poly fuel tank questions

yjmudder90 · #1 (**permalink**) 05-03-2008, 05:26 PM

first off, do 90 yj 4.2/ax-15 come with poly tanks??? second, can all poly tanks do the 20 gallon mod??

yjdave · #2 (**permalink**) 05-03-2008, 07:19 PM

yes and most if not all 6cyl come with 20 gal tanks

Bounty__Hunter · #3 (**permalink**) 05-05-2008, 01:03 AM

I think they used steel tanks until '91, and it's a 15gal unless it was spec'd with a 20gal tank.

You can only do the 15-20gal conversion on the '91-'95 poly tanks.

yjmudder90 · #4 (**permalink**) 05-05-2008, 07:58 AM

well i noticed that my tank is a poly tank.... maybe the po replaced it??? does that mean i can do the conversion??

dandoc · #5 (**permalink**) 05-05-2008, 10:54 AM

If you're able to talk to the previous owner, find out from them firsthand. Not all aftermarket poly tanks are capable of being converted to 20 gallon. The capacity of the tank should be stamped into the exterior (usually on the top). If you decide to drop your tank, be wise and have as little fuel in there as possible. How many gallons of fuel do you max out at now?

Bounty__Hunter · #6 (**permalink**) 05-05-2008, 11:19 AM

Quote:

Originally Posted by yjmudder90

well i noticed that my tank is a poly tank.... maybe the po replaced it??? does that mean i can do the conversion??

Looking at your jeep from the rear, notice the space between the tank and shackle where the exhaust pipe exits. Do you have a similar space on the driver's side? If so, you have a tank that's physically 15gal and can not be converted.

If the driver's side of the tank is up against the shackle, you should have a 20gal tank that may be limited to 15gal with the extended vent tube. Then you should be able to do the conversion.

My '88 4.2 with 15gal tank had an equally large gap between the tank and shackle on each side, was perfect for routing the dual exhaust that looked like original equipment.

lah2420 · #7 (**permalink**) 05-05-2008, 05:34 PM

My 87 has a factory poly 20 gallon tank. It's like Bounty said. There is only about an inch between it and the shackle on the driver's side. I don't know about the 90, but the 87 came with 2 different tanks. The 14.5 even had a smaller skid plate. I'm pretty sure the 15 to 20 gallon conversion only worked on 91 or 92 and up.

yjdave · #8 (**permalink**) 05-05-2008, 07:57 PM

My 87 also came with a 20 and when i did the 4.0L swap i put a 20 from a 95' with the FI pump w/o any probs