Intermittent shutoff problem

[kenh]

That's a tough one...This could be a bunch of different things. Trying to give ideas without the parts-cannon approach!

Wiggling the ignition switch would be the easiest way to make sure that isn't the problem. I know it sounds silly, but you don't let the key switch "snap" back after cranking, do you? ...Witnessed it before and gotta ask.

Best guess from me would say check your fuel pressure next, if that's good it might be the oil pressure switch or positive power related. I had both of these problems before, but I don't want to lead you on a wild goose chase.

@kenh : Yours almost sounds ignition related or power related? Spitballin' here...I've heard defective ignition modules getting hot sometimes zap out while cruising down the road. You guys got the tough problems!

I also had a bad fusible link once on a Vortec truck. If the computer loses power for a second, it stalls and all the dash lights come on. Restarts like nothing happened.

Tried to keep it short unless you want more details. Hope you guys figure it out!

I did have a ignition module go **** up on me. New module and no issues for about 2 months. The next time the truck died I replaced the module and then had the "old" one tested and it tested good so I have a spare now! It's funny how the truck will immediately start even while coasting to a stop. I'm thinking it has to be a power related issue????? My ignition key tumbler is jingly loose so I think that should be replaced. Maybe even the whole housing and tumbler?? The accessory position does not work. You can't turn the key backwards (90 c1500) to accessory. Probably just throw some parts at it like new ignition switch key tumbler + housing and see what happens. Like i said before, it's hard to fix something that isn't broken!

Ken

 

[thegawd]

I'll quote myself from another thread.... ignition switch is my bet, the electrical part.

if that ignition switch age is unknown, change it. Theres no easy way to test it unless when it stops working you get out the test equipment and start back probing wires.....

I had a failed ignition switch in my burb, I bought 3 from low mileage trucks from a u pull junk yard and the first one worked perfect. they are acdelco in the junkyard.

due to the fact that it starts right back up, I'll put my money on a failed ignition switch. there is carbon built up on the contacts and it interferes with the connection, then you turn the tumbler and makes contact again for a little while. then it dosent and you turn the tumbler again and it works.....

Al

 

[Steven Petersen]

I'll quote myself from another thread.... ignition switch is my bet, the electrical part.

I ordered a NOS Delco switch off Ebay yesterday. For $25 delivered it’s worth a shot. Another question. Could the key tumbler cause this issue? Just in case the ignition switch isn’t the problem.

 

[thegawd]

the key tumbler only moves the electrical part if the key fits... so no.

I have taken a ignition switch apart to see how they fail.... just a bit of carbon tracing...

 

[Schurkey]

As I said in the other thread...when that was my truck, it was the distributor mainshaft.

The magnet on the mainshaft by the pickup coil breaks into multiple pieces over time, causes weak and erratic signal to the module.

Common problem. Worth a look.

 

[Steven Petersen]

As I said in the other thread...when that was my truck, it was the distributor mainshaft.

The magnet on the mainshaft by the pickup coil breaks into multiple pieces over time, causes weak and erratic signal to the module.

Common problem. Worth a look.

Interesting. I’m suspicious of my distributor. Pickup only had 49,000 original miles when I purchased. The original owner took it to shops for everything and kept all the receipts which I have. For some reason at around 45,000 miles, he had a shop put a new distributor in. All the receipt says is it was a no start problem. I’m pretty sure they did not use an OEM distributor. So I’m suspicious of the current distributor. Plus wouldn’t a distributor failure at 45,000 miles be unusual?

 

[Medic0893]

I’ve had this pickup about 14 months now. It’s recently developed a very intermittent shutoff problem. It’s always right after starting it, and it will always immediately restart. It’s only done it 4 times over about 2 months. No codes on the scanner. All grounds have been double checked. Is there a way to diagnose the ignition switch or should I just replace it?

Same issue here... turned out to be the coil. I checked my distributor parts and all was well. Coils can have persnickety behaviors but test fine. Just my experience...

 

[Steven Petersen]

Same issue here... turned out to be the coil. I checked my distributor parts and all was well. Coils can have persnickety behaviors but test fine. Just my experience...

Did you test your old coil? I tried according to the manual but my multi meter leads won’t fit in the slits on the coil. I put a new AC Delco coil shortly after I bought it. But now I’ve learned everything AC Delco makes now is chinese garbage.

 

[DerekTheGreat]

Doesn't seem to matter how many miles are on your "new" replacement ignition part. I consider ourselves lucky if we get 12 months out of ICM's. I've had one fail within three months of installation and another just 14 months after installation. The BWD (Broke when delivered) ICM I put in my wife's truck is going pretty nicely, it's been about eight months now. Idle is really smooth, my truck is intermittently rough or smooth. Almost warm enough for me to start working on stuff again, so I'll throw my MT2500 on it and test the coil at that time.

 

[Steven Petersen]

Doesn't seem to matter how many miles are on your "new" replacement ignition part. I consider ourselves lucky if we get 12 months out of ICM's. I've had one fail within three months of installation and another just 14 months after installation. The BWD (Broke when delivered) ICM I put in my wife's truck is going pretty nicely, it's been about eight months now. Idle is really smooth, my truck is intermittently rough or smooth. Almost warm enough for me to start working on stuff again, so I'll throw my MT2500 on it and test the coil at that time.

I’ve got an MT2500 too. How do you test the coil with it?