ok here is maybe a very dumb question

[pushkick]

i just put new spark plug wires on my vanagon 2.1L now i decided to check the timing with a timing light and i checked #1 cycl. and it looked like it was ok the mark on the pulley was close to crankcase tdc mark while it was idling so i decided to try #3 spark plug wire and it was showing the same! how is this possible? this shouldnt happen should it? need some advice.

[mads-kaa]

Okay, my advise: Stop checking spark #3!

/Mads

[Randy in Maine]

Exactly what you want to see. The distributor goes around one every time the crankshaft goes around twice. Firing order is 1-4-3-2.

[vannygun]

no matter what cylinder is firing it should be around tdc.they dont produce much power when the piston is at the bottom of the cylinder when the spark plug fires.
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definition-Vanagon, "a ideal breeding ground for gremlins"
2000 jeep Cherokee sport (DD)
1990 vanagon gl 2.2 subaru(sold)
2006 jeep commander

[pushkick]

now thats funny mads!

shouldnt the same be true for #4 & #2 cycl. also?
but the timing light doesnt show the the same results cant see any marks on pulley when i hook up to #2 & #4 wires light flashes but no marks.

[Luckypabst]

You're still within a few degrees of TDC on 2 & 4 but 180 degrees out on the pulley. 1 & 2 fire at the "top" of the pulley where the mark is, the other two fire at the "bottom" of the pulley where there's no mark.

Chris
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'82 TD Westy
'81 NA Caddy

[OilNBolts]

Randy in Maine has the correct answer here- everyone else, back to school. When 1 fires, 3 is near the top of the exhaust stroke. When 3 fires 360 degrees later, 1 is near the top of exhaust.

[Alan Brase]

[Terry Kay]

<<BUT, be careful boys and girls when extrapolating>>

Now we're getting somewhere here sports fans.

Da Corn Husker be doin' some of dat extrapolatin'

LOL---

Good one Al--
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T.K.

[?Waldo?]

[tencentlife]

Yes, but of course #4 was in the same preheated cooling breeze. But #3-4 side is offset to the front, whereas the fan shroud centers over 1-2, so 3 is also further away from the center of the airflow, s that's how they compensated.

It's a four-stroke engine, pushkick. That means two full crank revs to complete one intake-compress-burn-exhaust cycle. Each part of the cycle takes one 180degree stroke, hence "four-stroke". The camshaft turns at one-half crank speed, as the valve cycle has to take four strokes or two full crank revs to complete. Each cylinder's cycle is spaced 180deg. apart from the others, hence an ignition event takes place at every half-turn of the crank. So every half-turn of the crank, there is a spark sent to one cylinder, and the sparks coincide with either the #1-3 TDC position, as 1 and 3 are opposed in the firing order (1,4,3,2 or 4,3,2,1), or the 2-4 TDC position, which is 180 crank degrees away, where there isn't a mark on the pulley because you're supposed to time to cylinder 1.

So when you take the strobe signal from #1, you're seeing it illuminate the pulley wheel at TDC on every second rev, while when you take it from #3, you're seeing the pulley wheel on every other rev. It appears the same to you, but you're actually seeing different events 360degrees apart.
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[pushkick]

thanks 10 cent that was excellent! and thanks everyone else for your input