1982 Coupe:Hot Start Issues

[Huw Powell]

> As the subject says.  CIS.  To date I have changed the fuel pump
> check valve, all injectors (for new), and the 2 small o-rings on the
> primary pressure regulator.  I have no leaks and unfortunately, no
> pressure gauges.  Under normal conditions, the car starts like a
> champ when cold.  Barely turns over one revolution before firing up.
> When warm/hot, it can take 5-12 seconds of constant cranking.  When
> it finally does start, it "chugs" or almost like it misses a little.
> That part is hard to describe.  After it catches itself and settles
> down to idle, it smoothes out, well, as smooth as a 22 YO Audi will
> get!  Anyway, have I missed anything?  I know if I where to test the
> holding pressure at the CSV, I would certainly be able to offer more
> info.  Any suggestions?

Well, you culd always retrofit CIS-E, there are hundreds of old (84-87) 
coupes and 4000s sitting around with usable parts in them.

But, writing more realistically, and hoping I can make at least one post 
without making some glaring error of fact (been on a real roll 
lately...), hot start issues can arise from several different places, 
some of which Audi/Bosch tried to address as the 80's progressed.

By the way, I developed some awful warm start problems with my coupe a 
few years back (after the CISE swap), which were mostly solved with 
suggestion 1. below.

1. Heat soaked starter.  Draws too much current, pulls voltage available 
to rest of car down too low.  Maybe ECU doesn't come on.  Maybe no 
spark.  Solutions might include a new/rebuilt starter, a new battery, 
cleaning up wiring connections, etc.

Starting in '84 or so, the starter included a switched battery terminal 
which ran back up the fusebox area to help out with the voltage on some 
things while cranking.

2. Good old fashioned vapor lock.  Again, the later cars added some Rube 
Goldbergian devices to lessen this problem.  Can be partially attributed 
to injector leakdown, or a bad check valve at the fuel pump.  (of 
course, you have replaced both of those...)

3. various and sundry tune up type parts being a bit old and not working 
well when hot.  I think this is less likely as they would probably 
interfere with a cold start more.  Still, no harm in looking at your 
ignition parts, etc.

4. Now my head hurts, because I have to think back to CIS, which I 
ditched about 6 years ago or so.

On a warm start, the warm up regulator shouldn't really be an issue, but 
the only way to really tell is to hook the system up to gauges and check 
the control pressure.

Perhaps your frequency valve isn't working properly, but it seems to be 
fine when the engine is running (or cold).  You should at least check 
its duty cycle (that's what the "spare" connector by the starboard strut 
tower is there for).

The auxiliary air valve could be closing too far, or sticking or 
something.  I doubt this, though, since all you'd have to do is push the 
pedal down a bit to get air to the engine to start it.

I think I would start by trying to look for things that could be getting 
heat soaked in the brief "off" period prior to an attempted hot start, 
at least until you can get some gauges on the fuel system.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/