Truck only starts sometimes (Distributor?)

[Restoredrust]

Does it have spark while cranking when it doesn’t start?

I pulled two plugs and to my surprise the truck started up while I was doing the test so I turned the key off, plugged them back in and she started up again but now she starts but dies out in a couple seconds unless I have my foot on the pedal.

 

[MrMarty51]

I pulled two plugs and to my surprise the truck started up while I was doing the test so I turned the key off, plugged them back in and she started up again but now she starts but dies out in a couple seconds unless I have my foot on the pedal.

Is it blowing black smoke out the exhaust ?

 

[Restoredrust]

So I unplugged this wire like it was before and she didn't start at all, plugged it back in and I got her to start again, but only for a second. As you can see the wire is in horrible condition. I'l try fixing it up and trying again, I'll keep you updated

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[1987 GMC Jimmy]

He’s in Hawaii lol

Oh, I know. I was just making sure it wasn't shipped there later from the nation of California.

It's just a 49 state truck with the ESC module and regular cab

Okay, that makes things easier. That truck won't have an ECM or a feedback type carburetor; just the module and the regular carb. Like it was mentioned before, the most important thing you need to know is if you're getting spark whenever it's not wanting to cooperate. It sounds like it was whenever you just tested. If not, I'd suspect the ignition module before anything. I can speak to the ESC system working well in conjunction with an ECM on the CCC and TBI systems, but I've never had a truck that had that standalone circuit. I can say that anytime GM implemented some kind of proto-computer, it was met with a lot of disdain, and I'm sure some of that had to do with inherent problems, but I don't think problems are 100% to blame. Anyways, if your ESC system is working properly, you should be able to get a timing light, point it at the balancer while it's running, and see the timing mark bouncing around really fast. Post-HEI distributors are just rotating assemblies so it's just a rotating assembly with a bushing that can fail with a lot of wear, a capacitor, a pickup coil, a module, a cap, and a rotor. It's not like an HEI distributor with a lot of guts that have to be in check. Do you know what your timing is? Is there a difference in how it runs with the four wire ESC connector unplugged? You said fuel was going into the carb. How's it coming out of the carb? You should be able to work the throttle, look down in there, and see to healthy squirts of fuel that begin the instant you start moving the throttle.

 

[Restoredrust]

Is it blowing black smoke out the exhaust ?

It does blow smoke from the exhaust but it's more of a white color and only on start up, if I drive it for about 10 seconds the smoke stops coming

 

[1987 GMC Jimmy]

Okay, so that's just a regular HEI distributor. I thought you were running an ESC type. Disregard the stuff about the distributor function and ESC diagnosis. That wire is your 12V supply to the distributor and tach wire. You need to be getting 12 uninterrupted volts with the key on, engine off to that wire. No breaks in the insulation or anything that could otherwise compromise that.

 

[Restoredrust]

Okay, so that's just a regular HEI distributor. I thought you were running an ESC type. Disregard the stuff about the distributor function and ESC diagnosis. That wire is your 12V supply to the distributor and tach wire. You need to be getting 12 uninterrupted volts with the key on, engine off to that wire. No breaks in the insulation or anything that could otherwise compromise that.

Okay I'll test the voltage right now, thanks

 

[Restoredrust]

It reads 12.24v but there are a ton of crimped spots on that wire, I'll see what happens if I clean the wire up and solder rather than crimp

 

[Restoredrust]

Okay, so that's just a regular HEI distributor. I thought you were running an ESC type. Disregard the stuff about the distributor function and ESC diagnosis. That wire is your 12V supply to the distributor and tach wire. You need to be getting 12 uninterrupted volts with the key on, engine off to that wire. No breaks in the insulation or anything that could otherwise compromise that.

^

 

[1987 GMC Jimmy]

I've got a crimp in mine where a rat chewed it in half. I think the problem lies elsewhere, but I think it's good measure to repair tacky things the right way so they don't become problems down the road.

 

[Restoredrust]

I've got a crimp in mine where a rat chewed it in half. I think the problem lies elsewhere, but I think it's good measure to repair tacky things the right way so they don't become problems down the road.

Probably true, I looked down the carb it looks to be doing perfectly fine, what would the next step be?

 

[1987 GMC Jimmy]

You've confirmed good spark, right? A snappy, whitish one? Yellow spark is the one that you don't want.

 

[Restoredrust]

You've confirmed good spark, right? A snappy, whitish one? Yellow spark is the one that you don't want.

I just did another test because the first time could of been just pure luck, this time around 2/3 test showed no spark but one time it did, color was white

 

[1987 GMC Jimmy]

So you're saying you did this three times for the sake of repeatability, and it didn't spark two of those times. The plug was grounded the same way and everything? If I understand correctly, that's a problem. Such flaky intermittent spark loss sounds strange to me. I've never had a pickup coil problem, but I imagine it would go something like this. Is that an MSD distributor? I've heard of people having problems with them, but I've never ran one so I can't speak to it. If it were me, I'd clean up what the PO hacked up under the hood and install a remanufactured Delco-Remy HEI distributor since it seems the ESC stuff is gone. I'd like to see what others have to say about these developments. @Honky Kong jr

 

[Restoredrust]

So you're saying you did this three times for the sake of repeatability, and it didn't spark two of those times. The plug was grounded the same way and everything? If I understand correctly, that's a problem. Such flaky intermittent spark loss sounds strange to me. I've never had a pickup coil problem, but I imagine it would go something like this. Is that an MSD distributor? I've heard of people having problems with them, but I've never ran one so I can't speak to it. If it were me, I'd clean up what the PO hacked up under the hood and install a remanufactured Delco-Remy HEI distributor since it seems the ESC stuff is gone. I'd like to see what others have to say about these developments. @Honky Kong jr

It's not an msd but i agree, it needs to go