Dennis Durrell writes:

Reading Doug's comment about the '89 with oil consumption made me wonder what the spec. compression is for a the 240. My '91 DOHC has 108k on it and shows 195-185 PSI using a threaded compression gauge on a semi-warm engine. Seemed really good to me considering the miles. Just curious if anyone with a manual had the info.


DMD -91 240SX SE


Hi Dennis-

From the Factory Service manual:


Measurement of Compression Pressure

1. Warm up engine.
2. Turn ignition switch off.
3. Release fuel pressure (See How to Change Fuel Filter)
4. Remove all spark plugs.
5. Disconnect distributor center cable.
6. Attach a compression tester to No. 1 cylinder.
7. Depress accelerator pedal fully to keep throttle valve wide open.
8. Crank engine and record highest gauge indication.
9. Repeat the measurement on each cylinder as shown above.
Note: Always use a fully charged battery to obtain specific engine revolution.

Compression Pressure kPa (kg/cm2, psi) / RPM
Standard = 1,236 (12.6, 179) / 300
Minimum = 1,040 (10.6, 151) / 300
Difference limit between cylinders = 98 (1.0, 14) / 300

10. If cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinders through the spark plug hole and re-test compression.

* If adding oil helps compression, piston rings may be worn or damaged. If so, replace piston rings after checking piston.

* If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat.

* If compression in any two adjacent cylinders is low and if oil does not help compression, there is a leak past the gasket surface. If so, replace cylinder head gasket.


Hope this answers your question,


'91 s13