Ideas for engine cutting out under load.

Posted by Redhexagon On 2022/10/3 2:30:21
I have a lot of experience with 1960's and newer cars, but not with Packards. I want to run my problem and thought process past you folks who have more Packard-specific experience than I do to see if I'm headed in the right direction for these specific cars.

My 1955 352 cuts out under load. Sometimes I can blow up hills at 70 mph with all the power in the world, and other times I cannot hold 40 mph on a level. It's getting worse, too. It actually stalled in traffic last week and refused to restart. All it would do was cough and spit on the starter, but it would not catch and run. I let it cool down for an hour with the hood open, primed the carburetor with a bottle of fuel, and got it started. It ran perfectly so long as I kept my speed down: I had to limp home at 40 mph like there was an egg under the throttle pedal or else it would cut out. I thought it was vapor lock, but it was only 60 degrees outside!!! I have never in my life seen a car vapor lock in weather that cool.

- I rebuilt the carburetor and distributor before I ever drove this car outside of my driveway for the first time.

- I've tried three different mechanical fuel pumps with no effect.

- The fuel line from the fuel pump to the fuel filter on the carburetor is routed away from heat sources and the fuel filter has been perfectly clean this entire time.

- The gas cap vents properly.

- I replaced the ignition coil and it made no difference. I even removed the RFI suppression capacitor attached to the coil in case it was causing a short, and there was no change.

- I blew back through the fuel line to the fuel tank from the fuel pump end with 90 psi shop air and got plenty of air flow through it, so I don't think the line was restricted. If it was, I blew the restriction back into the tank. Again, the fuel filter has remained perfectly clean this entire time, so I do not think my gas tank is filled with rust or sediment. HOWEVER: I have not driven the car since I blew back through the line to know if it fixed my problem.

I am starting to suspect the following:

- The new ignition condenser is breaking down when it gets hot and is causing a misfire. Defective made in China parts are a thing...

- Possible breaks or shorts in the primary ignition wires. The vacuum advance flexes them as it operates, and I've seen that cause freaky problems on other cars.

- Low voltage at the ignition coil, potentially caused by a faulty ignition switch, ballast resistor, or connection. Possibly a poor distributor ground. I have not done any voltage drop checks yet.

- Potential pinhole air leaks in the fuel pickup tube in the gas tank. It seems like all my problems have happened when the tank was less than half full, but I cannot be sure about that. I have not tested for it. This possibility is my 100% absolute worst fear because it is the hardest and most expensive thing to fix. I REALLY hope this is not my problem!!!

- Pinhole air leaks in the main fuel line between the tank and the pump, or the line might be routed too close to the exhaust.

Does this all sound about right to you?

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