In-Line Fuel Filter for running Biodiesel

Well this seemed like too simple of a modification to bother posting a "How-to" on it but I had a request for it from BeetleGo so here it is. This is my first one so feel free to add your comments. Including correcting any mis-information.

First, thanks much to everyone for posting so much great info. I'm a newbie to TDIs and TDICLUB and the info here has been great! This is my first contribution to this great collection of TDI info!

I bought my 2000 Golf for the explicit purpose of running biodiesel. From everything I've read here and elsewhere, the TDIs run well on it. I have a fairly long commute to work, 70 miles / day round trip, and didn't want to put all those miles on my Jeep Cherokee. So I started looking at high mileage vehicles and discovered the TDI. As I read more, this became the obvious best choice, ATC. Fortunately, I work in Boulder, Colorado and there is a ready supply of quality BD at a pump here.

One thing I learned, even before buying my Golf, was that when starting to run a diesel engine on BD after many miles of PD, the fuel filter can often get clogged by the gunk residues from PD that BD dissolves. The BD experts at Boulder Biodiesel, www.boulderbiodiesel.com and http://biodiesel.port5.com recommended putting a cheap in-line fuel filter before the main fuel filter to catch all that crude and thereby save your main $$$ filter. They recommended using one with a clear plastic housing so you can see what's really going on in there and be able to see when it really needs to be replaced. Obviously this could apply to any diesel vehicle running BD or PD. Or even gas for that matter. So that's what I did. It’s very easy, almost trivial. At least on my Golf. It should be pretty similar on other models.


Parts
I used these Fram in-line fuel filter with clear plastic housing for under $3 because that's all my local auto parts store had. I'm sure there are other equally good ones out there. The G2/G12 size fit the existing hose. They come with, G2, or w/o extra short hoses and clamps, G12, for connecting it. I got one G2 for the clamps and several G12s for replacements.



Location
So then I located the fuel line coming from the tank to the fuel filter by following it back from the main fuel filter which has arrows showing the direction of flow. Be careful, these TDIs are a little tricky with the return fuel line back to the tank! That was new one to me. There isn't a lot of room to put the in-line filter so I put it where the hose runs behind the coolant reservoir and the front shock support, perpendicular to the engine compartment side wall.



Actual Installation:
- Cut a short section out of the fuel line, the length of the filter body, in the area behind the coolant reservoir. Have a small container and rags handy to catch any fuel that drains out.
- Slide the hose clamps over each of the cut ends of the hose.
- Insert the filter ends into the cut ends of the hose, making sure its facing the right direct for the flow of the fuel.
- Move the hose clamps over the ends of the filter to secure.
- I didn’t bother pre-filling it. When I started the engine, it quickly filled up from the end I expected it to so I assume I had the right hose and right direction.
- I put a piece of folded paper towel behind the filter as padding because it was leaning directly on the metal engine compartment wall and I didn't want it to wear the plastic and create a leak. So far no leaks!
- You could also take off the hose from the filter and tank connection if that’s easier and cut out the necessary length of hose.

Operation
When I first installed it, and started the engine, the in-line filled up quickly and completely as expected. I noticed a thin stream of very tiny bubbles coming from
the tank and eventually the filter leveled out at about half full of fuel and half air. It stayed that way for a week or so with several hundreds of miles of driving. It eventually filled back up and is now staying full. Not sure what that means. Maybe the inline is getting a little clogged as it fills up but it does not look like it from what I can see.
It has run fine the whole time. Eventually I'll replace it and open it up just to see what's in there if anything.

I’m also going to keep a close eye on it this winter to see if the fuel is gelling. I should be able to tell pretty easily.

When this current tank of fuel gets down low I'm going to take out the fuel sender in the tank to check the tank to see how much gunk, if any, is in there. I'll also fix the sender to prevent gelling as described in the Cold Weather Design Flaw, Secret Recall from VW? thread while I'm there.

One obvious improvement would be to use a filter that doesn't have plastic housing in case it breaks or cracks and leaks! But I haven’t found anything better yet. So always carry a spare filter and a pair of pliers to replace it in an emergency!

I hope to go many K miles w/o having to replace the main filter. At $25-35 for the main filter, I can afford many cheap in-line filters. They are a whole lot easier to replace too.
I’ll update this with any additional info on this little experiment.
Anybody else do this and have useful info to share?

Just did the same thing to my car this week after buying two new filters due to some bad B100. So far so good.
Good write up.

I like the high visibility so you can always see exactly what is going on with your diesel. I can't really imagine what would break the filter housing.

The reason it is filling up is probably as you are driving little bubbles of air are shaking loose into the fuel stream and being replaced by fuel. The filter is located on the suction side of of the system and would only draw in what is sucked into the IP.

I am considering a similar filter for my looped return line and moving my new WVO filter to a more remote location.

I'm not convinced that a small pre-filter is all that beneficial.
The added filter has an area of maybe 20 square inches. It would plug up when that much goop got into it.
The main filter has filter area measured in hundreds of inches. You'd run out of fuel due to plugging the inline filters five times over before that main filter would have plugged.
For this to be of a benefit to me I'd want close to the same area on the coarse pre-filter as are in the main filter.
Or at least the ability to back flush or blow out the pre-filter on the road side before the rain soaks through my jacket.
I'm also now a firm disbeliever in the "BD dislodges petro sludge" mantra. My present Passat had 151,000 miles of, presumably, petrodiesel use before I bought it. I specifically did not change the filter. I have been using B100 in the car almost exclusively. It now has well over 10,000 additional miles and still hasn't plugged up the filter.

...I'm also now a firm disbeliever in the "BD dislodges petro sludge" mantra.

Click to expand...

It happened to the Kubota we bought used with 615 hours on it. At about 620 hours she died with a clogged fuel filter. The guy I bought it from was bragging about how it had seen nothing but rot gutt dyed fuel but still ran like a champ.

I think it`s all a matter of the quality of fuel that has been put in the vehicle over it`s lifetime.

Could a cheap prefilter possible have any negatives? I would just like to know if any big stuff is getting caught in any fuel filter without having to cut open the big one, destroying it.

The main filter is easy to change and it does not cost that much... Why bother with trying to jury rig another filter when the one designed to do the work, works fine??? I thought there is a filter made by some one else that filters down to 2microns??
I do like the idea that you can see if it is starting to cloud or gel though.
Marty S.

How does this modification affect your warranty, if any?

It will probably affect it as much as running chunky biodiesel or dirt laden petrodiesel. VW specifically does not cover damages caused by contaminated fuel.

The possible detriment of a prefilter is if it is not compatible with biodiesel. Any natural rubber components in the attaching hoses, or as internal gaskets, *could* break apart and add to the main filter's contaminant load.

A small volume of contaminant will block a small pre-filter. That same small volume of contaminant will not block a larger filter. The added flow restriction will add to the pressure drop against which the injector pump will have to draw. There will be a greater chance of air in the injector pump intake line. The large pressure drop will also exist with a dirty main filter, but less frequently than with a small pre-filter.

Operation update:

After ~2400-2500 miles, on this in-line filter, I finally started having some
major hesitations accelerating up big hills. I also was the first cold/snowy
day of season down here in the Denver metro area so I was not sure if it may
be due to gelling. I had ~1/2 tank of B50 with some anti-gelling additive
but wasn't sure.

The actual filter material in the in-line filter had started to turn a much
darker color in the last week but I couldn't actually see any gunk in it.
I had been wanting to do the sending unit modification, drilling out the
check valve in the intake tube, so I decided to do that first.
See the discussion on Cold Weather Design Flaw, Secret Recall from VW?:
http://forums.tdiclub.com/favlinker.php?...amp;postmarker=

There were no obvious lumps of gelled fuel in the sender but I was glad to
have it done. After doing this I test drove it again and still got the
hesitations uphill. Went home replaced the in-line filter in under 5 mins,
test drove it again. No hesitations and none since.

HOWEVER, I think that doing the sender modification may stirred up
stuff in the tank because I now definitely see a build-up of "stuff" in
the new in-line filter. Since the filter is laying horizontally, the fuel
comes in and stuff is getting deposited in the corners below the
intake end. It will interesting to see how long this one lasts.

ALSO, when I changed the in-line filter, I took off the outtake end first.
When I did this, the fuel in the filter, and probably some of the gunk too,
drained back into the intake line. At first I thought this was great because I
didn't spill a drop! But now I think that some of the gunk in the filter
probably back flushed into the line and may be some of what I see in the new filter.
This plus anything stirred up in the tank from doing the sending unit.

If you haven't done the modification to the sending unit, it may not drain back
into the fuel line because of the check valve in the fuel sender.

The sending unit was not very gunked up from what I could see,
There was a thin film of dark stuff on the inside bottom of the sending unit
which I cleaned out. Since the tank itself is black plastic I could not
see anything in there either. So it was hard to tell what the petro diesel had left behind.

So, I see adding this in-line filter as a matter of personal preference.
I like being able to see what the fuel is doing.
Either from any petro gunk or tempurature gelling.
But since I was able to put it right behind the coolant reservoir,
it should stay warm enough to keep from gelling.

The possible detriment of a prefilter is if it is not compatible with biodiesel.
Any natural rubber components in the attaching hoses, or as internal gaskets,
*could* break apart and add to the main filter's contaminant load.


A small volume of contaminant will block a small pre-filter.
That same small volume of contaminant will not block a larger filter.
The added flow restriction will add to the pressure drop against which the
injector pump will have to draw. There will be a greater chance of air in the
injector pump intake line. The large pressure drop will also exist with a dirty
main filter, but less frequently than with a small pre-filter.

Click to expand...

Excellent points.
If you have to replace any hoses, use the type that will handle BD.
There are discussions somewhere in the forums here about that.
It would be interesting to find out how much extra drag, resistance, an
in-line filter would add. And how much that drag increases as the filter gets
more and more clogged. And how well the injector pump can handle that extra drag.
I'm guessing that a new clean in-line will not add much resistance and
that the pump can easily handle it.

The in-line probably will clog up faster than the main filter because they are so much smaller.
But $3 and less than 5 mins of time to change it out is well worth it to me.
The main filters are ~$35 at the dealer, ~$25 on-line and takes a good 30 mins to replace.
At least for me. Plus you have to have spare clean fuel to prime the main filter because it's so big.
The in-line is self priming because it's so small.
I would prefer to change a small one more frequently than the main one less frequently.

But if your not having any problems without it, that's great too.
I'm sure it somewhat depends on the quality of fuel that was previously
used in the vehicle.

If there any in-lines that could be back flushed and reused that would be good too.
I just haven't found any.
But come to think of it I may try that with the current one with the stuff piling up near the intake.

----------------

"You pays your money and you takes your choice"

Another update.

The prefilter is still working OK.
I have been running B100 from Blue Sun Biodiesel all summer.
I just changed the filter and got 5000+ miles out of the last one and
it was still not really showing any signs of clogging.
I probably could have gone longer but didn't want to risk it.
I keep a stock of filters handy to change them easily.

This 5000 miles was all, 100%, on B100 from Blue Sun Biodiesel.
I'll be very interested to see what happens when I have to start using
B20-B50 this winter when it starts getting cold.

Last spring when I was still using ~B50, I checked the filter one day and
it was visibly clouded with a whiteish gunk but was still running fine.
That filter only had ~1400 miles on it and it was plenty warn outside so it
should not have been from partial gelling.
So I guess it was from dirty petro in blend.
I changed it shortly there after and have been running B100 all summer with no problems.

One thing I really like about it is being able to see the fuel and filter element.
I wish I could see the main filter as easily.
The element visibly gets darker as its used more and more.
This last filter with 5000 on it, beside the element looking darker,
was still looking fairly clean. There was no other gunk or debris, etc,.
So the Blue Sun B100 fuel itself was looking quite clean.
We'll see what B20 looks like this winter!!
Or the occational B0 when there's no B20 available.

...I'm also now a firm disbeliever in the "BD dislodges petro sludge" mantra.

Click to expand...

It happened to the Kubota we bought used with 615 hours on it. At about 620 hours she died with a clogged fuel filter. The guy I bought it from was bragging about how it had seen nothing but rot gutt dyed fuel but still ran like a champ.

Click to expand...

RC, have you had any problems with the fuel lines failing in that Kubota? On the farm where we're processing our biodiesel, the entire farm is running on B100 (in addition to many non-farm vehicles ). Mostly John Deeres, which are all fine, but some Kubotas, which all quickly had fuel line failures. At least on tractors the fuel lines are much easier to replace than on a car.

Yes Mike, but I wouldn`t call it a total "failure". The lines have been deteriorating for the last three years now, but not to the point of "failure", simply sweating. I had another filter clogging issue last month and I believe it was due to fuel line material melting which made it`s way to the filter and clogged it. I was just about to order some new Viton for replacement when I had my little accident so that task, along with many others, has been sidelined. The only reason I didn`t replace the fuel lines on the Kubota right from the start is that the supply and return lines are a PITA to get to on this particular model... and I guess I just wanted to see how long they would last; the guinea pig in me I guess.

I will be getting to those lines this winter for sure. I suggest you do the same unless you have stock in some fuel filter company.

I've been thinking about adding an in-line filter...but for the purpose of eliminating water from the fuel. I've already got the CAT 2-micron filter, but it does not have water block media nor a water catchment. And thus, the need for a water block pre-filter. Do you know if this one uses a water-block filter? Do you know of another that does?

biodezl, I'm sure you've read the posts that basically say you don't need the water separator. I'm guessing you want one for the piece of mind/just in case/just gotta have it reason.
Just in case, I've got to ask why you want the water separator? Have you drained any water from your stock filter? I've never seen any in mine. The CAT filter is also big enough to allow water in the fuel to settle out, so if you really were worried about it you could just remove and drain the filter occasionally, then reinstall it.
HTH

The phrase is "peace of mind." That's one of those ones that gets mixed up all the time.

I have had a few old diesel Mercedes (and have worked on hundreds of them). Anyway, they all had prefilters much like the one you put on your car. It's nice to have that clear filter so that you can see what's going on. However, they do clog up a lot faster than the main filter.

I finally had to replace the main fuel filter on my '85 300D. I purposefully left the existing one in place when I obtained the car in... february, I think. I immediately started running the car on B100. The car had about 300,000 miles of petrodiesel use at that point. The other day, I was driving to work and noticed that it was hesitating a bit. I replaced the main filter and it now has more power than it did when I got the car. Because of that, I believe the filter was pretty clogged to begin with. I doubt the biodiesel use had a whole lot to do with it clogging. Hard to tell, though.

I changed the fuel filter at work. The nice thing was that my hands only smelled like veggie oil instead of diesel fuel!

Oh, and I have put a lot more than just bio through that car. Along with one tank of petro-diesel, I have also put in used ATF, SVO, WVO and a few gallons of kerosene. Those old cars can run on just about anything!

I hope that my next tank in the 300D will be home-made bio. I just need to do some more plumbing work and to get my hands on some bulk methanol. Oh, and I need a lot of free time and spare money. That's not too much to ask for, is it?

I thought the CAT filter does not have the water-block media, no? I have experienced problems with my fuel temp sensor (replaced three times now). I have read the sensor is sensitive to damage from water...but again, perhaps I am mistaken. Once when I was replacing the fuel temp sensor I saw what appeared to be a "bead" of water sitting between the two connectors. And so, having observed water where it should not be, I thought I would find a way to eliminate or reduce the potentential for it to be a problem.

My personal theory is that small amounts of water dissolved in the B100 gets boiled out of solution when the fuel goes above 212 degrees, then when the engine cools off, the steam condenses at the highest spot in the fuel system...the top of the fuel injector pump.

Have you drained any water from your stock filter? I've never seen any in mine.

Click to expand...

the old style OEM A4 filters had virtually no ability to seperate fuel from water, and they did not employ water blocking filter media. however, they've updated the OEM A4 fuel filter - it's made by Bosch and Mahle in Austria, and it has a much better water seperation design / capacity.

there <u>is</u> water in diesel, and i think it's a good idea for the filtration system to have some ability to block / seperate out water and drain it off. if your system lacks this capacity, then use additives like FPPF, Primrose or Howe's to chemically treat the water in your fuel.

only thing i see bad in this is i used something almost similar but used just the little filter and when it got below 32F it shrunk and would not allor fuel though causing car to not run. so watch using those little ones

I read somewhere that the typical water-block media filters break down under exposure to biodiesel and no longer separate water from the B100. Any truth to this?

I just installed this exact filter system, using /Fram G2 components.
Whole thing took me only 4 minutes after all prep work was done...it is quick. No need to prime the filter. I started the car, and the filter immediately filled up....straight to top.

I will carry extra filter and pliers , so if it clogs up , I can do a quick swap and put in new filter....

I installed a purolator filter in just this same fashion. I am getting a huge air pocket. Is this normal, or am I leaking air?

Back in the eighties this was the first thing most of us did to our motorcycles. Primarily because back then bikes did not have fuel filters. It was nice to be able to see the fuel and know it was getting to the motor.

I'd use the Mercedes filter, I believe it a better filter. Also, if your concerned about filtering install a CAT filter kit so you can filter down to 2 Microns.

philh said:

I installed a purolator filter in just this same fashion. I am getting a huge air pocket. Is this normal, or am I leaking air?

Click to expand...

My experience has been that is totally normal when the filter is new.
The fuel is flowing so fast through the filter paper, it does not get a
chance to fill up.
As the filter element starts to slowly clog up from the bottom up,
it will fill up more and more and get darker in color.

philh said:

I installed a purolator filter in just this same fashion. I am getting a huge air pocket. Is this normal, or am I leaking air?

Click to expand...

This is completely normal; unsure as to why it does this, but I've had multiple vehicles with these types of filters and they've never been totally filled with fuel.

Cheers!

Call me STUPID!

Just had some work done on my 2000 NB (352 k miles) by Landon (turbinewhine) up in Asheville. New timing belt, glow plugs,etc, etc. Since I was up in the "Land of the Sky" I decided to fill up with some B 20. I had done this occasionally, but ran on straight ULSD 99% of the time. I arrived at the pump, and they only had B50. I was near empty so I filled up.

I left Asheville and headed for home, 50 miles away. Everything was fine for the first 25 miles, then I began to loose power. I limped on for the next 22 miles, especially uphill. I took the off ramp nearing my home, and had to come to a complete stop. Needless to say, the trusty old NB was dead on the side of the road, 3 miles short of its destination.

I guessed that the B 50 had loosened up 352k miles of gunk into my fuel filter. I was excited when I found this thread. I figured I could change out the main filter with no problem. With my mileage, I figured that a $30 part was justified. I was also excited to see the pre-filter concept so clearly explained. Then I took a hard look under the hood! Where in the heck does one put this in a NB. Don't get me wrong, I love my NB. We've shared many miles together, but now I wish I had a Golf.

If anyone out there has any suggestions on how to pre-filter a NB, let me know, either through this thread, or a PM. Thanks

Here we go again!

Darn computer tells me I have no signal??? Posted a previous message To repeat in breif, changed filter, no space in the NB for an-line filter, still won't start, scheduled to replace injectors after the holidays, must tow 60 miles back to guru, hope it's not the *&^%$#@ fuel pump!! Appoligize for the computer malfunction. It requires that I sign in again, then sends in a duplicate. Guess it needs to be replaced, 10 years old.

Having learned that a toooooo long change out schedule will collaspe the add on filter & that it will expand again to look normal by the time you've opened the hood, I now change them yearly or at first sign of any filter / fuel issue.

A fuel vacuum (restriction) gauge reading up to about 8 or 10 inches of mercury will show when a fuel filter is causing too much restriction due to contamination, etc.

This allows one to a change the filter before performance is affected. When the vehicle begins to have problems with a filter, just note the reading on the gauge and you'll know at what reading you should change the filter.