Compression

[noah4009]

I have a 1971 55HP chrysler. How do I check compression? How much is the tool? I understand there is something you screw in place of plug. Do you remove all plugs together? Is the engine running when you check compression?

 

[Spinkick]

Re: Compression

I bought my compression tester at an auto parts store. If memory serves it was only $20-30. I found out a couple of things that will affect the compression via tria and error. Of course, there's folks here that tell you in GREAT detail what to expect, but here's what I found:
#1 Only one spark plug at a time.
#2 Don't let the engine start. It should just turn over a few times. I engaged the kill switch so it wouldn't start.
#3 Don't try it with a weak battery. I had a weak battery. Compression showed about 90 on all cylinders. I was very worried. Replaced the battery and compression went back up 120 range. Of course, compression ranges depend on your motor.
#4 Don't forget to release the pressure release button on the compression tool (you will see). You may get a false normal reading on a cylinder that may be low.

Hope my 2 cents helps.

 

[JB]

Re: Compression

Remove all spark plugs before you start, Noah.

The objective in a compression test of a 2 stroke engine is to detect any one, or rarely, two, cylinder that has lost compression compared to the other cylinders.

That means that psi readings need to be close to each other. Most of us recommend within 10%, but 15% is usually acceptable.

Step by step instructions are in about a dozen threads. SEARCH for "compression".

 

[noah4009]

Re: Compression

Thank You

 

[jerryjerry05]

Re: Compression

Remove plugs(all) Open throttle all the way hook up tester turn over.Take reading,repeat on other cylinders.Comp should be even or close,within 5-10#
Most force should be around 150# J

 

[noah4009]

Re: Compression

Remove plugs(all) Open throttle all the way hook up tester turn over.Take reading,repeat on other cylinders.Comp should be even or close,within 5-10#
Most force should be around 150# J

Why do you open throttle all the way if not starting or running?

 

[JB]

Re: Compression

Opening the throttle makes no difference at cranking speeds, Noah. It is not necessary but does no harm except to complicate the task.

 

[noah4009]

Re: Compression

JB, Thank You

 

[gunner1]

Re: Compression

Does the Force/Chrysler series of 50hp engines use the 14mm or 18mm adapter?