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Unread 09-21-2009, 10:37 AM   #1
HeepToJeep
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Questions about upgrading from 15gal steel to stock 20gal poly fuel tank

I need to replace the 15gal steel fuel tank on my 82 Scrambler and figure I'll upgrade it at the same time by using a stock 20gal poly tank. Prior to tearing it down I want to make sure I have everything I'll need. Other than the 20gal poly tank, sending unit and skid plate, what else would I need to change in this conversion? ie: are any of the hoses different, is the filler neck different, does the new tank and skid bolt in like the 15gal setup or are spacers needed.

I have diagrams and OEM part numbers but most of them are discontinued and/or I couldn't find any information about their dimensions.

Also, the tank strap for the stock 20gal poly tank assembly has had it. Does anyone know of a replacement part or a clever substitute?

Wm

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Unread 09-21-2009, 10:40 AM   #2
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I was looking at poly tanks last night in the Quadratec catalog. It states that extension brackets are supplied with the tank along with a new strap to use the existing skid plate.
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Unread 09-21-2009, 11:58 AM   #3
HeepToJeep
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Quote:
Originally Posted by 243 View Post
I was looking at poly tanks last night in the Quadratec catalog. It states that extension brackets are supplied with the tank along with a new strap to use the existing skid plate.
I believe that's referring to the 21gal aftermarket tank, the tank I'm working with is an OEM 20gal poly tank that came as an option on the later model CJs. The aftermarket tanks are cube shaped, the stock tanks have a channel across the top for the tank strap and the bottom edges are beveled. The stock 20gal poly tank also came with a boxed skidplate that totally encloses the tank, the stock 15gal skidplate is open on both ends. So far, the only part I've been able to find for this assembly is the sending unit, everything else appears to have been discontinued. Your route would definately save me a lot of grief and solve all my problems, but, I'm trying to restore this vehicle using OEM style parts.


Wm
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Unread 09-21-2009, 12:38 PM   #4
only in a jeep cj
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I will be doing the SAME tank swap on one of my Scramblers as well. The tank strap is a unicorn to find. You either get it in good condition with a good condition pan, or not at all as rust ate up both strap and pan. I bought just a strap once for a spare tank, but had to pay 50 bucks for it because they knew it was rare. Anyway, it will bolt it just fine,and as the 15 gallon does....same holes and all. You don't use the roll over valve unit up in the fender well, just straight vent hose to the can. The roll over units/ vents are in the top of the tank. The hard part is the CJ-8 20 gallon holes....no one can find them so you have to lentghen the CJ -7 20 gallon hoses via sections of copper pipe. Heres a pic I found on the net showing the mod.

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Last edited by only in a jeep cj; 09-22-2009 at 09:22 AM..
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Unread 09-21-2009, 01:44 PM   #5
HeepToJeep
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83-86 CJ8 Filler Hose
Original Replacement Parts 5364196 - Replacement Gas Filler Hose for 82-86 Jeep® CJ-8 Scrambler - Quadratec

81-86 Filler Hose (CJ7) but QT lists all CJs, maybe it's cut to fit?
Original Replacement Parts J5362158 - Fuel Filler Hose for 82-86 Jeep« CJ w/20 Gallon Fuel Tank - Quadratec

How about the grommets that hold the roll-over valves in the tank P/N 536 0059.....anyone know of a replacement or substitute? Mine are crispy critters....

The tank strap P/N is 536 3078 if anyone knows of some new old stock or suitable replacement?

The threaded end of the tank strap on my 15gal also snapped off. I solved that one by simply drilling a 5/16 hole through the part of the strap where the bolt had been welded to and put an eye bolt through it, I'd do the same on the 20gal setup but the eye bolt would wind up rubbing the tank.

Wm
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Unread 09-21-2009, 03:18 PM   #6
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You might see if the YJ tank strap will work for your use. The Roll over check valves and the grommets for them interchange with the CJ ones.
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Unread 09-21-2009, 08:31 PM   #7
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I changed my CJ7 oem 15gal tank to a after market 20 gal (23 actual) about a year ago. Some of the lengths are different between the CJ 7 and CJ8, and I used the existing skid plate with no sides. So we have some differences.

Upon removal, disconnect everything you can get to before dropping the tank , and don’t forget the grounding wire that should be screwed to the frame. Once you have the tank coming out you have to reach above the tank to remove the sending unit wire. It slips on and remove by pulling straight up.

The things that I learned that you may find useful. Once its in, you don’t get to repair anything, so put new fuel supply line, 5/16 and return line ╝. Lengths, I don’t know as you have a CJ8, so they may be different. Replace all clamps, with new worm type , clamps. And use dielectric grease when you reconnect your ground wire and sending unit wire to the new tank, both slip on (the ground wire is a spade, the sending unit is a stud with a connection to friction fit on that stud). Once those things are done, you cannot repair without pulling the tank so check, double check all connections and clamp tightness.

As you have changed to a chevy engine, the lines may be changed. So I would do an inspection of what you have.

One of the problems with the original supply line was that the tank was set up for passenger side line to the front which is good for in line 6, but my 304 V8 has the fuel pump on the drivers side and accordingly the line runs up the driver side. What all this means is that the outlet at the tank is pointing the wrong direction for drivers side and is easy to kink when you pull the line around 180 degrees. The other problem is if you put too much line to avoid the kink, the line can get pinched between the tank and the frame. It is pretty easy to kink or pinch the line because when you put the tank back in, you don’t have much control over what the lines are doing. It required me pulling the tanks out a second time. So I ran the line out the passenger side, came back to the drivers side on the frame in front of the tank to reconnect to the original fuel line. As you have changed to a Chevy V8 this may not be an issue.

On installation, connect ground line and the fuel and return line before you start installing the new tank. Its pretty easy to push the tank up by hand, but you need to hold it until you get the electrical connection done (blind). I made solid wire hangers that let it hang about 4 inches lower until all things were connected including the fuel and return line to the forward lines in the frame . Really makes life easier. The other pointer I will relay to you is to take the extra 5 min to pull the rear tires. Make an incredible difference in moving around and getting the old tank out and the things positioned when putting the new tank in.

One last thing, one of those "dugh" comments, that you assume all should know, make sure to work with empty (or near empty) tanks.
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Unread 09-22-2009, 07:28 AM   #8
JeepHammer
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Just went through this,

Hoses are different, vent hose is larger diameter.

Skid plate is different and has 'Boxed' ends,
Skid plate also needs a liner between tank and skidplate, Herculiner makes a GREAT liner for both tank and skid plate!

Tank Strap is shorter, but you will probably wind up bolting down a standard strap on the forward lip and making it work, since it's virtually impossible to find a short strap for the 20 gallon tanks, no matter what you order, you will get one for the 15 gallon tank...

One of the 4 front skidplate bolt holes is in a different place, so be ready with drill to re-locate that hole,

I needed longer fuel lines, the fuel sender is on the other side of the tank, so your rubber lines will need to be longer,

The sender will have an extra long arm, with an extra bend in the arm,
New fuel senders usually come with cheap plastic float... spend the extra money and get a brass float! The plastic ones sink in the first month,

Use an Ohm meter on the sender to set up the arm/float position so your gauge reads 'Full' & 'Empty' correctly.

DON'T FORGET TO TIGHTEN UP THE SKID PLATE BOLTS!
You have to leave them loose to get all the bolts started in the holes, but don't forget to go back and tighten up all the nuts on the bolts later!
(Ask me how I know that!?....)
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Unread 09-22-2009, 09:04 AM   #9
HeepToJeep
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Great info guys, sure to be helpful to myself and anyone else making the upgrade...or any other tank related changes!

JeepHammer,
Thanks for the grocery list, it's exactly what I was looking for. I knew the vent nipple on this 20gal tank looked a hell of a lot larger than what I remembered the one on the 15gal tank being from the last time I had it off. Did you stretch the hose to fit, splice in a larger end, get a new hose and crank it down at the top or change the hose and filler neck assy? Quadratec has the best price on the sending unit and has a good reputation so I was going to get my parts from there...but, you're right on about the float, it too is cheap plastic. See any issue with their unit if the better float was added? Where did you get your parts from? Any suggestions about the roll-over valve replacement? The valves 'look' ok but they're the original ones and the grommets are dry rotted, so, I figured it best to replace both prior to hanging the tank.

H2OJeep,
Slick tip about the temporary hanger wires. The last time I had my tank off I did something very similar with a ratchet strap. Using the strap allowed me to hold the tank up at a workable level and once everything was connected I simply tightened down the strap, which lifted the tank into place and held it there while I got all of my bolts started...much easier than having a floor jack or second person in my way.

Wm
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Unread 09-22-2009, 10:41 AM   #10
JeepHammer
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I purchased new hoses for the polly tank.
You can get the hoses for a CJ-7 from most of the Jeep places that will work,
But for CJ-8 I don't know...
You may have to add extensions like the guy did that used copper pipe to make them longer.

You will find the filler neck end is the same size as the 15 gallon tank, it's just the tank end that will give you fits!
----------------------------------------------

You will have a hard time finding a tank strap, or 'Liner' that goes between tank and skid plate or tank and strap.
I usually just put the 'Back' threaded bolt end into it's hole and put a washer/nut on,
Then take up the slack in the back and bend the strap so I can run a bolt through the forward lip of the skid plate or use a carriage bolt (rounded head) from the inside out to bolt down the strap and take up the excess.
Remember, this tank isn't going anywhere, the strap is just there to keep the tank from moving around and wearing it's self through on the skid plate, or crap that has got into the skid plate.

I just Herculined the tank, really thick coat where the strap rides,
And I lined the skid plate inside. Made for really good way to buffer the tank against the skid plate.

I think if I were doing it again, I use the side wall out of a tire, or an inner tube between strap and tank, along with the Herc.

Don't forget to clear some nice big drain holes in the skid plate after Herculine!
Herc likes to plug up drain holes and hold moisture in the skid plate...
Won't effect the tank anymore, but will rot out the skid plate it's self.
---------------

I usually find the places where the tank touches the skid plate, and weld or bolt on extra armor.
You can use carriage bolts from the inside, just make sure your extra protection turns 'Up' forward and backward so it doesn't catch on anything and try to pull the bolts out when you drag up.
-----------------

SOLDER the ground wire on the ground wire terminal of the sending unit before you install!
Give yourself enough wire to get out to a dedicated ground wire, then connect.

I solder on the sending unit also,
This stops a BUNCH of corrosion and grounding problems from the sending unit.
Just leave enough wire to reach off the top of the tank to the orignal wiring harness for connection.
Solder those connections, heat shrink them, and you shouldn't have any wiring issues with the tank anymore.
-------------

If you brass float off the factory tank is still working, use it.
BE CAREFUL! The brass floats are fragile!
But the plastic ones dissolve/leak after about a month or two and sink, then you are screwed!

I'm not above using a old Holley carb float and soldering it onto the arm when I can't find the proper cylinder float for the application.
(I always gut old fuel tanks to recover the brass floats, about the only place to get them)

The float you use doesn't really matter, I saw a guy use a little brass oil can one time, soldered up the lid and tip, stuck it right on the arm, and soldered it down.
Worked great these past 8 years or so since we did that tank...
It's just the plastic floats you get in the 'Discount' kits (like 'Omnx-Ada' or what ever) just don't live...

I've seen guys epoxy coat Wine Corks and use them,
That's the way All floats used to be made!, but I don't recommend that because eventually the fuel WILL find a way into the cork and sink it!
--------------------------------------------

This is the roll over valve I've been using, much more simple than the unit used by Jeep... (and cheaper too!)

DeLorean Motor Company - ROLL OVER VALVE

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

If you wheel A LOT and don't want to pull the sender every few years because the 'Sock' filter fell off or rotted out,
Solder a tube on to the fuel pickup, and keep trimming it off until the sending unit fits in the tank again.

Using copper tubing that slips over the steel pick up line is good, but brass tubing would be best...

Anyway, if you remove the filter 'Sock' off the pickup, you MUST run a large fuel filter just outside the tank to catch crap headed for the fuel pump...
Ford makes a great big, frame mounted, metal canister filter I use a bunch for this purpose.
Steel casing means you can use this filter fine for suction lines, it won't collapse,
Steel also means you don't crush it easily, even in deep mud.
The welded on mounting tab means you don't have to worry about the filter coming loose in mud, ect, and makes it REAL HANDY to mount/change when you service the vehicle...

Just a though for those of you tired of running out of gas with 1/4 or 1/3 tank still showing!
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Unread 09-22-2009, 01:18 PM   #11
HeepToJeep
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Excellent tips Chief, thanks for the info!

Wm
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Unread 09-22-2009, 08:16 PM   #12
HeepToJeep
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Here's some part numbers for anyone doing this swap or similar repairs.

J536 2090 20gal Sending Unit
J536 3078 20gal Tank Strap (NOS only)
J536 3317 Filler Hose (82 only)
J536 3316 Vent Hose (82 only)
52018823 Rollover Valve Grommet
J536 0058 Rollover Valve

Other Options
Ford Rollover Valve E7DZ-9B593-A
Ford Rollover Valve Grommet F6TC-9B076-AA
Ford Rollover Valve Grommet F6TZ9B076AA

Wm
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