To determine if the valves or rings are the cause of low compression, a test should be made to determine the cylinder compression pressure.
When checking compression, the cranking speed must be at least 180 RPM and the engine fully warmed-up (Engine Oil Hot). The lowest reading should not be less than 80% of the highest and no cylinder reading should be less than 2622 KPA (380 PSI)
1. Remove air cleaner then install intake manifold cover J29664-1.
2. Disconnect the wire from the fuel solenoid terminal of the injection pump.
3. Disconnect wires from glow plugs then remove all glow plugs.
4. Screw the compression gage J-26999-10 into the glow plug hole of the cylinder that is being checked.
5. Crank engine.
Allow six “ puffs” per cylinder.
NORMAL — Compression builds up quickly and evenly to specified compression on each cylinder.
LEAKING — Compression low on first stroke tends to build up on following strokes but does not reach normal.
