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37 LaSalle--Proper Electric Fuel Pump Use

Started by frank37, August 08, 2017, 07:48:09 AM

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frank37

I have a 1937 LaSalle with an Airtex electric fuel pump mounted near the fuel tank. The stock fuel pump is on the engine, rebuilt and works fine.  The electric pump was put on as an aid if vapor lock should occur.
Question is--- is it ok to leave the electric pump running all the time as an assist to the stock pump or could that push too much gas through the system ?  thanks   Frank Pezzimenti

























thanks....  Frank Pezzimenti --

HerbP

#1
I've been wondering this as well.  I also have an Airtex pump on my '40 LaSalle for the same reason as you.  I've been told by a reliable source that a carburetor in good working condition should be able to take the additional pressure, but I do notice a fuel smell when I shut the motor off immediately after using the electric pump and am wondering if I should install a pressure regulator.

Following with interest...
1940 LaSalle 5019
.
This stuff is FUN!
:)

Jeff Rosansky CLC #28373

I am also following this with interest as I am at that point on a 55.
Couple of questions that I think will need too be answered---- How is the electric pump plummed in? In series or has another line been run?
As of now, is it on all the time? If so then how do you know the mechanical is ok? Maybe worth shutting down the electric and running it on a hot day to see what happens.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Bill Ingler #7799

What are your reasons for running an aux pump the same time as the engine pump? The primary purpose of an electric aux pump, when I started using one, was to eliminate a vapor lock in the fuel system. Another purpose is to fill the carb and lines with fuel after the car has been sitting for a long period. The only time I have run the aux pump at the same time with the engine pump is on a couple of tours in Colorado and Arizona. Climbing some steep grades, I would turn on the aux pump knowing that I will probably get a vapor before I get to the top.  Other than climbing or operating at high altitudes I see no reason for running both pumps at the same time.     Bill   

Steve Passmore

Quote from: Bill Ingler #7799 on August 08, 2017, 11:26:11 AM
.  Other than climbing or operating at high altitudes I see no reason for running both pumps at the same time.     Bill

Me neither.
Steve

Present
1937 60 convertible coupe
1941 62 convertible coupe
1941 62 coupe

Previous
1936 70 Sport coupe
1937 85 series V12 sedan
1938 60 coupe
1938 50 coupe
1939 60S
1940 62 coupe
1941 62 convertible coupe x2
1941 61 coupe
1941 61 sedan x2
1941 62 sedan x2
1947 62 sedan
1959 62 coupe

Glen

I can you tell my father had an electric pump on his 1938 Cadillac that was always on when the ignition was on, and he never had any problems with it.  He insisted he needed it because the car was too long.  But I think he put it there to eliminate vapor lock. 
You cannot use an electric pump that exceeds the design pressure of the carburetor.  If you do the float valve in the carb will be over powered and you will have flooding issues. 
When the two pumps are connected as you propose the pressure at the carb will be that of the most powerful pump, the two do not add together.  If the electric pump has a pressure the same as the mechanical pump the mechanical pump will not pump, the diaphragm will be extended by the pressure of the electric pump.     
Glen Houlton CLC #727 
CLCMRC benefactor #104