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

Mechanical fuel pumps work through a double-check-valve spring-diaphragm system so just a slight fuel pressure should be enough to flow through both check valves and fill the carb.

How long do you leave it on? Might need to be 10 sec or more.

Unhook your fuel line at the carburetor, hold it over a can, and see if the electric pump pumps through.

If you have the optional glass bowl filter next to the carb you could also check and see how long it takes to fill that bowl. Modern gasoline -- at least the stuff sold here in Calif -- appears to be more volatile compared to the older 50s fuel. After you park the car the fuel sitting over a hot manifold tends to bubble or percolate away fairly quickly leaving an empty carb. In my cars sometimes the electric pump needs to run for several minutes to fill the tubing between the pump and filter and then fill the filter and carb float bowls. I usually keep it on while starting the engine and then after the engine is running and stable turn it off.

I know this is stating the obvious, but something is wrong.

a) You should not require an electric fuel pump, especially considering you have a rebuilt mechanical pump.

b) After sitting for only a day or two there should be more than enough fuel in your carburetor still to allow your car to start right up.

I don't understand the need for electric fuel pumps. I started my 53 Cavalier this spring after sitting for 5 months without priming it. To be fair it did have to turn over more than usual.

I just replaced the fuel line from the pump to my carburetor today, so that line was completely dry, and my car didn't miss a beat when I started it. (It hadn't been started for a couple of days.)

I've had many vehicles with mechanical fuel pumps and none of them ever needed an electric fuel pump.

Before the carb and pump were rebuilt, was the car running fine? When you say it doesn't start on a hot day, do you mean after it's been running, or just when it's hot out it doesn't start?

Maybe you have a vacuum leak? Carb not sealed properly to the intake? Maybe a bad accelerator pump? If you hold the choke open and pump the gas, can you see it spray into the carb?

Maybe the carb, or the fuel pump, or both, are faulty? Bad rebuilds happen. It sounds like you've gone through your entire fuel system, which is good, but it also makes it all suspect. Because once the car starts it runs, then it seems like the tank and fuel line to the pump would be fine. Also it seems that the fuel supply, which you can check, shouldn't be an issue either given you have a rebuilt mechanical pump which works when the car is running, and you also have an electric fuel pump. If after a couple of tests you find that you're getting lots of fuel supply, I would question if there is maybe something wrong with the carb.

All this to say, I don't think the problem was the lack of an electric fuel pump, which also means it's not the solution.

I only ever had one Packard with an electric pump (one should not be necessary) and it was the 6v diaphragm type (it was on my 1953 Clipper Deluxe when I bought it) so its check valves did not interfere with fuel flow when it wasn't running. It was also pressure- sensitive so even if it didn't have a switch, it could be left on (although it rarely was) as it pumped only when needed and then only a couple "bumps" when turning on the key and maybe an occasional one on the road. I can't recall if AC, Carter of someone else but I have accumulated several of them both 6v and 12v that I use primarily on a temporary bases for priming a freshly rebuilt fuel system.

Point of this rambling is that the modern vane type of pump can actually block the fuel flow BUT they should still provide enough to get the engine started quickly and that yours is not seems to imply that something else is wrong. Maybe check the flexible line before the stock pump which you can do only by removing it. It may seem nice and pliable on the outside but could have closed up on the inside. If it's okay, then maybe the screen inside the fuel pump is plugged.