Fuel Pump Assembly

[CEThomas]

Looking for a fuel pump Assembly with pump & sending unit as we need a new sending unit. I had ordered a new unit from Advance but it did not come close to fitting, think it may have been a XJ unit but did not have any XJ units laying around to look at. Auto Zone and RockAuto both show the same unit and part number as the 7072S unit I got from Advance :nuts:

 

So has anyone used a new assembly with a part number of 7072S and had any luck with it fitting??? I do not want to order another one just to find that I have to send it back :roll:

[chicofuentes0224]

Part number 7072s is for a cherokee fuel tank. It will not fit a MJ gas tank because it hits the pan in the tank.

The MJ fuel pump sending unit is no longer available new. Believe me I've looked everywhere.

Here's your options.

1)Get a cherokee gas tank and see if you can somehow mount it on the MJ.

Never tried it.

2)Buy an MJ gas tank without the pan in the tank.

This might work. But then your gas gauge will fly back and forth.

3)Try and find a used one.

It'll last a little but probably break just like yours did.

4) PM Wildman. He knows how to fix them and he'll send you a fixed one if you send him yours. At least that's what he was doing a little while ago. That's your best bet.

 

I take it yours is leaking at the metal tubes that go into the round base right?

I'll do a search on the instructions Wildman had to fix them.

[chicofuentes0224]

Here read this post. Wildman's info is at the bottom.

 

http://comancheclub.com/forums/viewtopic.php?t=9433&highlight=fuel+pump

[CEThomas]

No,

 

Pump works fine, just it's a 89 sending unit in a 92 system. Never know how much gas is in the system , and tired of running out of gas :mad: Any time after 1/2 be ready to run out of gas :nuts:

[jtdesigns]

No,

 

Pump works fine, just it's a 89 sending unit in a 92 system. Never know how much gas is in the system , and tired of running out of gas :mad: Any time after 1/2 be ready to run out of gas :nuts:

just fill it up and go by millage until you can find a fix.

[Wildman]

I know you've had this problem for some time........I thought you could swap the wires and it would work........Negative ground to a positive ground for the '91+ era :hmm:

 

Any Yes Chico........I'm still doing the sender unit swaps :D

 

And.......this shows the difference on the XJ and MJ sender units-

[CEThomas]

No,

 

Pump works fine, just it's a 89 sending unit in a 92 system. Never know how much gas is in the system , and tired of running out of gas :mad: Any time after 1/2 be ready to run out of gas :nuts:

just fill it up and go by millage until you can find a fix.

 

Never get the same MPG on a tank, so it a crap shot short of making a gas stop at 1/2 tank :nuts: And at the price of gas, can not leave a full can of gas in the back :mad:

 

Looks like YJ hunting time :roll:

[CEThomas]

I know you've had this problem for some time........I thought you could swap the wires and it would work........Negative ground to a positive ground for the '91+ era :hmm:

 

 

If it were a 2 wire system it would work, but the ground on the sending unit grounds to the pump cage to the tank to the bed :nuts:

[HOrnbrod]

No, Pump works fine, just it's a 89 sending unit in a 92 system. Never know how much gas is in the system , and tired of running out of gas :mad: Any time after 1/2 be ready to run out of gas :nuts:

 

The polarity of the fuel sending unit changed in 1991, that's why your gauge is reading in reverse. Locate a schematic for the 89 sending unit in the correct FSM (I don't have one) then ID the terminals at the tank. Swap the 12V feed with the ground wire that correspond to the potentiometer legs of the sensor. This will change the polarity of the potentiometer output (slider) to your fuel gauge, and it will read close to normal. But since the potentiometers are of different values in the Renix and HO vehicles, the fuel gauge will not be spot on, but at least it will indicate FULL and EMPTY in the proper direction. Make sense??

[CEThomas]

I did try to build a unit using a MJ cage and XJ sending unit. It worked the right direction but was also way off on the amount of gas in the tank :cry:

 

Not good if you are 25 miles away from gas at night :redX:

[Wildman]

What Mr. Hornbrod said is correct :thumbsup:

 

I'm just too tired tonight to type that much :roll:

 

If you 'built' one, and the fuel level was off, did you try bending the float arm to make the adjustment????

 

Or even replacing the the float with the MJ float and arm???

[HOrnbrod]

I did try to build a unit using a MJ cage and XJ sending unit. It worked the right direction but was also way off on the amount of gas in the tank :cry:

 

Not good if you are 25 miles away from gas at night :redX:

 

Well, getting the gauge going in the right direction is a good start. The reason for the inaccuracy is the resistance value of the potentiometer, the input sensitivity of the fuel gauge, and the upper and lower travel limits of the float arm. If I had a sending unit of each, I could compensate with either parallel or series resistor packs to provide reasonable accurate fuel gauge readings. But, I no have........ :cry: Interesting problem though.

[CEThomas]

Could not get the MJ float arm to work, and tired of the pull and bend the float arm and see if you have it right gig :nuts:

 

This is not a weekend rig but his DD and in 12 months he will be driving to college each weekend on a 112 mile drive with a 50 mile drive through a black hole with little to no cell coverage and not many people.

[CEThomas]

I did try to build a unit using a MJ cage and XJ sending unit. It worked the right direction but was also way off on the amount of gas in the tank :cry:

 

Not good if you are 25 miles away from gas at night :redX:

 

Well, getting the gauge going in the right direction is a good start. The reason for the inaccuracy is the resistance value of the potentiometer, the input sensitivity of the fuel gauge, and the upper and lower travel limits of the float arm. If I had a sending unit of each, I could compensate with either parallel or series resistor packs to provide reasonable accurate fuel gauge readings. But, I no have........ :cry: Interesting problem though.

 

Thanks,

 

That is the answer as to why my unit did not work. You colud not tell the difference between the 2 but was way off, that's the answer to why. Now jsut to find a used one.

[chicofuentes0224]

Ok, so you need a 91+sender and pump right?

Is your's a 4.0?

[CEThomas]

Yes,

 

Made the 89 2.5 to 92 4.0 swap.

[chicofuentes0224]

Well why didn't you just say so. I have a sender and pump out of a 91 4.0 Comanche eliminator I got a while back from another member.

 

http://www.comancheclub.com/forums/viewtopic.php?t=8002

 

This was off of his. I never tried to use it because of the gauge reading backwards problem so you'll have to ask him if it worked correctly. Anyways, it's yours if you want it. Just let me rummage thru my shed tonight and I'll make sure my two year old didn't use it for batting practice.

[CEThomas]

Great,

 

PM me with the details after you check :cheers:

[chicofuentes0224]

You got it :thumbsup:

I'll PM tonight about 11:00pm

[Grant]

My fuel guage seems to be way off. I have an 86 LB. did the tank measurement and capacity calculator which tells me I have a 27 gallon tank take out for the ridges and indentations 23.5. When the feed me light comes on, we can never put in more than 12-14 gallons. Factory specs call for either an 16,18 or 23.5 gal tank. sending units are 5200 3671 for 16 gal, 5200 3644 for 18gal, and 5200 3652 for the 23.5 gal ALL W/7' boxes.

 

also, my tach is off by what appears to be half. Idles at 18-2000, runs down the highway pegged in 5th gear doing 65. By my 51 year trained ear I know it not even close. Any Ideas. The amp guage and oil pressure seem to be correct, but op started doing a weird wiggle thing once in a while. Temp never moves off the blue cold range even thought the heater works awesome.

[Alan C]

Hi, All! This is the most helpful discussion I have found on this issue. Thanks for the thoughtful posts. The thread started 10 years ago, and I am having he same problem chicofuentes0224  described as "I take it yours is leaking at the metal tubes that go into the round base right?"  Either the tubes or the wires, yes.

 

The link to  Wildman's instructions has gone bad (and both seem to have not posted for a while). Anyone have a link or even a hint at searching?

 

My plan has been to find a used assembly and work on refurbishing it, then swap with my current one. I am hesitant to start working on my current one because even thought it seeps gas, at least it works and were I to break it I would be up the proverbial creek. But even finding a used one is proving difficult. Any thoughts on all this would be most welcome. My '89 MJ has been my DD since '89 and I am not ready to give up yet! Thanks!

 

[Tommot_1]

Modify a jeep Cherokee for your Comanche I have done it. Kaw4sale@yahoo.com

[Monte721]

Reposting from a similar thread but I replaced my fuel pump, and apparently the entire sending units are no longer available? 

 

My issue now after it was reinstalled is its leaking fuel from the center yellow electrical inlet which seems a little loose, without taking it back off yet and playing around with it, does anyone know if this an easy repair or require me to look for used one somewhere?