Bypass mechanical fuel pump

lvflyer

New Member
Hello - It seems I may have a problem with my mechanical fuel pump. I was wondering if anybody has bypassed the mechanical fuel pump after installing an electric fuel pump?

Thank you in advance for your replies
 

dougklink

Member
I did. I actually removed the drive arm and replaced the rubber diaphram with a sheet metal plate and rubber gasket. Still looks the same but the fuel just goes through it, the electric fuel pump is up front.
 

lvflyer

New Member
I also was wondering if I just install the low PSI electric fuel pump in the front after the electric 12V fuel shut off valve and then it would be before the mechanical fuel pump in the back, I would not have to disturb the fuel line going into and out of the mechanical fuel pump or the mechanical fuel pump itself. Would that be OK and have other people done that?
 

Jon Kanas

New Member
I recommend the use of a low pressure electric fuel pump on any older collector car as a supplement to the mechanical pump. If your mechanical pump and carburetor components are in good shape, the addition of the electric pump will not cause problems, and will make the car much more serviceable.

I have several old (pre-war) cars, and have gradually installed supplemental electric fuel pumps on the ones that I drive regularly. I install a suitably low pressure electric fuel pump, near the fuel tank, to feed coolest possible fuel to the mechanical pump. This enables me to effectively prime the engine when it has not been run in awhile, reducing cranking load on the battery and starter etc.

In a couple of cases, adding the supplemental pump caused the original fuel pump to leak. These leaks were due to ethanol in modern fuels consuming the rubber diaphragm of the mechanical pump. I then rebuild the mechanical fuel pump with Viton (ethanol resistant) components which solved the problem. Newer fuel pump rebuilding kits will contain Viton (or other ethanol resistant) components.

A related issue is that ethanol laced fuels also damage the accelerator pump components in the carburetor, necessitating rebuilding the carburetor with Viton soft parts.
 

RalphF

Member
I also was wondering if I just install the low PSI electric fuel pump in the front after the electric 12V fuel shut off valve and then it would be before the mechanical fuel pump in the back, I would not have to disturb the fuel line going into and out of the mechanical fuel pump or the mechanical fuel pump itself. Would that be OK and have other people done that?
That is what I did. If you do end up removing the mechanical pump, here is a source for the blanking plate and gasket
 

lvflyer

New Member
I recommend the use of a low pressure electric fuel pump on any older collector car as a supplement to the mechanical pump. If your mechanical pump and carburetor components are in good shape, the addition of the electric pump will not cause problems, and will make the car much more serviceable.

I have several old (pre-war) cars, and have gradually installed supplemental electric fuel pumps on the ones that I drive regularly. I install a suitably low pressure electric fuel pump, near the fuel tank, to feed coolest possible fuel to the mechanical pump. This enables me to effectively prime the engine when it has not been run in awhile, reducing cranking load on the battery and starter etc.

In a couple of cases, adding the supplemental pump caused the original fuel pump to leak. These leaks were due to ethanol in modern fuels consuming the rubber diaphragm of the mechanical pump. I then rebuild the mechanical fuel pump with Viton (ethanol resistant) components which solved the problem. Newer fuel pump rebuilding kits will contain Viton (or other ethanol resistant) components.

A related issue is that ethanol laced fuels also damage the accelerator pump components in the carburetor, necessitating rebuilding the carburetor with Viton soft parts.
Thank you Jon. I installed a 2.5-4 PSI electric fuel pump right after the fuel filter coming out of the fuel stopcock. I found that my mechanical pump was not working because after I disconnected the fuel line to the carburetor, no gas was coming out while I cranked the engine OR pushed the mechanical pumps manual lever. After I installed the electric pump, gas was going to the carburetor.
 
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