Finding TDC on #1 for compression stroke

Finding TDC on #1 for compression stroke

Postby jolkkonen [OP] » June 2nd 2009, 12:40pm

I've recently replaced the intake manifold gasket on my wife's van. Time consuming but I think I did it properly. Everything is back together, but I'm having trouble getting it to start.

Unfortunately...when I took out the distributor I didn't mark where it was and I made the mistake of cranking the engine. Now I'm trying to get the timing right.

I found a post with some nice pictures on how to set the distributor right on this forum, but I'm not sure if I have the #1 piston at TDC for the compression stroke or the exhaust stroke. Is there a way to find out...or am I not even close. As I turn the main pully and get close the first mark on the the balancer I do feel some resistance....as I get close the second mark...the resistance is much less.

While I was at it...I've replace the plugs, wires, cap and rotor. The cap and rotor are BWD brand...should I order the AcDelco cap and rotor [since I've read on this forum about bad things going with anything other].

Thanks for the help.

99 Safari, RWD.
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Re: Finding TDC on #1 for compression stroke

Postby webcat » June 2nd 2009, 1:16pm

After you line up your timing mark on your harmonic balancer , take the #1 spark plug out and stick a cloths hanger in the hole and see if you feel the top of the piston , if you feel it your at the compression stroke (TDC) if you dont feel it , your 180 degrees from (TDC) and you'll have to turn it one full revolution until you line up the marks again
i'm thinking you probally got it right because if you tryed to start the van with the timing 180 degrees off it probally would have backfired so loud it would of blew your mufflers off
you better check it and make sure
Last edited by webcat on June 2nd 2009, 1:38pm, edited 1 time in total.
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Re: Finding TDC on #1 for compression stroke

Postby jolkkonen [OP] » June 2nd 2009, 1:37pm

Thanks for the info...I'll check it just to make sure.

Since I'll have the plug out I'll also check to make sure i have spark...not sure why the engine won't start...unless i did the manifold wrong...as in tighten the bolts too much, or even worse have a blown head gasket. :screaming:
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Re: Finding TDC on #1 for compression stroke

Postby webcat » June 2nd 2009, 1:39pm

I doubt it has anything to do with the manifold
I dont know how to set the timing on the newer vans , be patient and someone else will come along and help you
Last edited by webcat on June 2nd 2009, 1:41pm, edited 1 time in total.
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Re: Finding TDC on #1 for compression stroke

Postby astro355 » June 2nd 2009, 1:40pm

webcat wrote:After you line up your timing mark on your harmonic balancer , take the #1 spark plug out and stick a cloths hanger in the hole and see if you feel the top of the piston , if you feel it your at the compression stroke (TDC) if you dont feel it , your 180 degrees from (TDC) and you'll have to turn it one full revolution until you line up the marks again
i'm thinking you probally got it right because if you tryed to start the van with the timing 180 degrees off it probally would have backfired so loud it would of blew your mufflers off


Exactly, 360* from the TDC position during compression is TDC during exhaust. Everytime the timing mark is lined up, cylinder #1 is at top dead center, be it on the compression or exhaust stroke. Since the cam rotates once per every second revolution of the crankshaft, the #1 cylinder will have two TDC's (compression and exhaust) per every rotation of the crank.

While rotating the engine, a cylinder will expel compressed air during the compression stroke and not during the exhaust stroke. To find TDC of the compression stroke, take the spark plug out of the cylinder head and rotate the engine. When you hear air being hissed, that is the compression stroke.
Diagnose 1st, never be a parts changer!

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Re: Finding TDC on #1 for compression stroke

Postby jolkkonen [OP] » June 2nd 2009, 3:00pm

ah ok...pretty close to what i was expecting...didn't know about not feeling air come out during the exhaust stroke...so now I know if I'm on the compression or the exhaust stroke.

Much thanks....now hopefully i'll figure out how to get this thing started...
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Re: Finding TDC on #1 for compression stroke

Postby astro355 » June 2nd 2009, 11:19pm

Yep, no problem.
Diagnose 1st, never be a parts changer!

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