Okay I'd like to get
@RangerRick to hopefully comment on this to one help others if they decide to try a engine swap and two to help point me in the right direction before I start on my wiring.
I have been scoring tons of build thread on V-8 swaps into TJ's using the magnum V-8. While it isn't a high H.P. engine it can make decent numbers with a little work. And even though they haven't been in production now for 13 years there is still a following of them. Facebook has a few groups dedicated to them and doing performance modifications.
So there seems to be two different ways to do your wiring when trying to tackle this swap.
1) Use the existing TJ wiring harness and then cut off the TJ sensor plugs and measure the length needed for the V-8 while using the V-8 sensor plugs. Then solder & heat shrink the wires from the V-8 plugs into the TJ harness. Then take the 2 or 4 needed wires for the additional injectors and pin them into the appropriate PCM plug. This seems to work best for those who are doing the swap and plan on retaining a manual transmission.
2) Use the Dodge V-8 harness by removing all the looming and removing any unneeded wires by depinning them. Then once that is done taking the TJ harness and adding the needed TJ wires into the Dodge harness. This method seems to be more popular with the people who are using the Dodge automatic transmission. At this point I am thinking this is the way I want to go when I attempt to build my new wiring harness. But I will of course default to those who have more experiance than I.
Because I have a early TJ as I said earlier it seems there is a difference in the wiring harnesses. I haven't had a chance to really look at the wiring diagrams but from what I have read the FSM doesn't show the differences in the early models. Again hopefully
@RangerRick will shed some light on the subject.
Perceptive of you to see this on the two ways of going with the harnesses in a Magnum V8 swap.
In my two cases of swaps I used the ZJ Grand Cherokee engine bay harness cutting it off at the plug on the firewall and used the Jeep 2.5L early harness for parts to add into the ZJ Grand's harness. I also used the TJ alternator and charging circuit wiring separately from the plug-in ZJ harness. On ZJ's and possibly RAMs the charging harness section for the alternator/generator plugs in with a 6 pin plug. I used the TJ's electrical connections for the alternator but used the high-amp ZJ alternator that was already mounted on the V8 engine.
I used both plugs that go into the firewall on the TJ, adding those to the ZJ harnesses, I also used the fuel pump wiring,plug and sender harness from the TJ and added it to the ZJ's harness since the ZJ harness has an in-cab harness for the fuel pump and sender. This way the routing and sorting of the loom over the finished harness was fitted to the V8 properly and the wiring that goes to the fuel tank & sender was the correct length and routed properly as well.
Using the ZJ harness meant that all the connections to the engine itself were in the correct spot and all the engine grounds with the exception of the added for charging were in the same spot.
I also added the TCR, (transmission control relay & its fuse) into an empty spot on the original TJ PDC mounted on the passenger fender. I added ALL the needed connections to the Jeeps original PDC rather than try to cludge the ZJ's PDC that was full of un-needed relays and fuses for things that weren't options on a TJ ever. In the end, it all looks factory and fit like it belonged.
The more I worked on these harnesses, the more I realized that they were the same beast and with the exception of very minor things, everything on a RAM, ZJ or TJ were basically the same. Even every pin on the ECM is in the same place, just some vehicles have more pins because they have more electronics on board. It all started to make total and perfect sense once I got into it.
Having the factory manuals as pictured in my build thread was a key to understanding the differences between vehicle platforms. The particular year 1997 has some unique things like early TJ's had all different connectors on the harnesses for different plugs only used on the early years 1996 & 1997 TJ's. The VSS, Manifold air TEMP, TPS, INJECTORS and COOLANT sensor plugs were ALL different than my 1998 TJ. It showed in the manual pictured in my build the EXACT pin difference as some had the power, return and grounds switched around in the connector compared to later 1997 and newer TJ's with the same bus system.
The manual actually compared the ZJ & TJ together side-by-side in the book showing the differences in wiring to the ECM and what was different. I CANNOT STRESS ENOUGH HOW IMPORTANT THIS ELECTRICAL BOOK SHOWN IN MY BUILD WAS FOR USING THE ZJ HARNESS ON THE TJ BUILD. It opened my eyes and from there I was able to fully understand the harness in detail so I could customize it to look factory.
Mind you, one ZJ was a 5.9L & the other was a 5.2L and other than the cooling system with the E-fan on the 5.9L, everything was identical harness wise and would fit either engine perfectly. A RAM, Durango or Dakota will be very similar to the ZJ harness so I would use the truck harness and add the TJ firewall plugs plus the TJ fuel pump & sender harness to the under-hood RAM/DURANGO/DAKOTA harness. I would also use the charging system sub-harness from the TJ and connect it to the alternator that is on the V8 already. I would just re-wire the ECM charge control wire and also use the TJ battery thermal sensor on the RAM harness for an automatic.
On a manual, it may be easier to just add the wiring from the RAM truck to the TJ harness and re-loom or re-shape the harness to fit the V8 with the added wiring as needed. You wouldn't need any of the transmission harness plug wiring with a manual but would want to retain the neutral safety switch and backup lamp wiring the way it was done in the TJ so that's probably the biggest reason manual transmission swappers keep the TJ harness over using the RAM/ZJ harnesses.
RR