John Deere stx38 - Manual (Page 46)

3 - 14
4/23/97
DIAGNOSIS ENGINE
DIAGNOSIS
MAIN COMPONENTS
Test Conditions:
• Machine PARKED on level surface.
• Park brake LOCKED.
• Key switch OFF.
• Transaxle/Hydro in NEUTRAL.
Test/Check Point Normal If Not Normal
1. Engine dipstick. Oil level between “L” and “F” marks
on dipstick.
Oil not burnt or contaminated with
metal particles or fuel.
Minimum crankcase vacuum 101.6
mm (4 in.).
Add proper amount of oil to bring
level to “F” mark.
Change oil and filter and inspect for
cause of contamination.
Check breather.
Check gaskets and seals for leaks.
2. Crankcase, head, and oil filter. No external oil leakage and filter
element clean. Replace leaky gaskets, seals, oil
filter, or drain plug.
3. Cylinder head. Minimum compression 345 kPa (50
psi). Adjust valves.
Check ACR.
Check condition of valves, pistons,
rings, cylinders.
4. Carburetor. Float chamber full of clean fresh
fuel.
Needle valve, passages, and jets
free from varnish or debris.
Float assembly functioning properly.
Main jet correct for elevation.
SLOW idle 1650 ± 75 rpm.
Domestic FAST idle 3350 ± 50 rpm.
Export FAST idle 3000 ± 50 rpm.
Choke, throttle, and governor set
and functioning properly.
Check for fuel in tank.
Replace fuel in tank.
Check tank vent.
Check for plugged, damaged or
pinched fuel lines.
Clean or replace carburetor.
Replace components as necessary.
Replace main jet with correct size.
Check linkage and adjust
carburetor.
Check linkage and adjust.
5. Air filter. Air filter element and canister clean
and undamaged.
Hardware tight.
Replace filter.
Repair or replace canister.
Tighten or replace hardware.
6. Fan, cylinder and head fins. Fan shroud and cylinder/head fins
clean.
Fins not cracked or broken.
Clean thoroughly.
Replace fan or cylinder or head.
7. Internal components. Wear within limits, all hardware tight,
no excessive vibrations. Inspect, repair, or replace
components as necessary.