Technical Engine Stops When Coasting or Idling

OK maybe you all can help me with this... my truck (65 c10 straight 6) had problems starting that were getting worse and worse plus it would die when coasting to a stop or even idling for a long time. I replaced coil and all ran fine for a while. When I replaced coil I also checked plugs, distributor cap, plug gaps and wires just for the heck of it. All good but points were were worn. Did conversion from points to electronic ignition. Now it starts great but engine will occasionally stop when coasting or idling. I don't have a tach so can't tell the exact rpm but it's high enough that it shouldn't be stalling. No sputter, backfire, missing, etc. when it happens or when the engine is running. The engine just shuts off like I turned the ignition off. Starts right back up with no problem though. Doesn't happen all the time but enough to annoy the hell out of me. Any ideas?

 

Is the ignition switch ok? Is the carb loose?

 

Carb is OK. I'm thinking ignition switch too but don't know how to test that.

 

I'd be looking at carb, esp the idle circuit although if float level is too low that would be a problem. I bet you have a 1bbl rochester and they'll have just 1 idle circuit, if it has a little trash it'll affect that carb more than a 2bbl that has 2 idle circuits. 1bbl carb has little room for error.

 

I do have a 1bbl Rochester that has been a ***** to maintain. In the past when there's been trash in it, it's impacted acceleration and the engine runs rough. That's not the case this time. Accelerates great, idles smooth. No sputter, etc. If it were carb would it impact more than just stalling at idle\low speed?

 

I had a similar problem with my '35 Slantback.....tuned out to be a bad connection at the ignition switch.
I replaced the switch and a connector......problem solved!

 

Byp*** the ignition switch and see if your problem goes away. Just run a jumper wire from your battery to the coil..

 

Did you check the distributor shaft for excessive side play? Common problem for Chevy inline 6s, at least with points. Don't know if it's quite as critical with electronic ignition conversion.

 

I had a 68 C10 with the exact same problem. straight 6 in it same type set up you have. I chased it for months until I finally pulled the gas tank out. the filter sock on the pickup was completely plugged up. Never thought to look there till my Dad told me to check that. It would always turn right off no sputter nothing. let it sit for a min and it would start right back up. I was convinced it was electrical. put a new filter sock on the pick up, cleaned out the tank, and never had problem. I guess those 1 barrel Rochesters just run out fuel real fast if they don't have any fuel to them.

 

just means that your ride wants to go fast at all times

 

When you come into town and drive at 25mph is it jerking & bucking like you need to downgear? If yes, then it is the idle circuit. Like others said, it'd be easy to add a jumper to byp*** the ignition switch and most carb problems are electrical as the joke goes, try that first and if the electrical is ok then you've got an area to check.

 

When you switched to electronic, did you increase the primary wire?
Same issue I had on my 235, when I modded a 250 hei for it...now I was still running a generator, but had to keep the idle about 800-900 rpms to get enough voltage for it, I changed the wiring out for 14 gauge and all worked normally after that.

 

easiest solution is to not take your foot off of the gas pedal. But I bet it's in the carb.

 

Have you checked vacuum?

 

I just had a 350 with an edelbrock that ran great on choke and at speed, but as soon as it was warmed up it would die at idle or coming to a stop. Ran great otherwise.

Turned out It was **** in the carb

 

Its the plug at the HEI, the prongs have lost memory. Unplug and pry female prongs open more.

 

Had the same problem , just die at a stoplight. Petronics ignition. Replaced ignition feed wire with #10 gauge and no more problem.

 

Check voltage where the primary wire attached to the old coil. I'll bet the primary wire is a resistance wire, dropping voltage to 5-6 volts at the coil. If you used this wire to power up your HEI, it won't be enough voltage. HEI requires 12 volts to work properly. Just a thought and worth a check.

 

I had that issue on a 55 Chevy. It had one of those fuel pumps/filters in the bottom of the tank. Switched to one in the gas line instead, solved the problem.

 

Throw a rebuild kit into the carb. They're easy to work on. New fuel filter for sure. See what that does before looking at the tank. Look at all your rubber gas hoses too.

 

Thanks for all the ideas. Gives me a lot to check and work on. Once I find the culprit I'll let everyone know.

 

Time will tell but I think it was the ignition switch. It looked to be as old as the truck. Replaced that and no repeat of problem.