1971 F-100 with 302 Issue with dying at idle after running at higher speeds

[bsneyd1]

I just recently bought a 1971 F-100. It has a 5.0 302 motor and is a 3 on the tree three speed.

When I drove it home and for the first several hundred miles, it ran fine. It leaks some oil from the PVC valve and possibly from somewhere below that, but that didn't seem to cause immediate issues.

Long story short, I took it out one day and it started acting like it didn't have any gas. When I pushed the pedal, it would hesitate, sputter, ect. This got worse and worse over the course of a few days. During this happening, the truck died at an idle while at a stop sign after I'd been on the interstate for about 30 minutes. Also, the turn signal light that always stays on is flickering. And lastly, it seemed to take longer and longer to get the truck to crank; I had to push the gas pedal a bit while cranking to get it to start.

So I thought maybe I got some bad gas or got water in the tank because of heavy rains and a faulty gas cap, so I changed the fuel filter and the air filter. I put some octane boost in the next time I filled up. This seemed to solve the problem for a couple of days. The truck was running fine. The hesitation had gone away almost completely and the truck seemed to run better than when I first got it.

But today when I went to work, I was on the interstate for about 30 minutes and the truck died at an idle at the stop sign directly after I got off the interstate. I cranked it up and it started but it was slow to start. When I went back home after work, same thing: it died on the off ramp coming off the interstate. This time it was harder to get started. Then it died at a red light a half mile down the road, and I just barely got it started. The engine seemed hotter than normal but not hot like it was overheating. Also, a bit of coolant had come out of the radiator at the overflow (not sure what it's called) just under the radiator cap.

One other thing to know about this truck is that the master cylinder leaks badly.

I've read posts on here about people with similar problems but they seemed to be having an issue getting fuel into the fuel filter. That is not the case here, as every time my truck has died, the fuel filter has been almost full.

Does anybody have any suggestions about what is wrong and what I could try next?

Thanks.

[sargentrs]

First I'd check for vacuum leaks with a can of starting fluid/ether. Pull your spark plugs and see if they're wet or look like they're firing correctly. After that I'd make sure the throttle vanes are set and opening/closing as they should. Before I tear it apart, I'd hook up a vacuum gauge and tune the carb. While it's hooked up, tweak the timing. If all that checks out and it's still acting up, rebuild the carb.

[390xlt]

I had a similar problem and it turned out to be the condenser. Would run fine for a while, but it didn't like the heat. Perhaps it's running fine on the highway, but heats up too much once the air stops circulating under the hood. Not sure that's it, but it's worth checking.

[bsneyd1]

Thanks for the ideas. I looked up some stuff about vacuum leaks and that sounds very possible. I'll look into the condenser. And a good tune up couldn't hurt anything. I think the truck sat for a LONG time before a guy got it running maybe 2 or 3 years ago, and then it sat for almost this whole past year in the yard of the guy I bought it from, so a lot of it seems like it's problems from sitting around so much. I'll try the stuff y'all suggested and we'll see how it goes. Thanks again.

[derekm803]

I've got the same truck as urs. 71/302/3 on the tree. Mine didnt like to idle at stops either til I put a new carb on it from guaranteed carburetors. It runs great now. Hands down the best money I've spent on it so far.

[Mach428]

I've had this problem before with other cars. It was the vacuum advance in the distributor. I would check by sucking on the hose going to the breaker plate and make sure that it moves freely and holds vacuum. Also, the vacuum advance line should be connected above the throttle plates.