Push or Pull - Diesel Forum

ajohansson · 01-01-2008, 05:02 AM

I am getting ready to do a major replumb of my Veg conversion. My biggest hang up right now is to pull VO through the filter or push it through and decide what pre and post pump protection is the best.

After reading alot on the properites of filters from manufacturers (racor, donaldson) it looks like they make a fuel water serarator filters for primary filteration whcih are typically have the water bowl on bottom (suction side before pump) and secondary filter would be after pump (spin on type).My racor is only rates at 15 psi so using it for pressure is out of the question. I have written some pros and cons for both and would love to here your thoughts. The following conversion is a 7.3 liter two tank system each with its own filter. IF pushing obviously each filter would have its own pump. Sucking it would use one primary pump. The sytem would have a regulated return.

Pulling/Sucking
Pros - the ability to have one pump for both tanks
Cons - No post pump filtering. I think you would want something post pump just in case your pump impeller was imploding and sending bits of plastic or metal through the line. The thought of having a very restrictive post pump filter or large paper filter post pump discourages me as it leads to cross contamination and long purge times as the VO kind of sticks to the paper element. As an alternative I have been looking at the Aeromotive 100 micron its only 5 inches long and a 2 inch diameter. It is recommended prepump but would something like this work post pump on a suction setup. This would be used to catch parts of your pump if it blew up but would still flow really well do to its 100 micron coarse build. The element is cleanable stainless steel and I would imagine during switch over back to diesel it would completely clean out quickly due to the high flow from my pump and my regulated return.

Pushing -

Pros - only need two filters (one for each fuel) no worries if the pump implodes. No worry of cross containation.

Cons - need two pumps (not really sure if this is a con or not yet)
Might need a prepump coarse (100 micron or larger prefilter to protect pump.)

Different kits have different stuff. DFA pushes and prefilters to his pump with a 100 micron on the V3. Others use suction without a post pump filter. Let me know what your preferences are.

Spotty · 01-01-2008, 09:13 AM

I push

hheynow · 01-01-2008, 10:47 AM

I pull

ajohansson · 01-01-2008, 01:22 PM

DO you have a post pump filter of any sort.

hheynow · 01-01-2008, 08:21 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ajohansson</div><div class="ubbcode-body">DO you have a post pump filter of any sort. </div></div>

Nope. The 1st generation Powerstrokes ('94-'97) use a manual fuel pump. That's why I pull. It's a two stage pump that sucks from the tanks then pressurizes then is regulated at the FPR then sends fuel through the rails to the engine. The pump is located back under the turbo so there is no way to put a filter post pump.

Minuteman3 · 01-02-2008, 01:35 AM

This is question of how much money do you have and want to put into your system. With one filter, post pump is best, and you can solve the problem of damaging the pump by being sure you filter everything that goes into your tank. My truck has a post pump Donaldson installed...I'm running the VS2 from DFA. I also like the idea of prefiltering however, and would have preferred to have a larger filter pre-pump...just to catch anything big and keep it from going through the pump. I could always retrofit this however, but for me...it's a question of money...so right now I deal with what I have. Still, my recommendation is if you have only one filter, have it in push, after the pump.

ToddT · 01-02-2008, 06:11 PM

Some pumps have a maximum micron rating for filters on the feed side. The Mallory 110fi should not have a filter finer than 100 micron as a pre-screen. But, I have a feeling it can handle pumping biodiesel or diesel through two filters.... just not robust enough for veggie.

I'm currently using a regular automotive oil pump 25 to 30 microns as a pre-filter and a 6 micron as a post filter on my FASS pump. I'll probably move to a 30 micron water coalescing filter on the pre-pump side, wrapped with a Vegistroke 12v heater blanket. I'll keep the 6 micron on the post pump side.

ajohansson · 01-03-2008, 12:37 AM

Todd,

I have talked to the folks at DPP and they recommend nothing more restricitive than 140 microns prepump which is how the FASS is set up. Now the FASS is set up to pull through this 140 water seperator and then push right through a 5 micron filter air seperator. Now if the DPP/FASS HPFP is just pulling only through a five or 10 micron filter and has no post pump filter I wonder how it would do. I have been pulling through a 2 micron racor with my stock fuel pump that is failing. If I keep this same set up, will my DPP/FASS HPFP be harmed? I prefilter to 2 microns. FOr ease of intall just swapping my stock pump with the DPP/FASS HPFP would be the thing to do but is it the righ thing to do?

ToddT · 01-03-2008, 01:58 AM

That's good to have some definitive answers from the FASS folks. If they say not to go smaller than 140 microns on the pre-pump/pull filtration, it sounds like they only want a screen on the inlet to protect the pump internals. As I recall, it has a screen inside, though I'd rather have something in addition to that.

Placing a filter before the pump will likely cause cavitation and overheat the pump as well as the motor. If they say don't do it.... that settles it for me. Pre-screen only. All filtration is post-pump. The FASS is such a strong pump I don't think it would be too much to have two filters downstream: water trap and final polish filter.

luckuslucas · 01-05-2008, 09:12 PM

I have a FASS 95 HPFP, and I pull with it. I'd rather it push, but two pumps aren't in the college kid budget right now.

ajohansson · 01-06-2008, 02:47 PM

I have finally figured out my ultimate plan for upgrading my GFS system. I will have both tanks plumbed to their own 100 micron water separators the same ones the fass 150 uses, then to a valve, to pump, to valve to respective diesel and VO secondary filters then to valve, to motor, to valve which will route to diesel tank or vo loop/purge valve. So an extra 2 valve and some filter heads and I am in business. I will be using one HPFP for whole system and ITP's regulated return fuel bowl delete kit and I can have both fuels running in the 70 psi range.

Halitosis · 01-06-2008, 09:06 PM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ToddT</div><div class="ubbcode-body"> As I recall, it has a screen inside,
</div></div>

Are you sure? I have had to disassemble my FASS pump twice (as part of the Vegistroke Kit), and I don't remember seeing any screen or mesh in there...

Halitosis

Spotty · 01-06-2008, 11:04 PM

Why does vegistroke want you to disassemble your FASS?

Halitosis · 01-07-2008, 01:51 AM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Spothead</div><div class="ubbcode-body">Why does vegistroke want you to disassemble your FASS?</div></div>

I was an "early adopter" of the FASS (I think I got the 2nd or 3rd one on a Vegistroke kit)...

It was found that the original "base" platform where the spring is located had just enough play in the channel to wear a groove into the aluminum, break the spring, and effectivly shut down the pump.

Both my father's pump and my pump had the original FASS "base" (for lack of a better term... I don't know what the real term is)

My first pump (base) lasted about 15,000 miles before it tanked. (The pump itself was OK, but base was hosed).

The replacement base came from from FASS (via Vegistroke), and apparantly the channel that the spring now sits in is something like 1/20,000 of an inch narrower...giving the spring less play. Dunno if this just delays the inevitable, or whether this is truly a FIX... jury is still out on that one.

The original was base was red, the replacement is just raw, brushed aluminum (silver).

Anyhoo, the SECOND time I had it apart was just recenly, when I had the pump fail at 30,000 miles... (I should update my signature). Jason was really surprised at that one.. I guess core FASS pump failures are pretty rare. Jason's diagnosis was that the bearings in the pump had actually seized.

In both cases, with the way that pump is assembled, I had to take out the four "corner bolts" that essentially hold the entire "tower assembly" together. (Those of you who have a FASS know what I am talking about).

To bring this message back on track in the thread: when I was rooting around in there... I don't remember there being a mesh screen anywhere.

Halitosis