Troubleshooting Tips; Low Power - Detroit Diesel MBE 900 Technician Manual

INTRODUCTION
1.3

TROUBLESHOOTING TIPS

This section provides tips on troubleshooting complaints of low power, excessive oil consumption,
exhaust smoke, coolant loss, and intermittent concerns. The following lists of questions are only
guidelines. The service outlet need not consider every question to resolve the complaint. The
questions to consider should depend upon the circumstances surrounding the vehicle symptoms.
The technician should ask the operator questions for these seven basic concerns. They are
Low Power, Fuel System, Air System, Oil Consumption, Exhaust Smoke, Coolant Loss, and
Intermittent Concerns.
1.3.1

LOW POWER

The basic questions to check for Low Power are:
What caused you to suspect low power?
When did the low power concern start?
Are you aware of any diagnostic or performance codes?
Are you running an unusually heavy load?
Has the engine been serviced recently? (If yes and the concern occurred after servicing,
the servicing outlet should be involved.)
Is the air filter clean? (Verify that inlet air is not restricted.)
Are the fuel filter and water separator clean? (A plugged filter will restrict fuel flow
and result in low power.)
How many miles are on the unit? (If mileage is high [several hundred thousand miles],
valve lash may need adjusting or nozzles may need replacement.)
Is the unit hard starting? (If there is a hard starting issue, there may be a fuel system
related concern or low compression.)
Are the vehicle fuel tanks vents are open? (Make sure the vents are open. Plugged vents
will create a vacuum in the fuel tanks as fuel is consumed and result in a gradual power
loss as the vehicle is operated.)
Is there a misfire at idle or at no-load speed? (If yes, there may be a fuel or mechanical
system concern.)
Has there been a history of low power complaints? (Check warranty claim status and
prior Remedy tickets.)
Is there evidence of white, black, or blue exhaust smoke? (If yes, see smoke
troubleshooting guide.)
Is the fuel level in the fuel tank low? (If below 1/4 tank, it may result in high fuel
temperature above 80 C (176 F). High fuel temp can also cause low power.)
Is the exhaust flap fully open and are the exhaust system restrictions eliminated?
1-4
All information subject to change without notice. (Rev. 5/05)
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