Boost and TDC and distributors

Sun Jun 23 16:37:41 EDT 2002

If you ONLY removed the distributor and left the cam and crank TDC's intact
(as described), you CANNOT put the distributor in 180 off, or it won't run.
You can physically put the distributor in any way that fits, you just need to
rotate the body until you have rotor pointing at number 1 (window plate hash
mark and nick in dist aligned).

If you are 180 out you will have the distributor 180 degrees from the nick on
the outer lip when the crank shows TDC -0-.  When this happens, you can't
start the motor, because the timing reference pin and the dist window need
this condition for Motronic to fire the car.  AFTER the car is started, the
dist window is ignored, so you can rotate the distributor and the car will
continue to run, but should toss a code.

Ned and I had several discussions on TDC windows over the years, mostly on
the MC and early urqs.  At one of the Grattan track events in the early 90's
there was an urq that wouldn't start when warm.  What happens in the urq's
(and could happen in any car that is teetering on the edge of the dist
window) is that the head warps slightly causing the distributor to misalign.
Car still runs, but at hot shut down and restart the window was out of whack.
 Car cold, no problems.  Did this on my '84 when I first got it too.

WRT 20vt stuff Dan, you could have too much slop in the gears (metal or
plastic), or you were just on the edge of the window.  That said, when you
install the distributor, many times you will find that the TDC reference hash
are off a bit sometimes causing a "perfect" tdc reference to be not so.  Your
procedure of moving the distributor CW and CCW is what most of us end up
doing with the same problem.

I'm not at all with the thinking that you were 180off in timing Dan, but -0-
on the distributor is +/- 2 degrees if service tech manual recall serves.
That's a 1% rotational error.

Scott Justusson

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