Distributorless Timing

[KPTHEMP]

working on a 2000 XJ 4.0, engine ran before being disassembled, but not driven so I am unaware of its power or lack thereof, I am looking to Replace the timing chain but feel the timing is off.

I am familiar with the method of setting the engine at TDC compression stroke and then the toothpick method of lining up the holes in the distributor like so:

the problem with mine is that the timing marks are not pointing at each other after the above pic, the Crank is right but the cam is 180 degrees off like so:

this video looks like my engine, but then the cam sensor is 180 degrees out and not the toothpick method
http://www.youtube.com/watch?v=Ko75NEe2khY

and this video has the timing marks aligned, but again not the toothpick method
http://www.youtube.com/watch?v=3Avy1mOUsAM

so, which one is right ?

 

[techno1154]

Yes, you said it,...it is 180* off and will not start.
You need to remove the distributor, align the crank and cam shaft then re-install the distributor. Usually, when an engine is rebuilt or disassembled for any reason, the cam and crank alignment is done first then the distributor/ignition timing.

 

[winterbeater]

Yes, you said it,...it is 180* off and will not start.
You need to remove the distributor, align the crank and cam shaft then re-install the distributor. Usually, when an engine is rebuilt or disassembled for any reason, the cam and crank alignment is done first then the distributor/ignition timing.

Turn the crank one full turn and line up again.

 

[KPTHEMP]

Im in the process of rebuild, I haven't removed anything yet, and this engine will still run if i put it back together.

If I turn the crank one full turn the marks will align, at it will be at TDC but thats the exhaust stroke, not compression.

on my other 2000 cherokee motor the timing marks aligned at the compression stroke, this one is opposite, and the 2 videos are opposite of each other.

is it possible the timing marks align with out regard to which stroke (compression or exhaust) that it is at ?

I want to put a new timing chain on, but if someone rebuilt it in the past wrong, I want to make it right.

I read these engines will still run 180 degrees out because of the shared coil pack it fires every cycle and not every other

 

[McQue]

Somebody correct me if I am wrong please..
you said "If I turn the crank one full turn the marks will align, at it will be at TDC but thats the exhaust stroke, not compression."

So...after you do that .... if you turn the crank TWO full turns, the timing marks should align and it will also be at TDC on the compression stroke. no?

 

[Runnin'OnEmpty]

......I read these engines will still run 180 degrees out because of the shared coil pack it fires every cycle and not every other

That is called a 'lost spark' ignition system, and I'm
pretty sure that's what you have with the 2000.

It will run very well being 180* out of phase, but I'd
still re-index the cam sensor to the correct phasing.
It's less confusing for possible future trouble diagnosing...

 

[winterbeater]

It still makes no sense that the cam sprocket mark could be toward the crank with the cam lobes in the exhaust position. I don't care how many times you turn it around.

 

[old_man]

All I ever do is put the marks as close to each other as possible. That should be TDC.

 

[Runnin'OnEmpty]

You all are correct in that when the marks are aligned
the cam and crank are timed. The crank turns twice for
every cam turn, and here's where the confusion comes
in...
In the 'lost' or 'wasted' spark ignition system, the coil pack
fires on every crank revolution instead of on every other
revolution, for any given cylinder. The exhaust and
compression strokes both get a spark, and that's why the
engine will run with the cam position sensor out of phase
by one engine revolution, or 180*. The cam and crank are
in phase, only the sensor is out of phase but it dosen't
matter since the coil sparks any given cylinder on every
engine revolution.

I don't know how many years Jeep used coil packs, maybe
only the 2000 model? The 01's had coil-on-plug I think...
I know my 96 still has a distributor.

 

[Saudade]

This happens because two cylinders are fired from the same coil. One on Compression, the other on exhaust. So the cam could be out 180 deg and still run fine. Having said that it's still wrong.

Naturally, this does *not* apply to the distributor models since only one cyl fires at a time.

The distributor-less was introduced in 2000 and carried to 2001, the end of the Cherokee line.

 

[winterbeater]

Still doesn't answer the question of how the sprocket mark and the cam lobes could be out of synch. Only possibilities I see are:

1. Sprocket key (integral) is sheared

2. Sprocket wrong part

3. O.P. statement of #1 compression stroke incorrect.

What have I missed? Sheared key ending up 180 degrees off seems unlikely, but not impossible.

 

[techno1154]

Still doesn't answer the question of how the sprocket mark and the cam lobes could be out of synch. Only possibilities I see are:

1. Sprocket key (integral) is sheared

2. Sprocket wrong part

3. O.P. statement of #1 compression stroke incorrect.

What have I missed? Sheared key ending up 180 degrees off seems unlikely, but not impossible.

Keeping in mind two of the above posts 6 and 9 I would assume that someone removed the distributor at some time and dropped it in 180* off. I cannot think of another reason.

 

[Talyn]

If I turn the crank one full turn the marks will align, at it will be at TDC but that s the exhaust stroke, not compression.

That is just where the timing set lines up. Not where you drop the cam sensor in. The method of bringing it to TDC on the compression stroke then dropping the sensor in is correct.

The timing set does not align on TDC of the compression stroke.

The notch in the cam for the cam sprocket is nearly inline with the exhaust lobe centerline. The notch is roughly about the 2 o'clock position when the timing set is installed and marks lined up. That would be the exhaust stroke. That would also be the end of the exhaust stroke where both the intake and exhaust valves are slightly open.

That is called a 'lost spark' ignition system, and I'm
pretty sure that's what you have with the 2000.

It will run very well being 180* out of phase, but I'd
still re-index the cam sensor to the correct phasing.
It's less confusing for possible future trouble diagnosing...

It won't run 180* out. Also, it is waste spark, but the cam sensor is primarily used to set fuel injector firing.

Also, if the key is sheared it won't keep any kind of time because the bolt doesn't have enough clamp to hold the sprocket to the cam.

 

[KPTHEMP]

Thanks all, Talyn said it best, I just aligned the marks like the service manual says and replaced the chain, I guess the whole TDC of compression had me worried, but no big deal. Thanks agian.

just one question, if the marks are aligned its TDC of exhaust stroke and if the cam is 180 out, its TDC of compression stroke, right ?

so in the video by golen, they align the sprockets 180 degrees (on the compression stroke) and set the cam sensor 180 degrees from the toothpick method (which toothpick is supposed to be TDC compression), why does the cam sensor work if its 180 degrees out ?

 

[Runnin'OnEmpty]

Thanks all, Talyn said it best, I just aligned the marks like the service manual says and replaced the chain, I guess the whole TDC of compression had me worried, but no big deal. Thanks agian.

just one question, if the marks are aligned its TDC of exhaust stroke and if the cam is 180 out, its TDC of compression stroke, right ?

so in the video by golen, they align the sprockets 180 degrees (on the compression stroke) and set the cam sensor 180 degrees from the toothpick method (which toothpick is supposed to be TDC compression), why does the cam sensor work if its 180 degrees out ?

It helps to think of the timing chain and cam synchro/sensor alignments as two separate operations. First
align the chain and then do the cam synchro on the compression stroke of #1.

why does the cam sensor work if its 180 degrees out ?

As was stated, the cam synchro indicates to the PCM the position of #1 cylinder on the compression stroke, to time
the fuel injectors. When the synchro is 180* out, the signal is actually occuring at the #6 cylinder. The injector then sends fuel to #6, and the plug also fires on #6 because of the lost/waste spark igniton. (Numbers 1 and 6 are paired on the coil pack and fire together). The other cylinders fire
in sequence and the engine runs.

The engine will run with the cam synchro out of phase, but it really should be installed correctly...

 

[Talyn]

The injector then sends fuel to #6, and the plug also fires on #6 because of the lost/waste spark igniton.

That still doesn't make sense as #6 would be firing the air/fuel mix on the exhaust stroke.

 

[winterbeater]

That still doesn't make sense as #6 would be firing the air/fuel mix on the exhaust stroke.

Yup. Something doesn't add up!

 

[Talyn]

Their method of installing the sensor was stupid anyhow.

 

[Runnin'OnEmpty]

That still doesn't make sense as #6 would be firing the air/fuel mix on the exhaust stroke.

You guys are right, the engine won't run with the synchro
180* out of phase. The injectors would be timed wrong.
Might give a pop or two from the residual fuel in the
intake runners, but it wouldn't be drivable...

By the way, the pics have the synchro timed correctly, right? With the cam/crank marks separated 180* and the sensor aligned with the toothpick. If the harmonic balancer was installed, then the TDC mark/pointer would align on the
#1 compression stroke...?

 

[Talyn]

By the way, the pics have the synchro timed correctly, right? With the cam/crank marks separated 180* and the sensor aligned with the toothpick. If the harmonic balancer was installed, then the TDC mark/pointer would align on the
#1 compression stroke...?

That is correct.

I'm half tempted to try the method in Golen's video and see what happens. But I don't have time for that right now.