Help! Engine developes miss after hitting bump

[Munypit]

This is the 3rd time this has happened, The first time I hit a pothole and the engine died, Found that the coil wire coming off the solenoid was loose. Corrected this, jeep ran fine the next trip out. 2nd trip engine would die but would recrank after a few seconds of turning over. limped her back to my house. Changed fuel filter thinking it was starving for gas. Yesterday,(3rd) time took the kids out for a joy ride, drove about 15 miles out with no problems, turned around to come home, made it about 5 miles, hit a bump and a miss developed,Engine did not die but lost power, hit the clutch and pumped the skinny a few times and would pick back up and every now and then backfire from the tail pipe. it did this for about 9 miles then went dead. I was able to recrank the engine quickly and made the last mile with no problems. I feel like I am a decent mechanic but this is about to blow my mind. Any suggestions in where to look?

 

[Petescj]

Did someone do the nutter bypass on your Jeep? Since it seems to happen after a bump is guess some sort of loose electrical connection where the wires were spliced together. There's guess number 1.

 

[Torxhead]

The coil wire from the starter solenoid is for the primary or starting ignition system. Along the way it connects with the secondary ignition or run circut. This is where the resistance wire comes in from the alternator prior to the coil. There could be an issue with that resistor wire. It is dark brown in color and rather small in diameter, it cannot be soldered due to its material. This could still be the problem as it is making a poor connection, crimping it down is about the only way it can be secured. Guess #2

 

[Munypit]

Going home this evening to start chasing down wires. The wiring in the engine compartment is a mess. PO had the engine rebuilt and there is a ton of wires not going to anything. Is there an aftermarket harness for the engine compartment? I would love to be able to "clean" it up.

 

[Torxhead]

Painless, is one brand that comes to mind, but there is a less expensive version out there. You could also clean it up on your own with parts from a local electronic parts house and a CJ wiring schematic to make sure. Also at the wire intersection from the solenoid to the skinny dark brown resistance wire is also two red w/tracer wires, one from the starter switch and one from the ignition control module.

 

[Peanut Butter]

I would also check the float in the carb. The fact that pumping the gas pedal made a difference the last time out indicates multiple problems. Rod

 

[Petescj]

This is going to be an interesting one to watch.

The fact that pumping the gas pedal made a difference the last time out indicates multiple problems. Rod

 

[hagar]

With the engine running at idle, I would start systematically moving wires and connectors around.
But first I would check where the ground wires attach at the engine block.

 

[Posi]

^^ this

 

[Munypit]

Chased wires for about an hour. found loose tach (dk green) wire. This should not cause the problem. also found the wires at the ignition module are really gummy from brake fluid leak at master cylinder. This problem seem to start around the same time as the reman mastercylinder change in another post. That reman leaked from day one and has been changed to a new so no more leaks. Started the jeep and it idled fine and let it sit and idle for 15 min. Could the ignition module cause this type of problem. If so I can get another from NAPA pretty quick. Another Jeeper told me to check the rotor in the distributor. Can't check anything today daughter has a basketball game.

 

[hagar]

You could tap lightly on the ignition module with a rubber mallet.

 

[Torxhead]

Chased wires for about an hour. found loose tach (dk green) wire. This should not cause the problem. also found the wires at the ignition module are really gummy from brake fluid leak at master cylinder. This problem seem to start around the same time as the reman mastercylinder change in another post. That reman leaked from day one and has been changed to a new so no more leaks. Started the jeep and it idled fine and let it sit and idle for 15 min. Could the ignition module cause this type of problem. If so I can get another from NAPA pretty quick. Another Jeeper told me to check the rotor in the distributor. Can't check anything today daughter has a basketball game.

From what I have seen a bad icm will get warm to the touch when they start to go bad and as they warm up a miss will develop. It is good to know what things look like under the distributor cap. You should have the Team Rush conversion which is the large snap on cap, adapter, Wire change, and extended rotor.

 

[Hedgehog]

You could try cleaning the module. I'd get out a can of Gunk (or similar) and spray - clean - spray - clean .... until your module is as bright and shinny as is possible. Then check the wires for integrity and go for a test drive. Naturally the dist. cap should be as clean as possible. WD-40 is good for that sort of thing. Who knows, you might have water in there that causes trouble when bumped.

 

[Petescj]

From what I have seen a bad icm will get warm to the touch when they start to go bad and as they warm up a miss will develop. It is good to know what things look like under the distributor cap. You should have the Team Rush conversion which is the large snap on cap, adapter, Wire change, and extended rotor.

Sometimes they get warm enough to melt from the side that's bolted to the fender. If it's not brake fluid that goo could be the ICM burning up.

 

[hdgapeach]

Swap in a new ICM and test drive. If the problem goes away, great! If the problem continues; 1) You eliminated the ICM and now have a spare one to put in the console (like it ought to be!), and 2) You need to inventory, and check for quality, the underhood wiring.

Sounds to me more like a loose connection, broken wire that intermittently separates, live wire grounding, loose components in the distributor.....(the list goes on, and on). Once your underhood mess is cleared up, re-evaluate and try to reproduce the issue.

Your biggest problem is you have too many possibilities! Narrow 'em down one at a time and you'll eventually get the problem eliminated. Kinda like eatin' an elephant, one bite at a time!

 

[Munypit]

Changed the ICM this weekend. Old one had all the rubber/plastic? melted on the back. Tried running, cranks and idles fine, but seems to be starving for fuel. It went dead on me a couple of times within a mile of the house. Finally got it to die close to the house so I could see what I could find. Fuel filter was about half full, carb bowl only had about 1/4 capacity. Thinking maybe fuel pump? or rubber hoses from sending unit at tank. The PO had the engine rebuilt just before I bought it 2 years ago. I may have put 500 miles on it since purchasing. Don't know if he reused the fuel pump. Pump does appear to be new. The PO did install a fuel filter between the tank and pump. I relocated the filter yesterday to between the pump and carb. I dont know how much pressure these pumps should put out but it seems to take a while to fill the filter up. It seems to explain why when I lose power I can hit the clutch and let it catch back up and run a little while it will take off again for a short distance. and all the pumping of the skinny peddle causing a cylinder to load and backfire.

 

[Torxhead]

So was time to change the icm, hopefully you bought a good one. Good catch on checking the float bowl, a fuel pressure check would verify a bad fuel pump. The hoses from the tank to the pump can develop cracks, so maybe check those. The later CJs had a fuel filter between the pump just before the carb with a return line to the tank. The icm wiring comes with a black ground wire from it to the distributor with is not very good. A bad ground here will burn up an icm.You could splice into the icm ground and run that wire direct to the battery ground. On my rig I have just run the black wire from the icm direct to the battery ground.

 

[hdgapeach]

Changed the ICM this weekend. Old one had all the rubber/plastic? melted on the back. Tried running, cranks and idles fine, but seems to be starving for fuel. It went dead on me a couple of times within a mile of the house. Finally got it to die close to the house so I could see what I could find. Fuel filter was about half full, carb bowl only had about 1/4 capacity. Thinking maybe fuel pump? or rubber hoses from sending unit at tank. The PO had the engine rebuilt just before I bought it 2 years ago. I may have put 500 miles on it since purchasing. Don't know if he reused the fuel pump. Pump does appear to be new. The PO did install a fuel filter between the tank and pump. I relocated the filter yesterday to between the pump and carb. I dont know how much pressure these pumps should put out but it seems to take a while to fill the filter up. It seems to explain why when I lose power I can hit the clutch and let it catch back up and run a little while it will take off again for a short distance. and all the pumping of the skinny peddle causing a cylinder to load and backfire.

Making progress! My CJ did the same as yours not too long ago. My issue turned out to be a bad mechanical fuel pump. Thank God it was intermittent and didn't manage to strand me out in the middle of nowhere. Found my problem by swapping out the ICM with the one I had stored in the console and not noticing any change. Changed the pump, re-newed rubber fuel lines and changed the oil and filter and all was good. Had to change the oil because gasoline had leaked into the crankcase because of the cracked fuel pump diaphragm.

 

[Hedgehog]

If it's not electrical it's fuel, I'd swap out the pump.

 

[Munypit]

Swapped the pump last night. Pump was not the problem. Engine dies at almost the same spot in the road everytime. Going to drop the tank this evening to see if something is blocking the intake at the sending unit. and check integrity of the hoses coming off the sending unit.