Engine goes rough, dies, won't start -- spontaneously fixes itself?! (1st drive)

[67L48]

67 350 w/ powerglide.

Last summer, the engine was missing on ~3 cylinders and required new plug wires and a carb rebuild.  Everything worked great for the next 500 miles.  Put the car away for the winter.

Got the car out this past weekend.  Fired right up.  Let idle in the driveway for around 15 minutes.  Then went on a short ride.  Drove perfect for around 5 miles.  Stopped and shopped.  Came back out and took off.  Went another 2 miles and then the engine had a complete melt-down.  Felt like half the engine stopped firing.  It wanted to die.  Fortunately, I was going to a gas station at the time.  Didn't quite make it when the engine died.  Coasted into the station.

When I tried to start it, the starter would turn, but it didn't sound or feel like it was cranking the engine.  It was weird.

So, I had it towed to the shop.  That was Sunday afternoon.  Monday, when the shop opened, there apparently was no issue.  Started and ran fine.  They ran it periodically throughout the day and could detect nothing.  Everything was dialed in good.  The carb was clean and free from gunk.  Fuel and air were flowing fine.

I picked it up and drove it home.  Handled like a dream.  Happy to have a $0.00 issue, but not real confident in the car right now.

So, what happened?  I think I had stabilized fuel in the tank, but let's assume that I didn't.  Could some chunk of crap broken free and clogged a line or cylinder for a while ... and then get shaken and pumped through the system during the course of trying to start it and/or being towed across town?

Should I be freaking out ... waiting for it to die again, or should I feel confident that what I experienced was a one-time-only artifact of the first drive of the year after having sat for 5 months?

Thanks.

[rich69rs]

What gas was in your tank over the winter?  Did it have more than 10% ethanol content?

Most gasoline today can have up to 10% ethanol - doesn't have to, but it can.  (The designation "E10" stands for 10% ehtanol; 90% regular gas.)

Athough still relatively rare here in the U.S., there are places in the U.S. where you can purchase E85 (85% ethanol; 15% regular gas).  E85 is for "flex fuel" vehicles only. 

Ethanol is a blend of gasoline and ethyl alcohol. Ethyl alcohol is an excellent solvent and is hydroscopic, that is it adsorbs water.   Ethanol added to a fuel tank contaminated with water can cause what you experienced. Water in the tank will combine with the ethyl alcohol in ethanol to produce a noncombustible liquid in the tank that will stop most engines cold. 

Did you put fresh gas in the tank while at the station?  If so, maybe you have been lucky enough to have gotten fresh fuel to the carb, engine runs, etc. and any remaining non combustible liquid was/or is in the process of being purged out of the fuel system via the fresh gas.

[tom]

Almost sounds like water in the gas. Enough moisture in the air, and some will find its way into the gas. Gas & water don't mix. This is what they used to sell "dry gas" for. Don't know if it's still around. Way back in the day, sometimes when there was water in the fuel the water would get into the line, and when it hits the carb, the motor quits. After it pumps through, you get back to the gas, and the motor runs fine again.

[67L48]

Thanks.  I know that we do have EtOH in our gas here.  I'm in Colorado.  I had about 1/4 tank in the car as it sat.  And, no, I didn't put any fresh gas in it between when it died and when it started working again.  I did fill it up with fresh gas, though, to hopefully dilute any water or crud that may be in the old gas.

I'll update if anything else happens ...

[crobjones2]

67 350 w/ powerglide.


When I tried to start it, the starter would turn, but it didn't sound or feel like it was cranking the engine.  It was weird.

Was the starter actually turning the motor? if not, I would look at the solenoid and possibly replace the batery cable, as I have had a cable that went bad and only reared its head when the motor was hot

[hotrod68]

Check the junction block on the radiator support at the battery. If you lose this connection you lose all power! I've been through this and it's maddening to diagnose if you don't know what to look for. The electrical system will get just enough juice to let the car run, and it may run great or run rough or not run at all. Just a thought. Good luck!