1938 Buick

My father in law is trying to hunt down the problem with his 1938 model 41 with the 248 cu. The car will act like its not getting enough gas when traveling at a steady speed. It kind of jerks back and forth but if he pushes down on the gas pedal it seems to run fine. This only happens when trying to stay at a consistant mph. Very noticable aroung 30 mph or so but will do it even at 55 mph. Carb has been rebuilt and the in line filters have been changed going to the fuel pump. Timing has been checked and new points installed. No change. Any ideas?

Hi,

1. fuel pump

2. coil is intermittent

3. fuel pick-up clogged by stuff in tank

4. cap cracked

5. Cap has carbon tracks inside

6. Condenser shot

7. Fuel float level off, or fuel float sinks

8. Ignition plug wires shot/coil wire shot--look for fireworks under the hood at night

9. Distributor shaft bearing worn--shaft wobbles

10. Gasohol fuel is boiling--insulate fuel line.

--Tom

11. Air leak at the Manifoldgasket.

Reminiscent of a problem I had. Jerky running while coasting at say 30mph on the flat. No problem under power. A wee bit of air was getting in where the carb bolted to the manifold. Tweek the car hold-down nuts before you dig deeper.

An easy check is to spray WD40 around the intake manifold and carb flange while at idle. If the engine speeds up, you found the leak.

Wire in dist from side connection to points. They are cloth wrapped and the retard-advance movement of breaker plate eventually wears a hole in fabric. Tough to find problem.

Bill

Hi,

Good insight, Bill. I had that happen on a 1950 Studebaker--took me a lot of investigating to find it.

--Tom

Hi, I had the same problem a few years ago with my '39 248 engine. I could not pin it down, so of course I started replacing all the ignition, then the carb, no good. A friend of mine mentioned that years ago his father had a'46 Cadillac with the same problem. Turned out to be sticking valves. I started using Marvel Mystery Oil in the fuel, about 8 ounces at every fill up. It took quite a while, maybe 6 months, but it runs great. Now I am down to 4 ounces per fill up, just to maintain the good running.

Just my 2 cents worth.

Gary