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Old 11-12-2012, 08:17 AM   #1
Registered User
Join Date: Jul 2012
Location: Liverpool
Posts: 1,523
My Ride: 320i SE Coupe
WHY should you change your fuel filter?

I have read on many occasions that fuel filters should be replaced and I have thought "Ok. When its been on there for a while I guess it wouldn't do any harm I suppose". But then another voice in my head says "Hey. We are talking about petrol here. There can't be anything cleaner outside the passenger area than the fuel tank and the petrol you pump into it. So where's the advantage?". Right? So where would the alleged crap come from to block up the filter?

Anyway. I went out and bought a new filter. Exactly the same as the old filter. Got it home. Took it out of the box and, just out of curiosity, blew through it. There was absolutely no resistance to me blowing at all. Like it wasn't there.

Its now on the car and I have the old one in my hand, drained of petrol of course. So I have blown through that to see if there is any difference.

Knock me down with a feather!!!!! Have you ever tried to blow up a balloon? You know that tough bit where you have to get it to start off and the air goes everywhere except into the balloon? Well not as bad as that but not far off. So there is a CONSIDERABLE resistance to air flow in the old one. So much so that I wouldn't like to be the fuel pump having to push fuel through it towards the injectors. That's got to be hard work.

I am suddenly aware that this must inevitably have an impact on performance. In fact, having been for a run, it now goes like sh*t off a shovel. (That's a British expression. Means FAST. It comes from the olden days. Days of terraced houses and untethered dogs what used to roam the streets sh*tting at liberty. The solution was to scoop up the crap on a shovel and flick it into a the realm of the dog's owner. Preferably so that it hits the front door keyhole. I was an expert. Its all in the wrist action!)

I suppose it will be injector O-rings next (the ones on the inside of the injector not the outside) unfamiliar, as they must be, with having to confront an unrestrained fuel pump. I shall keep an eye on them. Dribbling may be imminent.

So there you go. Mine eyes have been opened. Change that fuel filter guys. This still doesn't explain where the crap comes from. I am going to try and split the old one open and see what's in there. I will post some pics of the guts of the old one in due course.
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Last edited by RayPooley; 11-12-2012 at 09:01 AM.
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