Operation and maintenance manual

Troubleshooting Symptoms Charts QSB4.5 and QSB6.7
Page TS-34 Section TS - Troubleshooting Symptoms
Engine Speed Surges Under Load or in Operating Range
Cause Correction
STEP 1
Fuel level is low in the tank
.............
Fill the supply tank. Refer to the OEM service
manual.
OK
Go To Next Step
STEP 2
Electronic fault codes are active
.............
For instructions on how to read active fault codes,
refer to Section 1. If fault codes are active, contact
a Cummins Authorized Repair Facility.
OK
Go To Next Step
STEP 3
Moisture in the wiring harness connectors
.............
Dry the connectors with Cummins electronic
cleaner, Part Number 3824510.
OK
Go To Next Step
STEP 4
Air in the fuel system
.............
Check for air in the fuel system. Tighten or replace
the fuel connections, fuel lines, fuel tank standpipe
and fuel filters as necessary. Vent air from the
system. Refer to Section 5.
OK
Go To Next Step
STEP 5
Fuel filter is plugged
.............
Measure the fuel pressure before and after the fuel
filter. Refer to Section 5.
OK
Go To Next Step
STEP 6
Fuel supply is not adequate
.............
Check the flow through the filter to locate the
source of the restriction. Refer to Section 5.
OK
Go To Next Step
STEP 7
Idling with excessive load
.............
Use the PTO feature for loaded conditions at low
engine speeds. Refer to Section 1.
OK
Go To Next Step
STEP 8
Vehicle parasitics are excessive
.............
Check the vehicle brakes for dragging,
transmission malfunction, cooling fan operation
cycle time, and engine-driven units. Refer to the
OEM service manual.
OK
Go To Next Step
STEP 9
Clutch is malfunctioning or is not correct
.............
Compare the drivetrain specifications to Cummins
recommendations. Check the clutch for correct
operation. Refer to the OEM service manual.
OK
Go To Next Step