87Warrior Posted March 12, 2013 Share Posted March 12, 2013 I am striving to get one of my 91's driving. Follow the link in my signature for more information. One is a 2.5L HO (with engine harness chewed through) and the other is a 4.0L HO (3' section of frame rotted away, on one side). My goal is to build one running truck with a 4.0L HO. Both trucks are HO and have the Chrysler fuel injection system. My question is, will the 4.0L HO engine bay wiring harness mate up to the 2.5L HO dash harness? The plugs at the firewall are the same shape/size, but I am unable to find plug pin outs for the harnesses in the FSM to confirm. I do realize the 2.5 tach might not work correctly with the 4.0. I am trying to see if I can avoid swapping the dash/dash harness in the 2.5L truck that will hopefully be running a 4.0 soon. Thanks! Link to comment Share on other sites More sharing options...
Geonovast Posted March 12, 2013 Share Posted March 12, 2013 I'm not 100% sure, but I don't think they will. And for the tach, it shouldn't matter. 91+ tach was controlled by the ECU. The gauge cluster in that 2.5 came out of a 92 with a 4.0, and it reads accurately. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 12, 2013 Share Posted March 12, 2013 Are you referring to the firewall bulkhead connector? If so, the pin outs are shown on Wiring Diagrams 101 & 102 in the 91 Electrical FSM (pgs. 8W-252 & 8W-253). Link to comment Share on other sites More sharing options...
87Warrior Posted March 12, 2013 Author Share Posted March 12, 2013 Are you referring to the firewall bulkhead connector? If so, the pin outs are shown on Wiring Diagrams 101 & 102 in the 91 Electrical FSM (pgs. 8W-252 & 8W-253).Yes, the firewall bulkhead is the plug I am referencing. I must have a defunct digital version of the FSM as those pages are not in there. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 12, 2013 Share Posted March 12, 2013 I have the hard copy FSMs. I don't have a scanner, but I could snap a couple of hi-res pics and email to you. Link to comment Share on other sites More sharing options...
87Warrior Posted March 12, 2013 Author Share Posted March 12, 2013 Thanks Don. Check your PMs :) Link to comment Share on other sites More sharing options...
Eagle Posted March 12, 2013 Share Posted March 12, 2013 Considering that the MPFI conversion kit Jeep used to sell for the 4.2L carbureted Wranglers was nothing but the engine room harness from a '94 4.0L with MPFI, my guess would be that the dash harness is going to be okay. Why would they make two different dash harnesses for the same vehicle? The tach should have a potentiometer on the back to adjust between 4-cylinder and 6-cylinder. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 12, 2013 Share Posted March 12, 2013 On the way Brett. I didn't see any 2.5L or 4.0-specific pin outs. There are XJ-MJ diffs of course. BTW, the 91 bulkhead connector is a one-of a-kind HO animal and was changed completely in 1992. Link to comment Share on other sites More sharing options...
87Warrior Posted March 13, 2013 Author Share Posted March 13, 2013 Considering that the MPFI conversion kit Jeep used to sell for the 4.2L carbureted Wranglers was nothing but the engine room harness from a '94 4.0L with MPFI, my guess would be that the dash harness is going to be okay. Why would they make two different dash harnesses for the same vehicle? This was my thought as well. On the way Brett. I didn't see any 2.5L or 4.0-specific pin outs. There are XJ-MJ diffs of course. BTW, the 91 bulkhead connector is a one-of a-kind HO animal and was changed completely in 1992. Thanks Don! The images where clear as day :) I immediately noticed a difference in the bulkhead connector assembly, in comparison to my '92, when I started pulling the first one apart. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 13, 2013 Share Posted March 13, 2013 Great. If you need anything else while in progress on the 91's, just let me know. Link to comment Share on other sites More sharing options...
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