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84 245 Fuel Injected - 1 Fuel Pump Instead to 2??

Terry1941

New member
Joined
Sep 9, 2020
Location
Federal Way, Washington
Has anyone modified their fuel system to eliminate the in-tank pre-pump and the main pump and replaced them both with just one more efficient and easier to maintain inline pump? What is the purpose of having 2 of them?
 
Yes, people have modified their fuel delivery system to only have one pump. They usually use a fuel injection rated intank pump to supply all the fuel. The purpose of two pumps as stock is to provide a lift pump to provide the fuel to the main pump which makes the higher pressure needed for fuel injection. Volvo went to a single pump on the Rex/Regina cars.
 
I recently did this. Put a DW200 in-tank, ran new line from the tank to the engine bay where I put the fuel filter and jumper to the rail. Much more quiet and less power use than the stock setup.
 
Do you have to go with an in-tank pump or could a single line pump work just as well? It seems like it would be more efficient, maintenance wise, to not have to mess with an in-tank fuel pump?
 
Pumps don't like to suck, they prefer a flooded inlet.
If a pump has to suck too hard it will cause cavitation, which is very hard on the pump itself.
This is why fuel pumps are built into the tank.

The feed pump in the tank floods the inlet of an externally mounted pump.

An external pump (with no feed pump) will survive because they are mounted very close to or below the bottom of the tank.
However output volume capacity will fall off as the fuel level drops closer to the level of the pump.

Also an external only pump should have as short of a feed hose as possible and it should be a larger line to reduce any flow restriction.
You will note that many cars with an external pump have 10mm - 12mm inlet hoses (larger than the usual 8mm pressure line).
 
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