Originally Posted by kazenza
I am redoing my fuel system from the tanks to two Ford Lehman
120's on an older trawler
. the lines coming from my tanks both have small electric
fuel pumps just before they get to my Racor centrifugal filters which then feed to the fuel pump
on the engine.
Is this a typical installation
and do the racor's need that much extra pressure in order to perform properly?
No, it is not typical for FL120's, but not unknown either. The FL120 mechanical lift
pump is plenty strong enough to bring fuel from the tank to the engine. The Racors don't require any "feed pressure" at all.
Some folks installed electric pumps inline before the Racor to facilitate re-filling the Racor bowl after changing the filter cartridge. The electric pump would only be turned on then, and left off during normal engine operation.
Be aware that those electric pumps have a filter inside, and it will get clogged. You can unscrew the bottom of the housing and you will find the filter there. Putting the electric pump BEFORE the Racor means the pump's filter is the first to see any dirt coming from the tank. For this reason, the best way to plumb an electric pump used to prime the Racors is to use some valves that allow you to bring the pump on-line in the fuel system only when you need it, and isolate it from the fuel lines when it is not in use.
Having an electric pump plumbed this way also makes a good emergency
backup if your mechanical pump should fail. You can energize the electric pump and it will keep the engine running until you can replace the mechanical pump.
There doesn't seem to be a way to turn them on independently so I'm assuming they tie into the ignition circuit somehow.
That is possible. Many Westerbekes are wired that way, because they don't have a mechanical lift pump. But again, not needed on a FL.