Bypassing pre and post fuel filters with single? - PeachParts Mercedes-Benz Forum

m1tch · #1 10-28-2015, 04:06 AM

Hi all,

I am yet again chasing air leaks in my fuel lines on my W210 E300 turbodiesel, I have a feeling its the seal on the pre filter again so will carry on fault finding.

Anyway, I was just wondering if anyone had replaced the whole fueling setup to just have a single fuel filter going from the tank feed to the cutoff solinoid?

As far as I am aware the fuel pressure is only at around 1 bar rather than the usual 50psi found in petrol engines fuel systems as its just a case of moving fuel from the tank to the injection pump.

I know of the requirement to have clean fuel going into the pump owing to all of the intricate passages within the pump and injectors but was just thinking if I could get a single large filter instead.

Does anyone know the size of the fittings on the fuel cut off solenoid? I guess I could look into simply attaching fuel line over the OEM connector and use the OEM connector as an adaptor so to speak.

Ideally I would just want to have:

Fuel feed > large fuel filter > cut off solenoid > fuel injection pump > fuel return

Has anyone done anything like this at all? I am guessing there have been other setups when using WVO due to the need for larger filters? Tempted to go along with the Lotus philosophy of "simplify then add lightness".

Stretch · #2 10-28-2015, 07:44 AM

Quote:

Originally Posted by m1tch

... Tempted to go along with the Lotus philosophy of "simplify then add lightness".

Before you adopt that philosophy you need to understand what Mercedes were up to in the first place. When you get them right an old Mercedes will be a joy to own whereas an old Lotus...

?

?

?

m1tch · #3 10-28-2015, 08:00 AM

Surely a single fuel filter rather than having a pre filter and then main filter would be simpler though? Its already partly filtered from the tank as well. Electric pump to single filter to cut off solenoid to injection pump inlet might work?

shertex · #4 10-28-2015, 09:11 AM

FWIW MB moved to a single filter in 05.

Shortsguy1 · #5 10-28-2015, 09:15 AM

Quote:

Originally Posted by shertex

FWIW MB moved to a single filter in 05.

One more reason to stick with two.

Diesel911 · #6 10-28-2015, 10:35 AM

Quote:

Originally Posted by m1tch

Hi all,

I am yet again chasing air leaks in my fuel lines on my W210 E300 turbodiesel, I have a feeling its the seal on the pre filter again so will carry on fault finding.

Anyway, I was just wondering if anyone had replaced the whole fueling setup to just have a single fuel filter going from the tank feed to the cutoff solinoid?

As far as I am aware the fuel pressure is only at around 1 bar rather than the usual 50psi found in petrol engines fuel systems as its just a case of moving fuel from the tank to the injection pump.

I know of the requirement to have clean fuel going into the pump owing to all of the intricate passages within the pump and injectors but was just thinking if I could get a single large filter instead.

Does anyone know the size of the fittings on the fuel cut off solenoid? I guess I could look into simply attaching fuel line over the OEM connector and use the OEM connector as an adaptor so to speak.

Ideally I would just want to have:

Fuel feed > large fuel filter > cut off solenoid > fuel injection pump > fuel return

Has anyone done anything like this at all? I am guessing there have been other setups when using WVO due to the need for larger filters? Tempted to go along with the Lotus philosophy of "simplify then add lightness".

I am not sure what issue you are trying to deal with.

If the Filters are getting plugged faster then you would like you need to deal with the contaminated fuel issue.

If you are trying to eliminate another connection and possible source of an Air leak it is simply easier to fix the existing setup.

My 1982 Volvo GL244 Diesel has only one Fuel Filter. The Stock Filter is longer then the Mercedes and has a drain at the bottom. However, it is a 10 micron filter which is the same as the stock Mercedes filter.

On my 84 300D there is a Plastic/Primary Filter. If your Car dies on the Road due to that Filter being plugged you can often remove it and thump or blow stuff off and out of that filter and re-install it and continue down the road till you get some place for a better fix.

If your system is one that uses O-rings to seal the Fuel Lines you could aquire Viton O-rings and get more longivity out of the O-rings.

vince77 · #7 10-28-2015, 10:59 AM

We're constantly chasing leaks (air, oil, hydro and fuel) on our equipment out here. They all get tracked down to damaged hoses, bad packing (seals or o-rings) or damaged seating faces. You may have a warp, crack or scratch in the filter mount, but more likely, it's just a crack/pinhole in a line.

Tank to IP, it is a simple low pressure system. Have you swapped all the soft bits yet? Oh, and I totally understand how frustrating it is not being able to nail down the cause... mind starts coming up with all sorts of inventive ideas...

Mxfrank · #8 10-28-2015, 12:04 PM

One of the concerns with Diesel that doesn't occur to the same extent with gas is water in the fuel. The secondary filter is supposed to trap moisture as well as dirt. The fuel also tends to contain more dirt, although I think modern refining methods are better at cleaning it up.

babymog · #9 10-28-2015, 12:17 PM

It can be done, I've had CAT and Detroit engines that had a single filter system. The nice part of the pre-filter (aka: secondary) in the older Mercedes is that it's clear, you can see the screen in it and tell if there's something amiss, similar to the Racor filters we used in our coaches. Buy a nice heated Racor with water-in-filter warning system and clear bowl and you need nothing else, but it is overkill for a car that burns good clean pump diesel.

leathermang · #10 10-28-2015, 01:03 PM

Quote:

Originally Posted by babymog

.....The nice part of the pre-filter (aka: secondary) in the older Mercedes is that it's clear, you can see the screen in it and tell if there's something amiss,.....

For instance... if you see little black specs growing in that clear filter... you know you need to look for dealing with fungus growing and possibly blocking your in tank filter.... a great heads up easy to see each time you check your oil level....
You will be looking to keep that tank filter from stranding you out on the highway... by using something like Biobar ..... and preventative cleaning of the tank filter...

funola · #11 10-28-2015, 01:27 PM

Quote:

Originally Posted by babymog

It can be done, I've had CAT and Detroit engines that had a single filter system. The nice part of the pre-filter (aka: secondary) in the older Mercedes is that it's clear, you can see the screen in it and tell if there's something amiss, similar to the Racor filters we used in our coaches. Buy a nice heated Racor with water-in-filter warning system and clear bowl and you need nothing else, but it is overkill for a car that burns good clean pump diesel.

Minor detail: Mercedes calls the small clear filter the "primary" filter, the large spin on is called the "secondary" filter.

m1tch · #12 10-29-2015, 03:49 AM

I think I have chased down the leak this time, seems it was one of the clips weren't fully home between the filter and the stop solenoid - I reseated them and it seems much happier.

I will at some point be looking to remove all of those filters and replace it with a single all in one DAF filter - has a primer, large filter as well as a water trap all in one. I will also be doing away with the stop solenoid (which is apparently part of the immobiliser) and be adding in an electric pump at the tank end.

The fuel lines are actually in a good condition, it seems that they have been replaced recently (before I got the car) as they are all clear with no yellowing at all, looks like they might have just replaced the lines rather than the O ring in the smaller filter which was leaking last time.

mannys9130 · #13 10-29-2015, 06:58 AM

I appreciate having the 3 stage filtration. The tank strainer catches boulders and prevents Jimmy Hoffa from being sucked up, the primary catches flakes and bacterial colonies that maybe broke off and got past the strainer, and the secondary main filter catches all of the water and fine grit that made it that far. If you have a crud issue, you'll see it in the primary and you'll be able to go longer and change it easier as opposed to the feed going right to the secondary. Also you'd be able to blow out the primary and use it over since it is just a finer screen. If you have a tank infection, blowing the primary out as your biocide works will save lots of cash on new primary filters. Last, good GOD, you'd need to carry 3-4 spin on filters for an emergency. One bad tank of fuel and you'd be done for. The hassle if changing the secondary is 10x worse than the primary, and for 60X guys it's harsh on the (aged) starter motors.