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Fass blows out seal on primary fuel pump

I have a 2006 Century with a MBE 4000 450 hp engine.

Last year I installed the FASS fuel system. Within four days the seal blew out on the engines fuel pump. This is a gear pump that has a weep hole on the bottom side of the pump. The fuel was shooting out under pressure, when I switched off the FASS pump the fuel stopped shooting out but it still dripped. The engine was five years old so I thought it was a co-incidence.

Last week it blew out again. I did check the fuel pressure off the FASS and it is correct at 6 psi.

Anyone else having their pumps blow out seals?

Answer this question I have this problem too

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8 Answers

I am not sure what FASS model you have but I know the model I purchased for my Series 60 Detroit was set at 16 lbs of fuel pressure and could have it bumped up to 28 lbs. So are you sure its only 6 lbs.

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Oops, Your Right it was 16 psi, I miss typed.

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Allan I am not sure what could be the problem but I did take my FASS system off cause I was having other problems. I can also tell you that the last time I was in my local Detroit Shop they had 3 FASS systems sittings on there counter that they had to take off cause of problems with running properly.

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If you have a FASS for sale, let me know!

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for the coin you had paid for The FASS system ...did anyone call them?

Because now i don't want one....

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I sent mine back to FASS and they rebuilt it even though it was brand new but still had problems so I decided it wasn't worth the trouble.

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I emailed them but never got a response.

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Allan FASS is not one of the most customer oriented companies to work with. Just their customer service is enough to keep myself from buying their product again.

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you have a fass that is showing correct fuel pressure, yet it is too much pressure for the mercedes fuel pump seal/gasket? i have never had that problem with my fass on my ddec 3 detroit. it seems that the problem is the quality of gasket and/or pressure on it, because fuel leaks there before at the relief valve (weep hole), for which the design purpose is to let off excessive fuel pressure. i don't know the exact design of a mercedes pump, and where it connects (to the gear case or air compressor?), but you might could install higher grade mounting bolts (grade 8, or stainless steel) to be able to increase the torque on them, and thus pressure on the gasket. a thicker, higher quality gasket i would think would help. napa sells small rolls of high quality thick paper gasket that you cut your own, which i use because most often gaskets that come with auto parts are lower quality.

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It has a metal gasket. It is mounted on the back side of the front cover. It is a small gear pump very similar to the Detroit.

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Sorry, but 16 psi of pressure should not be blowing any seals.

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Everybody is unhappy with FASS but no one wants to sell!! What gives??

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I sold mine about 3 months after I bought it.

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I've been running mine for about five years, now. I'm certainly not unhappy with it.

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I know two different guys that have FASS just sitting on their workbench in the shop, the units used to be on the trucks, not sure why they took them off, but they did.

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I still have it on, I have the pump wired to a switch, so I have the electric FASS pump shut off right now and just using the filters in a normal manner.

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Allan will be eternally grateful.
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