FW: Ignition Switch Failure Mode

Kent McLean kentmclean at comcast.net
Fri Jun 19 07:50:32 PDT 2009

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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