Low compression V4 bottom two cylinders

P

patenglish1948

Cadet
Joined
May 26, 2013
Messages
6
I have a V4 1989 88 hp that I have had problems at idle. I rebuilt the carburetors and that didn't seem to help. Went through the link sync procedure, then check my compression. Seems that cylinders 3 and 4 have low compression. 110, 110, 95, 85 respectively. I pulled the port side head and the cylinder walls look great. No carbon, no scratches. The engine has never been into internally. Looking for suggestions. What next?
 
B

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Low compression V4 bottom two cylinders

Put it back together, do a GOOD Decrab on it and then look for the real problem.
 
BonairII

BonairII

Commander
Joined
Jun 7, 2011
Messages
2,727
Re: Low compression V4 bottom two cylinders

Do a decarb to see if compression comes up a bit. Might be a couple of stuck/sticking rings.
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Low compression V4 bottom two cylinders

A decarb may help bring the compression up a little.. The 85 lb cyl is a problem. 25 lbs lower than the two top cyls. I'd examine the piston top and determine if the top ring is still intact all the way around that piston. Any chance that powerhead was severely overheated at some point? When you have the head off, verify that the rubber water deflectors are still in proper place around both lower pistons. Internal heat buildup can affect ring tension/compression over a long period of time.
 
P

patenglish1948

Cadet
Joined
May 26, 2013
Messages
6
Re: Low compression V4 bottom two cylinders

I have owned it for seven years and it has not been overheated since my ownership. Top of piston looks like new. No signs of overheating. Questioning my compression gauge. Cylinder four is hard to get to. Will recheck compression once it is back together.
Thanks.
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Low compression V4 bottom two cylinders

How to the seal rings look on the head gaskets around cyls 3,4? Any chance the bottom carb has some debris in the jets, restricting fuel somewhat. (making the engine run lean)
 
You must log in or register to reply here.
Top