Long story short i traded a ZJ for another 1999 XJ. Guy before me slung a rod and replaced the engine with a 4.0L from a 96 XJ. Ive just finished bolting the flex plate to the torque converter down and putting inspection plate in. All the wires and sensors are plugged up....except for the Oil Pressure Sensor (99 terminal wont fit 96 sensor, so im going to get a 99 one) and also the small sensor at the back right handside on the top of the engine (temp sender i think).

When we moved onto attempting to start it, it turns over but wont start. Firing order is right, Fuel pump charges when started, Fuel is in fuel rail, Spark plugs are firning last we checked, engine has compression, and Crank Shaft Position Sensor is connected.

We've realized the spark plugs aren't wet when we take them out after cranking. We've sprayed starter fluid into manifold and wont even sputter or hit once. and we've checked all the fuses just for S&G's.

At this point we're lost and scratching our heads so any info or advice at all would help greatly please!

 

Did you take the distributor out during the swap? I would confirm timing and firing order. Also, have you checked the CPS? The port on the top of the head near the back driver's side is for the temp sensor that's in the older XJ. When they started with the 0630 head they eliminated that.

 

Nyet comrade! ...just f'n w/ya.

Seriously though, sounds like a power/ground issue...

 

Hmmm..I'm suspicious of the fuel/spark situation. There's very few circumstances where you can have both fuel and spark and not have it start.

 

He mentioned he has fuel to fuel rail, but didn't say anything about verifying that the injectors are triggered. It's possible that the computer isn't sending the signals because of something else.

 

So is the temp sensor nessory or not? and no its the same distributor. And i have heard of grounds not being connect allowing the CPU to not respond right. How many total grounds are there? And we checked the Injector sensors with an Ohm meter and theyre getting power to them.

Would the Oil Pressure Sensor cause the CPU to mess up the ignition sequence?

 

I don't see any relationship of the oil pressure sensor to starting the engine.

Concentrate on spark and then fuel. In that order.

*Verify spark. It is absolutely the #1 thing I do for any no start. Pull a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground, have a buddy crank the engine while you watch. You're looking for a strong, blue, snapping spark. Having spark is not enough. It must be a BLUE spark. Weak spark can be linked to a failed ignition coil.

*Verify fuel pressure at the fuel rail. Easy to do with a fuel pressure gauge. You need 49 psi to start the engine.

 

I bought a 1999 xj that didn't run. However, the previously owner said that it was the crank position censor. This is located on top of the transmission drivers side. After getting the xj home and I installed the censor then charged the battery. It would crank but still wouldn't start. Then after talking to the dealership they said that if the computer was throwing a code for the crank censor it could also be the stator which is located in the distributer under the rotor button. I bought and installed this part try to start again and it started immediately. I hope that this helps.

 

This.
And this.

 

my last 99 i had a problem just like that. have you checked the ASD relay and the fuses that deal with that. try that and see what happens. its located under the hood in the relay box. let me knoe what happens.

 

SuperXJ2000: all the fuses are good we checked that just before i posted it becuase the ZJ i traded had that problem. thanks though. i was hoping it was that simple lol.

Big_Clyde: stator? Crank Shaft Postion Sensor im taking...

And i know it has spark idk about blue spark though because my grandpa checked it while i cranked it. ill make sure again tomorrow. Along with the fuel pressure.

Also i did have to splice the wires leading to the distributor and coil because the 99 wiring harness would not plug into the 96 sensors. but all the wire colors matched up and i know for sure they have good connection.

 

Ok so today I checked the fuel pressure and got a solid 40 psi reading. and we had spark the first time we cranked it. it was and orange spark though. Not a blue one liked i'd hoped for.

So we questioned the Cam to Crank timing and i put the engine to TDC and it read 0 on the timing spikes and the distibutor matched to the #1 cylinder. So thats all good.

But heres were it got tricky again, when we tried to check for spark again we got nothing. On any of the spark plugs. We tested the wires leading to the coil and from the coil to the distributor and it was good. We got 12V to the coil and i cant remember what coiming out of it...maybe 6V.

So any clues to why it'd spark the first time but then never again. And why i have orange spark and not a strong blue one?

 

Weak spark is usually linked to a failing ignition coil.

Test your ignition coil.

 

No when I was talking about the stator it is different from the crank position censor. The dealership said that it throws the same code. The stator is located in the distributer you have to remove the distributer and the rotor button it should be the next piece. I can't recall if my xj had a spark though. I was hoping that it would help. Just wanted to explain the piece that I was talking about.

 

i do believe that some vehicles cut the signal to the engine if there is no oil pressure so you cant blow it up
also crank position sensor will cause one not to run i know some chrysler cars had that problem (namely the neon) i don't know if it was common in the jeeps though