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Really need some ideas on this ! Random dying issue

Chevk587

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Just got back from the rubicon last night had to cut the trip early due to this issue honestly never should have left the staging area but anyway .

this problem started on my last trip to FORDYCE it will just randomly die for no rhyme or reason . Since FORDYCE I replaced the fuel pump that seemed to do the trick drove it as hard as I could around town for over a month with flawless performance! so I figured problem solved well negative .

Friday I get to the staging area and literally pulled it off the trailer was letting it warm up and about 5-10 min in boom it showed it’s ugly face again ! So now having learned my lesson I carry a spare with me so I changed it out again this was a cheap pump from oreiley but seeing how easy it is to change for me literally a ten min job I left it in just assumed it took a crap because that’s what their Electric parts are crap . So threw in the new one started right up no problem ran around the staging area awhile no issue decided to continue made it almost to soup bowl and boom there it is again random dieing . I’d sit wait les than five min and boom start again drive for ten fifteen mins boom dead and repeat .

It dies when cold ,hot shock or no shock something is not telling the pump to turn on then it will start with some time less than five mins I’m leaning towards distributor ,computer iono stumped are this point and this guy isn’t happy either but he had a great time lol! FC1A2F80-1F5D-4692-92B8-E32916F3384B.jpeg
 

Bent77

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@onetonbb74 was having similar issue on his TBI truck. He messed with all the above, and later found the harness was skived inside the cab
 

Wes Harden

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Yeah I was thinking the controls too. The oil pressure switch, relay, wiring. When the key is turned to run, the comp turn pump on 2 seconds, to prime system. when you crank, the ign switch should turn relay on. After engine fires the oil pressure switch grounds the relay in run.
 

Chevk587

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Ok I redid my wireing brand new harness grommet is in perfect shape so is the wireing. The ign and computer are on a different switch. The ignition turns on power and I switch the comp on manually ?
 

Chevk587

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The distributor has never been changed neither has the computer it’s been running in my driveway now with no issue for about ten min so frustrating
 

Wes Harden

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wiggle the wiring while running, try at different sensors, and out puts, while running
 

Chevk587

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I’ll try again but it doesn’t seem to matter . When it dies I literally sit there doing nothing but waiting turning everything on and off waiting to hear the pump prime once I hear it prime it starts every time !
 

ktmoutfront

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I had this same problem. Hauled the Jimmy to Grand Junction. Unloaded it and drove around town, no big deal. The next morning I was heading to the meet up place to drive over the mountains to get to BB. Dies as I pulled into the gas station where we were meeting. Re-fired a couple of times, but would die. Gave up as everyone else needed to leave and got a ride back to pick up my semi. Loaded it with the help of a couple of people. Drove to Moab. Worked on it for 2 days. Bypassed the fuel pump controls so the pump ran full time. No help. Was not getting spark. Gave up for the weekend and broke another guys truck driving it.

Let it sit on the semi for a week when I got home. Went to unload it and it fired up. Daily drove it for 2 weeks. Then one day going up hill on the highway, it died. Pulled over and looked for something obvious for 5 minutes. Fired up and quit another mile up the hill. Restarted after it sat for 5 again. Got over the hill and it drove home fine. Messed with it for 2 days trying to recreate the issue. Drove it up that same hill and it quit again. So I assumed that nose high was the issue. Got it home and drove it on the semi and it quit.

Now I am realizing that every time, including the first time, it was pointed up hill. Tells me it is wiring. Start going through everything when it was running and finally found it. The 2 wire pig tail from the coil to the ICM in the distributor had a part time connection. When going up hill, it disconnected. Was in the sealed wire end. I could not see the failure. I was able to recreate it on the bench with am OHM meter.

I carry a full under hood harness including these wires, distributor and ECM in the Jimmy now. I have not needed any of it, but others have benefitted from them.
 

Wes Harden

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so it will crank, but not start ? since the wiring has been changed, i am thinking relay or signal to relay(computer). when it doesn't start, have you seen the injectors spray, or no spray?
 

Chevk587

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so it will crank, but not start ? since the wiring has been changed, i am thinking relay or signal to relay(computer). when it doesn't start, have you seen the injectors spray, or no spray?
No they dont
 

Chevk587

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I had this same problem. Hauled the Jimmy to Grand Junction. Unloaded it and drove around town, no big deal. The next morning I was heading to the meet up place to drive over the mountains to get to BB. Dies as I pulled into the gas station where we were meeting. Re-fired a couple of times, but would die. Gave up as everyone else needed to leave and got a ride back to pick up my semi. Loaded it with the help of a couple of people. Drove to Moab. Worked on it for 2 days. Bypassed the fuel pump controls so the pump ran full time. No help. Was not getting spark. Gave up for the weekend and broke another guys truck driving it.

Let it sit on the semi for a week when I got home. Went to unload it and it fired up. Daily drove it for 2 weeks. Then one day going up hill on the highway, it died. Pulled over and looked for something obvious for 5 minutes. Fired up and quit another mile up the hill. Restarted after it sat for 5 again. Got over the hill and it drove home fine. Messed with it for 2 days trying to recreate the issue. Drove it up that same hill and it quit again. So I assumed that nose high was the issue. Got it home and drove it on the semi and it quit.

Now I am realizing that every time, including the first time, it was pointed up hill. Tells me it is wiring. Start going through everything when it was running and finally found it. The 2 wire pig tail from the coil to the ICM in the distributor had a part time connection. When going up hill, it disconnected. Was in the sealed wire end. I could not see the failure. I was able to recreate it on the bench with am OHM meter.

I carry a full under hood harness including these wires, distributor and ECM in the Jimmy now. I have not needed any of it, but others have benefitted from them.
Sounds very similar except incline doesn’t affect it I’ve had the icm go bad on me and it’s very similar issue but it will do it on flat ground also and it’s not consistent what’s so ever .
 

ktmoutfront

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Sounds very similar except incline doesn’t affect it I’ve had the icm go bad on me and it’s very similar issue but it will do it on flat ground also and it’s not consistent what’s so ever .

My point was, I think you are looking at the same type of issue. Electrical, either in the harness or ECM. Can you swap the ECM? That would isolate it and put it in the harness.

Does it have spark when you are cranking it right after it dies? I am assuming no.

Do you have an oil pressure gauge that you can see what the pressure is doing when it dies? The oil pressure switch, not the oil pressure gauge sending unit, can shut spark down also. I personally have not seen a pressure switch go intermittent. Usually just fail.
 

Chevk587

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My point was, I think you are looking at the same type of issue. Electrical, either in the harness or ECM. Can you swap the ECM? That would isolate it and put it in the harness.

Does it have spark when you are cranking it right after it dies? I am assuming no.

Do you have an oil pressure gauge that you can see what the pressure is doing when it dies? The oil pressure switch, not the oil pressure gauge sending unit, can shut spark down also. I personally have not seen a pressure switch go intermittent. Usually just fail.
Just died finally I have spark but no fuel all seems to be work but something isn’t telling the pump to come on
 

ktmoutfront

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Bypass the fuel pump wiring. Go straight to the fuel pump with wires from the battery. Just as a temporary check. This is where a Power Probe comes in real handy.
 

Fastereddie

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My Buddy had a 4.3 V6 TBI. Had the same issue no fuel no injector pulse but it did have spark. We replaced The fuel pump filter regulator still no dice. I thought for sure it couldn’t be in ignition problem because we had spark. Someone told us to replace the distributor. It fired right up. Apparently there is a way for that module to fail where it doesn’t signal computer for fuel but it still sparks.
 

Chevk587

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Bypass the fuel pump wiring. Go straight to the fuel pump with wires from the battery. Just as a temporary check. This is where a Power Probe comes in real handy.
Powered the pump from the relay hot test wire it’s working
 

Chevk587

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My Buddy had a 4.3 V6 TBI. Had the same issue no fuel no injector pulse but it did have spark. We replaced The fuel pump filter regulator still no dice. I thought for sure it couldn’t be in ignition problem because we had spark. Someone told us to replace the distributor. It fired right up. Apparently there is a way for that module to fail where it doesn’t signal computer for fuel but it still sparks.
So your say you could have just replace the module ?
 

Fastereddie

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So your say you could have just replace the module ?
Possibly. This was 15-20 yrs ago. We figured the disty had 100k plus on it so we just changed the whole thing. I will say when his quit that was it. It wasn’t intermittent like yours.
 
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