fuel injection

I was wondering what all I would need to change over if I was converting a 89 4.0 injection system to newer 94 4.0 injection system. Any help would be apprecciated.
Thanks:huh:

A better question is why do you want to do it.

The changeover is not trivial and would require a full new wiring harness along with computer and dash electronics. The power changes in the HO are overrated. The difference comes mainly from the head and intake manifold, not the injection and computer..

thats all I need to know but will the injectors from the newer motor work on the older motor the reason I ask is because I have a complete newer motor with a bad crank????

Stay with the RENIX! I have 4 XJ's 90'(RENIX) 94'(OBDI) 96'(OBDII) and 01'(OBDII). The 90' has much more low end torque, I've towed my boat with all 4 and the 90' is the only one still on stock gearing that can easily pull 3100#'s of boat and not struggle on take off.

The RENIX takes some getting used to but is much easier to diagnose.

If you need injecters get the Ford 5.0 HO yellow top 19# per hour units.

Your later model injecters should be fine as well just replace the "O" rings.

xjtrailrider said:

Stay with the RENIX! I have 4 XJ's 90'(RENIX) 94'(OBDI) 96'(OBDII) and 01'(OBDII). The 90' has much more low end torque, I've towed my boat with all 4 and the 90' is the only one still on stock gearing that can easily pull 3100#'s of boat and not struggle on take off.

The RENIX takes some getting used to but is much easier to diagnose.

If you need injecters get the Ford 5.0 HO yellow top 19# per hour units.

Your later model injecters should be fine as well just replace the "O" rings.

Click to expand...

i thought the earlier xj's had some different trans ratios but i could be wrong. but i had a renix too. i loved it until i tried bolting all that stuff to a 4.2 with a 4.0 HO head. things didnt work out to nicely. but yeah it did have a lot more torque compaired to my 96.

you can keep the same injection system and replace the head intake, TB, linkages, and exhaust manifold and down pipe with a HO version. but its alot of work. do i search, i think there should be some info on switchingit over. hope that helps!

Beware that the new intake does not have a place for an EGR valve and takes a different throttle body.