1990 Jeep YJ 6 cyc. Won't Start---No Spark From Coil

check all fuses first, every time, something fails EFI.
the scan tool will tell you why 90 % of time.
connect scan tool
key on
crank for 5 seconds, see scan tool show 300 RPM? about.
good, no RPM is bad sensor (Cmp or ckp)
release key , do not turn off yet
see DTCs stored, now, bingo, its telling you what is bad. OMG.
p0340/ 355? and the like? are bad CMP, bad CKP, or others get em
post em or look them up in the FSM. or at alldata.com
Theory:
the ECU creates spark
there are the 2 sensors that tell the ECU when to spark (inputs)
and the ECU DRIVER the ignition IGNOTOR, that runs the ignition coil.
1 coil or 6 coils. depends on year.
4.0L I6 Jeep engines.


did you check for spark directly at the 1 coil car or at all 6 coils for 6 cop coil cars?

cops are coil over park plug, i think your car is 1 coil, had a 99 jeep.
and this old six still had one, coil, so does this one coil make spark
to a test spark plug, Y/N
if yes, the dizzy cap is bad or wired wrong. to plugs.
I no spark here, do the DTC scans above.!!!!!
post back results.

There should be a plug on the bottom of the transmission to drain and a plug on the side to fill it.
No spark could be a relay or the coil among other things. You may need a shop manual and wiring diagram to troubleshoot the ignition system.

Technically if the engine has compression, is getting spark at the right time and fuel, it should start.
Have you checked the spark plugs to see if they are fuel or oil fouled ?
Are you getting spark at the plugs or at the coil ?
Have you tried using carb cleaner or starting fluid in the throttle body ??
Have you checked fuel pressure to see if you are getting enough fuel to the injectors ?

try a new coil.some times a new coil will fail

Car not starting or turning over indicates towards multiple possibilities. It can be issue with battery or weak battery. But if battery checks out ok, then it can be starter issue or faulty alternator or problem with low fuel pressure or no spark at spark plugs due to dirty spark plugs or faulty ignition coil or injectors getting cracked or dirty and needs to be cleaned.

To confirm the problem, the basic troubleshooting is required.

Click this link below and follow the troubleshooting:------

http://technoanswers.blogspot.in/2012/02/car-starting-issues.html

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This will help.
Thanks.

I take it that it cranks over but will not start. Spray some starter fluid into the throttle body. If it runs, you have a fuel problem. You may have disconnected the fuel system by unplugging a connector or grounding a wire blowing a fuse.

First try shooting some starting fluid in intake manifold, and if fires up but still won't keep running, my guess next would be your looking and checking out your fuel pump. You can check that out my removing a line and see if fuel is pumping out of the out put of fuel pump. Because it it carburated its pretty easy to trouble shoot. It's going to be in most cases spark plugs , fuel pump.

try checking the ignition module inside distributor cap...a flat thing with little connectors on it

check your coil, plugs, wires, basically your entire ignition system - test a plug wire by sticking a new (known to spark) sparkplug onto the end of the (known to work) wire and see if there is spark, if not, change out your coil and test again - if neither, check the timing of your distributor

Sounds like a bad distributor control module. You blew-up your muffler because there was no spark.....lots of fuel in the exhaust....then an intremittent spark......BOOM!
Once the module cools off, it works again, because the crack in the circuit board re-connects....until it gets hot again, and opens the circuit........no more spark. Replace the module.