Actron CP7821 User Manual

COMPRESSION

TESTER

INSTRUCTIONS

Before making this test it is a good practice to check and be sure that all cylinder head bolts are tightened to the engine manufacturer's torque specifications.

1. Run the engine for about 15 minutes until it reaches normal operating temperature.

2. With the engine off, loosen all spark plugs about one turn, then use an air hose to blow all the dirt out of the spark plug wells. Then remove all of the spark plugs and gaskets. Place them on a clean flat surface in the order in which they were removed. This will help to correlate any compression problem with the condition of the plug from the particular cylinder involved.

CP7821

240

270

150

120

kPa x 100

Compression

Tester

180

210

16 18

300

3. Remove the air filter and block open the carburetor throttle plates to maximum. Remove the high tension lead from the center of the distributor and ground it.

4. Hold the compression tester in the spark plug hole and crank the engine for at least 4 compression strokes or until pressure stops rising on the tester.

5. Record the compression reading and repeat the test on all remaining cylinders.

6.On a normal cylinder, the needle should advance on each stroke until it reaches a peak. All cylinders should test within the engine manufacturer's specifications and readings should not vary more than 10% from cylinder to cylinder.

7. If the needle fails to advance normally or if it remains the same for several strokes and then starts to climb, the cylinder has a sticking valve.

8. If the compression reading is 15 or more pounds above the manufacturer's specification, it is indicative of carbon build-up in the cylinder.

One Year Warranty

If within one year from the date of purchase this equipment fails due to defect in materials or workmanship, return it to Actron and Actron will repair it free of charge.

This warranty gives you specific legal rights, and you may also have other rights which may vary from state to state.

2-202103

9. If a reading on two adjacent cylinders is 20 pounds or more lower than the rest of the cylinders, a defective head gasket is indicated.

10.

If readings are low or uneven between cylinders, pour a teaspoon of S.A.E. #30 oil into each cylinder and retest. If the readings increase considerably, the fault is poorly seated or worn rings. If the readings remain about the same, the valves are at fault.

11.

When tests are completed, put the spark plugs back in the engine and return the high tension lead to the center of the distributor. Unblock the throttle and replace the air filter.

Customer Service

For product information or customer service please call 1-800-ACTRON-7 (1-800228-7667) Monday through Friday, between 8:30 a.m. and 4:30 p.m. Eastern time or fax anytime at (216) 651-2388.

Actron can also be reached by Email or on the Internet.

Email address: sunpro@actron.com Internet home page: http://www.actron.com

Actron Manufacturing Company

9999 Walford Avenue Cleveland, Ohio 44102-4696