[DIY] Created an inline fuel filter - Will that solve the injector issue?

Hi. I just finished installing an inline fuel filter for the E92 M3.

That's an attempt to address the injector sticking open problem.

In case you would like to do it too, check out the video I made.

Any questions, feel free to ask.

10-micron paper filter: EPMAN EP-ZZOF01-BK

40-micron washable filter: ADDCO ADF09901 (edit: this filter is not a good idea)

You'll also need:
05x Metallic lock quick release fuel fitting FEMALE 7.89mm or 5/16" - MALE AN6
05x Male quick release fuel fitting 7.89mm or 5/16" - MALE AN6
01x Triple display for air pressure for air suspension kit 0-220 psi with 03 1/8" NPT sensors
01x Adapter Female M10 X 1.0 - Male 1/8 NPT
02x 90º angle fitting female an6 - female an6
3,0m of fuel injection hose 8mm or 5/16" ID, 13mm OD, 10 bar pressure
08x hose clamp 11-13mm
03x tee AN6 male - AN6 female - 1/8 NPT
03x adapter male an6 - male an6
04x 45º angle fitting female an6 - female an6
01x tap-a-fuse kit (mini or standard, I'm waiting for it to arrive to know)
01x 5 amp fuse (mini or standard, matching the tap-a-fuse kit)
02x adapter male AN6 - male 1/4 NPT
02x adapter female AN6 - male 1/4 NPT
01x electrical wiring harness tape 9mm x 15,0m
02x hose adapter fitting female an6 - 8mm or 5/16" barb fitting
02x hose adapter fitting male an6 - 8mm or 5/16" barb fitting
Variety of zipties

I bought everything from Aliexpress (except for fuel hose, that was promptly available here in local shops). Cost less than 200 usd.

Ps.: when doing an air pressure test, do it without the filter media, to avoid damaging the media if things go wrong, or even because of any moisture build up, that could damage the paper media.

ps2.: before connecting filtering system outlet to the rail, let it pump a little gas to a container, hence washing the new items you're about to put in the system. don't need to crank the engine, just turning ignition on will start the pump for a couple of seconds (you'll need to repeat it for several times until you achieve one or two liters of gas washing the system)

Would like to add some information.


About heat absorption, in my solution, that places filters in the front of the engine, I can confirm they get hot, but doesn't get hotter than hoses and lines got earlier. Only difference is when you compare by touching them, because rubber hoses have lower "thermal conductivity coefficient" than aluminum, so that they don't seem to be so hot when you touch. And when you touch aluminum, it seems pretty hot. But all of them are staying about 50/122 ºC/ºF or 60/140 ºC/ºF. I don't see a problem there. Sure you can wrap in a reflexive tape, but after a while of engine running, everything will come to a thermal equilibrium and sit at the same 50 ~ 60 ºC.


About pressure drop, in my solution, that uses a 42mm diameter (like NRW and EuroPowerMotorsport products) and 43mm lenght filter (that's half the lenght of NRW's), I faced a 4 psi pressure drop at max load engine redline.


About filter span, can't say, because I didn't run a significant mileage yet. But will soon. I'm willing to monitor that by the pressure drop increasing over time.


I heard people talking that the root cause of injector sticking is the pump strainer getting old and desintegrating. Would prevent that replacing the entire pump. Okay, no problem with that, but there's no certainty on it too. One certainty is, if you have a 10-micron filter, you'll be protected from that.

Also, the original pressure sensor relocation:

NRW took a good step relocating the pressure sensor to after the filter. EuroPowerMotorsport is offering a filter too, but doesn't relocate the pressure sensor.

I think that may be dangerous, because if the pressure drop in the filter gets too high, ECU will be blind and may have trouble regulating mixture or even protecting the engine against lean mixture scenario.

NRW:

https://www.nrw-design.com/products/e9x-m3-s65-inline-fuel-filter-kit



EuroPowerMotorsport:

https://europowermotorsports.com/product/fuel-filter-kit-bmw-s65-s85/

Haven't see the videos yet, but good write up.
Is their good evidence now that it is dirt that is jamming the injectors up? Last I looked into it, it was just a theory.

Re heat into the fuel pipes/metal filters.
Like you said the fuel filter will feel hotter even where the temp is the same, but don't forget that the higher thermal conductivity of the metal filters means more of the heat will be transferred to the fuel.
Although perhaps the impact is minimal, I think it would be worth insulating the filters to be safe, remember that the incoming fuel will be cooler than the under bonnet air, so temps won't equilibrise, but will stay lower with sufficient insulation.

Btw, any idea what micron size the standard filter is?

Assimilator1 wrote

Haven't see the videos yet, but good write up.
Is their good evidence now that it is dirt that is jamming the injectors up? Last I looked into it, it was just a theory.

Re heat into the fuel pipes/metal filters.
Like you said the fuel filter will feel hotter even where the temp is the same, but don't forget that the higher thermal conductivity of the metal filters means more of the heat will be transferred to the fuel.
Although perhaps the impact is minimal, I think it would be worth insulating the filters to be safe, remember that the incoming fuel will be cooler than the under bonnet air, so temps won't equilibrise, but will stay lower with sufficient insulation.

Btw, any idea what micron size the standard filter is?

Not that I'm aware, there's no good evidence. Just a guess based on the fact that every car has a filter before injectors and E-gen Ms don't. And for the price, I think it's worth trying.

I think you're right about temperature not equilibrising. I'll wrap the filter in reflexive tape.

About the standard filter, I don't know. But I know it's not restrictive, because it would disturb the pump suction pressure, as well as saturate soon, not being able to be considered by BMW as life-time part. People say that the practice in the racing/automotive world is to use 100-micron filter in pump suction.

I believe there is a 20-25 micron filter built in the injectors..
From my research, for those who prefer to keep things OEM, I’d replace injectors every 50-60,000 miles & in tank fuel pump every 70-75,000 miles.. of course this is just my opinion, not evidence based..
Also if dirt is already partially clogging the injectors, adding an additional filter would not make a difference but will definitely help keeping them clean going forwards.

Most modern petrol cars (here in the UK & Europe at least) haven't had a separate fuel filter since about the mid 2000s, in tank non-replaceable filter has been the norm for 20 odd years, yet injector failure is rare in general (not to say their aren't specific cars which have injector failures though).

I don't see that the filtration by the standard filter is insufficient as it would cause problems much earlier on otherwise, but maybe they're breaking up now??
But don't the injectors have built in filters to stop that? (should it happen).

BimmerMan33 wrote

I believe there is a 20-25 micron filter built in the injectors..
From my research, for those who prefer to keep things OEM, I’d replace injectors every 50-60,000 miles & in tank fuel pump every 70-75,000 miles.. of course this is just my opinion, not evidence based..
Also if dirt is already partially clogging the injectors, adding an additional filter would not make a difference but will definitely help keeping them clean going forwards.

Yeah, that's what I'd be doing forever too, but I felt like searching for a one-time fix (not that I have found it yet, but...).

I'm not expert in injectors, but I have the impression of having read here some saying that E9X M3 injectors don't have that screen. Also, I think it's a huge gain having a serviceable filter instead of servicing the injectors. And, it's known that servicing injectors (not replacing for new ones) don't avoid the sticking problem.

And I'm with you about the initial state of the injectors at the moment of implementation of the filter. In my case, my injectors have run less than 15,000 miles, only with top tier fuel, having ran a can of fuel cleaner after my old injectors had gotten stuck.

Assimilator1 wrote

Most modern petrol cars (here in the UK & Europe at least) haven't had a separate fuel filter since about the mid 2000s, in tank non-replaceable filter has been the norm for 20 odd years, yet injector failure is rare in general (not to say their aren't specific cars which have injector failures though).

I don't see that the filtration by the standard filter is insufficient as it would cause problems much earlier on otherwise, but maybe they're breaking up now??
But don't the injectors have built in filters to stop that? (should it happen).

Maybe something about spray pattern requirements in E9X (and E60, E63) turning injectors into a more sensible construction, more risky to stick? I don't know.

The filter before pump being insufficient, I think there's no argument against that. I can only think that problems don't happen more often because the fuels are clean enough for the system to hold on for years. Otherwise, an adequate pre-pump filter would rapidly saturate. But you can find injectors sticking open cases with low mileage E9X M3s and E6X M5/6.

Take a look at that article:
https://www.holley.com/blog/post/how_to_choose_a_fuel_filter/

The filter before pump being insufficient, I think there's no argument against that. I can only think that problems don't happen more often because the fuels are clean enough for the system to hold on for years.

In which case the filter is sufficient , it seems that (more) failures have been occurring in more recent years, so perhaps it's more time related than mileage related?
So a degrading pre-filter goes with that.

Reporting back.

5.000km after that, everything is fine. No problems with fuel vapour lock even in hot sunny days (37ºC) with heavy traffic. No problems also related to fuel pressure drop.

Only problem I faced was the metal screen glue didn't support the gas (maybe the engine bay temperature?). But filter screen itself was pretty clean, so I removed it, and now I'm only running the paper filter alone.

Also, a friend of mine discovered this pretty simple option for using stock filter (from other car obviously, I think it's a Volvo). You will only need to buy a 180 degree 6an fitting and two 6an-5/16" quick connect fittings. Can find the quick connect on improvedracing.com:

https://www.improvedracing.com/raceflux-6an-male-flare-to-5-16-quick-connect-female-plastic-button-adapter-fitting.html

And the 180-degree on ebay or any other store:

https://www.ebay.com/itm/174480357651?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A13qghg8RMSuijy865Pt768g44&norover=1&mkevt=1&mkrid=21527-227144-2056-1&mkcid=2&itemid=174480357651&targetid=358765038384&device=c&mktype=pla&googleloc=2076&poi=&campaignid=19957998899&mkgroupid=149539536442&rlsatarget=pla-358765038384&abcId=&merchantid=102015103&gad_source=1&gclid=CjwKCAiAxqC6BhBcEiwAlXp452d4Xs82yXr8vNcCsZmNJfBLLxZ0COuhjprY8ZclAer1zOUmvYrvdhoC8MsQAvD_BwE


This friend of mine said he didn't face any problems for not relocating the fuel pressure sensor.

Filter is HENGST H490WK.

awesome~

Does this mean that when using this fuel filter, there was no drop in fuel pressure or insufficient fuel quantity (change in A/F ratio)?

I wonder if there were any problems while driving on the track.

jvictormp wrote

Also, a friend of mine discovered this pretty simple option for using stock filter (from other car obviously, I think it's a Volvo). You will only need to buy a 180 degree 6an fitting and two 6an-5/16" quick connect fittings. Can find the quick connect on improvedracing.com:

https://www.improvedracing.com/raceflux-6an-male-flare-to-5-16-quick-connect-female-plastic-button-adapter-fitting.html

And the 180-degree on ebay or any other store:

https://www.ebay.com/itm/174480357651?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A13qghg8RMSuijy865Pt768g44&norover=1&mkevt=1&mkrid=21527-227144-2056-1&mkcid=2&itemid=174480357651&targetid=358765038384&device=c&mktype=pla&googleloc=2076&poi=&campaignid=19957998899&mkgroupid=149539536442&rlsatarget=pla-358765038384&abcId=&merchantid=102015103&gad_source=1&gclid=CjwKCAiAxqC6BhBcEiwAlXp452d4Xs82yXr8vNcCsZmNJfBLLxZ0COuhjprY8ZclAer1zOUmvYrvdhoC8MsQAvD_BwE


This friend of mine said he didn't face any problems for not relocating the fuel pressure sensor.

Filter is HENGST H490WK.

maicol76 wrote

awesome~

Does this mean that when using this fuel filter, there was no drop in fuel pressure or insufficient fuel quantity (change in A/F ratio)?

I wonder if there were any problems while driving on the track.

Did a trackday last month. No problems with fuel pressure, didn't even remember there was a fuel filter in the engine.

A/F ratio is managed by ECU and throws fault code if it's off the setpoint. Not happened neither.

Edit.: sorry, I was talking about my filter, not my friend's. He didn't take it to the track yet.

Do you have new Information about your friends fuel filter?

Recently installed e36 m3 inline filter on my 2008 dct e92 m3.
Have done 4-5 tanks now with some spirited backroad driving and with some high rpm winter fun.

Have not yet checked the fuel pressure or condition of spark plugs but overall cant see, feel or hear anything different - will update in few months when the weather is warm and track is dry.

As the filter is located before the fuel pressure sensor i doubt that there are any issues. Seems like the Chinese market e9x m3 has same kind of filter in same location.

Also was not feeling confident about installing fuel filter right above the veeery hot exhaust manifolds.

In total ~5cm of the original fuel line was cut off so that the original fuel line holder brackets can still be used. Also after cutting the line its not hard to clean lines from debris - can access the line from engine side and from tank side can just turn the ignition on and fuel pump blows the remaining debris out. Also flanged the fuel lines - that required hydraulic flange tool .. PITA.

Made simple aluminium bracket - didnt want to cut holes into the cars frame so used the original underside panel holder hole for one side (underside panel didnt have hole for it) and other is just aluminium sheet turned into U shape, added some rubber protection for the aluminium bracket and also fuel filter so there will be no metal to metal contact. The filter is fixed and super solid - no movement at all and with underside panel on cant see anything.

Todo: 3d printed bracket for fuel filter, replace rubber fuel line with braided and use AN fittings? or something more solid - nothing leaking but before going to track just want to be sure.
- does anyone have picture from underside of the Chinese markets car? There is probably part number for the original bracket

Sorry for ugly pics - car is extensively covered and filled with Dinitrol ML.

andrihallik wrote

Recently installed e36 m3 inline filter on my 2008 dct e92 m3.
Have done 4-5 tanks now with some spirited backroad driving and with some high rpm winter fun.

Have not yet checked the fuel pressure or condition of spark plugs but overall cant see, feel or hear anything different - will update in few months when the weather is warm and track is dry.

As the filter is located before the fuel pressure sensor i doubt that there are any issues. Seems like the Chinese market e9x m3 has same kind of filter in same location.

Also was not feeling confident about installing fuel filter right above the veeery hot exhaust manifolds.

In total ~5cm of the original fuel line was cut off so that the original fuel line holder brackets can still be used. Also after cutting the line its not hard to clean lines from debris - can access the line from engine side and from tank side can just turn the ignition on and fuel pump blows the remaining debris out. Also flanged the fuel lines - that required hydraulic flange tool .. PITA.

Made simple aluminium bracket - didnt want to cut holes into the cars frame so used the original underside panel holder hole for one side (underside panel didnt have hole for it) and other is just aluminium sheet turned into U shape, added some rubber protection for the aluminium bracket and also fuel filter so there will be no metal to metal contact. The filter is fixed and super solid - no movement at all and with underside panel on cant see anything.

Todo: 3d printed bracket for fuel filter, replace rubber fuel line with braided and use AN fittings? or something more solid - nothing leaking but before going to track just want to be sure.
- does anyone have picture from underside of the Chinese markets car? There is probably part number for the original bracket

Sorry for ugly pics - car is extensively covered and filled with Dinitrol ML.

Great move!

Only observation I could make is: those "bolt/nut" style hose clamps (not the worm type, the other one).

You should inspect it often, because when I used it here, it tended to get loose overtime and begin dripping. Don't know why. It even disconnected the hose once . I ended up moving to PTFE AN Fittings. I could make a video of how to install the fitting in the hose if you want.

But I don't see a risk there because it's far from exhaust and you'll feel the smell before it gets severe.

Kobramonsta wrote

Do you have new Information about your friends fuel filter?

I just messaged him right now. When I get a response, if something went wrong with it, I'll report back. If I don't, you know it's been fine.

Kobramonsta wrote

Do you have new Information about your friends fuel filter?

He said he just moved the sensor to downstream the filter, only for peace of mind. But didn't track the car, neither had any trouble when the sensor was upstream.

Thank you for the information. I appreciate that.

jvictormp wrote

He said he just moved the sensor to downstream the filter, only for peace of mind. But didn't track the car, neither had any trouble when the sensor was upstream.

Of course there will not be an issue upstream, it’s a low pressure sensor. If the filter get clogged it will never read low.

Also NRW uses Aeromotive fuel filters in their kit. Aeromotive releases all their tech data about their products online and free. There is a reason the filter has to be a certain size. I’d trust Aeromotive over someone trying to make something just because it fits better.