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Fuel Pump diff between 87-91


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OK i have just started research since not much wrenchn' is going on since the baby came. I am doing a swap to the 91+ 2.5 with MPI from My tired 87 2.5 MPI. Now I'm pretty sure that the Fuel pumps and sending units are Diff cause the fuel pressure should be Diff between MPI and TBI. I just want to make sure I'm correct.

 

My main question is would a 91-94 or so XJ fuel tank swap into my truck in plce of the stocker. Or could i make it work easily?

 

Also could I get a sending unit and pump that will fit my stock tank and work on the motor.

 

Now i know i could find alot of this out with a few min-hours online searching but i don't want to spend alot of time on here right now. Thanks for all your answers.

 

Cole

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OK i have just started research since not much wrenchn' is going on since the baby came. I am doing a swap to the 91+ 2.5 with MPI from My tired 87 2.5 MPI. Now I'm pretty sure that the Fuel pumps and sending units are Diff cause the fuel pressure should be Diff between MPI and TBI. I just want to make sure I'm correct.

 

My main question is would a 91-94 or so XJ fuel tank swap into my truck in plce of the stocker. Or could i make it work easily?

 

Also could I get a sending unit and pump that will fit my stock tank and work on the motor.

 

Now i know i could find alot of this out with a few min-hours online searching but i don't want to spend alot of time on here right now. Thanks for all your answers.

 

Cole

 

cherokee tanks aren't interchangeable with comanches. not even near the same dimensions.

 

BUT i think you could combine the cherokee and comanche pumps to make one that would function with your truck. they're the same dimensions about, just different pressures.

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xj is in the front upper side, comanche is the right upper side.

 

and I will explain further for your better understanding.

 

in a manche tank, you HAVE to use the main part of the pump assembly.

 

however, I believe that you can swap out the PUMP ITSELF into the comanche "pump carrier" which is the piece that plugs into the tank.

 

 

cherokee/comanche sending units are NOT interchangeable, neither are the tanks.

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Ok, I put a new fuel pump in my Comanche. I bought it off ebay. I had to do some modifications because the two pumps were different. The original was a bosch, I think, and the essential difference was the mounting bracket because the original unit is for the optional 23 gallon tank, or something close to that. The replacement was for the standard gas tank, around 14 gallons I think. The unit was a complete replacement with the sending unit. The pump motors were different so I had to do some fooling around to fit the new pump to the original bracket since I needed the extra length of the sending unit on the original. I believe that there were three fuel pump motors from different suppliers, all for the same tank sizes. This is for 1990.

 

Likely the replacement will be for the normal fuel tank size and you probably will not have to do any thing. :USAflag:

 

I would suggest you make sure the pump runs in the right direction before you install it. I just used a bucket of water. Run a couple of jumpers to find which lead is needed for the power in order for the pump to run the right direction. Yea, guess how I found out about this one? It's nice to only pull the pump once, it's always exciting working around an open fuel tank, so save yourself the trama of this learning curve.

 

Fuel pressure increased with the 91 model year and the introduction of the HO cylinder head. At any rate, I would think the pressure regulator would handel that aspect.

 

TBI has pressure only with the pump running and my book says its at 14 -15 psi at idle.

MPI or multi port injection, they say multi point injection, has an vacuum assisted pressure regulator; with the vacuum line attached the pressure should be about ten pounds lower, or around 29 PSI. With engine off and key on the regulator should read 39 PSI. CAUTION, This could be reveresed as my book first says with the line attached, and latter with it detached it should read 39 PSI. Pretty sure its lower with line attached and the truck running.

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OK a second plan would be to run a inline pump. HAs anyone got any experience and what do you think about doing it. I'm not sure but i would prob have to unhook the conections and such from the stock one but somehow let it still allow fuel to flow. I am starting to think i might make a fuel cell but i really don't know if i want to as of yet. I just want to do it as easy and simple but keep the cost down without compromising the function and reliability. Any inputs are welcome. BTW JeepcoMJ I see what your saying as far as adaptibility and all. I was hoping i could swap the tanks and be done but its a JEEP so i knew it would be more complicated.

 

Cole

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