B3000 SE Regular Cab 4WD V6-3.0L OHV (1998)
Compression Check: Testing and Inspection
Compression Test
COMPRESSION TEST
1. Make sure oil in crankcase is of the correct viscosity and at the proper level and that the battery is properly charged. Operate the vehicle until the
engine is at normal operating temperature. Turn the ignition switch to the OFF position, then remove the spark plugs.
2. Place the transmission in PARK (A/T) or NEUTRAL (M/T) and apply the parking brake.
3. Block throttle plate in the wide-open position.
4. Install a compression gauge in the No.1 cylinder spark plug hole.
5. Install an auxiliary starter switch in the starting circuit. With the ignition switch in the OFF position, and using the auxiliary starter switch, crank
the engine a minimum of five compression strokes and record the highest reading. Note the approximate number of compression strokes required
to obtain the highest reading.
6. Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.
RESULTS
The indicated compression pressures are considered within specification if the lowest reading cylinder is within 75 percent of the highest reading.
Refer to the Compression Pressure Limit Chart.
If one or more cylinders reads low, squirt approximately one tablespoon of clean engine oil 10W40 on top of the piston(s) in the low-reading
cylinder(s). Repeat the compression pressure check on these cylinders.
INTERPRETING COMPRESSION READINGS
1. If compression improves considerably, piston rings require service.
2. If compression does not improve, valves are sticking or seating improperly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on piston does not increase compression, the head gasket may be
leaking between cylinders. Engine oil and/or coolant in the cylinders could result from this condition. Use the Compression Pressure Limit Chart
when comparing cylinder compression readings to determine if the lowest reading is within 75 percent of the highest reading.
