Wrong gas cap causes starting/running issues?

[1971RR]

Confirmed last night that the fuel vent system seems to be working. Hooked a hose to the tube in the engine bay and just blew into it. No restrictions felt. Sucked on it and got a lung full of high octane gas fumes. Rerouted the fuel line further from the exhaust manifold. Didnt make any difference. Once warm the car started acting the same. One other thing I found out last night is the cooling system is not pressuring up. Hopefully just a bad cap. My first thought was headgasket but I would think I would see a hint of white smoke out the tailpipe and an over-pressureized cooling system. A friend gave me some suggestions which include veryfying compression, which I hate on these motors. Access to plugs is not the easiest. Also he recommended bottle feeding the car while its running to eliminate the fuel system entirely. It would be nice to have a hole in the fuel line somewhere. I know my spark is good. I took the coil wire off the coil while it was running. The spark was still jumping even with the wire over an inch away from the coil terminal.

 

[67 coronet]

if your gas tank is below 1/4,try driving with gas cap off.that will tell you if the vent is your problem.

 

[1971RR]

Called Mallory today to get some operating parameters of the distributor, coil, ballast and wires. The tech immediately called "bad coil". I pray he is a genious. Send old part back. Mail new one. Let hope.

 

[hendo0601]

To me it almost sounds like you have a problem with fuel boiling/evaporating the in the line/carb after you shut the motor off and it heat soaks. I had this same problem on my 66 Newport...it would run great until I shut it down and it sits for 5-10 minutes and trying to restart it resulted in hard start/sputtering/stalling. I noticed that after the engine was at operating temperature and I shut it down, after a few minutes the fuel in the filter would begin to boil and evaporate, thus resulting in a hard start. I re-routed my fuel lines away from the exhaust and back to the factory location and never had that problem again. Since you have a clear fuel filter I recommend you start the engine and let her warm up completely then shut it down...10 minutes later pop the hood and look at the filter to see if it is still full of gas. If it is empty I would recommend you re-route the fuel line away from the hot exhaust and try it again.