Hello, I have a problem with a 1967 coupe , and I would like some possible solutions. I've been restoring it with my grandfather for three years now. What the problem is, is that after 25-30 minutes of running completely fine, the engine seems to suddenly almost die but not quite. It'll run really rough and I won't get any throttle response. Sometimes after a few minutes of running rough it will die. If I shut the engine off for a couple of minutes and restart it it'll run fine again. We've also had the issue of it suddenly quitting without any warning. That doesn't seem to follow any pattern though. Almost everything has been replaced in the engine bay. Its a new 302 engine, new carburetor, new 3 row radiator, and other stuff. The only things that haven't replaced is the alternator, power steering pump, and ignition system. The ignition system is a 26 year old mallory ( both the distributor and ignition coil). The vehicle did sit for 13 years in an Arizona garage (it developed a head gasket leak in our 289 which seized the engine and that why it was replaced). We did take it to a Mustang shop but they didn't tell us much regarding the problem because we asked them to help it pass emissions. They suggested we replace the primary jets on the carburetor (it is a edelbrock 1906 650 cfm) from .101 to .098. My guess now is that it might be the ignition system but I'm not sure. If anyone has some ideas, i would appreciate it very much.
PS: I am not currently with the car, so there is nothing I can quickly check. I would just like some ideas when I do go back to Arizona to fix it.
Sounds a lot like a bad coil or condenser (assuming it's a points ignition). Typically , in my experience, if a car runs fine when cold, but poorly when it's warmed up, the coil is breaking down, or the condenser is dying. Both are cheap, if it were me, I'd ditch the Mallory and put a rebuilt stock distributer in it, with a Pertronix conversion and coil. I have it in my car and couldn't be happier.
I have now replaced the coil and have yet to test it fully. I did start the engine real quick because it hadn't been turned in a couple of weeks, and after a minute of running fine it quit unexpectedly again. I did some other research and thought it might have something to do with the ballast resistor, but what i found says if a resistor goes bad the car won't stay at idle at all. This leads me to think it might either be the ignition switch or a wire short or... I wouldn't know what else. Any ideas?
Are you saying that it could be a fuel problem? I am fairly certain that I'm getting fuel to the carb because I have a clear filter in the engine bay that seems to fill just fine. I'll try to check the sock anyway.
Did you change out the condenser under the distributor cap as well, or just the coil? If it's points ignition - the points also need to be at least adjusted regularly if not replaced.
From what I've seen in the past, problems with dirty filters usually show themselves when the engine is loaded. They usually just reduce power, not cause the engine to die or run roughly. It would be worth looking at, though. When cars sit, there can be all kinds of problems caused by bad fuel or debris in the system. Rough running could potentially be from garbage in the carburetor as well if the carb hasn't been cleaned for a while.
Its been a while since I found the problem but I thought I might as well explain what it was.
I was draining the fuel tank in preparation to take out the fuel sending unit when I noticed this connected to the fuel lines. At first I didn't know what it was but soon came to realize it was a electric fuel pump. My uncle who had once driven the car before me had installed it but it had somehow been disconnected and wasn't even turned on when the car was going. I took it out and now she runs like a proper pony should. I got it registered yesterday and I am super excited. Thanks for all the help.