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electric fuel pump

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Im thinking in install a electric fuel pump to prevent vapor lock during hot weather. It happend last summer when the car was really hot and i guess it was fault of the mechanic fuel pump.
Now i just don't know which fuel pump to install. one friend told me it was fuel pumps with pressure or with impulses.. pressure was better. it's true? which pressure i need? i have a 767cc engine but with a weber 32dmtr and a fiat uno 45 head (bigger valves).

How to install this? can it work together with the mechanic? i was thinking in install near the gas tank.. should i remove the mechanic forever? how to eliminate it? can ij ust put a pipe from the in to the out of the pump? or it's better remove it and put a metal plate in place?

Should i install the electric pump.. or no?


I may be wrong, but I don't think an electric pump will prevent vapor lock. Vapor lock occurs when the gas in the fuel lines up by the carb gets hot enough to vaporize.  To prevent that you have to have a constant flow situation in the fuel line, so cool fuel from the tank is constantly flowing thru the line by the carb.

This is done by having a fuel line that returns to the top of the fuel tank. Somewhere near where it reenters the fuel tank you have a small orifice so pressure is maintained in that line. From this line you have a T connector that supplies the carb.

So you would need to have 2 fuel lines running between the tank and engine and another opening of some kind in the top of the tank for the return hose.

Jim Oddie

Paul vander Heyden:

Modern fuel injection systems use the type of system that Jim describes.  Weber carburetors, for the most part do not use this system.  The problem is two-fold.  First there must be enough pressure to operate the needle valve that is operated by the float.  For this type of system to work you would need a low pressure 'bypass' type regulator, not simply a pressure regulator.

It does not really matter whether the pump is a pulse type or a constant impeller type.  I have used both successfully.  Here are the things to keep in mind.

1.  You must have have both flow and pressure.
2.  Pressure should not be more than 3-4 PSI.  This generally means an adjustable fuel pressure regulator in line.  Malpassi - Filter King make a combination regulator/filter that I think is very good. The fuel system is much like your cooling system.  When it is under pressure it will tend to vaporize less easily.  Once it vaporizes, no pump is capable of pumping it.
3.  Route fuel lines away from hot areas in the engine compartment.  Yes, the standard Fiat arrangement is not the best.  If need be get some heat shielding and put it around the fuel line to the carburetor.  The cooler the fuel the more horsepower.
4.  Make sure fuel filters are clean.

An electric fuel pump should be located close to the tank, and if possible lower than the tank.  These pump will handle a small amount of 'head", but they are not designed to suck petrol all the way from the front of the car.  They are designed to 'push' fuel through the pipe.  If you are going to use an electric pump, then remove the mechanical one.  This keeps the fuel line away from the hot exhaust.

Diaphram type fuel pumps get tired.  The diaphram gets hard, they leak fuel, and they become inefficient. 

Hope this helps.

Paul Vanderheijden

Thanks Paul :)

my name is Lubo from Bulgaria, new to this forum.
I'm currently working on a 600D with 1050cc A112 engine, or abarth 1000tcr replica.
I would like to install an el.fuel pump.The only one that I found around is a HARDI ,12v, 100l/h, 0.15bar.
I will be running the engine on standart internals, the only thing that I might change in the future - a 36DCD or 40DCOE.
Would 100l/h and .15bar be sufficient for that set up?


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