Questions on installing a Downey aux tank as primary main tank

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Hello all, I have purchased a @Downey 22 gallon aux tank and intend to install it into my 9/73 FJ40 as my main tank. I would like to get some input from those that have already done this and get the following questions answered.
  1. Sending unit: Does the OEM sending unit get installed into the Downey tank? Does it need to be modified in any way to work correctly? Any tips on installing it?
  2. Routing to OEM fill tube: The Downey aux tank was designed to be connected to a new filler door cut into the rear quarter panel. I would like to route this to the OEM fill tube instead. It looks like this will require cutting a hole in the tub. Has anyone done this and are there any tips on routing?
  3. Removing charcoal filter: I intend to get rid of the charcoal filter and other EPA crap and seal off that line. Any tips here? This rig will never be registered in CA and is no longer required to go through a smog check in Portland.
  4. Fuel pump: Is an additional fuel pump needed due to the extra distance? Is it better to mount a pump to the frame rail or use an in-tank filter? I was thinking an external pump would be easier to access but have read that the noise can be bothersome. Is there a preferred fuel pump brand?
Hopefully Jim will chime in with best practices for installing this tank as a primary replacement tank and will add this option to his instructions sheet.
 

JohnnyC

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Don’t know if this will help you at all … but… here is the install instructions

Scroll down a little bit in this thread:

 

hobbes

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Removing charcoal filter: I intend to get rid of the charcoal filter and other EPA crap and seal off that line. Any tips here? This rig will never be registered in CA and is no longer required to go through a smog check in Portland.
I’m not sure why you want remove the charcoal canister. It’s 100% reliable and costs no performance. If you cap the input line to it you’ll need to find a way to vent the vapor pressure that builds in the fuel tank as you drive. Most common way is/was to drill a hole in the fuel cap. But then it will smell of fuel when you park it and, for some, when they sit stopped at a light. Newer fuels are probably worse for this.

You can probably remove everything downstream of the charcoal canister and keep the smell down. Start by unplugging the canister output line, put a small filter on it, and drive it a bit. See if that’s ok.
 

Downey

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1. You can adapt a stock sender into my tank, but (a) you will have to modify the length of the float arm since the 22 gallon tank is deeper, and (b) you will want to mount the sender so that the float arm is pointing straight rearward (pointing towards rear wall of the tank). This keeps the swing of the float right on the center line of the tank where the fuel is always the deepest, so fuel sloshing in the tank does not give big swings/bounces on your fuel gauge all the time.
2. I'm not sure that folks who attempted to use the stock filler neck for the rear tank were tickled pink with the results, I've read some pros and cons here over the years.
3. Over the years guys who have converted to V8's have totally de-smogged (including charcoal canister) with no fuel smell complaints whatsoever, so now why are Mud guys saying you have to keep the charcoal canister to avoid fuel smells. Many post here where guys re-attached the charcoal canister and got rid of fuel orders ???.
4.Many install an in-tank fuel pump with my in-tank fuel pump mounting kit because (a) they run cooler and quieter, and (b) they can install any pressure needed for their engine's requirements (various pressures needed for various types of fuel injection for instance).
 

hobbes

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3. Over the years guys who have converted to V8's have totally de-smogged (including charcoal canister) with no fuel smell complaints whatsoever, so now why are Mud guys saying you have to keep the charcoal canister to avoid fuel smells. Many post here where guys re-attached the charcoal canister and got rid of fuel orders ???.
Well, it worked in my case. When I bought mine it had the charcoal line plugged and a hole drilled in the fuel cap. Now that everything is proper, the wife doesn’t complain any more.

I believe the new fuels vapor pressure has changed. Certainly, a higher percentage of FJ40s are parked in garages than ever before. These both probably increase the likelihood of smelling fuel.

I’m sure there are plenty of guys happily running without a canister. You can easily remove the charcoal canister (or reinstall it if you want it back), but again I’m not sure why you would unless you need the space. I do understand removing the VSV components (I don’t have those). Those do fail over the years.
 

Downey

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When we needed good 1985-86 FJ60 smog components for Federal testing we were doing in 1998 (now 12-13 year old smog components), we couldn't find any that were not already roached. We literally had to epoxy one piece together to conduct the Federal testing. Sooooo, right or wrong, my opinion is that any smog devices still remaining on FJ40's, 55's, and 60's are there just for make-pretend.
 
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1. You can adapt a stock sender into my tank, but (a) you will have to modify the length of the float arm since the 22 gallon tank is deeper, and (b) you will want to mount the sender so that the float arm is pointing straight rearward (pointing towards rear wall of the tank). This keeps the swing of the float right on the center line of the tank where the fuel is always the deepest, so fuel sloshing in the tank does not give big swings/bounces on your fuel gauge all the time.

Thanks Jim. Do you have any input on what is needed to do to lengthen the float arm?
 

Downey

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Yep, get some additional steel rod, then:
You can use Everbilt Aluminum Ferrule Clamps, put 2 rods into clamp, either hammer tight, or tighten in vise.
You can use 1/8" zinc plated wire rope clamps, they come in a 2 pack, just tighten nuts.
You can use Crimp-on Butt Splices, again hammer tight or squeeze in vise.
 
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I don't see any advantages to removing the charcoal cannister, but I can imagine a lot of potential problems.

I run the stock fuel pump with an aux tank and have never had an issue with the added distance.
 
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We opened up the OEM tank to extract the sender and found a new challenge. The oblong shape of the fitting doesn't match the circular hole in the Downey access plate. Does this mean I have a different year OEM tank in my rig? @Downey , what's the best approach here? Should I mod the access plate opening? Source a different sending unit?

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00576717-0b55-4250-8a2b-ed769a4a943c.jpg

b7d5f879-cb71-4a3a-aa44-edc83519fd0d.jpg
 

Downey

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Just oblong the hole in our aluminum top plate- - -easy deal. Make sure you point the float arm rearward, towards back of tank, on center line of the tank.
 

V8FJ4078

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@Downey What size connections are needed for your in tank pump kit as shown above with the nipples attached?
I am thinking of purchasing and using this for my rear tank. I believe I saw you had one with pump and all.
 

Downey

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Not sure I understand your question, but all the fittings we use with our tank are 6AN.
 
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1. You can adapt a stock sender into my tank, but (a) you will have to modify the length of the float arm since the 22 gallon tank is deeper, and (b) you will want to mount the sender so that the float arm is pointing straight rearward (pointing towards rear wall of the tank). This keeps the swing of the float right on the center line of the tank where the fuel is always the deepest, so fuel sloshing in the tank does not give big swings/bounces on your fuel gauge all the time.
2. I'm not sure that folks who attempted to use the stock filler neck for the rear tank were tickled pink with the results, I've read some pros and cons here over the years.
3. Over the years guys who have converted to V8's have totally de-smogged (including charcoal canister) with no fuel smell complaints whatsoever, so now why are Mud guys saying you have to keep the charcoal canister to avoid fuel smells. Many post here where guys re-attached the charcoal canister and got rid of fuel orders ???.
4.Many install an in-tank fuel pump with my in-tank fuel pump mounting kit because (a) they run cooler and quieter, and (b) they can install any pressure needed for their engine's requirements (various pressures needed for various types of fuel injection for instance).
Does anyone have pictures of your tank using the stock filler location. I would like to see the routing and materials needed. Is the main issue with the stock location slow filling?
 
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samc2447

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Does anyone have pictures of your tank using the stock filler location. I would like to see the routing and materials needed. Is the main issue with the stock location slow filling?
The main issue is that stock location is meant for filling the in cab tank. Downey's tank is in the rear under the tub between the frame rails. You'd have to route it through the tub to the rear, it's a long path with tight access to get to the fill location.

The best option if you want to use Downey's tank as your primary is to cut out the stock fill panel and move it to the rear. Replace the stock area you cut out with the section from the rear. You get the stock look and a much cleaner path with fewer bends to the 22 gal tank. This is typically what I do. Other's have documented it this forum with photos.
 

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