Fuel Tank Module Mods for FASS Install

4x4dually

Moderator
Here's what I've been up to. I got a FASS 95 Platinum when I put on a new IP a month or two ago. I also tried the draw straw in the tank only to see the 1/4-1/8 tank issue which I was not happy with. So, all, here's the solution and it is relatively cheap.

Step 1 through 14. Drop your tank. :hehe: Use pry bar to get the front strap off because some jack-wad at Dodge can't design very well.

The thing that I noticed was that the tubing inside the module was .375" I.D. which would probably support a FASS 95. The problem is that the barbs that it slides onto on each end is .24" I.D. I think the same guy desiged this. So, let's get rid of the chock points, shall we?

Once you figure out how to get it all apart, here's what I did.

Cut the top screen off the bottom piece. This will increase the return fuel rate dropping out of the module when it is needed. This was a donor module from Roachie and was quite filthy. I also cleaned it good. THANKS AGAIN MAN!

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Then drill out the hole the fuel goes through to be picked up. This will increase the I.D. from .440" to .520" using a 1/2" bit.

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Next, make a riser out of 1/2" O.D. stainless pipe from NAPA or anywhere else. The I.D. is about .400". Use a tubing bender to create the same offset as the factory piece you cut out. Use brass compression fittings so the I.D. is not reduced any by the fittings. Leave the top extra long so you can cut it to length later.

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Heat the plastic cylinder with a heat gun a little so it won't crack when you thread the fitting into it. Use a .625" drill bit then just screw the fitting in.

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Shove that stuff into the module and snap the screen back on the bottom. Next, get a Vulcan draw straw 1 and trash the straw (or another brand). The one I bought had 3/8 NPT threaded into the bottom so the fitting just screwed right in same as on the bottom. This is where you'll have to figure out exactly where to cut the top off the tubing so that the module stays on the bottom of your tank once the module is installed and tightened down. It is easier if the tank is beside you so you can use trial and error. You must tighten the top compression fitting before putting the module in the tank and it must be the right overall length.

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Now, the choke point of your pickup is the 1/2 hose barb on top of the module which sets around .385" I.D. when new. Take a drill bit and put it in a vise and open it up. I opened mine up to .410" I.D. which leaves around .040" wall thickness on the narrowest part of the barb. (pic shows .405 but I wasn't holding the calipers tight)

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I then took some steel over braid and put it over the supply and return hoses. Then I covered that with heat shrink and shrank it all. This will keep my frame rails from rubbing holes in my hoses in the long run. Especially since the under side of my truck is always plauged with mud and rocks.

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Then I made a bracket for my FASS and installed it. It runs at 17 psi idle, 15 cruisin', and 14 WOT. BUT....I still haven't takin' out my stock filter up front so I expect that to all change soon. :D

And exactly WTH does FASS expect anyone to do with the little bracket that comes with it? That was a waste of aluminum. :badidea: You'll also notice by the time you get to the bottom picks, I dropped the clear hole spacers that came with it too and I shortened the short side of the bracket to get the filter up further off the ground. It is as high as I can get it now without the bracket rubbing on the under side of the truck.

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Over all improvement was minimum I.D in the supply path was increased from .240" I.D. to .410" I.D. which is the inside diameter of the stainless pipe. Seems to work great and tank operates like stock with no low fuel issues (loss of pressure on corners or fast starts/stops).

I haven't pushed the numbers but increasing the I.D. almost 60% should greatly reduce the flow resistance and decrease the amount of work the lp has to do to suck fuel. I'll try to remember to post back up the difference after I drop the front filter. I wanted to leave it since I had the whole system opened up. I wanted to catch all the debris before my brand new IP ate it. :D
 
Jory just leave the front filter in there. I am running a fass 95/150 on mine and have ran the stock fuel filter for probably 5 years. Just a little extra insurance.
 
I was wondering if it would throw a code if the fuel heater and water-in-fuel sensor were to be unplugged. Or maybe just pull the filter and leave the canister?

The whole point to a FASS is to get the entrained air out. My questions is, if the fuel goes through another maze of passages, another filter, etc, will it get all bubbly again? ...or does the fact that all the air is removed and bubbles can't be created because of its absence correct?
 
I was wondering if it would throw a code if the fuel heater and water-in-fuel sensor were to be unplugged. Or maybe just pull the filter and leave the canister?

The whole point to a FASS is to get the entrained air out. My questions is, if the fuel goes through another maze of passages, another filter, etc, will it get all bubbly again? ...or does the fact that all the air is removed and bubbles can't be created because of its absence correct?

I eliminated my stock fuel heater and filter after my 150 install... no codes.
 
I have returned the stock filter to the truck. However, I still have 1/4 tank issues so obviously I missed something. If anyone sees something else I can do, I'd be thankful to hear it. Apparently the canister can't hold enough fuel in reserve to turn a corner or stop quickly. I'm quite certain I put the valve at the bottom back in correctly.
 
1/4 tank issue CURED! In this picture, take the little center piece out of the valve so you have a about a .375 diameter hole down into the bottom cavity. This allows the reservior to drain fast enough for the pump not to draw air. Leave the outter ring and spring in.

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I ran the truck out of a 5 gallon bucket last night. The resevoir would fill up while idling and run over the top. I could lift the whole dang thing out of the bucket and run the truck for at least 60 seconds and still had some fuel left in it after that, but I dropped it back all three times. When I removed the whole valve, spring and all, the opening is about .500 diameter. This allows the fuel to drain fast enough that when the module is in fuel, it will only stay full to about 2 inches from the top and never attain a full reserve. That is why I had to leave the outter ring part in it.

I drove the truck down to vapor this morning and hit corners hard. NO drop in pressure. Daddy is happy again....and it cost me NOTHING.
 
my module is completely different then the one you got.... has metal sliders and 2 red screen filters on the bottom

the top "lid" for my module also has 3 holes not 2
 
my module is completely different then the one you got.... has metal sliders and 2 red screen filters on the bottom

the top "lid" for my module also has 3 holes not 2

That is the older version module. I have a tank out of a '96 like that but I don't know what year they went to the all plastic one. Your module actually has a float in the bottom of it, not just a check valve like mine does.
 
well... i ripped it all out ecept the bottom screen, drilled a hole for my drawtube and tossed it back in... still waiting on fittings to get it on the road and test drive it tho
 
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