Compression tests are a lot like snake oil in my opinion.

I am installing a 1.8L "RV" Digifant II motor in a customers 1982 Vanagon
(formerly Diesel)(OK, have installed, as of tonight).  With the engine on my
test stand with a VW Rabbit starter it did 170-170-170-170 PSI across all
four - this is with a warm engine (oil at >80C) and a fully charged battery.
Installing the engine in the Diesel Vanagon resulted in 205-205-205-200 when
it was warm.  Why?  The Diesel starter sure spins the engine over in a
hurry!  Also, how many "chugs" do you count before you stop spinning the
engine?  I count 10.  Do you hold the throttle open or closed - there are SO
many variables with a compression test.  The thing to do is a leak down test
along with a compression test - much more meaningful results.

David Marshall

Fast Forward Automotive Inc.
4356 Quesnel Hixon Road
Quesnel BC Canada  V2J 6Z3
mailto:info@fastforward.ca <mailto:info@fastforward.ca>
http://www.fastforward.ca <http://www.fastforward.ca>
Phone: (250) 992 7775           FAX: (250) 992 1160

. Vanagon Accessories and Engine Conversions
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-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Steve Sullivan
Sent: September 17, 2001 10:45 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Engine shot? Odd compression readings

Just completed my first ever compression check on my 1.9L with 170k on it.
Recently had a "bottom end" (why do they call it that?) job of re-ring, new
rod bearings, and completely rebuilt heads. Am concerned about the readings
I got, need you expert's help diagnosing results. (Not sure I have the
cylinder numbers right.)

#1 (RR): 152 psi
#2 (RF): 115 psi
#3 (LR): 160 psi
#4 (LF): 131 psi

According to friend Bentley, that's mostly within specs:

Range
Ideal: 145 - 189     My van: 115 - 160

Minimum
Ideal: 116     My van: 115

Max difference between highest and lowest
Ideal: 44     My van: 45

The two front cylinders are low, the two rear cylinders are OK, all are low.
What gives? After re-ringing the pistons, honing the cylinders, and
rebuilding the heads (and a great break-in), shouldn't the readings all be
correct? Or are my valves out of adjustment (haven't adjusted since
assembly, been a couple thousand miles since)?

Thanks for the help. Wanted your advice before calling the rebuild shop, so
I know what I'm talking about.

Steve
Calvin, the 84 Westy

Steve Sullivan
Off the Map Consulting
1326 S. 13th St.
Mount Vernon, WA 98274
360-428-7018
steveis@speakeasy.org