[Vwdiesel] cyl compression

B & R Decker bdecker001 at centurytel.net
Thu Dec 7 12:35:54 EST 2006

Hi Ray;
	Checking glow plugs is easy so I would do that first. Your mechanic
should have the electrical tester to measure draw. Each glow plug draws
about 12.5 amps so when you turn on the glow plugs the total draw should be
about 49 amps. For each plug that is dead you will draw about 12.5 amps
less. Since you state that it seems to start on less than 4 cyl's. I think
you are probably down a glow plug. When I buy a VW diesel and I don't know
when the timing belt was last changed I ALWAYS install a new belt. The VW
diesel is an interference engine and if you lose a belt you WILL bend
valves. If you know your engine had a recent timing belt I would just check
the glow plugs and if one or more is bad I would just run it. If you don't
know when the timing belt was changed then do the compression test since
there is not much sense of going to the time and expense of changing the
timing belt if the compression isn't in spec's. If your compression is low
you will need to do valves or rings or both.
Brian Decker

-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of raymond greeley
Sent: Thursday, December 07, 2006 8:38 AM
To: Vwdiesel at vwfans.com
Subject: [Vwdiesel] cyl compression

My mech. wants to do a compression test before we install new glow plugs, to

make sure that the
hard starting is glowplug caused. since i purchased this 91 td jetta 18 
months ago i don't know
much about the cond. of the engine and think this diagnostic test is worthy.

I am wondering though
what kind of numbers i should look for. the way i read bentley: new engines 
are around 493 with a wear min of 412 and cyl varience of 73 psi. The engine

did and does run well and has started in this
cold weather i  am experiencing in chicagp. It does run on less that all 
four when started and
quickly evens out when i pull out the cold start handle. I use the cold 
start feature after it starts
as it seems to slow down the engine turn over if i initiate it before start 
up. I assume this indicates
a need to check timing, which will be done in the next maintenance phase. I 
look forward the some
points of discussion on these issues. thanks, ray

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