Can Someone Please Explain Timing?

[reno]

OK, I am troubleshooting a truck and ran into something I don't understand. I understand when you pull the SPOUT it is locked at base timing. So with the timing light connected to the number one plug wire, the timing pointer on the balancer should be at the 10* mark. In an attempt to see if the others were getting spark from the distributor, I checked the timing on the other cylinders just to make sure there were at least making the timing light flash. When I did this, they all were making the timing light go. This, I thought, was good. Now here is where I get confused. On all 6 cylinders the timing light illuminated the balancer in the exact same spot, on the 10* mark. I check this on another known good running truck and got the same results. How is this possible? Keep in mind this was was all done with a VERY cheap timing light.

You're kidding right? Look at it this way, the distributor only "sees" one point of spark at a time, the crank brings the specific piston up at the given time (10*BTDC) and the cam has turned to its given mark which turns that rotor at the given time. All together to fire the gas\Oxygen mixture, expel it, and start all over again.
Each cylinder does the same Exact thing as the other cylinders, whether it is 4,6,8 or 12. They all fire at the manufactuers settings, if it is 10*BTDC, then ALL CYLINDERS fire at 10*BTDC.
Understand? The computer on the newer engines only looks at that one cylinder to fire at that degree at a time, in the firing order.

 

[85_Ranger4x4]

Correct. You get the gold star. I'm surprised the mighty brain of tech support didn't point this out.

All plugs fire at the same number of degrees before TDC when that cylinder is compressing and getting ready for the power stroke. Number one is used for timing convenience and as a standard. Why would you use #6? However,I have seen some cases where another cylinder is used for initial timing by another mfgr. I don't remember which one(s) right off hand.

You can time the distributor with any cylinder as long as it is at the top of the compression stroke, and the distibutor rotor is pointing to the plug wire for that cylinder. shady

You're kidding right? Look at it this way, the distributor only "sees" one point of spark at a time, the crank brings the specific piston up at the given time (10*BTDC) and the cam has turned to its given mark which turns that rotor at the given time. All together to fire the gas\Oxygen mixture, expel it, and start all over again.
Each cylinder does the same Exact thing as the other cylinders, whether it is 4,6,8 or 12. They all fire at the manufactuers settings, if it is 10*BTDC, then ALL CYLINDERS fire at 10*BTDC.
Understand? The computer on the newer engines only looks at that one cylinder to fire at that degree at a time, in the firing order.

Yes all the cylinders fire at 10 degrees, but the crankshaft is only marked for TDC of cylinder #1, each cylinder comes to TDC at a different crankshaft orientation.

 

[reno]

I was trying to give a speed information of general happenings (Hey I'm G.W. making up words now ) not technical. Just so he can basically can understand, that is why I put in "set positions" and the Firing order. Whether it be a rotor inside the distributor or a computer, they only look at that one spark plug at that degree to be fired.

 

[shadetree]

Yes all the cylinders fire at 10 degrees, but the crankshaft is only marked for TDC of cylinder #1, each cylinder comes to TDC at a different crankshaft orientation.

The crankshaft marks are for determining top dead center, and the number of degrees before and after top dead center. It doesn't pertain to any particular cylinder as they all fire at the same number of degrees before top dead center. The marks simply denote a crankshaft location, not cylinder. The crankshaft journals will be in the same location when at top dead center no matter the cylinder.

On a 4 cylinder engine, #1 and #3 pistons are at TDC at the same time, but only #1 plug is firing on the power stroke. #3 is at the top of the exhaust stroke. One more crankshaft revolution and #3 plug is firing the power stroke. The timing marks will be in the same place as they were when #1 plug was firing.shady

 

[Jorley]

The firing order is 1-4-2-5-3-6. The crank turns twice as fast as the cam. For 360* rotation of the crank the distributor turns 180*. 0* on the crank marks TDC for #1 and #5 cylinders. That is how you can get timing 180 out.

Every time the crank moves 120* it brings a cylinder to TDC, the rotor moves 60*.( 360*/ 6 cylinders). Assuming timing set at 0*- #1 fires, 120*-#4 fires, 240*- #2 fires, 360*- #5 fires, then starts over for #3, #6, and #1. The rotor contacts a plug wire every 60*.

 

[skinner]

Do you realize that when you hook the timing light into one cable that you are checking the timing on that particular cylinder?

Just because #1 fires at 10*btdc doesn't mean that cylinder #2 is going to fire at 40*btdc... Each cylinder fires when THAT piston is at 10*btdc.


If this doesn't help you then I must not have understood you completely. Your wording did screw me up a bit.

Correct. You get the gold star. I'm surprised the mighty brain of tech support didn't point this out.

All plugs fire at the same number of degrees before TDC when that cylinder is compressing and getting ready for the power stroke. Number one is used for timing convenience and as a standard. Why would you use #6? However,I have seen some cases where another cylinder is used for initial timing by another mfgr. I don't remember which one(s) right off hand.

You can time the distributor with any cylinder as long as it is at the top of the compression stroke, and the distibutor rotor is pointing to the plug wire for that cylinder. shady

 

[shadetree]

Ya think???You're probably right......shady

 

[1986ranger]

Who knew I would start such a debate over something that should be so simple? I guess I am not the only one that doesn't understand all that clearly. I am inclined to believe these answers:

Yeah but the marking on the pulley should only apply to #1, not all 6 cylinders.

Yes all the cylinders fire at 10 degrees, but the crankshaft is only marked for TDC of cylinder #1, each cylinder comes to TDC at a different crankshaft orientation.

The firing order is 1-4-2-5-3-6. The crank turns twice as fast as the cam. For 360* rotation of the crank the distributor turns 180*. 0* on the crank marks TDC for #1 and #5 cylinders. That is how you can get timing 180 out.

Every time the crank moves 120* it brings a cylinder to TDC, the rotor moves 60*.( 360*/ 6 cylinders). Assuming timing set at 0*- #1 fires, 120*-#4 fires, 240*- #2 fires, 360*- #5 fires, then starts over for #3, #6, and #1. The rotor contacts a plug wire every 60*.

Yes, all cylinders fire at the same 10* BTDC, but the marks on the balancer only apply to #1 (and #5 in this case).

Which brings me back to my original question: Why did each cylinder illuminate the balancer at the 10* mark??? Jorley, got any ideas? I am going to go with:

I suppose it MIGHT get tripped by "crosstalk" if the pickup were excessively sensitive. That would mean it lights at 3x idle speed (so it shows at 10 deg BTDC, 110 deg ATDC and 130 deg BTDC for every cylinder).

Any wire will pick up signals in a nearby wire, though one would expect this to be a very small effect.

Can anyone specifically confirm or deny any of these statements?

There does seem to be a bit of this going on:

 

[Jorley]

I've been thinking about this all day and can't think of a reason, unless it's like MAKG suggested. But, I haven't given up yet. If I come up with something I'll let you know.

 

[skinner]

ok so to elaborate, no all cylinder won't read 10 degrees on the balancer. The balancer spins with the crankshaft. According to a couple unnamed people(ok i quoted them), all pistons move at the same time in the same place apparently. Any monkey could realize that this would cause huge balance issues. This is not the case. On most engines, the balancer is marked for TDC of the NUMBER 1 PISTON. When Number 1 Piston is at 10 degrees btdc, the balancer shows this. How on earth would all other pistons be at this position? They ARE when they fire, but the balancer doesn't show that.
As to your problem...well, it just doesn't add up. I DO want to make sure that you know how to check timing. Because I was thinking about it and it just didn't add up. Even crossfire in wires wouldn't cause your result. SOO...
not to insult you, but do you know how to correctly check timing?
The balancer, as mentioned, is marked for the no 1 cylinder. When you find 10 degree mark on it, per se, you MUST mark that line with white out or chalk or what have you. The timing tab is static and doesnt move. Now if all cylinders at a given rpm all have the timing tab on that mark, there is something terrible wrong. And two engines in a row mean something is terrible wrong with the gun or the way you are checking it.
I know this because I've hooked the gun to the number 2 cylinder on a 302 on accident and got radical timing readings(it was in a ranger, room is tight and it was the first one i saw)
take care,
alex.

 

[MAKG]

Can anyone specifically confirm or deny any of these statements?

YOU can. Idle speed fires each cylinder at around 7 Hz. How many times per second do you see the timing light fire? You can easily see individual flashes at 7 Hz. 20 Hz will be quite difficult (e.g., movie projectors work at 24 Hz).

 

[snake]

However,I have seen some cases where another cylinder is used for initial timing by another mfgr. I don't remember which one(s) right off hand.

[/QUOTE]

1995 1.6 Suzuki fires on #4 on a 4 cylinder. Got one in the shop right now. Screwy bastards... like this hasn't caused a little confusion before we figured it out!