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Navistar WorkStar 7400 - Troubleshooting

Navistar WorkStar 7400
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Maintenance Instructions
Troubleshooting
Problem: No Restriction Reading
POSSIBLE CAUSES HOW TO CHECK
Plugged tting 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 tting is plugged. A slow return is normal due to safety
lter in tting.
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 ow too low to generate a
restriction reading after being reset
RevenginefromidletofullRPMmultipletimestoincreaseairow enough to create an initial reading.
Air cleaner element split open Visually inspect element.
Problem: High Restriction Reading
POSSIBLE CAUSES EXPLANATION
Plugged main air lter element Normal operation will cause particles to collect in the air lter element. If observed, replace main
air lter element.
Plugged inner element (if equipped) Normal operation will cause particles to collect in the air lter element. If observed, replace inner
air lter element.
Plugged inlet screens or ducts Check system upstream from air lter 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 lter
element dries out. COLD AIR MAY BE SO DENSE THAT HIGH RESTRICTION MAY NOT REDUCE
ENGINE POWER BEFORE ELEMENTS ARE DAMAGEDFROMHIGHVACUUM.Ifgaugeislocked
up at red zone, check elements for damage.
184 3879634R1

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