Distributor replace/align

[pmndlt]

Hey all. 1988 GMC Sierra C3500 5.7L. Stalling when warm. Previously thought fuel issue now dealership has confirmed no pulse from distributor at stall. Looking to replace distributor but have never done one.

At TDC the rotor is NOT pointing to the #1 cylinder. Plenty of marks on engine and firewall suggest someone has mucked with this before.

I intend to remove, re-index new with rotor pointing to cylinder #1.
Anything I need to watch out/set other than exhaust vs intake stroke?
Could a distributor that is out cause uneven spark plug wear too? Plugs are 1 month >500km and range from white and dry to black and wet with fuel.

Thanks

 

[pmndlt]

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[89RCLB]

Sounds like the ICM is getting hot and causing no spark condition. Maybe try replacing it first? If that corrects the issue then re-stab distributor...

 

[pmndlt]

Sounds like the ICM is getting hot and causing no spark condition. Maybe try replacing it first? If that corrects the issue then re-stab distributor...

Thanks @89RCLB For the suggestion. I will swap that out first and see how it goes!

 

[RawbDidIt]

Did you test multiple cylinders for spark, or just 1? Is the cylinder you tested running black and/or wet with fuel? Could just be a bad rotor and/or cap. Either way, probably won't need to replace entire distributor. You'll also want to be checking the timing with the spark advance wire disconnected. Shouldn't make a lick of difference mechanically as you're checking it now, but is important when you're checking it while running. Just wanted to mention it since you hadn't, not sure if you knew that and also knew that it wouldn't affect where the lead is pointing at TDC, or if you just didn't know. Make sure you're at TDC leaving the compression stroke, entering the power stroke (exhaust and intake valves closed).

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[pmndlt]

Thanks for the reply @RawbDidIt some I knew some I didn’t so it’s good to hear it all lol! I never checked individual cylinders, never even paid attention to plugs until I had them all out to rotate engine.

if I follow, as long as timing is set with est plug disconnected, then reconnected, and truck runs well (no obvious misfires or lopes) the rotor location/distributor index is not necessarily an issue?

Cap and rotor were replaced, idles well, runs strong but then stalls out at low speed or idle. Starts right up after and under throttle not an issue.

 

[HotWheelsBurban]

Thanks for the reply @RawbDidIt some I knew some I didn’t so it’s good to hear it all lol! I never checked individual cylinders, never even paid attention to plugs until I had them all out to rotate engine.

if I follow, as long as timing is set with est plug disconnected, then reconnected, and truck runs well (no obvious misfires or lopes) the rotor location/distributor index is not necessarily an issue?

Cap and rotor were replaced, idles well, runs strong but then stalls out at low speed or idle. Starts right up after and under throttle not an issue.

When modules and coils are starting to go bad, heat really affects their performance. This is part of why GM moved the coil, and eventually the module, out of the distributor.

 

[pmndlt]

Thanks @HotWheelsBurban Interesting. Makes sense but something I would’ve never thought of... I’ve got lots to learn about this old but new to me technology!

 

[HotWheelsBurban]

Thanks @HotWheelsBurban Interesting. Makes sense but something I would’ve never thought of... I’ve got lots to learn about this old but new to me technology!

My dad worked in an auto parts store when I was a kid, and then we bought the business. From 75 to 88, spent most of my time there( other than school), and we had many HEI equipped GM vehicles too. That's where I learned about how important a quality cap and rotor are with these systems. Better plastic and brass contacts are a very good thing for these. In our experience, we found that Blue Streak and Accel make a cap with brass contacts. They're more $$ but well worth it! Will last a lot longer!
My 99 Burb 5.7 vortec gets daily driven, all over Houston, Texas area traffic, in most any weather. So I figure that's a good test of components.....
My truck probably didn't know what to think about the snow and ice and not being used for 5 days ( it usually never gets that much time off!).

 

[pmndlt]

That’s how you got an education then! I’m hoping I can get this beast figured to have as a daily driver. You guys got slammed pretty hard down there. We have friends in Harlingen they got cold but not much snow. Up here we test trucks in opposite weather. We hit -52 at beginning of March