No start

1999 4.0

Went to start the motor one day. Would turn over, wouldn't catch. Juggle the throttle and it will run a tad but blow white smoke and then die as soon as you stop juggling the throttle.

Did a compression test, came out a reverse bell curve. Bad headgasket? Took the head off, it was cracked. 0630. Cylinder walls were smooth so I had it sent for a hone, they had to bore thirty over.

Get it all back together with a reman'd odessa head and new everything else. Full rebuild, no corners cut. Does the same thing, just with good compression and less worn motor.

Cranks and cranks and cranks.

New CPS so it's not that. New cap, rotor, wires, plugs, coil, all fine. Timing gun on wire #1 shows we have spark.

Fuel is at 48ish PSI on the rail. Jumped the fuel relay and fuel valve on the rail and it will push fuel just fine. Spray a ton of starter fluid in the throttle body and it still wont run.

This leaves me to believe it is clogged injectors, or electrical. Bad ECU, sensor, ground. I'm out of ideas guys.

Might also be cam sensor. Distributor was reused. Not seeing anything in my FSM about testing it.Unsure if cam sensor would cause a no start.

Try a noid light on the injectors to see if you're getting fuel.

Noid lights were expensive at napa so I'm going to make my own.

We tried again tonight. Since it doesn't do anything even spraying starter fluid into the throttle body....

Checked spark with a timing gun. It's firing WAY off, which makes no sense to me since the timing should be set pretty tight mechanically since everything is keyed.

Interesting thing... My bluetooth can't find the ECU on keyon. It's a POS chinese one I use with my phone, figured it was unpowered. Brought out my dads ECU link that connects into a laptop. Link wont light up and software can't find the ECU. Could the ECU be dead and screwing up my ignition?

I'm still not sure if it's CPS, cam sensor, or ECU. Coil should be fine as it's brand new, wires, cap, rotor only a few months old.

Are you getting ign on all of your plugs? You can usually feel your injectors clicking

Also do you have theft alarm? Unlock your doors with the remote and then try it

Have you tried "freshening" all grounds? Also try swapping the ASD relay with another (located in the power distribution center under the hood). Where did you buy your crank sensor? There have been a few guys with new aftermarket crank sensors that were dead right out of the box. I buy my crank sensors only from Jeep.

Have you checked the base timing, making sure the distributor is properly indexed ?

Where did you get your new Crankshaft Position Sensor ? Cheap CPS from Advance/IdiotZone/O'Reilly have been proven to be out of specifications or even failed right out of the box. Have you tested the CPS ?

Once you have tested all the sensors, checked all the fuses and relays, freshened/cleaned all your wire connectors and wire connections, eliminated any shorted or open circuits, you can consider the possibility that the failed CPS killed your ECU. This an extremely rare occurrence and replacing the ECU should be your last resort after covering all the other potential failures or problems.

The cam position sensor located under the distributor can cause the same symptoms as a dead crank position sensor, I wouldn't rule it out...

I'm still guessing cam and crank sensor. The symptoms are exactly like a CPS failure.

My folks have a 1995 cherokee they use for plowing (who says you can't plow with a unibody). CPS plug is different, on the 95 from the 99 so I got one from advance, yes I know not a dealer one. Tonight I'll rip the cam sensor out of the plow jeep and throw it in my 99.

Just to update this.

Got it running. Replaced all the sensors and ECU with ones from another rig. Nothing.

Figured it was the cam position synchronizer that was screwed up, took the distributor out and the ears on the case sheered off. Ordered one off rock auto, through it in. Started up first try. New motor runs like a champ.