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RE: Engine diagnostocs help (tr4)

To: <triumphs@autox.team.net>
Subject: RE: Engine diagnostocs help (tr4)
From: "Randall" <tr3driver@comcast.net>
Date: Sat, 3 Sep 2005 18:04:37 -0700
> So in trying to track it all down I ran a compression check on the engine
> this morning and the results don't come out well: 115   30   155  0 (or near
> 0)  from cylinder 1 to 4. With numbers like this how is it even running at
> all?

Probably starts on #1 and #3, then at higher rpm the other cylinders have enough
compression to fire.  But just 1 & 3 would be enough to run (although not well).
After all, that should give you half power, which is more than the original VW
bug had.  And my favorite old tractor had a 2-cylinder engine that fired the
same way !  I once drove home a VW Rabbit that was only running on #1 and #4.

> My next check was to check the adjustment of the rocker arm for proper valve
> adjustment but baring that working (and I don't hold much hope) what does
> the collective wisdom of the list think. Where should I go to next?

The next logical step is to try to determine where the compression is going.
Check the compression again after giving the cylinder a squirt or two of oil
(not a whole lot, maybe a teaspoonful).  If it rises dramatically, there is a
problem with the rings.  If not, then the problem is likely to be valves or head
gasket.

For a more thorough test, you can try pressurizing the bad cylinders with
compressed air and see where the air comes out.  But it's almost a certainty
that the head is going to have to come off (if you don't find any gross problems
with the rockers when you check the lash), and the problem should be obvious
with the head off.

Randall




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