E46 Fanatics Forum banner

WHY should you change your fuel filter?

12K views 102 replies 27 participants last post by  Mango 
#1 · (Edited)
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.
 
See less See more
#3 ·
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.
 
#5 ·
...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.
 
#66 ·
...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.
Sounds like me. Or someone had the same problem as me.

But yes it just suddenly wouldn't start. I ended up buying a new filter from Tischer and I have noticed no performance problems whatsoever.
 
#11 ·
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!
 
#13 ·
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!
:lmao:

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

http://forum.e46fanatics.com/showthread.php?t=937253
 
#26 · (Edited)
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.
 
#27 ·
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.
 
#28 · (Edited)
Im all for sensible (ie not all) preventive and reg maint. As a result Im enjoying driving my trouble free driving machine.

OP the paper element inside your old fuel filter dried up and expanded that is why there's restriction. It's like soaking plywood and drying it. It expands.

I bet if you pull your *new* fuel filter and let it completely dry, you'll get restriction just like the old fuel filter.

So advice on filters: Once wet, keep them wet if you happen to pull them out for some/any car work you're doing.
 
#35 · (Edited)
Finding a site that thousands of other people knew about before you does not make you an expert on spending wisely and neither does getting good deals. I could buy all new appliances on Black Friday and get great deals, but that doesn't mean I needed them or that I spent my money wisely. I think you know what I'm getting at, but I know you'll keep stepping around the issue. What you do with your money is your business. If you want to buy your car twice, then that's fine. It's just not worth it for other people. The shotgun approach is very effective, but it is not economical or very efficient.
 
#36 ·
Like I said, I've personally helped thousands of members here save BIG on parts. You don't understand Los Angeles. BMAparts and other companies like WorldPac primarily cater to Los Angeles independent mechanics. They are not a BMW vendor by any means. Their online store was little to NOT KNOWN AT ALL prior to me hammering every thread on here two to three years ago (long before you were ever a member) the only other member here who I can confirm that knew about BMA parts is Alex323ci. I'm sure he's been shopping there longer than me, but he or nobody else ever hammered the forum with it to help people save money. Now it comes up in every thread.

There's no "issue" to step around. I have never recommended to anyone to do exactly the things I do to my car. Otherwise there'd be another car like mine floating around--and there isn't. (There's only one or two cars on here I can really admire)

What I recommend is only 50% of what I do to my own car. The rest of the stuff I do goes beyond maintenance and is just a hobby/obsession. You think you know the whole story behind the advice I offer and why I offer it but you don't. Pay a little more attention.
 
#43 ·
I use to haul fuel, Some places after youd empty the tank there would be DIRT at the bottom of the empty tank...
 
#44 · (Edited)
I'm with Mango.
Preventative Maintenance is definitely a way of life, its addictive, and a pleasure for me.
I get parts at resale, and the parts house gives me a tab that I settle monthly, If this weren't the case it would be much more difficult.

I realize that, not everyone can afford to go through their cars replacing everything, and there is no rule against diagnosing, isolating, and fixing just the problem, but when you have been around these cars long enough, you realize there are certain PM items that are non-negotiable, or that the only negotiation is to be left stranded, or at best waiting for a tow.

My commute is 1 mile round trip, and yet I put roughly 200 miles a week on my car in remote canyons, where cell reception, and civilization is non-existent. That being said I would be an idiot to roll the dice, and wait for problems to surface before fixing.
Does that make me immune from a breakdown? No, however my chances are greatly reduced, and the reward of getting to work on my own car is just a perk.

You can fix it cheap, but it wont be thorough, or You can fix it thorough, but it wont be cheap.
 
#46 ·
I'm with Mango.
Preventative Maintenance is definitely a way of life, its addictive, and a pleasure for me.
I actually agree with that premise. But the fact that Mango and other like minded individuals are OCD about replacing parts that don't need replacing doesn't make it the right thing to do. Nor does it make it the right advise to give to people on budgets who, more often than not, are looking for a cost effective solution based on a sensible and rational diagnosis rather than a "replace everything" obsession. No auto shop could survive if it conducted its day to day business on that philosophy. The difference between me and Mango is that I own my car. My car doesn't own me.
 
#45 ·
To relieve fuel pressure, just pull fuel pump fuse, start car and when engine dies, your fuel pressure will be 0.
 
#47 ·
Fuel filter is a must. It's just like any filter that must be replaced. Put it this way. Does anyone buy a new car and never ever change their cabin filter? You will be breathing in crap and thats what the engine does with a bad fuel filter. I took my filter out and pitch black gas came out.
 
#51 ·
This would be evidenced by a lean running motor? Acceleration not as good as it should be? Of course, when it comes to acceleration, small decreases over time are hard to notice. I supposed it's good maintenance to do anyways.

It might also be why it occasionally acts just a little funny. The slightest hesitations at lower RPMs.

That delay just annoys the crap out of me. On a 5 speed it really screws with you.
 
#58 ·
Pull fuse for pump or filter as the pump will likely have pressure on the output assuming the pump check valve is not leaking down.

The fuse trick is quick and easy.
 
#89 ·
Actually, that ain't exactly so. Yes you can do the static adjustment but you can't compensate for the dynamic changes while driving that the leveling system allows for. You still are going to be a public nuisance by scattering the light rather than focusing the light and that is what makes other drivers want to use a hammer on your lights.

Change your fuel filter at 30K intervals. You will be glad that your did. Your car will too.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top