My kid wanted a Jeep, she's getting a 77 FJ40 LS Swap instead

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Augustiron said:
Don't assume your harness is ok if everything else has been eliminated.
I have heard enough stories about new harnesses from even the best suppliers having issues to not overlook them.
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Verifying the harness pin outs is what got me on the road. I had one, don’t remember which, loose and I couldn’t get it to fire. I was dreading diving back into the harness, but once I started it was pretty straight forward. Find a good pinout guide online and verify each pin individually. Even if that’s not it (it was for me), it’s good to know they are done right.
 
archie73 said:
Verifying the harness pin outs is what got me on the road. I had one, don’t remember which, loose and I couldn’t get it to fire. I was dreading diving back into the harness, but once I started it was pretty straight forward. Find a good pinout guide online and verify each pin individually. Even if that’s not it (it was for me), it’s good to know they are done right.
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thanks. Yes I am dreading it of course, until I verify power at the end and rule out the CKP I am still scratching my head. Hopefully this weekend I can get to the bottom of it.
 

If you can work through the 1999 geocities formatting, all the harness pin out info is there....

Pics to share the pain....

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welp, I believe I have a short. Now I need to find it. I pulled the starter, tested the crank sensor wires (ground/power), and then reinstalled the starter and scratched my head. I have 5v on both outside wires, after some research I found that I should only have 5V on one of the outside wires. I found another article on my steps going forward to find the short (let the fun begin):

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its a rare occasion I get time to work on the truck lately, and like most I dread wiring (except Coolerman). Its a methodical process that is more research than execution for sure. Since last night I have done more reading and experimenting on how power flows from the ECM to the CKP. Luckily I was able to pull the CKP wire topside so it was easier to diag. I systematically figured out that the CKP runs from the starter area to the grey plug on the ECM. I then did a continuity test of the wires and were able to see where they are pinned in the plug. I then after identifying where the wires are powered checked voltage on each of the wires. The ECM puts out 5v on several wires and for this purpose the BW wire from the CKP and not the WB wire. Somewhere in the harness I have a short and at the CKP I have 5v on both the BW and WB wires, the WB corresponding pin does not have power. Both the ECM and CKP grounds are GTG.
So the next step is to pull the harness and find the short.
 
How much did you pay for the harness?

If it was one of those $700-$900 ones from a "reputable" company, I'd ask for a replacement.

The value the "reputable" harness guys are selling is the notion you won't have these problems with their harness vs the $100 Amazon harness and they will be plug and play.
If they aren't plug and play, the 5-7x cost of a no name is lost.

But I understand your wanting to dig into it and have a look and understand the problem.
Of course you have to rule out installer error (damage) also

Good luck
 
Todays update. My drivers side flashers and turn signal didn't work. As this isn't my first rodeo, I pulled the hazard switch and tore it down. It really is super easy to work on a lot of the items on the truck, after some cleaning and a little dielectric grease I put the switch back together and the lights worked. Later in the day when I saw my daughter, I wanted to show her that the turn signals and lights worked. Well, the turn signals worked but the flashers didn't. That's a total head scratching moment as you need the hazards to work for the turn signals to work. So in the last two photos you will see the broken spade for the flasher. I tried to patch it back together with no success. I made a regular flat spade work with some trimming and I adjusted the switch side to make it work. I also cleaned the grounds and my rear side marker lights are also working too.
These are small items to distract me while I wait on the engine harness repairs.

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Nothing major on the project over the past week. I have been working through my no start issue, the harness builder asked I send them the ECM to see if there is something wrong with what the tuner did. Hoping to know something by mid-week if the ECM was the cause or not. Should it not be the issue then I need to pull the harness, dreading it but it may be needed to find the short.
I added the line for the fuel vapor separator through the body, I will need to run it the rest of the way. I need to figure out how to tie it in the LS purge valve and how to power it as well. I have the stock purge valve on the harness. I also installed the OE license plate bracket.

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Update. So BP automotive said there were somethings off in the tune and the VATS were not turned off, ironically though the other stuff the tuner did was there. The ECM came in this afternoon and I threw it in. The truck started, I shut it off right afterward just to check everything over. I started it two more times and it fired right up. On my fourth attempt it didn't start. I might have run the battery down or there isn't enough fuel in the tank but all in all it was a success. I put the battery charger on it and will throw some more gas in it tomorrow or over the weekend.
I do have some codes too, two are for the O2 sensors. As I dont have any pipes this is easily explained. The next one C0300, most likely the rear speed sensor. I guessed on the tolerance as I missed that on the adapter assembly until it was too late to check the sensor depth. I can try a quarter turn and out to see if it changes. I basically bottomed it our and backed it out a quarter turn. I also had a B2AAA (might be from my code reader) and also P0102 MAF voltage or something.
I will chalk it up as a win, still more to do and I can work through a lot now that it starts.
 
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Two steps forward, seven steps back. I added some gas and put the charger on it to see if it would start without success. It cranks but then bogs down and voltage drops. I have spark and fuel on the rail. Its reminiscent of a flooded engine. I will pull a plug tomorrow to see if its flooded. I am guessing the short cycle starts and a fuel rail fully pressurized was just enough to bog it down.
 
ok, so the battery is a little more charged up so I cranked it some more with the pedal mashed and it popped a few times and ran for a second or two. I do believe it was slightly flooded and the pump was sometimes firing so I may be on to something. I think I will call it a night and try again tomorrow. Not having an exhaust is interesting when it does fire. Wondering if the injectors are a little gunked up from sitting so long and might be the cause of the flooding. I will pull both an injector and spark plug tomorrow and see.
 
So another day without it running. It will fire for a second and die, I did unhook the MAF sensor (may have not wired it right when I changed the plug) and at least I am on to something. I did get a code for a CAM sensor (already changed it so maybe its the wires) so over the next week I will recheck the wiring "AGAIN". I spent some time with Raptor lining the roll bar and of course I was just shy of what was needed to finish the back two bars. I also got a Fuel tank cover and spent part of the day cutting holes for the GM pump to fit through.
The downside of a LS engine is that there is almost too much info out there. I ran across one thread where someone was having the same issue and used starting fluid to get it over the hump and then it would run, kinda leary of that approach. I plan on going back over everything but there isnt a lot of free time this coming week. It almost like the VATs aren't disabled or something where it fires and dies. I have a fuel gauge coming tomorrow so that will help me verify fuel pressure.
The leaves are starting to drop and its a cold wind the last two days so my time to do things is also almost gone until spring.
 
JKIII FJ40 said:
So another day without it running. It will fire for a second and die, I did unhook the MAF sensor (may have not wired it right when I changed the plug) and at least I am on to something. I did get a code for a CAM sensor (already changed it so maybe its the wires) so over the next week I will recheck the wiring "AGAIN". I spent some time with Raptor lining the roll bar and of course I was just shy of what was needed to finish the back two bars. I also got a Fuel tank cover and spent part of the day cutting holes for the GM pump to fit through.
The downside of a LS engine is that there is almost too much info out there. I ran across one thread where someone was having the same issue and used starting fluid to get it over the hump and then it would run, kinda leary of that approach. I plan on going back over everything but there isnt a lot of free time this coming week. It almost like the VATs aren't disabled or something where it fires and dies. I have a fuel gauge coming tomorrow so that will help me verify fuel pressure.
The leaves are starting to drop and its a cold wind the last two days so my time to do things is also almost gone until spring.
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Check all the pins in the ecu plug and make sure they didn't push back into the plastic connector. Check all your fuses.
 
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