I'm a bit stumped. I have a 1969 Cutlass, 350 V8, stock., The engine has all new parts completely rebuilt, plus a Holley carb, new fuel pump, new plugs, cap, rotor, wires, new coil, new fuel tank pick up and sending unit. The car starts and runs great, until you drive it for maybe ten minutes or so, then it dies and won't restart. Seems to restart after cooling down for 30 minutes or so. I had replaced the points with an electric module, and then changed back to the points to see if that was the problem - but no change. A solid 12 v wire was used for the electronic module and a resistor wire was used for the points set up. Almost acting like a vapor lock, but it does it every time. It has fuel hose from the pump to the carb, so that shouldn't get a vapor lock. Anyone every experienced this and found a solution?

 

You need to determine whether your having a fuel or ignition problem for a direction, there are many causes for your issue. Have you checked for spark or fuel spray looking down inside the carb when you operate the throttle when it won't start?

 

With the symptom you described I would suspect the coil over the points. The coil may have some heat related issue.

 

I tend to like the notion of suspecting the coil - the 2° windings in the coil go bad. Although, peculiarly enough I had a friend wire his coil incorrectly once - reversed (+) & (-) on the coil. Darn car started and ran - same kind of symptoms - would run about 15 minutes then shut down. Let cool, start back up. Ad infinitum. Took him a couple days to figure this one out. I was never clear on how that could have occurred but it did.

 

You say you dropped the tank to do work. Did you put new hoses on when doing this? I did this years ago, and when I replaced the hoses, I made them a little longer. When I drove it, it would run, then it would die, kept doing this. So I dropped the tank, being that was the last thing I had done. I made the hoses just a little bit to long, and was kinked a little, so it was slowing down the gas flow, cut hose,and ran fine.

 

When it dies remove the gas cap. It sounds like you could be drawing a vacuum in the fuel tank. Verify tank vents are open and not restricted.

 

X2. did you put a new gas cap on it? That is about the length of time it takes to suck a vacuum on it... Tedd

 

Thank you all for your inputs, I appreciate them. I did try to exhaust everything I could think of before posting here. In addition to the info I originally posted I can add that I have checked the carb and it does continue to squirt gas after it dies. The engine seems to sputter, or load up, right before it dies. I have briefly restarted it by keeping the gas pedal floored, as you would when a car gets flooded. The resistor coil wire has been replaced. The coil is new, and I have even tried two different coils (both the kind of coil that requires resistor wire or an external resistor, correct for this car). The gas cap is a non-vented cap, and the small vent above the gas tank is new and breathing. I have tried removing the cap but it did not solve the issue. I also checked for loose grounds. The hoses on the tank are the same length as the original ones, no kinks.

My guess at this point is that either there is an issue within the carb (which I doubt) or there is something electrical that is failing when it gets hot. As far as something electrical, I am at a bit of a loss as to what else it might be. Just about the only things left are the alternator and regulator. I ran it at idle today and after 15 minutes it died. I restarted it by flooring the gas pedal and let it run, and it died after a minute or so.

 

See my Post #4 and visually validate the wires are hooked up EXACTLY as they should be. Yes, an IGN coil can be hooked up backwards and the vehicle will still run with SIGNIFICANTLY less than optimal spark. Essentially a reversal of polarity of the electrons in the opposite direction.

 

The alternator and regulator have nothing to do with the engine running. Both can be removed and the engine will run off the battery.

 

Yes, I realize that. I was just saying they are the only other electrical items, that is why I am stumped.

 

And yes, the coil is wired correctly. Minus to the dist. and plus to the ign.

 

What’s in there now? Contact points + condenser or electronic IGN module? If contact points, did you R&R the condenser when you did the R&R of the contact points? The condenser is essentially a capacitor and will/can go bad.

 

It has a new condenser with the points now. The condenser sucks up the voltage spikes to keep the points from burning up, but I've never seen it intermittently fail like the problem I'm having. It did the same thing when the breaker less ignition was in it so I'm ruling out that as a problem. Thanks Norm.

 

OK Just tying to brainstorm this issue.

 

Have you tried a different coil?

 

If I think this through regarding ‘heat’ as a possible source of the issue, most will recognize a basic tenant of wires and heat. As heat increases, molecular motion increases (e.g. in this case electrons). As the heat increases and the motion of electrons increases resistance w/in a wire increases substantially. It can increase to the point of possible complete resistance e.g. no or limited electron flow which equates to no or limited current. Curious how hot any of your wires are becoming when this issue develops?

 

I read through everything again and I think this is significant and points to a carburetor / fuel issue.