FW: Ignition Switch Failure Mode

[Ed Kellock]

Well, since the discussion has already diverged from the original focus...

My 89 200q MC2 had a hard to start episode long ago.  It was a problem
mostly when it hadn't sat overnight and mostly during warmer times of the
year.  It was the fuel pump check valve.  It hadn't failed, it had come
loose.  I believe it had been replaced at some point, but not torqued down
enough apparently, and was allowing the system pressure to bleed down.

Another similar experience was with my urq.  It went from starting and
running to not over a period of months.  I tried and tried and tried,
swapping/replacing parts, even the ignition switch, but finally resolved it
by pulling the injectors and tightening the injector seals/seats.  Basically
my problem was a big air leak via the injector seats.

If the car is hard to start when it has run and been parked for 30 minutes
up to a number of hours, I'd say fuel pump check valve.  If it is still hard
to start the next day, after all temperatures and pressures have had time to
stabilize overnight, then I'd say air leak, of which there can be many
sources.

Just my $.02 worth.

Ed

-----Original Message-----
From: 200q20v-bounces at audifans.com [mailto:200q20v-bounces at audifans.com] On
Behalf Of Geraint Lloyd
Sent: Friday, June 19, 2009 9:01 AM
To: quattro at audifans.com; 200q20v at audifans.com
Subject: RE: FW: Ignition Switch Failure Mode


Actually it sometimes starts fine after it has been sitting for a while. I
was assuming that a check valve failure would be mechanical, so unlikely to
be intermittent. But I appreciate that i could be wrong And the b at 5tard
check valve is only 2 years old anyhow.....



-----Original Message-----
From: 200q20v-bounces at audifans.com [mailto:200q20v-bounces at audifans.com] On
Behalf Of Kent McLean
Sent: 19 June 2009 10:51
To: quattro at audifans.com; 200q20v at audifans.com
Subject: Re: FW: Ignition Switch Failure Mode

kneale at knitknacks.com wrote:
> Do you know that you have no spark or fuel while cranking?  If so, I'd 
> suspect the ignition and engine speed sensors.  They have to be 
> providing the ECU a signal in order for it to activate the fuel pump 
> relay and sparking system.  Those things are twenty years old now.  
> They fail commonly much sooner on V8s because they're located near the 
> driver side exhaust plumbing on V8s.  On 10valve cars they escape that 
> heat issue, but they're still subject to age.

Given that it's hard to start only after it has been sitting for a while, I
suspect the check valve at the fuel pump. Does the car start after 5-10
seconds of cranking?  Then it's the check valve.

I don't believe the ignition switch would not work after it's been sitting,
but then magically work if it hasn't been sitting. Usually it will fail to
spring back, leaving your key in "start" mode; you can turn it back a bit to
set it to "run". Either that, or it fails all together.

-- 
Kent McLean
1999 A4 Avant, V6 Tiptronic
1991 200 TQA #3, with mods
1990 V8 w/5-speed and other mods
gone: '91 200 TQA x2, '94 100 S Avant, '89 200 TQ "Bad Puppy"

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