DAGAD

@wombat My dad wants to do what you suggested - change out the fuel rail - purchase a 1990 pump and sending unit, and at the same time switch out the computer to a 1995 so that there isn't an emissions code from the fuel tank. I'm not even sure the 95 computer will plug into the 96 harness? My goal is all 1996 (or newer) - so I think I need a charcoal canister looped back on itself so the sensor can have something to plug into??

the new '92 xj-style pump does not fit in my 1987 mj tank - the pickup hits the sump/baffle and it won't install. Also the '92 pump sending unit does not work with my 1996 dash (though I heard they are supposed to work). I plugged it in and moved the float with no change to my gas gauge. (could this be a grounding problem?) I finally found on here what I was looking for thanks to @Swampy- He has an older project similar to ours. 1996 drivetrain into a comanche. it turns out at least some of the aftermarket tanks don't have a sump/baffle, so the xj sending units work. I'll check and if they don't reach the bottom of the tank, I think I can modify it easily to get there.

@gogmorgo Thanks - regarding what you said: This pump worked >10 yrs ago, sat unusued for a long time, and then worked again when we put a battery in the truck. but it never ran longer than 20 min because the cooling fans aren't working. We did consider something coming apart in the tank - but that wasn't the case when I pulled it out. The hoses in there certainly weren't "submersible" though. They were really rough. that's helpful to know the 91-96 clusters are the same. I noticed there is a bump in the middle of the sump at the bottom of the tank - it looks like a little perch for the pump to sit on. If that's the case, the strainer/pickup doesn't quite reach the bottom of the tank anyway. I have to wonder how different it is to put a cherokee/right facing pump in there if it doesn't rest on the bottom of the tank regardless. Perhaps the perch helps keep the strainer from falling off? I'll be sure to report back on what we finally do so this info can be on the interwebs for others to find later:-)

@Eagle_SX4 thanks for the reply - especially to a stranger/new member:-) The MTS units are all the same size and shape - even the 91 and 92 units. The parts store and amazon show a an overlap of xj and mj units for 91 and 92. You are correct, the float and strainer point toward the front of the vehicle (right) if it's an xj unit. The youtube video referenced above clearly shows an right (forward) turning fuel pump in an MJ tank. I'm wondering if the after market tanks are specifically made to accept either direction pumps? The crown unit you referenced is the one I'm considering. The MTS JPSU-7 will have different ohms on the sender and not interface with my gauge cluster w/o the meter match solution shared by ohm. I'd really like the xj unit to work in the mj style tank - just like the youtube video shows. . . has anybody tried this?

Sweet. Thanks Ohm. That is one solution to the gas gage problem. This mj has been sitting since the '96 swap about ten years ago - I think I'm going to replace the sending unit regardless as I'm hoping to be a part of a 1000+ mile trip this summer that is going to push the jeep. If I end up replacing the sending unit with a one not compatible with the dash - I guess I can spend another $90 to get a working gas gauge :-) I'm really need info on if the aftermarket gas tanks that look OEM are different inside making them able to accommodate either style pump. If they are the same - I'd love to hear from someone who has run an early xj style pump (forward facing float and screen) in the mj fuel tank. One other person on here said it can work but requires mods. . .

we have an '87 comanche short bed with a 1996 drivetrain, electrical, dash, etc. We have rigged up the in-tank fuel regulator required for the '96 to the original 1987 pump and sending unit in the original '87 tank. The jeep ran for a bit but has now stopped. There is no fuel at the rail despite hearing the pump turn on. The gas gage never did work since the swap. We are looking for solutions: a working gas gage and a reliable, quiet pump. I've heard the 1996 pumps are great (smaller and quieter). The aftermarket, oe style fuel tanks are advertised as replacements for 86-92, despite the 1991, and 1992 having very different pumps. The 1992 comanche fuel pumps/sending units (entire assembly) on Amazon are different than the 87s and and are advertised as working in both the xj AND mj tanks. We purchased the 1992 mj/xj sending unit on Amazon but are likely sending it back because it looks like it's not made for our '87 fuel tank. the 1992 sending unit float and screen point toward the front of the jeep, not the back like the 1987 sending unit. The 1996 sending unit appears to be the same shape and also has a float that points toward the front of the jeep just like the 1992. The 1987 tank (I can confirm) has the ballast at the back of the tank and it seems the 87 float and fuel screen likely sit in the ballast. This youtube video by "major weakness" shows a 1991 tank with a ballast at the back of the tank despite a float and screen assembly that point toward the front of the vehicle but the pump and sending unit work great??? Here is the video name: Fuel Tank and Filler Hose Replacement Jeep Comanche MJ #jeepmj #jeepcomanche Can I purchase an aftermarket mj fuel tank and put in a 1996 fuel pump assembly w/o modifications to the xj sending unit? I'm willing to modify, but if I'm purchasing new items regardless, it seems superior to complete the 1996 drivetrain with an oe style pump/sending unit/regulator. Cost is $100 for an MJ fuel tank and $200 for 1996 pump/sending unit. Old fuel tank is full of garbage (old pieces of fuel hose, etc) but does not leak - If the new tank works, I was considering mounting the old tank on the passenger side for a dual tank setup in the future.

I'm interested in hearing more about your jeep that you're considering selling:-)