Navistar WorkStar Series, Operator'S Manual

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Maintenance Instructions
Troubleshooting
Problem: No Restriction Reading
POSSIBLE CAUSES HOW TO CHECK
Plugged fitting or vacuum line Apply vacuum to gauge until locked up at red zone. Re-connect line and hold in reset button.
Indicator will fully return unless line or fitting is plugged. A slow return is normal due to safety
filter in fitting.
Leak in vacuum line Apply vacuum to gauge until locked up at red zone. Re-connect gauge and close end of line air tight.
Hold in reset button. Indicator will drop slightly and then not move unless vacuum line has a leak.
Leak in gauge Repeat above except close gauge connection airtight.
Engine air flow too low to generate a
restriction reading after being reset Rev engine from idle to full RPM multiple times to increase air flow enough to create an initial reading.
Air cleaner element split open Visually inspect element.
Problem: High Restriction Reading
POSSIBLE CAUSES EXPLANATION
Plugged main air filter element Normal operation will cause particles to collect in the air filter element. If observed, replace main
air filter element.
Plugged inner element (if equipped) Normal operation will cause particles to collect in the air filter element. If observed, replace inner
air filter element.
Plugged inlet screens or ducts Check system upstream from air filter restriction gauge port for debris, damage or improper
installation.
Heavy snow or rain Temporary high restriction can occur during a rain or snow storm and it disappears after the air filter
element dries out. COLD AIR MAY BE SO DENSE THAT HIGH RESTRICTION MAY NOT REDUCE
ENGINE POWER BEFORE ELEMENTS ARE DAMAGED FROM HIGH VACUUM. If gauge is locked
up at red zone, check elements for damage.
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