Ok

Here is my swap that I am doing and I have a few questions on it

I have an 89 2.5L with the crummy but reliable Throttle Body Injection system (T.B.I.).

The motor has 128k hard miles on it and is very tired and has low PSI in all cylinders!

I am going to be picking up a nice 2.5L and an AX5 from a 97 TJ very soon and I am looking into installing it with the nice and newer Multi Port Injection system (MPI).

The motor is complete with all EFI, Computer and etc…. It doesn’t have the ENTIRE harness but 99% of it is there.

My questions are this:

-Which fuel pump would I need?

-Is the one from a 91+ 2.5L with MPI the same as the TJ ones? Do they produce the same PSI? I am assuming I need a new tank from a 91+ YJ as well to accommodate the new pump and sender unit. I know that the MPI and TBI ones are different and these put out different PSI’s

-Would I be best of using the wiring harness from a 91+ 2.5L YJ instead of the TJ one? The AX5 I am getting has the CPS for the newer MPI! What are the changes with emissions and such with the TJ?

-What, if any are the differences between the YJ and TJ MPI?

-Sensors? Brackets? Etc..

Anyone done the TBI to MPI swap before??

Any small things to look for??

Any info or tips would be great!!

Thanks a lot!!

Shoot, i dont know much about the new MPI stuff.
I would think that a 91 or newer plastic Wrangler tank, and a pump for a 4.0 would be more than enough to handle the 2.5 MPI.
The engine management harness will have to be from the newer, engine as it will be hooked up to the neccessary engine sensors and components. I wouldnt mess with the rest of the vehicle wiring harness, as you should be able to patch the the monitoring sensors to the gauges.
The I way I would do it, is to yank the old engine, install the new engine and start solving problems, as they appear.

The 2.5 liter MPI used the same fuel pump as the 4.0 liter MPI, so either is usable. I swapped a 93 tank into my YJ when I still had the TBI injection running and had no problems. Remember to change the fuel lines to HIGH PRESSURE ones (available at just about any parts store) and use high pressure hose clamps (they are smooth).

Also, as one more pearl of advice..... it just so happens that the 2.5 liter MPI fuel pump WORKS to power a Tuned Port Injected Chevy V8. I speak from experience.


Matt

btt