Electric Fuel Pump location

[k76]

My car has an electric solid state fuel pump installed. Functionally it was ok, but the mounting is a bit dodgy(1 screw only on a flimsy bracket) so I plan to  redo it. I've read that electric fuel pumps should be installed low and close to the tank, mine is currently the opposite of this, high up just next to the carby. Since it was working fine I wonder if I should just secure it properly where it is, or move it somewhere to the back of the car. If I move it to the back should I install it under the car, or in the boot?
Also, with regards to track work: Is it better to wire it to a separate switch, or is it OK to have it wired together with the ignition?


Kris

[Colin Byrne]

Defiantly move it to the back of the car below the tank.  Fuel pumps are designed to "push fuel" not "pull it" . You want to make it as easy as possible for fuel to get to the pump (hence why you should only use a corse filter before the fuel pump).  Also make sure the orientation is correct, most pumps require the correct mounting position so that the don't get an air lock in them, if it's a facet pump (small and square) you need to mount it with the ports pointing vertically, which makes them a pain to mount under the floor

As for the switch keep it on the ignition otherwise you will forget to turn it off!  As far as track work goes its best to have it switched on by an oil pressure signal with a relay, or use a tachometric relay, so that the fuel pump stops when the engine stops rotating
Hope that helps

[k76]

Thanks Colin, that definitely helps. Now that I'm doing my own car I'm starting to think about details I haven't really thought about before, so forgive me for asking elemental questions. There will be many more to come!

I have to check tonight, but yes, it is a small & square pump. The tachometric relay makes sense, I will definitely get that in the circuit.

Since I will be modifying my fuel system anyway now, I might as well think about a surge tank? Are they necessary, or something you only fit if you start having issues with fuel delivery? I've also seen the foam cubes that are supposed to keep the fuel in place. It looks convenient except the fuel sender won't work anymore...



Kris

[Colin Byrne]

Assuming you have carbies, a surge tank is not really needed (unless you find a specific problem).  The float bowls in the carbie act as a kind of surge tank, because if the pump does grab a mouthful of air there is still enough fuel in the float bowl to keep the engine running until the fuel supply has returned.  An EFI system does not have this luxury as the moment the pump breaths in air, the fuel system looses the pressure required for the injectors to function and the engine will miss. 
Some people swear by the fuel foam, I will never use it again after it disintegrated and destroyed a pump on a race car I was working on, a properly designed tank shouldn't need it, and most of the Alfa tanks seem all right

[k76]

I didn't think about the difference between carbies and EFI in that respect, but it makes sense. Makes my life easier, I don't like fitting gadgets just for the sake of it.


Kris