no spark/ no start

[97 mj conversion]

I have a 97 4.0 automatic XJ all inside my MJ. I had to replace the PCM (chipped to my VIN), main and engine harness due to the Left front being destroyed in a accident. I have installed new 4 port injectors, new OEM (it was advertised as that) CPS, sparkplugs, cam pos sensor (I had a 54 code, then went away after replacing cam sensor), coil and fuel pump. I do not seem to get power to the coil. I have done the following....I disconnected the coil, turn the ignition to the on switch, then turned the crankshaft. I can hear the fuel pump turning on. I was told this tells me the cps is working. I am getting around 45-48 psi on the fuel rail. I had my engine rebuilt, too. I have gotten it to backfire and or pop a couple of times after sitting for 10+ hours, then nothing more. Never has it ran at all. I am not getting any power to the white wire going to the coil. I thought that was a constant 12V when the key is on? I am looking for what supplies power to the plug side of the coil and how to troubleshoot that system/ harness. I have removed the passenger side airbag. Could that be inhibiting spark? I hope this gives you enough info. I tried to give you as much info as I can to limit the common fixes. I appreciate any advice. TIA

 

[8Mud]

Did you swap in the PDC also? White wire throws me.... dark green/orange is in power in on the 97 ignition coil, grey is out and goes to the PCM which triggers/grounds the coil for spark.. Power is only there when the ASD relay is closed and the fuse(20) is good. The ASD only closes when the PCM gets certain sensor signals. Not sure about the 97 but some years it takes a certain RPM while cranking to close the ASD relay along with certain sensor signals.
The fuel pump will run for a few seconds as soon as the key is turned to run for a prime, but the fuel pump relay won't close for real until the ASD relay closes.
You can test the ASD relay closing at the 20 fuse on a 97 if you swapped over the 97 PDC. The 20 fuse only has power with a closed ASD relay.
Not knowing how much of the 97 harness and peripherals you swapped over I'm kind of guessing here.

 

[lawsoncl]

As mentioned, the fuel pump (and maybe the ASD relay) will run for a few seconds at key-on. Then it waits until it sees the engine spinning. If the original engine was a non-HO, the flexplate changed and won't work with the 97 PCM.

 

[97 mj conversion]

the fuel pump is working bc I hear it kicking on and I have appx 45-48 psi. I found that my #1 injector is bad. It seems like the whole rail goes dead of it. I used a relay checker to verify the ASD relay is good. I checked all of them.

 

[97 mj conversion]

I literally swapped out everything from the 97...... only thing I didn't swap was the tail lights. The white wire may be gray and the other is green/ orange. I thought it was white, but it does seem gray now that you say that.
I had a friend come over and help.
I am down to 2 things
I am getting a spark, but it is very light. I have some Taylor spark plug wires I am going to try tomorrow. Several Forums say I need a blue spark and my is yellow ??
I found that one of my "new" injectors isn't working.. If I have this correct, it seems with the one dead, I am not getting power to the rest. I do have power to each of the connectors.
Finally, I am not sure if there is a kill safety switch on the passenger air bag? I am thinking if that isn't bypassed, it will not let my MJ start.
thanks for the help everyone

 

[97 mj conversion]

Re: low spark/ no start

As mentioned, the fuel pump (and maybe the ASD relay) will run for a few seconds at key-on. Then it waits until it sees the engine spinning. If the original engine was a non-HO, the flexplate changed and won't work with the 97 PCM.

I have everything form the 97XJ. The engine/ trans/ transfer case are all HO. The only thing MJ is the bare hull, fuel tank and the tail lights.

 

[8Mud]

The injectors share all the same power source and are switched individually on the ground side at the PCM. Maybe it is a bad splice? Opinion, but one faulty injector is unlikely to affect anything else. Unless the wiring diagram is wrong you can voltage test the number 20 fuse (20 amp) with the motor turning over. The diagram shows the 20 fuse as power out ASD. Maybe a voltage test from the 20 fuse to battery ground?