Prowler V6-3.5L VIN G (1999)
Compression Check: Testing and Inspection
1. Before performing a cylinder compression test, ensure the battery is completely charged and the engine starter motor is in good operating
condition. Otherwise the indicated compression pressures may not be valid for diagnosis purposes.
2. Check engine oil level and add oil if necessary.
3. Drive the vehicle until engine reaches normal operating temperature.
4. Select a route free from traffic and other forms of congestion, observe all traffic laws, and accelerate through the gears several times briskly.
CAUTION: Do not overspeed the engine. The higher engine speed may help clean out valve seat deposits which can prevent accurate
a. Clean the spark plug recesses with compressed air.
b. Remove all spark plugs from engine. As spark plugs are being removed, check electrodes for abnormal firing indicators fouled, hot, oily, etc.
Record cylinder number of spark plug for future reference.
c. Disconnect the coil connector for Direct Ignition System (DIS).
d. Be sure throttle blade is fully open during the compression check.
e. Insert compression gage adaptor into the # 1 spark plug hole in cylinder head. Crank engine until maximum pressure is reached on gage.
Record this pressure as # 1 cylinder pressure.
Repeat Step e for all remaining cylinders.
g. Compression should not be less than (689kPa) 100 psi and not vary more than 25 percent. from cylinder to cylinder.
h. If one or more cylinders have abnormally low compression pressures, repeat steps 4e through 4g.
If the same cylinder or cylinders repeat an abnormally low reading on the second compression test, it could indicate the existence of a problem
in the cylinder in question.
NOTE: The recommended compression pressures are to be used only as a guide to diagnosing engine problems. An engine should not be
disassembled to determine the cause of low compression unless some malfunction is present.
5. Clean or replace spark plugs as necessary and adjust gap. Tighten to specifications.