TFGgarage Posted April 28, 2023 Share Posted April 28, 2023 My first ever forum post, advice is more than appreciated! Gotta provide a tiny bit of history. This Comanche had been sitting about 12 years till I got around to it due to needing new floor boards and running extremely rich. I cleaned the ground on the firewall, replaced MAF and 02 sensors, oil was flushed then changed, flushed all other fluids, and it ran like a dream for a couple weeks till I did some more work on it. I replaced cap and rotor, ignition control module, coil, plugs, wires, some broken vacuum lines, power steering and alternator/generator belts, newish (2 year old and unused) recharged battery, PCV valve, coolant bypass hose and finally the fitting on intake manifold. When I went to flush and bleed the coolant after all that, it started up and idled absolutely perfect like nothing happened. After about 5 minutes it shut off but it started right back up. Finished bleeding the coolant and went to back it out of my shop and it died as soon as it was out the door and would start but die immediately after. I ordered and installed a new fuel pump and sending unit from “justgastanks.com”. Once I did that itll run for a couple minutes and then die and won’t idle again unless I leave it be for a while but will start and instantly die like before. I then replaced the CPS, fuel pump relay and 02 sensor heater relay with “URO parts” brand from autozone and I cleaned the multi plugs associated with the relays. Now I can reliably start it by priming the fuel pump three times using the ignition, and it’ll start up for a couple minutes then dies but usually starts up after priming the fuel pump a couple times again. Currently cleaning the ground behind drivers tail lamp and removing the trailer harness that some one botched (what are you towing with an anaemic 2.5 anyway). TLDR MJ randomly dies after lots of work. Link to comment Share on other sites More sharing options...
TheDirtyJeep401 Posted April 28, 2023 Share Posted April 28, 2023 Sounds a lot like a sensor issue. Have you tested the CPS to see if it’s in spec? Aftermarket sensors on these things can be brand new and actually be out of spec. I would be going through and testing sensors. Link to comment Share on other sites More sharing options...
OldSch88L Posted April 28, 2023 Share Posted April 28, 2023 Did you clean and flush the gas tank to get rid of the 12 year old junk inside? New fuel filter? Feels like fuel starvation to me. I'd test the fuel pressure for starters... Link to comment Share on other sites More sharing options...
TFGgarage Posted April 28, 2023 Author Share Posted April 28, 2023 34 minutes ago, OldSch88L said: Did you clean and flush the gas tank to get rid of the 12 year old junk inside? New fuel filter? Feels like fuel starvation to me. I'd test the fuel pressure for starters... New fuel pump, sending unit, sock, filter, fresh gas and some injector cleaner for gits and shiggles. I used a tractor oil pressure gauge that reads up to 30lbs and had the right thread to fit the testing port on the TBI, was reading 11 lbs. Should have included that in the original post! Currently trying to figure out the cause of that but even when idling it’s running at 11 lbs so the gauge could be off Link to comment Share on other sites More sharing options...
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