PERIODIC MAINTENANCE 2-29
ENGINE VACUUM CHECK
Engine vacuum is required for proper operation of the
Multi-Stage Induction system used on the DF225 & DF250.
Engine vacuum is also an indicator of general engine condition.
1. Warm up engine to normal operating temperature.
Make sure engine idle speed is within specification.
2. Stop engine and disconnect vacuum outlet hose from PORT
side of intake manifold outer cover (collector cover).
3. Connect special tools (vacuum gauge, hose and 3-way joint)
between engine vacuum hose and collector cover hose con-
nection.
! 09915-67311: Vacuum Gauge
09918-08210: Hose joint
09355-35754-601: Hose
09367-04002: 3-way joint
4. Start engine and run at idle speed. Vacuum reading on
gauge should be within specification.
Vacuum specification (idle speed at sea level)
61 – 71 kPa (457 – 533 mmHg, 18 – 21 inHg)
5. If vacuum is not within specification, further testing (leak-
down test, compression test, etc.) and evaluation of engine
condition is required.
Possible causes of incorrect engine vacuum
• Piston ring leakage
• Incorrect valve timing
• Poor valve/valve seat/valve guide condition
• Intake leakage
• Cylinder head gasket leakage
• Restricted exhaust
1
2
1. Intake manifold outer cover
(Collector cover)
2. Check valve
To collector cover
To vacuum tank
Check
valve.
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