Troubleshooting help for a rookie

[BigBen]

1987 Silverado 350 converted to Carb cut out on me on a busy 2 lane road in the middle of a thunderstorm. I am a learning tinkerer, most complicated project I have done so far is change pinion seal on rear dif. Had to have the wife tow me home with her CRV with ratchet straps as I was only a mile and a half from home.

Truck was running fine (as well as it normally does) and all of a sudden heavy heavy bog when on gas, then 10 seconds later complete shutoff. It restarted the first time, stalled again as soon as I dropped into gear and hasn't started since.

Cranks fine, lights and radio work, but when starting the gauge shows only 8 volts or so.

About the truck:
1) Bought on ebay sight unseen (I'm so smart?) a few months ago
2) Someone cut off EFI and put on an Edlebrock 600 with manual choke
3) I have changed all fluids incl rear diff
4) I have changed air filter and spark plugs
5) Truck has some sort of hang up when rolling in neutral once per rotation. Not sure if its an issue with the rear end, or brake rotors yet but its not noticeable most of the time driving

I don't even really know where to start, what should I check? I know it has gas, and I changed plugs a month ago or so. Thanks for any guidance you can offer on how to diagnose.

 

[Honky Kong jr]

1987 Silverado 350 converted to Carb cut out on me on a busy 2 lane road in the middle of a thunderstorm. I am a learning tinkerer, most complicated project I have done so far is change pinion seal on rear dif. Had to have the wife tow me home with her CRV with ratchet straps as I was only a mile and a half from home.

Truck was running fine (as well as it normally does) and all of a sudden heavy heavy bog when on gas, then 10 seconds later complete shutoff. It restarted the first time, stalled again as soon as I dropped into gear and hasn't started since.

Cranks fine, lights and radio work, but when starting the gauge shows only 8 volts or so.

About the truck:
1) Bought on ebay sight unseen (I'm so smart?) a few months ago
2) Someone cut off EFI and put on an Edlebrock 600 with manual choke
3) I have changed all fluids incl rear diff
4) I have changed air filter and spark plugs
5) Truck has some sort of hang up when rolling in neutral once per rotation. Not sure if its an issue with the rear end, or brake rotors yet but its not noticeable most of the time driving

I don't even really know where to start, what should I check? I know it has gas, and I changed plugs a month ago or so. Thanks for any guidance you can offer on how to diagnose.

Was it fuel starved? What is the means of delivering fuel? Ie. Intank factory pump external electric or mechanical? Is there a regular involved? If so is it a return style? Factory pumps don't like being dead headed it cuts thier life span way down not to mention possibly being 30 years old.

 

[1987 GMC Jimmy]

Yes, I'd also dig into the fuel system first. I'm curious to know how it's getting fuel or perhaps in this case not getting fuel. Something that you mentioned that's also disconcerting is the voltage when cranking. 4+ volts being dropped through cranking is not good. I'd verify that your battery is fully charged to 12.4-12.6 volts and I'd see how much it's loosing when you crank it over. I'd test all this with a multimeter. You didn't mention your starter dragging in your post, but if those voltage figures are correct or even close, it should be. You can test spark a couple ways. You can get you one of those little spark testing lights that tee in between the wire and the plug, or you can pull a plug, ground the metallic portion of it (away from fuel, fuel sources, and/or combustible materials!!!!), and see if you're getting a bluish-whitish spark. I'd suspect a fuel problem first and foremost, though. Take the air cleaner off, look down the carb primaries, work the throttle, and see if fuel's coming out. If not, I'd suspect the pump. It sounds like most of the TBI stuff is gone, or I'd suggest converting it back. If the motor has a block off plate where a mechanical pump would go, I'd go that route. Otherwise, I'd just do a low pressure external pump.

 

[BigBen]

Thanks for the start. I'm leaving town for a few days on work but will check fuel when I get back. I have no idea what fuel pump or anything is in it. Pulled it off the transport truck and have only done maintenance type of work on it while driving as much as possible.

 

[BigBen]

Resolved?! I'll know for sure when I try to drive it to work tomorrow.

Crappy clear / see thru fake chrome aftermarket fuel filter was cracked and leaking bad (directly onto one of the headers). Don't know how much worse it was leaking over time, but was probably also the source of constant slow-to-cold-start which I attributed to manual choke. most likely was gas leaking out of top half of fuel line after turning the truck off.

 

[1987 GMC Jimmy]

Good luck! Hope it works well!