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rdjustham

FUEL PUMP

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went to pepboys to buy a new bosh pump and the one they sold me had the name carter on it. the salesperson said carter and bosch murged? took it home went to swap it in and the dang thing is like two inches too long and way to fat :fs1: :fs1: :fs1:

 

any ideas? is there a possibility the PO put a differrent fuel pump mounting deal in? anyone know the dimensions of the fueld pump its self so i can measure both the old and new

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The difference you describe sounds like the differences between a 2.5's pump and a 4.0's.

I don't think a 4.0 can run on a 2.5 fuel pump. Here's pic's of both

 

2.5

 

 

4.0

 

 

 

Maybe it will help.

 

:cheers:

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neither one looks like mine...

 

Image Not Found

 

the piece that holds the fuel pump is off in this pic ill try to get one today of the whole assembly put together

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I have to change the pump holder for rust issues.

 

I bought an pump assembly from a 2.5 and change the pump.

 

Everything work fine. :clapping:

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I have to change the pump holder for rust issues.

 

I bought an pump assembly from a 2.5 and change the pump.

 

Everything work fine. :clapping:

 

o k so you bought the 2.5L pump but it says on your signature that you have a 4.0L would the pumps being different affect power and fuel dilevery :dunno:

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I have to change the pump holder for rust issues.

 

I bought an pump assembly from a 2.5 and change the pump.

 

Everything work fine. :clapping:

 

o k so you bought the 2.5L pump but it says on your signature that you have a 4.0L would the pumps being different affect power and fuel dilevery :dunno:

 

No, what he is saying is that he has the 2.5 assembly( sending unit and holder ) and put a 4.0 pump on it.

 

That is the same thing I did above. The pic of the 4.0 pump is on the before pic's 2.5 assembly.

 

Image Not Found

 

I've never seen one like this but then again, I've never seen an a real 4.0 assembly for an MJ. The 4.0 from an XJ looks like the 2.5's (except pointing in the opposite direction in the tank and having the larger pump)

 

Thought maybe that was an old 2.8 sending unit that had been moddified for the pump. :dunno: Does it look like the tube has been brazed on it?

 

And in case your wondering, here is a pic of the 2.8s assembly. They had a mechanical fuel pump so all it had was the sending unit.

 

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I put the Bosch pump on my '87 2.5 and it was definitely not a bolt in replacement. I had to modify the sending unit to make it fit. If I remember correctly I had to move the sending unit ground and a few other things around so I could move the retainer bracket up. It works ok though.

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At least for the Renix years, 87 through 90, all the assemblies I've had go through my hands (3 of them so far), fit both a 2.5 pump and a 4.0 pump.

 

But a 4.0 will not work with a 2.5 pump, and a 4.0 pump may overpower the pressure regulator on a 2.5. The 2.5l TBI runs a lot lower pressure than the 4.0 MPI.

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could it be pep boys gave me the one for the XJ which is larger, and that is the reason it doesnt fit? Next ques, anyone know where i can get a new assembly and please don't say jy we don't have one here that i know of..

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could it be pep boys gave me the one for the XJ which is larger, and that is the reason it doesn't fit? Next ques, anyone know where i can get a new assembly and please don't say jy we don't have one here that i know of..

 

If that pic you posted of the carrier is what you have, it does look like a XJ carrier to me. Biggest difference is the straight hose outlets, the XJ's are flat as the tank position is 90degrees different between XJ/MJ. If same motor, I see no reason why it wouldn't work, its just different. I am NOT sure about the interchanging of 2.5 and 4.0 pumps.

 

CW

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Comanche pump and Cherokee pump are identical. The sender/pump assembly is different between the two, and not interchangeable. Problem is nobody makes Comanche ones any more, and the manufactures (and therefore store) insists they are the same and will work; which they don't.

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The XJ fuel pump assembly does not fit in an MJ tank. The MJ tank has a pan inside it welded to the bottom. The XJ sending unit float goes the wrong direction and interferes with the side of the pan.

 

Some after market tanks do not have the pan. In those tanks an XJ assembly *might* work.

 

And I repeat, an XJ pump is the same as an MJ pump. The only difference between the pumps is 2.5l/4.0l and Renix (86-90) versus Chrysler (91-92).

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Yeah, no, I went thru this problem a while ago.

Nobody has a new carrier/sending unit as far as I know even though everyone will try to tell you they are the same for the XJ/MJ. (They are not.)

 

IIRC Dr. Thunder modified one but I can't remember how. You'll have to search the forum for it, and I don't think he ever made a write up.

 

Also if IIRC Wildman has a write-up on how to refurbish the senders and I even think he'll send you a rebuilt one. Sorry If I'm wrong about that being you Wildman. Somebody correct me if I'm wrong.

 

Or you could post up a WTB ad in the classifieds for the correct sender (hopefully in good condition) and just buy the actual pump new from the store.

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I've got a Renix sender/harness assembly that I pulled out of a junkyard 2.5 MJ. The only problem is that the faceplate has a couple (typical) cracks in it where the hard lines exit. I was going to have my neighbor buddy take it into his work and TIG it and keep it as a spare, but if you need it and can repair it locally, shoot me a PM and we can maybe work something out. I really don't want to sell it because of it's rarity, but if it means keeping another MJ on the road, I can be persuaded to ;)

 

 

 

Jeff

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The XJ fuel pump assembly does not fit in an MJ tank. The MJ tank has a pan inside it welded to the bottom. The XJ sending unit float goes the wrong direction and interferes with the side of the pan.

 

Some after market tanks do not have the pan. In those tanks an XJ assembly *might* work.

 

And I repeat, an XJ pump is the same as an MJ pump. The only difference between the pumps is 2.5l/4.0l and Renix (86-90) versus Chrysler (91-92).

 

Eggzakerly right. Makes you wonder why the AMC/Mopar engineers didn't design the tank baffle plate so the MJ and XJ sending units were interchangable in the tanks. :nuts:

 

The hardest sender of all to find is the 91-92 MJ-specific HO sending units mainly because there were less of the MJ HOs manufactured. But at least by then the MJ and XJ shared the same pump regardless of engine size, and the MJ tanks were standardized, so there was only one HO MJ sending unit. I found a new sender on Ebay by doing an advanced search using the correct factory part number. The guy had no idea what the sender fit, but did include the p/n in the description. There are many many sellers on Ebay that sell NOS parts on Ebay and are clueless as to what they fit. So, ascertain the correct factory part number of what you need, and do an advanced search on Ebay motors for it. And with all the Chrysler dealers going belly-up and selling off all their NOS parts, sooner or later they'll show up on Ebay. Prolly be plenty of MJ tail light assemblies showing up too. :cheers:

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The XJ fuel pump assembly does not fit in an MJ tank. The MJ tank has a pan inside it welded to the bottom. The XJ sending unit float goes the wrong direction and interferes with the side of the pan.

 

Some after market tanks do not have the pan. In those tanks an XJ assembly *might* work.

 

And I repeat, an XJ pump is the same as an MJ pump. The only difference between the pumps is 2.5l/4.0l and Renix (86-90) versus Chrysler (91-92).

 

Eggzakerly right. Makes you wonder why the AMC/Mopar engineers didn't design the tank baffle plate so the MJ and XJ sending units were interchangable in the tanks. :nuts:

 

The hardest sender of all to find is the 91-92 MJ-specific HO sending units mainly because there were less of the MJ HOs manufactured. But at least by then the MJ and XJ shared the same pump regardless of engine size, and the MJ tanks were standardized, so there was only one HO MJ sending unit. I found a new sender on Ebay by doing an advanced search using the correct factory part number. The guy had no idea what the sender fit, but did include the p/n in the description. There are many many sellers on Ebay that sell NOS parts on Ebay and are clueless as to what they fit. So, ascertain the correct factory part number of what you need, and do an advanced search on Ebay motors for it. And with all the Chrysler dealers going belly-up and selling off all their NOS parts, sooner or later they'll show up on Ebay. Prolly be plenty of MJ tail light assemblies showing up too. :cheers:

I guess by 1983-4 the AMC designers weren't as efficient as in the Brooks Stevens day of reusing parts for different models and applications.

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guys thanks for all the help...found a member on here whos shipping me one. appreciate it, hope this works, no tellin what else was redneck engineered on this thing...

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