Random Loss of Spark - Please Help

[Alexf2002]

Something worth taking a look at is the icm connector. I went thru this several years ago and after spending money and time on a mechanic I dug into it myself and found the connector badly corroded. I didn't buy a new one just cleaned it and it worked.

thanks for the tip. I’ll have to take a look into this and see how mine shapes up.

 

[Postmech]

I have a 1998 k1500 that ran fine and then one day I turned it off after getting to work and would not restart that afternoon. Crank sensor died.

 

[Josh Reed]

I have a 1996 K2500 that randomly dies while driving, not bucking, sputtering, etc.. To me, it's like someone throws a kill switch.....no warning, no nothing, it just either looses spark or has no fuel. At first, it would start back up again once I put it in neutral and cranked it over again, but now it's getting to the point that in order to restart, I have to cycle the FP a few times and then press the pedal to the floor (I Know that shouldn't matter, but it seems to work). I have a multi-point fuel injection system.

 

[Josh Reed]

I have a 1996 K2500 that randomly dies while driving, not bucking, sputtering, etc.. To me, it's like someone throws a kill switch.....no warning, no nothing, it just either looses spark or has no fuel. At first, it would start back up again once I put it in neutral and cranked it over again, but now it's getting to the point that in order to restart, I have to cycle the FP a few times and then press the pedal to the floor (I Know that shouldn't matter, but it seems to work). I have a multi-point fuel injection system.

**UPDATE**

Check Engine light wasn't on but I checked the codes and I had a 'P1351 CHEVROLET - Ignition Control Module Circuit High Voltage'. Would this cause the symptom I'm having?

 

[Pinger]

I have a 1996 K2500 that randomly dies while driving, not bucking, sputtering, etc.. To me, it's like someone throws a kill switch.....no warning, no nothing, it just either looses spark or has no fuel. At first, it would start back up again once I put it in neutral and cranked it over again, but now it's getting to the point that in order to restart, I have to cycle the FP a few times and then press the pedal to the floor (I Know that shouldn't matter, but it seems to work). I have a multi-point fuel injection system.

I was having a look through the workshop manuals someone here provided links for and 'pedal to the floor' (opening > 60% IIRC) is a permitted strategy to recover from flooding. Ie. it will crank but without providing fuel.

 

[PlayingWithTBI]

^^^Yup

 

[Josh Reed]

I was having a look through the workshop manuals someone here provided links for and 'pedal to the floor' (opening > 60% IIRC) is a permitted strategy to recover from flooding. Ie. it will crank but without providing fuel.

Good to know for sure. This works to get it started again after randomly dying and then it seems to run ok for awhile. Do you know what would be causing it to die int he first place? Simply driving along at normal speed and suddenly engine dies like fuel has been stopped OR spark has been lost. I have a IGM code and I'm wondering if that could be the issue. I thought it was the fuel filter at first, so I changed that out, but then it happened again today.

 

[Pinger]

Good to know for sure. This works to get it started again after randomly dying and then it seems to run ok for awhile. Do you know what would be causing it to die int he first place? Simply driving along at normal speed and suddenly engine dies like fuel has been stopped OR spark has been lost. I have a IGM code and I'm wondering if that could be the issue. I thought it was the fuel filter at first, so I changed that out, but then it happened again today.

Generally, when holding a throttle open and cranking to clear flooding, the fuel can be smelled at the tailpipe. If you are smelling that then almost certainly it is spark you are losing.

Generally (again) ignition failures on the HT side are at there worst (and provokable) under load (harder to introduce the spark in a fuller cylinder) but yours sound like it's dying faster than you could perform that check/test.

Generally (yet again), the guys (and gals!) here know a hell of a lot more about these motors than I do - they're in a better position to help you than newbie here who only got his truck earlier this year. They are pretty up with scanners to detect faults - I've not quite caught up with that.

Old school check for when it dies though is to pull a spark plug and have a sniff. If there's a smell of fuel - you're losing spark. If no smell, then suspect lack of fuel. If your WOT cranking gets it going again, you can as good as perform the same test at the tailpipe - just stop the cranking before it fires up. Maybe at least identify if missing fuel or spark is the issue.

 

[Schurkey]

What is the fuel pressure when driving?

Does the fuel pump prime when the key is turned from "Off" to "Run"?

As usual, connect a scan tool and look at the data stream. Issues with the crank sensor, for example, could lead to loss of ignition and fuel injector operation.

 

[Busted Knuckle]

Long time follower of the forum... first time posting. Very glad this forum exists. I’ve gotten a lot of info from here but I’m at a loss of ideas for what’s wrong.

Truck started having an issue with randomly shutting down while at idle or while driving. When it first happened it shut off and never started again until I replaced the ICM and ignition coil. Once those were replaced it started and ran fine for a few weeks. Truck started having the same shut off then no start problem so I took out the new coil and ICM and got them replaced under warranty. Truck started and ran fine again for a few weeks. The random shut off issue started up again and I decided to do a basic ignition tune up and replace a few sensors that I had been told could cause shut off issues. After installing all new plugs, wires, cap, rotor, fuel filter, crank sensor, and camshaft sensor the truck ran better than ever for a few days, but eventually the truck shut off while driving again and now here we are....


I cannot consistently get the truck to replicate the issue. Every so often it will have a bad day where it shuts off while driving and takes a few minutes before it’ll start again, but it could be minutes, hours, days, or weeks before the issue will ever happen again. It can shut off at both idle and while driving.

I bought a fuel pressure gauge and inline spark checker when the issue started happening. Fuel pressure is good, but during the period where the engine shuts off and refuses to start for a few minutes there is no spark at the cylinder.

I’m at a complete loss for what could be wrong. If anyone has had an issue like this before or has suggestions as to what could be causing my random, inconsistent loss of spark please leave me some suggestions. Thank you guys for all your help in my build.

Try a new fuel pump relay, clean up the ground at the fuel pump wire to chassis. Check the oil pressure sending unit for oil intrusion. The Oil P sender holds the fuel pump hot once the engine is running so in case of rollover the pump is off.