Fuel pumps??

I am having a gas flow issue with my 6 cyl. 1939 Flathead Plymouth. I had to replaced the original gas tank, which had a bottom gas outlet, with an after market gas tank that has a top gas outlet. The mechanical fuel pump could/would not pump the gas from the top outlet tank. Therefore, I replaced the mechanical fuel pump and installed an electric inline fuel pump(as far back and as close to the tank as possible). I have gone through three fuel pumps and suspect that the pumps are heating up and subsequently burning out. Would it be all right to re-install a NEW mechanical fuel pump along with a NEW electric fuel pump. My thinking is that the two will help solve the problem of getting gas out of the top outlet. You can e-mail me at jpzz1@earthlink.net or reply to this post.

Your input and help will be greatly appreciated.

Chrysler products of the late forties and early fifties had a high mounted fuel line from the tank. It shouldn't make any difference if you have a good fuel pump.

I would check that fuel can flow freely from the tank, the tank pickup is not plugged, blow out or replace the fuel line from the tank to the pump, and use a good stock fuel pump.

The fuel line from the pump to carb needs to be routed correctly and a stock heat deflector used between the pump and exhaust manifold.

Also check that the gas cap is vented or the tank is vented.

You should have no trouble with the stock setup except possibly in extreme hot weather because of gasohol.

Rusty,

Thanks for the info. and insights.

I failed to mention that I have an inline fuel filter between the tank and the fuel pump. Do you think that the fuel filter is restricting the flow of the fuel, perhaps making the pump heat up and and could be solved by placing the fuel filter ahead of the fuel pump and before the carburetor?

It's not restricting the fuel flow if it is not plugged up. Who knows if it is. As I said, I would check that the line is clear from front to back, and fuel flowing from the tank. Then depend on the stock fuel pump. It doesn't matter where you put the filter if it is not plugged up.

Because of gasohol and other substances added to today's fuel, an old fuel pump diaphragm can dissolve in the new gas. If the pump has been rebuilt within the last 20 years it is probably ok but if it is older than that it makes sense to rebuild or replace it.

They made and sold millions of those motors in cars, trucks, military vehicles, industrial equipment etc etc etc. If the fuel pump was weak they would have found out about it and fixed it. There is nothing wrong with the stock fuel pump. I hope that is clear. Your problem is not caused by the stock fuel pump being inadequate.

So, what is causing the problem? I don't know because I am not there looking at the car but I can suggest where to look.

1) fuel line from the tank plugged

2) fuel line to the fuel pump plugged

3) fuel filter plugged

4) gas tank cap vent plugged

5) fuel line from pump to carburetor exposed to exhaust manifold heat and not protected by factory supplied heat shield, or not routed in the factory approved manner.

If everything is working correctly and installed in the factory approved manner you should have no trouble, except possibly in extremely hot weather. Today's fuel is more prone to vapor lock than fuel of old but this does not show up unless the outside temp is over 80 and you take a long drive and get the motor good and hot. Even then, you probably won't have a problem.

There is one other possibility I did not mention and that is a leak somewhere in the fuel line between the pump and the tank. If the fuel line is sucking wind the pump will never prime and never work properly.

Running 2 pumps in series can give you way too much pressure. Your carb works best on 2 or 3 pounds. If you have 2 pumps each putting out 4 or 5, you can have 8 or 10 PSI to the carb which is way too much and will flood it out.

Interesting. Could you elaborate for those of us who have not thought this through? I understand the basics of how the check valves work and that the spring tension determines the pressure rating. Thanks

Thanks to all for all the input. The problem was with a sticky carb. float.

Joe