[Vwdiesel] Found low compression problem (Long version)

java@xprt.net java at xprt.net
Mon Aug 8 21:01:18 EDT 2005

After dorking around for a couple of weeks, I finally came up with what I
think is a way to determine whether low compression in a cylinder has to do
with bad rings or valves. I removed the injectors and made sure the valves
were closed and at TDC on the cylinder in question I filled the cylinder
with a light oil,up to the top of the injector port. The bad cylinder leaked
as fast as I could fill it. I tried this test again on a different cylinder
that had good compression, it filled up quickly and did not leak out.After I
completed the test I cranked the engine a few times to blow the oil out,
number 3 (the good cylinder) made a serious mess blowing a lot of oil out
the port while port four only a small amount of spray came out. One more
thing to add, I used an external starter switch I bought from Harbor freight
for about $5.00 and did not have the ignition switch on so there was no fuel
or glow plugs operating at the time.
If there is another way to do this, I don't know about it, (Hagar's
suggestion of searching the archives sounds good, but I have yet to find a
search tool to do that on this list, Is there a search utility? Other than
reading every subject line?) Anyway I pulled the head and dropped the pan.
Removed number 4 piston to find the top ring collapsed and the second ring
in pieces. ( It still read 275 psi) (I've got pictures if anyone wants to
see them) The cylinder wall looked good so I ran a hone a few times and
cleaned a massive amount of carbon from the piston and reassembled it. I
still need to put the oil pan on and replace the timing belt, but it appears
piston #4 was pretty trashed, I'm guessing at this point it was due to a bad
injector as the carbon trail on the piston looks like its trailing from top
to bottom.
A friend has an injector tester he's going to loan me next week so I will
test my stack of spare injectors and see how they look. (BTW if anyone in
the Portland Oregon area has some injectors to test drop me a line and we
can do all at once) I'm curious if its possible for an injector pump to fail
and pump too much fuel to an individual port or if fuel quantity is not an
individual cylinder issue.All my manuals state the injector pump has no user
serviceable parts and that to me is Bosch asking (no begging) me to take a
I have several extra injector pumps and I'm thinking about making a test
stand using a small electric motor to power the pump under test and use
graduated cylinders to measure pump volume on each port. I guess what I
really need is a good bosch diesel pump reference, Is there such a thing
available to Joe average? After the rabbit is on the road, I've got a cabby
that is next in line. I like to know what I'm doing before I dive into
stuff, or at least think I know what I'm doing.
Oh and my exhaust manifold to header pipe is 6 bolts and a PITA to mess
with, C clamps are definitely easier!

Thanks Steve

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