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

quk@isham-research.demon.co.uk (Phil Payne) wrote:
>> >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?

Sorry, I've seen some but don't know what they're called.
>> ...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).

That figures.
>> 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."

We'll see- I'll let you know what comes out!