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Unread 11-26-2014, 08:11 AM   #1
89WhyJ
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'89 Gas Tank Swap Questions

In my 89 2.5L YJ, I currently have the rectangular steel 15 gallon original gas tank...and its leaking. I recently managed to pick up a poly tank pretty cheap as a replacement. However, its the trapezoidial type, and I believe 20 gallon. My current steel tank has the circular opening for the fuel sending unit, while the new poly tank has the square opening. My current fuel pump and sending unit work fine. However, I haven't verified if the new pump is functional. So, here's my questions:

1) Will this new tank fit in the stock rectangular skid plate? Will I need to do any mods, extend the filler hoses, get longer straps, etc?

2) Are there any YJ model years with the trapezoidial tank from the factory? If so, what year...just in case I need to get a new sending unit, check valve, or fuel pump?

3) In a pinch, can I reuse the fuel pump in my current tank with the new sending unit in the new tank?

4) Last, if I can use this new tank, do I just connect the two check valves together, and tie them into the existing vapor line that runs to the charcoal canister?

Thanks for all the help!

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Unread 11-26-2014, 10:59 AM   #2
Randonexplosion
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Quote:
Originally Posted by 89WhyJ View Post
In my 89 2.5L YJ, I currently have the rectangular steel 15 gallon original gas tank...and its leaking. I recently managed to pick up a poly tank pretty cheap as a replacement. However, its the trapezoidial type, and I believe 20 gallon. My current steel tank has the circular opening for the fuel sending unit, while the new poly tank has the square opening. My current fuel pump and sending unit work fine. However, I haven't verified if the new pump is functional. So, here's my questions:

1) Will this new tank fit in the stock rectangular skid plate? Will I need to do any mods, extend the filler hoses, get longer straps, etc?
I believe you will need the skid plate and straps for the poly tank

2) Are there any YJ model years with the trapezoidial tank from the factory? If so, what year...just in case I need to get a new sending unit, check valve, or fuel pump? All 91-95s had them and 87-90s with the 4.2 had them

3) In a pinch, can I reuse the fuel pump in my current tank with the new sending unit in the new tank?
I have no idea if it will fit

4) Last, if I can use this new tank, do I just connect the two check valves together, and tie them into the existing vapor line that runs to the charcoal canister?

Thanks for all the help!
When you say trapezoidal, you mean this tank right? http://www.mtscompany.com/images/jeep/0065_v1.jpg
All YJ poly tanks are the same. The "15 gallon" tanks just have a longer fill tube.
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Unread 11-26-2014, 12:43 PM   #3
89WhyJ
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Yeah, that's the shape of the tank. Looks like I'm going to need that skid plate and straps. Is the poly tank that much better, that its worth going through the trouble of getting parts to make it work?
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Unread 11-26-2014, 01:05 PM   #4
Randonexplosion
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The poly tanks can leak too. Where is yours leaking from? Could it be repaired?
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Unread 11-26-2014, 05:47 PM   #5
timatoe
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When I swapped the steel 15 gallon tank out for a poly 20, I used the tank skid for it as well. I don't think there's any way the 20 will fit in the 15 skid. I also had to change fuel hoses, but I'm already in a different kind of predicament since I moved the filler to a TJ filler in the TJ location.

I used THIS THREAD for reference.

I'm pretty sure mine came from an 80's four banger Jeep, I used the sender etc in the tank.
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Unread 11-26-2014, 08:41 PM   #6
89WhyJ
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I haven't pulled the tank yet. But its leaking down the back corners on both sides. I hadn't thought about repairing it as an option.

Thanks for the link and the info timatoe.
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Unread 11-26-2014, 09:10 PM   #7
87TPIYJ
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Yeah you will need the new skid I did it a few years back.

http://www.jeepforum.com/forum/f12/g...k-swap-854035/
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Unread 11-27-2014, 01:14 AM   #8
timatoe
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Originally Posted by 87TPIYJ View Post
Yeah you will need the new skid I did it a few years back.

http://www.jeepforum.com/forum/f12/g...k-swap-854035/
Excellent comparison shot in that thread.
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Unread 11-27-2014, 09:13 AM   #9
jbolty
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Don't overlook to option of switching to an external fuel pump. It would allow some creative plumbing inside the tank and add the benefit of access if the pump fails later. All you need , aside from a pump, is to make a pick up tube to replace the pump inside the tank and perhaps a different fuel gauge to match the ohm reading on the new sender.
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Unread 11-28-2014, 08:53 PM   #10
YJ8
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I agree with all the information above, but I will add my experience-- I swapped a poly tank in place of a 15gal metal tank, 90 YJ, 4.2L

A) You may find the new poly tank slightly taller and may contact the underside of the body just before you fully tighten it up, not a big deal but know it is close, and position hose clamps for max clearance. If you have a body lift then no worrys. It is easy to space down if you have this problem.

B) in my case I used the poly in-tank pump (from a 95YJ), cut off the sending unit and reused/ rewired the original sending unit in its place. I used pop rivets to hold it to the pump assy, it almost looks factory. This way I could retain my working fuel gauge. This was my solution to Ohm differences on YJ fuel gauges.

C) I have run external electric pumps (Ford E2000) and the internal factory pump is the way to go, if you are worried about changing pumps cut an access hatch in the floor while the tank is out-- That is what I did/am doing.
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