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Old 11-12-2012, 07:17 AM   #1
RayPooley
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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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Old 11-12-2012, 07:22 AM   #2
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The crap comes from the petrol tank at the station.

It wouldn't hurt to clean the pick up on the pump if you change it again in 60k and find the same amount of resistance.
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Old 11-12-2012, 07:49 AM   #3
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You will find next to nothing in the pump pick up screen. The screens are far more coarse than the fuel filter element.

I am a firm believer now that you really need to change the fuel filter every 30k miles as the paper element is rather fine and picks up all sorts of crap.

If you bother to cut open a fuel filter, you will likely find the inside element caked in a black sludge. Depending on how dry the filter is, the black will be an ultra fine powder that you can scrape off.

You will be surprised how thick this black gunk will actually get.
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Old 11-12-2012, 07:57 AM   #4
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You will find next to nothing in the pump pick up screen. The screens are far more coarse than the fuel filter element.

I am a firm believer now that you really need to change the fuel filter every 30k miles as the paper element is rather fine and picks up all sorts of crap.

If you bother to cut open a fuel filter, you will likely find the inside element caked in a black sludge. Depending on how dry the filter is, the black will be an ultra fine powder that you can scrape off.

You will be surprised how thick this black gunk will actually get.
I will leave it a day or two to dry off then take a hacksaw to it.
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Old 11-12-2012, 08:11 AM   #5
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I will leave it a day or two to dry off then take a hacksaw to it.
I'll do the same to mine and post pics in this thread. Will be changing it at 140k in a couple months, I am on my second filter I imagine.

Mine is from late 2009 so I'd assume it has about 60k on it

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Old 11-12-2012, 08:08 AM   #6
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...and a couple of other reasons to change it:

I read here that one fanatic had a no-start issue because of an original fuel filter not being changed up to 130K miles.

Also, when I did mine after an indefinite period of time (got the car as third owner), I got an extra 1.5 mpgs., so even if you pay someone to do it, you get a pretty short payback time.

If you don't know when it was done, start logging your mpg/mph data, change the filter, and compare the difference...bet you'll find a noticeable one.

Jfoj, I'm not sure about the 30K mile interval though...I'm thinking it's an Inspection II item, which I believe means 60K miles.
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Old 11-12-2012, 08:42 AM   #7
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Mine has 67k on it. I might keep it around to cut it open as well. I imagine mine is ****ed. I need new pressure regulator vacuum fittings as well.
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Old 11-12-2012, 09:45 AM   #8
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This guy is starting to see the PM light.
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Old 11-12-2012, 09:54 AM   #9
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This guy is starting to see the PM light.
Indeed.

It's funny that this is overlooked so often. There is a filter there for a reason, and that is gas is actually pretty dirty. Anything that's a filter, fluid, or moves/rotates a lot will always wear out at some point.
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Old 11-12-2012, 10:06 AM   #10
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This guy is starting to see the PM light.
I can't figure out how to respond to this. tell me waht the PM light is and I will let you know if I starting to see it.
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Old 11-12-2012, 10:28 AM   #11
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I can't figure out how to respond to this. tell me waht the PM light is and I will let you know if I starting to see it.
In a manner of speaking, it's also a kind of a Kool Aid light, if you're old enough know what that reference is about. It's pink, and it only comes on once, usually rather late in life.
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Old 11-12-2012, 10:44 AM   #12
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In a manner of speaking, it's also a kind of a Kool Aid light, if you're old enough know what that reference is about. It's pink, and it only comes on once, usually rather late in life.
You sure its not brown? This PM light. You know. The color of bullsh*t?
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Old 11-12-2012, 11:15 AM   #13
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You sure its not brown? This PM light. You know. The color of bullsh*t?
No. That would be the color of your fuel.
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Old 11-12-2012, 10:25 AM   #14
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It's both a night light to help you find your way to the bathroom at night, and it's the light you see, when your car is properly preventatively maintained...and you can bask in the glow from the security it gives you. Kind of makes me cry what a warm feeling that is!

This, btw, is not to be confused with the Mango light, which spells doom and foreboding, especially if you ignore it. We've lost many e46s because of failure to see 'this' light...aka the low coolant warning light.

The PM light is a spiritual light--only believers can see it!
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Old 11-12-2012, 10:32 AM   #15
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It's both a night light to help you find your way to the bathroom at night, and it's the light you see, when your car is properly preventatively maintained...and you can bask in the glow from the security it gives you. Kind of makes me cry what a warm feeling that is!

This, btw, is not to be confused with the Mango light, which spells doom and foreboding, especially if you ignore it. We've lost many e46s because of failure to see 'this' light...aka the low coolant warning light.

The PM light is a spiritual light--only believers can see it!


Yes there was even a short-lived thread about it!

http://forum.e46fanatics.com/showthread.php?t=937253
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Old 11-12-2012, 10:46 AM   #16
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Gas isn't perfectly clean, of course you'll need to change it every 60k or during Inspection II.

Also I wouldn't put my mouth on it
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Old 11-12-2012, 11:17 AM   #17
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Gas isn't perfectly clean, of course you'll need to change it every 60k or during Inspection II.

Also I wouldn't put my mouth on it
Its ok. I don't have any infectious diseases!!!!
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Old 11-12-2012, 12:31 PM   #18
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Its ok. I don't have any infectious diseases!!!!
It'll filter out any infectious diseases anyway. That's reasonable logic, right?

Right?!
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Old 11-12-2012, 12:59 PM   #19
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I use my stuff 'til it shows signs of failure, or when the manual says to change it. That's what they're designed to do. My car is a car, it's not an airplane in which PM is absolutely essential for the safety of everyone on it.

Except the ET, that catastrophically blows up. I changed that already.
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Old 11-12-2012, 01:41 PM   #20
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It is a good idea to replace the fuel filter as a PM, but not absolute necessity. There are million more things in our cars that requires absolute attention than the fuel filter. Expansion tank anyone?

I replaced mine at 150k a couple of weeks ago(as a PM), I dont know when it was changed last time. I presume it never. Got sprayed on the face with pressurized petrol. No harm done though. Just ended up smelling like petrol for an hour till I took a shower and prayed no one comes near me smoking a cigarette.

I didnt hacksaw the old filter or anything, but the fuel that came out of it was indeed dark.
I'd say absolutely do it, if you are noticing any fuel starvation issues or smelling petrol around your car. DO change the little rubber hoses and the clamps as well.

However, if you are not noticing any issues, then you can let it be. Take care of your bald tires and brakes. Those save lives, not fuel filter.

I am not a firm believer of fix it when it breaks neither do "replace it all" (sorry mango), but I do tend to replace stuff that I suspect are broken.

PS: I was expecting some gain in throttle response and a significant gain in MPG. Alas, I didnt notice any increase in gas mileage after I replaced it with a brand new one. In fact, I noticed my MPG went down by about a mile per gallon. May be its because of the winter blend fuel, but nothing changed in my car except for mpgs.

I guess you can even get away with washing the fuel filter with carb cleaner or throttle body cleaner properly. But who is going to do that? If I am getting under the car to change the filter, I will replace it and be done with it. No way I am going to clean it and put it back. I dont even know what material is there inside the fuel filter as filter substance. If its a metal mesh of some sort, you can certainly clean it.
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