Re: Audi with cold start problems

[Robert Houk - SMCC WorkGroup Server Firmware <Robert.Houk@East.Sun.COM>]

   -- Hello!

'Owdi!

   I have been surfing around looking for Audi  sites. You see I have a=20
   problem with my cold-start valve on my Audi 100 cc(year of make:82)
   It=B4s hard to start when the cold-start is conected, and when it=B4s realy
   cold (-20 c) I have to "warm" the engine up before it runs. It=B4s fiers up.
   Then dies. Then it fiers up again. Then I have to knock gently on=20
   the injectors. and so on. After a while it starts or my battery is dead.
   If my cold-start were functioning this wodn=B4t happen. Or is somthing wrong
   with my injectors as well. I asked this question on the Quattro-list
   before, and one reply I got said that the engine should start=20
   without throttle even if the temprature is below -20 c. Is this correct?=20

I've found that a slight throttle helps start the car ('83 UrQ) cold.
(I suspect this is as much due to leaky injectors as anything; after
a second or two it idles happily on its own; no throttle needed to
keep it running.)

Be that as it may, I presume from your above that your engine "catches"
(fires) readily, but subsequently dies after starting? This is a *LOT*
different that "doesn't start"!

If the engine starts, your cold start injector is [probably] OK -- it
only works during cranking, and not during normal engine operation. If
the car subsequently dies unless you sit on the gas pedal, you've got a
problem in the "cold engine fuel enrichment" area. Assuming it's pretty
much the same setup as mine, there are two things I would check. First
is the control pressure regulator (ugly wart on side of block; two wires
run into it, two fuel lines run to it, possibly manifold connection as
well but I think that's turbo only). It's responsible for maintaining
a "high" fuel system pressure while "cold", and dropping the fuel system
pressure as the engine warms up (actually as it warms up, it's electri-
cally heated with a contribution from the block) thus providing an over-
all "rich while cold" mixture. Unless you have the gauges/taps/etc. to
measure the fuel pressure, it's probably easiest to just swap units
and see what happens. (Alternatively, disconnect the wires and see if the
engine can still run "hot" -- should be running very rich, the frequency
valve on the fuel distributor should be at 0%duty cycle (probably only
drops to 5% or so min) trying desperately to lean out the mixture...
use your handy dandy SunPro 7678 to measure the duty cycle...)

Second, there's another little widget called the "aux air valve" or
some such. This is mounted on/near the manifold, with an air inlet
from before the throttle plate and an air outlet to the manifold, plus
the same two wires as the control pressure regulator above (both switched
with the ignition). It is responsible for feeding extra air while the
engine is cold, with its internal electric heater reducing the air
bypass as it warms up. Easy test -- pull the two wires; as the engine
warms up the idle should continually rise; once hot the idle will be
1500-2500rpm; re-connect the wire and the idle should then drop (over
the next minute or three) back to normal levels.

Good luck!

					-RDH