Hard to start and wired Distributor placement.

[ckollenb]

Vehicle: 1999 Jeep Cherokee, 4.0L I6

It has been hard to get started. You have to crank it over several times to get it to start and once it is started it seems to run fine, but sometimes it will start and run like the timing is off. Then I have to shut it off and try to restart it again. I might have to go through this a couple times before it starts and runs good.


CEL DTC code’s:
P0340 No Cam Signal at PCM No fuel sync.
P1391 Intermittent loss of CMP or CKP loss of the CAM Position sensor or Crank Position sensor has occurred.

I decided to do a tune-up to see if this would solve the problem (after reading the many posts about hard start and poor timing) and have discovered that the rotor points in a different direction from what the service manual shows in the diagram on the firing order. It looks like my distributor is 180 degrees off and the plug wires were re-wired by the PO so the Jeep Cherokee would run. Any ideas on why this would be done? Also I notice that the rotor is gouging the post in the distributor cap and I checked the rotor shaft and there maybe .0010 of an inch in side to side play which leads me to believe it needs to be replaced. Would that be correct?


When I put the new distributor in do I follow the factory service manual settings? It think it should work, but not sure with Jeep's (my first jeep).
Also my replacement distributor has no alignment hole to align the rotor and cam shutter (the part that spins around through the cam sensor magnets), so how do I index the cam sensor and rotor and compensate for helix gear without an alignment hole?


Also I have an intermittent 5 volt cam sensor reference signal from the computer, so does this mean I need a new computer? I tested the wiring harness and I have good continuity from the cps to the computer. I can’t think of anything else it could be but the computer. I am I missing something here? Only can see this error using a scanner and only happens when starting the engine. I get these errors when it starts and acts like a timing issue.


I have also checked the fuel pump, possible leaky injectors, TPS, IAC, MAP, CPM (replaced), CKP and Coolant temperature (replaced) sensors and they are all working fine. (I have learned to do this from reading the many posts on this forum and Thanks)


So I have been chasing this problem for a few months now. The condition has gotten worse and the Jeep Cherokee is not reliable and I have come to believe that the distributor is bad and maybe the computer too. I am on the right track here? I would appreciate any help! I have included a few pictures too. Thanks.

 

[Matthew Currie]

It sounds as if you're on the right track. The distributor should be set as the factory specifies. Make sure you're on TDC for cylinder one. It will probably take a couple of tries to get the rotor in the right place, owing to helical gear and alignment of the oil pump slot, but it's not too hard to get it right.

Remember that the engine makes two revolutions for every one of the distributor. That means that one TDC mark on the crank will be the wrong one. It looks as if that's what happened with the previous owner. Rather than try again, they just rewired the cap. Even then, it appears they indexed it wrong, one tooth too far advanced, and that by itself can cause bad starting. Once it starts, the engine computer adjusts timing, and can cover a fair amount of error. I had a similar problem with an 87, which started badly but ran well with the distributor one tooth advanced.

Before you take the old distributor out, turn the engine over to the TDC mark on the crankshaft that appears when the rotor points to plug #1 (more or less). Now install the new distributor correctly, with the rotor pointing the way the book specifies, and it should be right. Start the rotor a little counter-clockwise of the desired location to compensate for the helical. You may have to experiment a bit with the oil pump drive slot to get it right.

If, while hunting for the TDC mark, you go too far, don't just reverse the engine. Make sure that you either go all the way forward two rotations, or, after reversing, go back further than the slot, and go forward again to take up any slack in the timing chain.

I would not worry too much about the computer yet if you know you have a bad distributor and suspect indexing as well. Do one thing at a time. The cam position sensor is used for injector timing, so it's quite possible that wrong injection timing is messing up your starting in addition to the indexing issue.

 

[xj_maniac_newb]

x2 on the cam postion sensor. Sometimes instead of just going out, they malfunction and cause problems. After about 3 weeks of working on a 00 xj and replacing numerous parts we had almost just decided that we had found a magical engine incapable of being put into correct timing. Then we replaced the CamPS and it fixed the problem. After we fixed it tho we were a little sorry we did, cause the damn thing was the perfect amount off to run like a scalded dog. With stock 3.55's and 33's the damn thing outran a stock xj with 100,000 less miles. Probably would have just left it alone if it didnt rattle like hell and take forever to crank how it was.