Packard Forum Index » Post-War (1946-54)

My engine is running very poorly when I accelerate at all. I have a slight grade in my road and it runs really rough.
In the shop it starts fine, warms up, idles good. I can run the engine up ite seems to be running good. I can speed up the engine.
The engine is not the best. I have low compression like 85, with 1 cylinder lower than that.
I set my timing and and I think I have it set correctly. I replaced my fuel pump with an electric pump. It seems to pump right up when I start my engine.

Sounds like ignition troubles to me. Maybe the coil?

Does it stumble on all acceleration or only on initial acceleration under load?

My '54 did that on initial acceleration (like from a stop). It turned out I had a torn accelerator pump in the carburetor, so it wasn't getting the squirt of fuel it needed.

That's an easy thing to check. Take off the air cleaner, open the carb butterfly, and look in. Manually move the linkage like you were accelerating quickly. You should see a squirt of fuel from the jets. If not, you probably have a kaput accelerator pump. This can be done without the car running.

Very likely a bad accelerator pump as Kev said. Fortunately also very easy to check.