I have a very low mileage '79 E-150 with 4.9L six, Carter 1 bbl yfa carb and manual OD trans.

Last week I bought a tank of gas and drove home. 2 days later I drove it about a mile (cold engine) and it suddenly lost power for a few seconds while accelerating. It recovered but ran rough for a minute. About a mile later when I turned into a driveway and depressed the clutch to downshift it died but restarted, then ran okay after that. I drove home okay.

Since I had a new ignition control module I swapped it out for the old one. I drove it a few times locally and it seemed fine.

Today I drove about 30 minutes from home and it suddenly lost power while accelerating. The engine kept dying whenever it slowed below 1000 rpm so I had to restart it every time I came to a stop or depress the clutch and keep the engine running about 1200 rpm or higher.

I turned around and managed to drive it within 6 miles from home this way before I parked it and called my brother. He got there an hour later and the engine was cold. It started right up and ran at fast idle okay, though it sounded rough. When it warmed enough to come off fast idle though, it kept dying.

Since it's a van, we couldn't look into the carburetor without a mirror so he drove me home for one. When we got back we took the distributor cap off and cleaned a small bit of corrosion off the rotor and pulled the air cleaner.

It cold started on fast idle and had a good stream of gas in the carb so the fuel filter and pump were working okay. And then it warmed up and went to normal idle (700 rpm) and ran normal. I drove home without any problems.

In the past 3 years I replaced almost the entire fuel system: Tank, sending unit, rubber fuel lines and filter. The pump is about 15 years old but has only a thousand miles on it.

The coil, distributor cap, rotor, plug wires and plugs are nearly new and I just replaced the aforementioned ignition control module.

The carb was rebuilt by a carb shop several years ago and has less than a thousand miles on it.

Since this problem happened twice now and we really didn't do anything to it I'm left wondering what the problem is. Water in the gas? We have ethanol gas here but I always add StarTron ethanol treatment to it.

 

Reads like a classic case of water in the carb. Find out if the station owner has had gas delivered recently, filling the underground tanks can add water and stir up the water at the bottom of the tank.

The water ***** up in the floatbowl of the carb and will roll over the jet instantly shutting off the fuel. If the water sloshes off the jet, fuel flow will return as the water settles into a low spot in the floatbowl.

Pull the fuel line at the carb, attach a hose and crank it until you get about a quart. Let the fuel sit and watch for water settling to the bottom. If you find water, drain and drop the tank to clean it. There is no other way. Carb and lines have to be cleaned as well. jim

 

I got the vacuum gauge to check the vacuum only not the timing but I understand what you mean. I thought about checking for water in the fuel but didn't really think it could be causing these symptoms but I suppose anything is possible. I was driving it around bedless while we were doing the body work on it so it's a good possibility. I'll try that and see where it gets me. Thanks everyone for all the tips and diagnosis I really appreciate it.