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how to find #1 top dead center

chopperz

NAXJA Forum User
Location
iowa
I need to find top dead center of the #1 piston. i replaced the cam synchronizer thinking it was in the same original position. well it started but idled a little rough so i turned the shaft a little till it ran good. well did some research and found out the cam sensor is suppost to face straight back at 0 degrees to the fire wall. by turning it, it only determines fuel snych. only. so now i must start all over but have to get #1 at top dead center. 2001 cherokee
 
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I just put a straw in the plug hole and watch for it to reach the pinnacle of it's climb, pretty sure you have to make sure it's TDC on the right stroke
 
There is a degree indicator on the harmonic balancer. That will get you TDC, but doesn't guarantee it is on the compression stroke. If it is running you are close. Actually, the cam sensor really isn't critical. The ECU just uses it to make sure that it is on the right stroke. Now as far as adjusting the rotation of the distributor, it should be fixed due to the casting on the mounting where the hold down bolt goes.
 
There is a degree indicator on the harmonic balancer. That will get you TDC, but doesn't guarantee it is on the compression stroke. If it is running you are close. Actually, the cam sensor really isn't critical. The ECU just uses it to make sure that it is on the right stroke. Now as far as adjusting the rotation of the distributor, it should be fixed due to the casting on the mounting where the hold down bolt goes.

as far as the mounting theres just a universal hold down plate to basically hold it in. theres nothing there to keep it in a specific spot
 
it runs great like it is. u think i should just leave it or try to position the sensor straight back to the fire wall
 
Remove spark plug on #1 cylinder. Put your thumb over the opening. Have someone rotate till you feel air pressure. Keep rotating till you don't feel it anymore. Stick a screwdriver and verify that the piston is at TDC.
 
OBD-II the Cam Postion Sensor has to be "close" or the PCM cannot compensate enough, so it is somewhat critical to be adjusted correctly.

The process is easy. You need a helper, a toothpick or small drill bit, some basic hand tools and a "mirror on a stick" so you can see the timing marks on the bottom of the cover.

Remove the first spark plug and the camshaft position sensor.
Carefully place a finger over the spark plug hole.
Have your helper bump the starter a little at a time until you feel pressure.
(or use the straw)
Break out your mirror and check your timing marks.
Use a ratchet or wrench, 19mm I think, to turn the crank forwards to the zero mark.
Loosen the retaining fork that holds in the oil pump drive shaft that sits under the camshaft position sensor.
DO NOT REMOVE THE OIL PUMP DRIVE SHAFT!
Find the small hole in the outside of the housing for the oil pump drive shaft.
Find the small hole on the magnet inside that indicates camshaft position.
Carefully turn the housing on the oil pump drive shaft until you can align those two holes and insert a toothpick or drill bit straight through them.
Tighten down the retaining fork, reinstall the camshaft position sensor, spark plug.
 
OBD-II the Cam Postion Sensor has to be "close" or the PCM cannot compensate enough, so it is somewhat critical to be adjusted correctly.

The process is easy. You need a helper, a toothpick or small drill bit, some basic hand tools and a "mirror on a stick" so you can see the timing marks on the bottom of the cover.

Remove the first spark plug and the camshaft position sensor.
Carefully place a finger over the spark plug hole.
Have your helper bump the starter a little at a time until you feel pressure.
(or use the straw)
Break out your mirror and check your timing marks.
Use a ratchet or wrench, 19mm I think, to turn the crank forwards to the zero mark.
Loosen the retaining fork that holds in the oil pump drive shaft that sits under the camshaft position sensor.
DO NOT REMOVE THE OIL PUMP DRIVE SHAFT!
Find the small hole in the outside of the housing for the oil pump drive shaft.
Find the small hole on the magnet inside that indicates camshaft position.
Carefully turn the housing on the oil pump drive shaft until you can align those two holes and insert a toothpick or drill bit straight through them.
Tighten down the retaining fork, reinstall the camshaft position sensor, spark plug.

DOES THE MARK ON THE CRANK FACE UP OR DOWN. IS THAT THE TIMEING MARKS?
 
I need to find top dead center of the #1 piston. 2001 cherokee

If it is the same as my 2001 XJ, the TDC timing mark is missing.
Every older XJ that I have looked at has one but not the 2001...weird
 
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