Ok all, here's a link to my original thread just asking some basic swap questions, https://www.cherokeeforum.com/f2/87-...stions-166413/

For the sake of getting more eyes on the problem I wanted to start a dedicated thread for my no starting issue.

Here's the quick and dirty version. My original 4.0 threw a rod. So I found a low miles 96 long block and did the swap. I used the 96 block and head, then 87 everything else, ie, accessories, intake/exhaust, sensors, dizzy, etc.

Once complete, the engine will turn over all day long but does not start. So I began troubleshooting.

I've got all new plugs, wires, distributor cap, indexed my timing, 2 sets of injectors. Per my other thread, I decided to try a new crankshaft position sensor, ignition switch and finally a fuel pump. Still no start.

What I have found is that if I prime the intake with starter fluid or gas, it will start right up and idle until it burns off the fuel. I disconnected the plug on one of my injectors and put a multimeter on it while turning the motor over. I read 0v at the injector. I would think I should still see a pulse of some kind?

I know this has less details but the other thread I linked you can see where cruiser and I have been going back and forth. Anyone else have this issue in the past? Are there any fusible links or relays that are only for the injectors? Everything else seems to work as it should. Like I said, when primed it will stay running until it burns all the fuel I put in. My current plan when I get off of work is to start tracing wires from the injectors back and looks for shorts, fuses, etc. Any and all assistance is welcome.

Thanks.

 

It's ECU, to C101, to injectors, with the C101 carrying both power and ground for the injectors.

 

Good to know. I've printed off the engine schematic and am highlighting my wiring (yes, I do things the old way).

Now let me ask you this. Is there anything before the ECU that could cause this as well? Or if I had a short or something before the ECU the whole thing wouldn't work? That make sense?

 

Power to the eCU could be missing. Comes from 86 on the latch relay.

How did you check for power at the injectors?

 

Wasn't sure if this was the right way or not, but I just disconnected one of the plugs going to the injector and put the leads on my volt meter in there. Then turned the engine over while watching the read out. I didn't think that was the right way, but I figured I would at least see a pulse or some kind of change in voltage.

In my googling, I found another suspicious item. Would the camshaft position sensor cause the injectors to not fire, or fire completely out of sequence? I read somewhere that you can disconnect the cam sensor and it will run in a kind of safe mode. Might be worth trying?

 

PROBLEM SOLVED!!!!!

So, I went home on my lunch break and was taking some pics of the wiring harness and other things to review while at work. When I came to the wiring at the MAP sensor. I noticed the red/white wire had been cut. So I stripped it back quickly and twisted them together. Get in the jeep and turn the key. BAM! It starts right up!!!

So I left it as is until I get off work. I'll then solder the splice back together. Put my newer injectors back in, put my new plugs back and burp the water and should be good to go!!

Cruiser, again thank you for all of your help with this. It's amazing to have knowledgeable people here who are willing to help.

 

Woohoo!! Good catch!!

That's voltage supply to the MAP.