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1990 MJ starts but won't stay running


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1990 MJ 4.0 with AX15

Original problem was it sputtered between 1500-2000 rpm. Tested and replaced bad MAP sensor and since i am trying to make this right for my son, i replaced the 02 sensor, coil, fuel pressure regulator and CPS. 

Now it will run for a few seconds then die like the key was turned off. 

Battery voltage is where it needs to be.

Any other ideas or thoughts would be greatly appreciated. 

I am in desperate mode at this point

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We had a similar issue with our Renix.  Turned out that the fuel pump was getting power to start, but after it started.  The power to the pump comes from one place while starting but another once it is started.  If you have power to the pump after it dies than this is not your issue.  I believe it was pin 30 on the fuel pump relay that was not getting power.  Not sure if that's what you have going on but it's easy to check.

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It now runs but besides the sputtering between 1500-2000 rpm, it will just shut off after running for 15-20 minutes. Hooked an actual fuel pressure gauge and it maintains steady pressure. It really seems to be ignition related i just can't figure out what exactly

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12 hours ago, jdog said:

next time it shuts off check for spark, bet your coil is getting hot

I've had this happen too, but it would start back up immediately after shutting down. So a dead coil may not stay dead for long enough to test for spark.

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If you bought a CPS from the parts store, return it and buy a Mopar one.  The parts store ones are absolute junk and I personally have run into a multitude of stupid problems because of them.  Including the starting and dying one you are describing.  

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52 minutes ago, cruiser54 said:

With it running, start wiggling wire harnesses. 

I have it fired up and running, been over 29 minutes so it seems like a new coil and wire fixed that issue. It still has a bad stumble between 1500-2000 rpms which i can't figure out plus seems to be running rich.

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