need help with a no spark problem

[hdfat95]

I have a 1988 yj with a 4.2 just did a frame off resto ran several times during the prosses. I changed the carb to a webber I have done this to several jeeps with no problems . I did all the proper diag on the ecm,ignition module,ect... .I tried a new coil ignition module ,ecm with no success. I have good power on the pos side of the coil and a very dim light on the neg side of the coil. I am hopping someone out there can give me some good things to try

 

[Tison78_CJ5]

I assume by '88 they had gone to the magnetic pickup in the distributer, instead of contacts.
You either have a problem with the wire from the distributor to the ecm, or the ecm is the problem.
The pickup in your distributor sends a pulse each time it wants the coil to spark. I need to check my books, at this point I don't know if the ecm wants a positive pulse or ground, to trigger the ecm to fire the ignition coil.

I'll shoot another post in a bit...

 

[superj]

Yes, electronic pick up because my 87 has it also. Is the cap making good connection to the rotor?

 

[Tison78_CJ5]

I can't find the diagram for your year, but I would suspect a loose connection between the distributer and ecm module.
Good luck,
If you can get any more symptoms let me know.