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Re: Distributor timing on a 1990 900S Posted by Cmyles [Email]  (#1126) [Profile/Gallery]
(more from Cmyles) on Sun, 9 Feb 2014 09:37:26
In Reply to: Re: Distributor timing on a 1990 900S, SaabStalker  [Profile/Gallery]
, Sun, 9 Feb 2014 06:45:23
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SaabStalker,
You wrote:
"If the rotor is pointing at # 4 electrode and the #1 cyl is nearing top dead center then I should not be able to see the flywheel timing numbers as they will be 180 degrees away from the alignment mark on the flywheel cover. Correct or incorrect?"
That is incorrect. Pistons #1 (nearest the firewall) and #4 (nearest the radiator) both reach TDC at exactly the same instant. As I said, they move in unison and since they reach TDC every time the crankshaft makes one revolution you will see the "0" timing mark align exactly with the stationary timing mark whenever those two pistons reach TDC. When the crankshaft is rotated 180 degrees away from the timing mark you will find pistons #2 and #3 at TDC (and #1 and #4 at bottom dead center).
Since the camshafts and distributor rotate at half the speed of the crankshaft the distributor rotor will point at tower #1 and at tower #4 in an alternating sequence with each single, full revolution of the flywheel (360 degrees). Rotating the crankshaft/flywheel one full turn (360 degrees) will drop the pistons (#1 and #4) from TDC and then bring them back up to TDC while turning the distributor rotor only one half a turn, from tower #1 to tower #4 or vice versa.
So when you have pistons #1 and #4 at TDC you WILL see the timing marks align but only one of those two cylinders will be firing and that depends on which tower (#1 or #4) the rotor is pointing at (as well as the cam and valve timing of course). The other will be on it's exhaust stroke.
FYI, the exact same sequence holds true for cylinders #2 and #3 EXCEPT that they reach TDC when the "0" timing mark on the flywheel is 180 degrees away from the stationary mark. The B202 engine has the simplest form of four cylinder crankshaft. The two outer rods/pistons are all the way up when the two inner rods/pistons are all the way down. If you ground the weights off it would lay flat on a table top.
If no work has been done to the car since it was last running, other than the removal of the distributor, then I would highly recommend that you install a distributor and arrange the plug wires exactly as described in my last post, crank the engine and if it fails to start check to see if a spark occurs at the plugs. If the head and timing chain have been off since it last ran then we need to ask whether the cams are timed correctly and that's not too difficult to find out. I suspect an electrical defect in the ignition circuit. That's common in these situations.
, Sat, 8 Feb 2014 15:56:43, Sat, 8 Feb 2014 21:15:06, Sun, 9 Feb 2014 06:45:23, Sun, 9 Feb 2014 09:37:26 <-- Viewing This Message, Sun, 9 Feb 2014 11:50:49
, Sat, 8 Feb 2014 17:20:01, Sat, 8 Feb 2014 17:31:09, Sat, 8 Feb 2014 17:26:19, Sat, 8 Feb 2014 17:32:38, Sun, 9 Feb 2014 06:31:16, Sun, 9 Feb 2014 06:49:03
, Sun, 9 Feb 2014 08:00:58
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