90 100q stalls out - the final solution [NOT!]

syljay syljay at optonline.net
Wed Mar 26 08:15:32 PDT 2008

Ben Swann wrote:
> Did you actually rule out the hall distributor by physically replacing it? 
**** Yes, I swapped out the 100q distributor with the distributor from 
my 5kq. And the problem disappeared.

> symptoms are more likely caused by a timing belt off a tooth or distributor adjusted so
> it goes out of window when the engine is cold due to change in belt tension due to temp.
> I have seen these exact symptoms several times and it was not a bad distributor.  You
> could see the hall window just on the edge of the window - enough that sometimes it
> would sync. With the flywheel sensor signals and sometimes not. Verify that the Hall
> Distributor is set dead middle of window when timing belt aligned as in doing a
> replacement - TDC seen dead on the flywheel pointer.
**** I checked the timing. I even painted the timing marks on the 
flywheel, and on the front crank pulley, and on the Timing belt cover. 
  The timing mark on the camshaft pulley was already painted when I 
put on a new belt many years ago.
All the timing marks lined up perfectly with the exception of the 
timing mark on the timing chain cover. That was off by about an 1/8 or 
1/4 inch. But, since this was sheet metal and the method of mounting 
was pretty loose in tolerances, I figured it was close enough. 
Besides, the flywheel position was right on the mark.

Why did I mark the timing cover? So that I could set the timing for 15 
deg BTDC. Very easy access at the front. I dont have an adjustable 
timing light.
I measured the circumference of the rear pulley of the crank vibration 
  damper. Then I divided 360 deg by the circumference. The result was 
5 deg per 1/4 inch of circumference. Using this number, I made a mark 
on the cover for TDC - after I had all the timing alignment marks 
lined  up. Then I measured 1/4 inch to left of TDC mark and made a 5 
deg mark, 1/2 inch for the 10 deg mark, and 3/4 for the 15 degree 
mark. Marks were to the left of TDC as the engine rotates Clockwise 
looking from the front.

I see your point about the distributor being off by just a wee bit and 
the timing being on the edge of the hall effect vane window.
On the other hand, I, myself, replaced the timing belt about 60K miles 
ago. I took my time about it and did it right. No excess slack in the 
belt, not too tight - the 90 deg rotate finger test.
And, all the timing marks lined up - therefore there was no slipped 
belt tooth.

> Did you at least check for the Hall voltage change per. Bentley instructions?
***** No. I know about the 5 volt square wave output when the vane is 
between the hall sensor and the magnet.
The fact is that the distributor worked when starting the engine. Then 
the engine stalled out after about 30 seconds or so of running. Most 
of the time, it would start up again and die again.
Because of these conditions, testing the hall effect sensor for output 
would only show that it worked.

Oh yes, I did eliminate the fuel/computer system as the culprit by 
disconnecting the cold start valve, the DPR, and the ISV when the 
engine was running. Engine still ran . .. and died after about 30 
seconds - just like before. And I had a fuel gauge connected and the 
fuel pressure was steady at about 96 lbs when the engine died.

> Don't waste your time shot-gunning.  By following procedure or methodology, you can rule
> the distributor good or bad - at least with reasonable certainty.  Yes the distributor
> can go bad - lose signal/poor voltage, but verify in window and voltage switching
> between approx. 0V and 4-5V when going in and out of window.
**** I have to fix the water pump issue on my 5kq right now. When I 
have time, I'll swap in the "bad" distributor and see/verify that the 
problem returns.

> Also - did you get any codes upon no-start condition?
**** I was a BAD boy and did not check codes. I have to make a 'light 
and switch doohickey' to check codes.
The engine almost always started - it just didnt keep on running. 
Every once in a while, the engine would not start. That might have 
been fuel flooding.

> Also - in re-reading, I note you have a 100 therefore NF, and so puts more weight on
> distributor being bad, since you have a 5 window.  So do check for voltages - you should
> see the voltage change.  The signal sync./in window test Does not count, but still the
> distributor might be mis-adjusted making the car hard to start.
***** As mentioned before, the car almost always started right up, 
especially from cold start.
The car was not hard to start - as from a slipped timing belt. Car 
starts up very easily. Therefore it was not a mis-adjusted 
distributor, or slipped timing belt.

> I take you check for spark from the coil or a plug is not present when the no start
> occurs.
**** Its not a no-start condition. Its a die-after-start condition.
I did put a timing light on the center lead and did notice the missing 
in the CENTER lead of the distributor. As the engine was dying, more 
and more sparks were missing till the engine died. This told me that 
the problem was before the Distributor Center lead.
Signal flow for the ignition system is:
Hall effect --> Knock sensor Control Unit --> Coil Current Switch(big 
transistor next to coil) ---> Coil ---> Center Distributor Cap ---> 
Rotor ---> Plug distributor cap ----> spark plug

Now the problem could also be in the Knock sensor control unit, or the 
  switch/coil. But, my reading on the subject indicates that the hall 
effect is the most likely culprit.

> Keep plugging - if you are certain it is the distributor then it does not take that long
> to change one out.
**** Car has been running fine for 3 days now. Smooth idle, no missing 
under any conditions.
Also, I went to the junkyard and pulled 2 distributors complete with 
caps and wiring, and 2 switch/coil assemblies. I have plenty of spare 
parts now. I know Huw is reading this, so be prepared Huw for getting 
an email from me about technical details of Hall effect sensors. :-)

For my peace of mind, I will swap out the distributor for the "bad" 
one and see if the problem re-appears.

Oh, by the way, my parts guy has a distributor rebuild kit 1 237 011 
110. The kit contains the Hall effect sensor mounted on the plate, 
gaskets, screws, O-ring, vane, etc.
The only problem is that this is for a vacuum advance style 
distributor for 5 cyl engine - probably 1987 and before.
His cost was $75, and he was willing to sell it to me for $25 to get 
rid of it. I grabbed it, but quickly realized that it was for a vacuum 
advanced distributor.
If anyone is interested in this kit, let me know. You most likely will 
get it at a good price - maybe not $25 - but at a good discount.

SJ in NJ

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