

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Do yourself a huge favor and get a fuel pressure gauge. Though you changed the pump recently, you are definately suffering from intermittent fuel pump symptoms, and the most reliable way to prove that I am wrong is to plug a gauge in, and stick it beneath the wiper and drive around til the pressure fluctuates. I fought this battle for ages, changing everything I could think of, (except the pump) and ran it thru 2 different shops, I had as much money tied up in this thing trying to fix it as I had in purchasing it.In one last ditch effort, I bought a gauge, and after 85 miles, the pressure started jumping around. problem identified. Mine would generally act up on the uphill after going downhill, and about 500 feet after leaving a stopsign or stoplight. Would idle either on all 8, or minimally on 5 or 6 cylinders, I could feather the throttle, generally enough to get the rpms up, in neutral, but placing in gear would pretty much kill it. While feathering up the rpms, to mash it would cause massive backfires out of both ends. Letting it rest for 30 minutes or so would clear things up, though the ecu would take a moment to stabilize everything to allow it to run nice again for awhile. (initial start was like it was loaded up with fuel) Very confusing, the gauge finally gave it away, no more trouble for the last 3 years or so, Other than one fail to start, which was sudden death of the main ignition coil, which I had a spare from the fuel pump fiasco... Good Luck!!! PS, there is no factory fuel filter, so that won't be the problem, unless it's been added.
 

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Discussion Starter · #3 ·
I will definitely give that a shot. Its funny you mention it b/c i've replaced a pump once before and it went bad after about 3 wks....so that very well could be. Now here's the thing though, the truck does all this at idle when it warms up (backfiring, loping etc), so i'm not sure if that makes a difference in your advice or not. Either way it's still worth checking, so that I will do.
 
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