MBE 4000 SERVICE MANUAL 17.1 FACTORS THAT AFFECT WHEEL HORSEPOWER The factors affecting wheel horsepower are listed in Table 17-1. To begin low horsepower diagnosis, refer to section 17.2 All information subject to change without notice. (Rev. 2007) 6SE412 0702 Copyright © 2007 DETROIT DIESEL CORPORATION From Bulletin 1–MBE 4000–07 17-3 Factors Considerations Power Rating Is the correct power rating programmed into the PLD? Is the driver aware of the effects that cruise power, or the lack of cruise power has on perceived power? Road Speed Setting Is the road speed setting causing a perceived lack of power?
Crank Case Overfilled If the crank case level is too high, there will be a loss of power due to churning losses created by the crank shaft throws contacting the oil. Fuel Blend (specific gravity) Check the specific gravity of the fuel/vehicle system. A good number 2 diesel fuel has a specific gravity of 0.840 or higher @ 60°F. It should be noted that No. 1 diesel fuel can reduce horsepower to 7% less than No. 2 fuel. Blends of No. 1 and No. 2 (common in winter) will produce less horsepower, depending on the percent of the blend. This is a common concern when dealing with low power complaints in cold climate locations.
Fuel Filter Restriction Check for fuel flow restrictions which can be caused by fuel heaters, water separators, fuel flow meters, undersize or improperly routed/damaged fuel lines, faulty check valves, contaminated fuel filters or high fuel pressure resulting from a plugged restricted fitting or regulator valve. Replacing the fuel filter is often the best recommendation in lieu of testing for the filter condition. Make sure the recommended fuel filter is being used. Refer to Technical Service Letter (05-TS-12REV – MBE 4000 Fuel Filter Update).
Fuel System Leak Fuel system leaks which result in aerated fuel are normally caused by a leak at the connections and /or filters between the suction side of the fuel pump to the supply tank and not between the pressure side of the pump and engine. Fuel Tank Vent Restriction A plugged fuel tank vent will create a vacuum in the tank and result in a loss in fuel pressure at the injectors. This will reduce fuel delivery rate. Air in Fuel Aerated fuel, caused by a fuel system leak, will result in reduced fuel delivery and late injection timing. Plugged or Cracked Fuel Tank Stand Pipe If the fuel tank stand pipe is plugged by a shop rag, fuel delivery will be restricted.
A cracked stand pipe will allow air to enter the fuel system and reduce fuel flow and cause late injection timing. Faulty Injector/Unit Pump A faulty injector/unit pump will limit fuel delivery and alter the combustion process such that power is compromised. Using Idle Smooth Balance (ISB) in DDDL can help identify a faulty injector nozzle. Valve Lash Incorrect valve lash will alter the combustion process such that power is compromised. Air Flow Restriction Air flow must not be inhibited by a plugged filter, or inadequate inlet air duct shrouding. Faulty Turbocharger A turbocharger that has wheel rubbing, oil leaks, bent blades, etc. will not provide adequate air supply.