Fuel Pump. Which One?

[gogmorgo]

Here's a picture of a brand new XJ tank sitting next to my '91 MJ's old one. Napa sent the wrong one, and wouldn't send the right one. The tank was returned, but it took a couple months to get the money back.

 

 

My tank is the biggest an MJ came with, so yours may look different. I didn't take any measurements and this was around Christmas 2012, so it's been a long time since I've had the tank. But you can see how it's shorter and wider. IIRC height was roughly similar, maybe the XJ's was a little shorter there as well.

I'm not positive, but you may run into clearance issues with the driveshaft if you try to stuff an XJ tank where the MJ's goes because of the extra width. You can also see how the filler neck mounts to the side of the MJ's tank, but to the end of the XJ's, as well as the difference in where the fuel pumps go in. The fuel pump location isn't so much of an issue, just run longer fuel lines, but the filler neck would require work. If you flipped the tank around to make it a little easier to route the filler neck, then you end up with the lock ring on the wrong side and right up against the frame rail. You also would have to work something out to hang the tank there, as the stock MJ tank hangers won't be wide enough.

You might be able to put the tank behind the rear axle, where the spare tire mounts, but that's not ideal if you plan on wheeling. It would, however, shift weight backwards leading to slightly better distribution and road handling characteristics.

Something a bunch of people have done is swap in the tank from a Dakota. I've never looked into it, but it's an idea. You may also be able to adapt the XJ setup to your MJ tank. I understand it's not an overly complicated procedure, but make sure you know what you're doing if you attempt it. Again, I never have.

[creep_in_the_jeep]

What you're running into is the tools that run the websites list the same sending unit as the Cherokee as fitting the Comanche. Such is not the case. That is an XJ Fuel Pump Assembly and will not fit. You cannot buy an MJ Fuel Pump Assembly from a parts store anymore. All you can get are the bits that go on the assembly (fuel pump and wiring harness and hoses and clamps by themselves) which is the same between the 2 vehicles.

 

If you want to replace the whole sending unit, some members here have had success by replacing the tank with a 22gal unit from a early 90s Dakota and using the Dakota's assembly as well.

do they bolt right up? what do you all have to change?and is it true the 4.0 comanche needs a high pressure fuel pump?

[Jackrabbit41]

On 3/6/2014 at 6:49 AM, RockMJ said:

Alright guys, thanks a million times over for the part numbers! I ended up going with that Bosch unit because I had a credit on Amazon that knocked it down cheaper than the Carter. I did get that lock ring kit and Airtex strainer (didnt have the Bosch one) for dirt cheap on Amazon. The electrical connector on the Bosch setup is different than the oem setup but it does not look like it will cause any issues. Looks like it includes a piece for the connector that holds the connections together. Thanks for the help guys, and for the future I will be doing a small write up as well with part numbers and what not to help everyone out. Thanks again.

 

Part Numbers:

 

Bosch    69302 Fuel Pump Kit

Airtex     FS104 Fuel Pickup Kit

Spectra LO01   Lockring Kit w/Seal

 

RockMJ

So if i get all those parts, is that everything I need to do a new fuel pump