Just finished hooking up the new engine, but wont start.

I have a 2000 and I just finished hooking up the new engine. It will crank over and start but as soon as it starts it immediately backfires and dies. It seems to be back firing out of the intake and not exhaust. I have the coil rail ignition so I thought Top Dead Center was not important. Am I wrong on that? I also thought that the coil pack and firing order was not adjustable since there is no distrubutor. Am I wrong on that? Can the CPS actually be adjusted?

The Cam Position Sensor needs to be timed. You can do it with a toothpick. The Crank Position Sensor (CKP) cannot be timed. (Often also called CPS, but not in the FSM.) Firing order can't be changed with coil rail.

winterbeater said:

The Cam Position Sensor needs to be timed. You can do it with a toothpick. The Crank Position Sensor (CKP) cannot be timed. (Often also called CPS, but not in the FSM.) Firing order can't be changed with coil rail.

Click to expand...

x2 on the cam postion sensor.Just follow the procedure in the service manuel.

Good Luck
Nick

winterbeater said:

The Cam Position Sensor needs to be timed. You can do it with a toothpick. The Crank Position Sensor (CKP) cannot be timed. (Often also called CPS, but not in the FSM.) Firing order can't be changed with coil rail.

Click to expand...

Okay, so I stuck a nail in the crank position sensor to line up to 2 holes while I set it in place. I also returned the engine to top dead center. The engine fired right up and is running better but far from perfect. It is running real ruff and when I increase the rpm's it will stall on me. I loosened the bolt that holds the cps in place and rotated it a little to get the engine to run smoother. It helped but not much. I can now run higher rpms but when the rpms come down the engine now wants to stall in the lower rpms. I faught with the cps for about 2 hours and could not get the engine to stop stalling at some rpm range. Is there a better way to adjust the camshaft position sensor? It is very disheartening to put a new motor into your jeep after 2 weeks of killing myself only to have it run like crap.

hanaxj87 said:

x2 on the cam postion sensor.Just follow the procedure in the service manuel.

Good Luck
Nick

Click to expand...

In regards to the service manual it is useless. It states to adust the camshaft position sensor/timing see a mechanic. That is REAL Helpful!

Did you use your flywheel or was there one on the new engine. I like to set both motors at TDC and mark the flywheel then transfer it to the new motor in the same position

bhicks said:

In regards to the service manual it is useless. It states to adust the camshaft position sensor/timing see a mechanic. That is REAL Helpful!

Click to expand...

Sounds like you may have the cam postion sensor set up with the wrong alignment hole.

The Haynes # 50010 manual I have goes through the dist install in chapter 5 page 5-8 and 5-9 . Theres two alignment holes. The one closest to the pulse ring is for the 4.0 engine.

Good Luck

Nick

The 2000 FSM I have does show the toothpick method for the 4.0. About the 2.5, which still had cap and rotor, it shows two holes like hanaxj87 stated, but the revised parts for the 4.0 show only one.

I suppose you have already run it for a while and it still runs bad? Mine runs like shit after disconnecting the battery until computer relearns.