John Deere stx38 - Manual (Page 49)

4/23/97
3 - 17
ENGINE DIAGNOSIS
6. Cylinder compression. 40—90 psi Low compression (below 40 psi)
can be the result of a stuck valve or
automatic compression release
(ACR) not functioning correctly. A
stuck valve could be caused by
stale fuel or an over extended
hydraulic lifter.
High compression (above 90 psi)
can be the result of the ACR not
functioning correctly.
7. Flywheel key. Not damaged or partially sheared. Replace
8. Starter Should not kick out. Engine oil weight too heavy. Only
multi-viscosity oil is recommended.
Replace UTC starter with Eaton
starter (only replace starter if the
proper oil does not provide better
starting performance). Eaton
starter is standard on 1996 model
year STX’s (270001— ).
Test/Check Point Normal If Not Normal
ENGINE BACKFIRES, HAS LOW
POWER, WILL NOT START, OR
TURNS OVER SLOWLY AND LOCKS
UP
STX38—EXPORT MODELS ONLY
(M00STXC210001—271587)
(M00STXE210001—271696) STX46—
(M00STXF240001—270000)
(M00STXG240001—270000)
IMPORTANT: Proceed with this diagnosis only after
completing the procedures starting on page 3-16.
Test/Check Point Normal If Not Normal
1. Plastic cam gear. Plastic cam gear “Not” rotated on
metal hub of camshaft. Replace plastic gear camshaft with
metal gear camshaft.
Replace any related valve train
components that have been
damaged or do not meet
specifications. This could include
valves, rocker arms, and push rods.
Make sure hydraulic lifters are
“bled” and “primed” before
assembly.
2. Automatic compression
release (ACR) spring.
Spring should not be binding on
retaining rivet. Replace plastic gear camshaft with
metal gear camshaft.Replace any
related valve train components that
have been damaged or do not meet
specifications. This could include
valves, rocker arms, and push rods.
Make sure hydraulic lifters are
“bled” and “primed” before
assembly.