Electric Fuel Pumps Before Racors on Trawler

[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? There doesn't seem to be a way to turn them on independently so I'm assuming they tie into the ignition circuit somehow.

[DeepFrz]

The fuel in Racor filters shouldn't be under pressure. They may be there to fill the filters after a filter change or if you have a long lift from the fuel tanks to the filters the on engine pump might not be strong enough.

[Boracay]

The instructions on the electric pump I put in required it to be after the filter.

[Simes]

I agree that the pump should be AFTER the filter.
As fuel is passed through a pump the sudden change of pressure and the disturbance of the liquid flow will probably emulsify any water present with the fuel. This will then allow the water to pass through the water separator and on into the injection system

Fit the pump AFTER the filter then the water will be removed from the system before it get to any of the expensive vulnerable parts (including the pump).

Simes

[Fuss]

+ the fuel is under vacuum through the filter so less likely to leak when filter before the pump.

[plottie]

Hey great post we have the same setup and are puzzling the possible alternatives. We have inherited a small electric pump before the Racor filter, and coincidently?! a rusty failed injector pump. Simes do you think this would atomise any water in the fuel? Reversing this would i think? create a vacuum... So how would the racor floating ball deal with that? Just exploring and interested in opinions

Heather & Neil

[westsail42]

I am with DeepFrz on this one. Whether this setup is "ok" or not may depend on what the pumps were originally intended. You indicated there is already a pump on each engine, so these don't appear to be for getting fuel to the engines. Sounds like they might be "priming" or "recirculating" pumps? Are the pumps always on when engines are running or manual switched? Is there some sort of overflow valve after the racors but before the engines? Answers to these may give some idea of what the pump is for.

[doug86]

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.

[DeepFrz]

Oh, my bad, I missed that last sentence about not being able to disable them. I would take them out then. They really aren't needed to run your engines and they pose a risk should you develop a leak anywhere upstream.

The fact that they could clog up the fuel line could also get you in a lot of trouble.

[kazenza]

This is very helpful. Having some diesel rebuild experience, I hadn't seen anything like this before. I'm trying to completely refurbish and simplify the existing fuel system. Is it difficult normally to get enough fuel to fill the racors after cleaning and maintenance.

Randy

[David M]

After. Normally off.

[donradcliffe]

Before. Normally off.

[Brazil]

Originally Posted by David M

After. Normally off.

A pump installed after the racor does not help you on bleeding the system or replacing elements . Imagine having to close an empty racor and then start the pump sending all the air trought your lines and engine. If you are worry about the pump clogging install a small prefilter or strainer. All this installation should be on bypass line and to be used only to change filters or on emergency to overcome a clogged racor.

[David M]

How does having a pump not help you pull fuel through the filter? That is the whole idea of the pump.

My engines have built in electric bleeding pumps where all I have to do is turn the key switch and the fuel system bleeds itself all the way from the fuel tank to the injector pump....when this is needed.

[DeepFrz]

Brazil, do you realize the complexity you are advocating? All so you don't have to fill a filter with fuel from a jug.