Re: Strange ignition problem

[zm@mhcnet.att.com]

Stamos,

I have a couple of general points about the problem with your car:

1. Most cars have a resistor in series between the battery and the primary
coil. This resistor is meant to be bypassed during engine cranking to provide
a strong spark for easy starting. Once the engine starts, and the key is
returned to the ON position, the resistor is back in the circuit. If this
operation is not working correctly, you get a weak spark. Now, I'm not sure
if Audis have this resistor setup or not (I have not looked at any ignition
related circuit diagrams for my Audi). If you have your car's service manual,
you may want to check the circuit diagram.

2. I have found that in a previous car (Dodge Colt) that I owned, I had the
same problem - the car would not start during cranking but would start as
soon as the cranking was stopped. I suspected the resistor but the manual
showed no such resistor for the electronic ignition mdel. But I found that
the contacts (posts) in the distributor cap and rotor
would periodically (may be every 12 to 20 K miles) get dirty, that is,
covered with a white oxidized substance. I would scrap the hard deposits off
with a utility knife and smooth them with fine emery paper and the starting
problem would go away. Essentially, these deposits would create a resistance
in the flow of spark and since the electrical system was loaded during cranking,
it would result in a weak spark. But as soon as the cranking was stopped,
the last couple of strong sparks were good enough to start the car. Whenever
the problem occured, before I got a chance to clean the distributor/rotor
posts, I would crank the car only briefly and let go - it would start
immediately. Cranking for a long time will flood the engine as you discovered.
Check to see if your distributor and rotor contacts are clean. If the contacts
are not worn and as long as the ditributor cap and rotor are not cracked,
there is no need to replace them. Also check if the carbon center electrode
is clean and not worn down.

You mentioned that you did not get a voltage at the primary coil during
cranking. If this is the case, then the resistor bypass theory may be more
applicable in your case rather than the dirty contacts. Let us know what
you find. Hope this is helpful.

Zafer