1992 jeep xj crank but wont start??

I have a 1992 jeep cherokee 4.0 il6 auto trans that is not in the best of shape but it is still there. I have just recently replaced the motor with a junk yard motor and after i got everything done and bolted up i had replaced all 6 spark plugs wires coil distributor with button and cap plus the crank sensor and o2 sensor. So it ran for bout 2 weeks after with no problems and then all of a sudden one day on my hr drive back home i left work pretty hard and drove for bout 20 mins down the road at 45 50 and then started to pull into a gas station and it shut off and hasnt started since then and have replaced all the above parts after it shut down that day. I have been fighting with it for 2 weeks strait now and need some help figuring this problem out!!! any suggestions please help me its my daily driver!! It fires from the coil but not very fast with turning the motor over with a plug in coil wire it only fires 4 times for bout 30 secs on constant turning of the motor??? with the distributor set at number one cylinder on tdc with wires correct it still back fires and shoots flames out the exhaust!

Because its a salvage yard motor I recommend doing a compression test.

After that, if the engine is in good shape, you need to fix the weak/intermittent spark condition. Fully charge the battery and have it load tested, clean both ends of your main cables, renew your grounds. Test the voltage to the primary side of the coil to see how many volts its getting from the ASD relay.

Post up what you find.

I was begingin to think bout the compression so tomorrow i will get a gauge and run it on all 6 and do the other things u said and let ya know what happens! im hoping it will start soon!! i miss them tsls roaring going down the road!!

If it is compression would it be cheap to just rebuild the motor with stock bottom end and just slap a little bigger cam and possible alum head on it? if so any suggestion on who to buy the cam and head from?? i want more power from it i run 4:11 with 33's and its got some go but want a little more maybe 50-100 horsepower over stock.

92 jeep cherokee crank but very slow spark at coil

Joe if u read this i had checked the compression and all the connections today for corrosion or bad connection and still nothing it turns and turns and still has barely any spark coming from the coil for some reason?? Like its is trying to only fire on 2 of the cylinders that how slow the spark is from the coil?? what to do it is the 4.0 il6 motor.

Re: 92 jeep cherokee crank but very slow spark at coil

coils probably bad. check for 12v to it when cranking. if thats good replace it do plugs wires cap and rotor while youre at it.

Re: 92 jeep cherokee crank but very slow spark at coil

Ok, I don't have a 92 FSM so this info is from the 95 FSM.

Use an ohm meter to test the primary and secondary resistance values of the coil.

There may be two different makes:

Toyodenso, primary 0.95 to 1.20 ohms; secondary 11,300 to 13,300 ohms

Diamond, primary 0.97 to 1.18 ohms; secondary 11,300 to 15,300 ohms

Post up the values you find.

EDIT: I'm going to merge this with your first thread so we can keep a straight track on solving your problem.

ok i will try that tomorrow i just cant get over this peice of **** lol it fires so the coil i know isnt bad or it wouldnt fire and same goes for the cps it fires real slow and battery is charged completely and checked voltage for everything idk im ready to just sell it not even a damn mechanic can figure it out. just dropped a jy computer in today also and still nothing but trying to breathe fire out the exhaust!!!!

I dont know exactly how to do what u just said im little bit mechanically inclined but never heard of that bud??? I just want this d*** thing to run again so i dont have to sell it!!! basically ur saying to check the input wires going to the coil at the plug???

Somewhat.

The connector that carries power and ground to the coil, that is the "primary" side of the coil. Remove the connector and using an ohm meter measure the resistance and post up the value.

Now, the "secondary" side of the coil is the spark, so measure the resistance between the coil's spark tower and the primary side, then post up that number.

Also, post up the brand of the coil, should be marked on the body somewhere.

Article with pictures on a round coil, same-o-same on your coil: http://autorepair.about.com/od/troubleshooting/ss/coil-test-ohm.htm

I'll bet money on the crank sensor being the culprit.

Bustedback said:

I'll bet money on the crank sensor being the culprit.

Click to expand...

Maybe, but crank sensors are usually fail/work. As the vehicle has spark odds are against a bad crank sensor. Crank sensors will experience "thermal" failure, where the engine will start and run fine until the crank sensor gets hot enough and then fail, but will work again as soon as it cools down enough--this can be hastened with cold water applied to the sensor.

Also, as the OP replaced the crank sensor--stated in his opening post--the prospect of it being the issue grows dimmer.