Re: 200 Won't Start

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <790ACAAC0F0AD211AAD50080D870109C02802B54@eamrcnt714.exu.ericsson.se> "P-O Selander (EUS)" writes:

> Sorry to hear about your problems. I'll just point to the fact (contrary to
> Phil) that on the non-turbo, the fuel pump is actually running when you turn
> on the ignition. Runs for a about 2-3 seconds until pressure has built up or
> possibly "timed out". Maybe it's different between the two injection systems
> on our cars. I'll hunt down the problem on the fuel side first. You're on
> the right track!

I don't think the 200 non-turbo should run either, but I'm prepared to
be corrected.  In general, Audi's CIS and CIS-E fuel pumps don't run
if the ECU (or some other lower-order intelligence) doesn't think the
engine is running.  Safety, etc.

The problem is that a healthy pump delivers (nominally) 900ml in 30
seconds at zero back pressure.  That's 3ccs a second.  The capacity
of the fuel accumulator is around 10ccs - so a two or three second
burst is not enough to restore full operating pressure to a CIS/CIS-E
system that has fully leaked down.  On a day that is not explicitly
'hot', waiting a full minute between tries both re-triggers the short
pump cycle and re-engages the full cold start valve cycle.

There is no mechanism, in _any_ Audi fuel injection system, that shuts
off the pump when a particular pressure is reached.  In fact, there is
no feedback _whatsoever_ from the fuel system to the electronics.  The
ECU cannot see fuel pressure - it makes assumptions.  The fuel pump is
shut off for two reasons - overboost and engine not turning.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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