Re: '98 A6 2.8 won't start- mechanics are at a loss...

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

In message <l03020903b3de43b3edd4@[194.134.104.7]> Tom Nas writes:

> >Oil overpressure.  Attach a manometer-style gauge in place of the G10
> >oil pressure sensor and compare base engine oil pressure with nominal.

Manometer is the wrong word.  What's the proper term for the
flattened-tube type of mechanical pressure gauge?

> ...and you didn't disappoint me. Called my mechanic friend, he got very
> excited as he ran over the symptoms and checked them against your theory.

The big indicator is an unexplainable delta between a leak-down test
(passes) and a 'spinning engine' compression test (fails).

> There is an auto-shutdown in these engines to protect against high oil
> pressures, and this is consistent with your theory.

You won't get ignition if compression isn't high enough.

> >(Excess pressure causes higher than normal flow into the hydraulic
> > lifters.  This becomes extreme as engine rpm increases, expanding
> > the lifters and dumping compression - engine spins like a turbo.)
>
> We think you're on to a winner, Phil. Your theory will be tested tomorrow...

If it pans out, strip the oil pressure relief valve and wash it in clean
kerosene (paraffin) in a clean container.  Strain the used kerosene
through some clean kitchen towel, then rinse the towel in water and dry
it with a hair dryer.  You might see a tiny grain of dirt - stick it to
the customer's invoice with some clear Scotch tape and an arrow pointing
to it - "THIS was your problem.  That'll be $1000, please."

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone: 0385 302803   Fax: 0870 0883933