# Walbro inline pump, can you install before fuel filter?



## WeeZFan69 (Aug 3, 2003)

I have a MK2 VRT, I have a MK3 VR gas tank with a VR pump in it, I'm running #36 injectors so I may push the limit of the stock pump, I'm going to add a Walbro 255 inline and keep the stock intank pump. Theres not alot of room there under the car to put the pump and the filter, the pump would fit alright before the filter but I think that its better to install that second pump after the filter. So that there is no restriction? But I'm just not sure so I'm wondering which is better having the extra inline pump before the fuel filter or after?


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## Bthornton10 (Apr 27, 2008)

Some people put fuel pumps under the hood right near the fuel rail and it also eliminates the sound of the pump.


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## WeeZFan69 (Aug 3, 2003)

anyone else??


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## BLSport (Dec 24, 2005)

You can install it before the filter, and I actually prefer this orientation; the filter is the last component in the fuel supply prior to the injectors, same as the factory design. 

Regarding flow restrictions, think of it this way… If the inline pump were the only pump in your system, it would be preferable to have any restrictions to flow (i.e., in this case, the fuel filter) located after its outlet, rather than before its inlet; the pump is much better at pushing fuel, than pulling fuel. 

The factory in-tank pump is the weakest link in this setup, hence the addition of the inline pump in the first place. The in-tank pump does not pose a flow restriction to the inline pump however, provided it doesn't need to develop outlet pressure. It can flow considerably more fuel when its outlet is at zero (actually less than zero; negative) pressure, than it can if it is required to maintain outlet pressure, as it must when it is the only pump in the system. Any restrictions between the two pumps, would only serve to increase the amount of work the inline pump must do at higher flow rates to pull fuel; again, not one of its strengths. 

Would the inline pump work if installed after the fuel filter? Yes, and I believe many folks have installed them in this manner. The difference in ultimate flow capability between the two different orientations, if any, would likely only be realized closer to the inline pump's upper limits.


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## Dub-Nub (Sep 27, 2005)

I have my bosch inline inside of my fender to eliminate sound. 

The inline can be installed before or after the fuel filter...doesnt really matter.


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## WeeZFan69 (Aug 3, 2003)

Awesome, than I shall install it before the filter, I was moreso even thinking is the fuel filter going to be able to take what the new inline pump is going to be pushing through it? and also I'm sure it would be better if the filter were before the pump just to keep any pieces of dirt from going through the pump. But as far as flow restricitons go they are about equal then...


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## BLSport (Dec 24, 2005)

WeeZFan69 said:


> and also I'm sure it would be better if the filter were before the pump just to keep any pieces of dirt from going through the pump


 When installed before the filter, the inline pump shouldn't be subjected to any more debris than the in-tank pump, which has a pick-up screen installed to keep the larger stuff out. 

FWIW, I believe Walbro's in-tank replacement pumps, at least some of them, are of simliar design to that of the inline pumps, and the only filter before their inlet is the pump pick-up screen.


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## slcturbo (Apr 19, 2010)

C2 recommends before the filter. That's where mine is. No problems.


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## WeeZFan69 (Aug 3, 2003)

installed it before the filter... works good :thumbup:

feels good to have that second pump in there.


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## pimS (Jan 7, 2009)

Got mine before the filter, 

Also eliminated the rather iritating sound of the pump, by hanging it up in some rubber bushings.


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