New Holland CX720 Repair Manual page 1676

ENGINE - Compression test (B.10.A - F.40.A.35)
CX720, CX740, CX760, CX780, CX820, CX840
1. TEST PROCEDURE
Be sure battery performance meets specifications.
2. Warm up the engine by operating for a minimum of
half an hour at 1200 rev / min.
Stop the engine and remove the injector and seat
3.
washer from no1 cylinder.
4. Clean the injector bore and crank the engine to blow
out any loose carbon particles.
5. Install an engine compression test gauge, From
kit No.291309 (NA-FNH02020) with fault injector
295039 (NA-FNH00882), into the injector bore, us-
ing a new seat washer and the injector mounting
bolts.
6. Connect the gauge and hose to the adapter.
7. Crank the engine at 200 rev/min with the electric fuel
shut off wire disconnected to prevent engine start up.
8. Observe the gauge reading, and repeat the compres-
sion test, steps 5-7 for each cylinder.
9. TEST READINGS
All cylinder compressions should be uniformly within
1.7 bar (25 lbf in2) of each other.
10. A reading of more than the 1.7 bar (25 lbf in2) below
the other cylinders indicates leakage at the cylinder
head gasket, piston rings or valves.
11. A reading of more than 1.7 bar (25 lbf in2) above the
other cylinders indicates excessive carbon deposits
on the piston and cylinder head.
12. A low even compression in two adjacent cylinders
indicates a cylinder head gasket leak. Check this
item before condemning the rings or valves.
13. TEST CONCLUSION
To determine whether the rings or the valves are at
fault, squirt the equivalent of a tablespoon of heavy
oil into the combustion chamber. Crank the engine
to distribute the oil and repeat the compression test.
The oil will temporarily seal any leakage past the
rings. If approximately the same reading is obtained,
the rings are satisfactory, but the valves are leaking.
If compression has increased over the original read-
ing, there is leakage past the rings.
During a compression test, if the pressure fails to
climb steadily and remains the same during the first
two successive strokes, but climbs higher on the suc-
ceeding strokes, or fails to climb during the entire
test, suspect a sticking valve.
POWER PRODUCTION - ENGINE
2 4/7/2006
B.10.A / 130