Compression Tester

ron69912t · 09-09-2002, 09:31 AM

I have my old but working compression tester of the type that you just hold-in-place, it has a tapered rubber tip, has no threads to screw into the spark plug hole. It has a 3" gage and an 6"or 7" extension (reach).

Is there enough room to use it? Have any of you used this type on your engine? You have to push it into the sparkplug hole firmly and hold it there while the engine cranks over.

Don't want to buy a new one if I don't have to.

Thanks,
Ron

Jones Low · 09-09-2002, 10:52 AM

My experience has been the threaded hose type would work better in our engines, especially when the engine is in the car with all the tin metal. It is very difficult to keep a tight fit when checking compression with the rubber cone tips.

Jones Low
69-912
00-Box

Morrie · 09-09-2002, 05:12 PM

Hi Ron!

IMHO you won't have much luck without threads. I recently did a compression test on my '67 and can't imagine getting good readings (without injury) while holding in the press fit version. Auto Zone sells a pretty decent thread in one for about 25 bucks....

Morrie

Green 912 · 09-10-2002, 05:30 PM

You can drill out and tap an old spark plug and then add a hose to the one you have. (But considering the cost of a hose type you might be better off just purchasing one)

ron69912t · 09-18-2002, 04:54 AM

To those of you who have used a CT with the flexible hose & fittings. How do you tighten the threaded adapter that goes into the spark plug hole if it has the hose attached to it? It can't be finger tight because it would leak.

It's hard enough trying to screw-in a spark plug with a rigid socket extension.

Most of the threaded adapters look to be as short as a plug. I could see a long one where you could get a grip on it to tighten it in the hole.

Thanks,
Ron D

Griznant · Griznant's Garage

Quote:

Originally posted by ron69912t
To those of you who have used a CT with the flexible hose & fittings. How do you tighten the threaded adapter that goes into the spark plug hole if it has the hose attached to it? It can't be finger tight because it would leak.

Mine has a rubber o-ring around the threaded portion, and I just tighten it up by turning the hose. Never had a leak problem, and fishing it down into the heads on the 912 is fairly easy. Did a compression check on mine when I first got it and it worked very nicely. I've since used it on a friend's turbo Corvair and worked great on that too (aside from finding one dead cylinder, that explained alot).

Later,

G

Morrie · 09-18-2002, 06:04 AM

Ron,

I had a pretty easy time with my compression test too. threads with an O- Ring on the flexible hose, fed in okay, spin the hose to snug it into the socket, then attach the gage....

Thr test process was fine, just wish the results had been a little better...

Morrie

John Brandt · 05-25-2006, 06:10 PM

do you have to crank the engine with the starter or can you hand crank it? When I hooked up a similar flex line with o ring unit (harbor freight) and fingertighened it I could only get about 35 psi on 2 different cyls whilst turning with a wrench
Didn't think to crank the motor

Jones Low · 04:51 PM

Crank using the car's starter. Make sure your battery is fully charged. Connect the compression tester to the cylinder, crank the engine four to five pulses (remote starter switch connected to the yellow wire and 12+ helps). Take three readings on each cylinder and average them (or throw away the odd reading). Do the test with dry cylinders and you can tell the condition of the valves. Doing the test "wet" (squirt 1-2 pumps of motor oil into each cylinder through the spark plug hole) will determine the condition of rings. Best to do on a warm engine. Make sure transmission is in neutral and parking brake is set.

JCF · 08-09-2006, 04:14 PM

Don't you need to disconnect the coil ?

John

John Brandt · 08-11-2006, 06:13 AM

yeah; you dont want the car to start. you may want to disable the fuelpump too... Its very easy on later cars...you just take out the dme relay