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RyanSD180SX

Trying to understand ignition timing reading on all cylinders.

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The other day I went to check my timing and found that with the inductive pickup around cylinders 3 or 4 the timing marks appear at the top where I can see them looking down in the engine bay. However to see the marks with cylinders 1 and 2 I have to be under the car, that is to say the marks are directly opposite where they should be.

 

My understanding is the pickup should be placed on cylinder 1 and being that cyl 1 and 4 are a matched pair the markings should line up the top for both of them. Cylinders 2 and 3 should be opposite as they should fire when Cyl 1 is near BDC.

 

The car runs well, has been for quite some time and I had no reason to suspect a cylinder was firing at the wrong time, this just goes against my knowledge and only noticed it with a timing light so I was hoping someone could clue me in as to what’s going on here. I will admit my knowledge of ignition timing isn’t perfect but I’m interested to know why this is.

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Are you using a short spark plug lead between the coil and plug on cylinder 1?

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Are you using a short spark plug lead between the coil and plug on cylinder 1?

 

No I'm not actually and I have read guides and they all seem to do it.

However I can fit the inductive loop between/after the insulation and the coil pack so I figured that would be ok. Surely that can't throw the reading out of phase by 180 degrees on some cylinders and not others?

Edited by RyanSD180SX

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I have tried to set timing using the loop off the back of the coil loom and found after using a short lead off the coil to plug to be much more accurate.

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Timing for TDC is only reference to cylinder 1 when checking timing, many have had issues with the inductive loops hence the normal method is to use a short plug lead on cylinder 1.

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#1 and #4 are 360 degrees apart in their firing time. The pistons look like they are a matched pair in terms of the crank throw but when #1 is on compression stroke, #4 is on exhaust stroke.

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Timing for TDC is only reference to cylinder 1 when checking timing, many have had issues with the inductive loops hence the normal method is to use a short plug lead on cylinder 1.

 

Alright I will check again with a HT lead when I get a chance.

 

#1 and #4 are 360 degrees apart in their firing time. The pistons look like they are a matched pair in terms of the crank throw but when #1 is on compression stroke, #4 is on exhaust stroke.

 

I understand that but the timing light/crank doesn't differentiate between the strokes therefore the mark on the crank should be the same.

The spark will fire every second revolution but at the same point relative to the crank.

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Very surprised that the spark plug lead made that much of a difference.

Got a much more stable reading from cylinder 1 showing it where it needed to be.

 

Thanks guys.

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Timing for TDC is only reference to cylinder 1 when checking timing, many have had issues with the inductive loops hence the normal method is to use a short plug lead on cylinder 1.

 

Alright I will check again with a HT lead when I get a chance.

 

#1 and #4 are 360 degrees apart in their firing time. The pistons look like they are a matched pair in terms of the crank throw but when #1 is on compression stroke, #4 is on exhaust stroke.

 

I understand that but the timing light/crank doesn't differentiate between the strokes therefore the mark on the crank should be the same.

The spark will fire every second revolution but at the same point relative to the crank.

:thumb:

 

I have always used the ignition lead method which as you found is a lot more gives much more consistent results

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