Help with troubleshooting C20 350 that dies after short drive

[vadriller]

Roundhouse: I just checked. The accelerator pump does spray after it shuts off. Right now, the truck isn't running long enough to drive (< a couple of minutes). If I pull down my driveway, I go downhill. The rubber fuel lines were both replaced this month when I put the new tank in.

GMC Jimmy: I don't think vapor lock is a problem. I am using the factory steel lines. It felt cool to the touch after the engine ran through a few "cycles" while I was diagnosing.
I have a 180 thermostat in (new radiator, hoses, and water pump this month). The IR thermometer I have said it got up to about 170 at the thermostat housing when the upper hose started to get warm.
Yes, it was doing this before I replaced the points, condensor, and coil.

Rusty Nail: I really don't know how accurate that pressure number is.

 

[1987 GMC Jimmy]

I hear you. Vapor lock should really only be a concern if you’re not running the factory steel lines. What’s the timing set at, and does the cranking sound normal? What I’m getting at here is too advanced timing. I doubt it’s a spark problem. You’ve replaced everything, and you’re dwell is fine. If the timing’s good, there’s not much else to fiddle with except checking plug gap. Besides, the fuel pressure debacle, which I understand is not a written in stone number, it sounds like you’ve done most everything with the fuel system. Do you have a vacuum gauge? I think it’d be good to know what that’s doing to see if it can give you a clue of where to go. The biggest leak point would be your intake gasket or your carb base gasket. I’m assuming you’ve replaced the base gasket recently, and if your vacuum isn’t super low, it’s likely not an intake gasket Agh, this is a tough one. @RustyPile, do you have any old school breaker point ignition tricks, or any other ideas otherwise?

 

[Rusty Nail]

Burns up coils,points,condensors, and you suspect a fuel problem?

lol?

 

[74 Shortbed]

Maybe I missed this somewhere, but when it dies and then won't start right away, was there a test to see if there was any spark while cranking???..

 

[Honky Kong jr]

I hear you. Vapor lock should really only be a concern if you’re not running the factory steel lines. What’s the timing set at, and does the cranking sound normal? What I’m getting at here is too advanced timing. I doubt it’s a spark problem. You’ve replaced everything, and you’re dwell is fine. If the timing’s good, there’s not much else to fiddle with except checking plug gap. Besides, the fuel pressure debacle, which I understand is not a written in stone number, it sounds like you’ve done most everything with the fuel system. Do you have a vacuum gauge? I think it’d be good to know what that’s doing to see if it can give you a clue of where to go. The biggest leak point would be your intake gasket or your carb base gasket. I’m assuming you’ve replaced the base gasket recently, and if your vacuum isn’t super low, it’s likely not an intake gasket Agh, this is a tough one. @RustyPile, do you have any old school breaker point ignition tricks, or any other ideas otherwise?

I do........switch to HEI. Points had their time, leave them where they belong. In the past.

 

[1987 GMC Jimmy]

Burns up coils,points,condensors, and you suspect a fuel problem?

lol?

I thought he replaced them preventatively or at least because he suspected a problem. If they’re burning up, that’s a different story.

 

[1987 GMC Jimmy]

Maybe I missed this somewhere, but when it dies and then won't start right away, was there a test to see if there was any spark while cranking???..

He said that he got his wife to turn it over, and he checked for spark, which it had. I think it was his last post on page 1.

 

[74 Shortbed]

He said that he got his wife to turn it over, and he checked for spark, which it had. I think it was his last post on page 1.

Oops, guess I missed it, my bad..

 

[1987 GMC Jimmy]

I do........switch to HEI. Points had their time, leave them where they belong. In the past.

I was thinking that, and I agree with you. The spark is much weaker, and more parts wear out over time. HEI is far superior. The two arguments you could probably make for breaker point is one, no ICM to burn out while driving down the interstate, which is somewhat mitigated if you have a spare, and two, if someone detonated an EMP over the country, the points car or truck would still work, and I don’t think HEI would. That’s doomsday thinking, but I think about it when I’m driving around sometimes.

 

[Honky Kong jr]

I was thinking that, and I agree with you. The spark is much weaker, and more parts wear out over time. HEI is far superior. The two arguments you could probably make for breaker point is one, no ICM to burn out while driving down the interstate, which is somewhat mitigated if you have a spare, and two, if someone detonated an EMP over the country, the points car or truck would still work, and I don’t think HEI would. That’s doomsday thinking, but I think about it when I’m driving around sometimes.

Lol

 

[Rusty Nail]

Correct. HEI will no longer function given an EMP.
Points distributors are BACK UPS, not primaries.
Maybe he has a concourse resto, maybe it's an all original show truck? There is no other good reason to no HEI.

More information is necessary and yet, here we are - on page 5 or 6.

 

[vadriller]

GMC Jimmy: the timing is set at at 8 degrees BTDC and the cranking sounds normal. I will hook up a vacuum gauge today and let you know.

Just to let everyone know, this is my dad's old truck that was sitting in his barn for the last 20 years. No restoration here. Just trying to get it safely back on the road for the memories. (and replacing points and condensor out of the glove box broken down in a hayfield is one of those memories)

 

[Honky Kong jr]

Correct. HEI will no longer function given an EMP.
Points distributors are BACK UPS, not primaries.
Maybe he has a concourse resto, maybe it's an all original show truck? There is no other good reason to no HEI.

More information is necessary and yet, here we are - on page 5 or 6.

How about the non coil in cap distributor HEI. It will give you the vintage look and give better spark.

 

[vadriller]

The weather forecast here was wrong today. It was freezing rain all morning and raining all afternoon. I hope that I can get out to the truck tomorrow and look things over. Perhaps walking away from it for a little while will give me a new perspective. The battery is on the tender and maybe I needed to recharge my own batteries.

I am open to trying anything. But I do have spark immediately after it stalls.

I will post back after I look over everything tomorrow.

 

[Dougnsalem]

The weather forecast here was wrong today. It was freezing rain all morning and raining all afternoon. I hope that I can get out to the truck tomorrow and look things over. Perhaps walking away from it for a little while will give me a new perspective. The battery is on the tender and maybe I needed to recharge my own batteries.

I am open to trying anything. But I do have spark immediately after it stalls.

I will post back after I look over everything tomorrow.

How good of a spark? Did you try using a cheap checker to see? Only reason I mention it, is because I've had a weak coil show what seemed like good spark, jumping it to a valve cover or whatever. It wasnt strong enough to light off the plug in the cylinder though. Coil breaking down when its hot? Just something else to maybe check.

(Another HEI vote here too. I got a complete used one for 50 bucks. Dist, cap, rotor, wires, coil....)