MBE 900 & MBE 4000 EGR

Section 1.3 Troubleshooting Tips

Section 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.‪

Section 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?
  • Are there any active or historic codes? (Record ALL codes in bold.)

    Note: If a printer is not available, record all codes with the repair order as they may be required at a later review.

  • Is the boost pressure normal? (See engine performance curve specification.)
  • Are the camshaft and crankshaft sensors installed correctly?
  • Is the valve lash correct? (Verify!)
  • Is the battery holding power? (Verify voltage is correct. Low voltage will result in multiple codes.)
  • Is there a misfire at idle or no load speed? (If yes, run a fuel system inspection according to the procedure listed in the service manual.)
  • For MBE 4000 engines with turbo brake, is the wastegate operating properly? (See Service Information Letter No. 03 TS -51.)
  • When the accelerator pedal is in the full throttle position, does the DDDL or minidiag2 sense 100 % throttle?

Section 1.3.2
FUEL SYSTEM

The basic questions to ask for the Fuel System are:‪

  • Are the correct fuel filter and water separator installed and clean?
  • Is the Fuel System in proper working order? (Inspect the Fuel System. Refer to MBE 4000 Service Manual, 6SE412 and MBE 900 Service Manual, 6SE414.)
  • Are the overflow valve and fuel pump operating properly?
  • Is the vehicle using fuel with the required specific gravity? (API 34-38 is required for No. 2 diesel fuel.)
  • Inspect the water separator for clogging.

Section 1.3.3
AIR SYSTEM

Inspect the Air System as follows:‪

  • Check air dryer for system leaks.
  • Check for leaks at all hose clamp locations, and charge air cooler.
    warning

    PRESSURIZED AIR AND FLYING PARTICLES

    To avoid injury to eye or face, wear a face shield or goggles when conducting a pressure test.‪

    NOTICE:

    Use proper tools for pressure testing Charge Air Cooler system. Tools not rated for adequate pressure or with improper connections can break free and cause engine damage.‪

  • Pressure check the air inlet system with 172 kPa (25 psi) regulated shop air. Use liquid soap to identify any leaks. Pressure check from turbo discharge connection to cylinder head noting and correcting leaks at hose clamps and on hoses or air-to-air charge cooler.

    Note: If air-to-air charge cooler is leaking from this initial check, pressure check it separately at 207 kPa (30 psi). Pressure must not lose more than 35 kPa (5 psi) in 15 seconds with shop air off.

  • Verify turbocharger is functioning properly.

Section 1.3.4
CHASSIS DYNAMOMETER TESTING

Run the vehicle on a chassis dynamometer and look at the following:‪

caution

EXHAUST FUMES

To avoid injury or injury to bystanders from fumes, engine or vehicle fuel system service operations should be performed in a well ventilated area.‪

Note: Ram air fans in front of vehicles and room ventilation are required .

  • Record the following data at 1650, 1500, and 1350 rpm, (Direct drive):
    • Wheel horsepower with vehicle fan on (Wheel horsepower above 80 % of rated power at the wheels is acceptable. Refer to performance curve.)
    • Intake Manifold Pressure (If reading is erratic, take a snapshot.)
    • Fuel Temperature and Pressure (If data is erratic, take a snapshot.)

      Note: Record vehicle specifications in the event there is a need to predict vehicle performance using Spec Manager.

  • Record crankcase pressure at high idle. DDC maximum specifications are:
    • For the MBE 4000 engines, the maximum is 0.37 kPa (1.5 in. H2 O) for non-EGR engines (1998) and 2.0 kPa (8.0 in. H2 O) for EGR engines (2004).
    • For the MBE 900 engine, the maximum is 0.37 kPa (2.5 in. H2 O) for both non-EGR engines (1998) and EGR engines (2004).

Section 1.3.5
EXHAUST SMOKE

The basic questions to ask for Black Exhaust Smoke are:‪

Note: Black Smoke is soot from partially oxidized (burned) fuel at high temperatures.

  • Is the air filter restricted? (Reduced air flow = lack of oxygen, incomplete/high temperature combustion and soot)
  • Are exhaust brake devices functioning properly? (Reduced air flow = incomplete combustion and soot)
  • Is the CAC cracked? (Reduced air flow = incomplete combustion and soot)
  • Are the intake air manifold gasket(s) leaking? (Reduced air flow = incomplete combustion and soot)

    Note: The MBE 4000 uses multiple air manifold gaskets to cover individual cylinder heads. The MBE 900 uses one gasket for every two adjacent cylinders on a single cylinder head.

  • Are there air bubbles in the coolant? (Head gasket failure = vaporized water in exhaust)
  • Are there air bubbles in the fuel? (Fuel line/pump leak = late fuel injection = raw vaporized fuel in exhaust)
  • Are the valve clearances correct? (Incorrect valve timing = incorrect combustion timing and soot)
  • Is the comparative cylinder compression test result correct/within specifications? (Low compression = incomplete/poor combustion)
  • Has a fuel nozzle failed causing excess fuel delivery? (Excess fuel = incomplete combustion and soot)
  • Is the EGR valve stuck open? (Excess exhaust gas recirculation = insufficient oxygen, incomplete combustion, and soot)
  • Is the Intake Manifold Pressure (IMP) Sensor/Turbocharger Boost Sensor (TBS) working correctly?

The basic questions to ask for Blue Exhaust Smoke are:‪

Note: Blue Smoke is partially burned lubrication oil that ends up as a raw vaporized oil in the exhaust soot from partially oxidized (burned) fuel at high temperatures.

  • Is the comparative cylinder compression test result correct/within specifications? (Low compression = incomplete/poor combustion)
  • Is the oil level above the maximum level? (Excess oil = poor combustion and raw vaporized oil in the exhaust)
  • Does the oil quality meet the recommended specification? (Poor quality oil = piston ring wear and poor combustion)
  • Is the turbocharger leaking oil into the exhaust? (Oil in exhaust = poor combustion)
  • Are the valve stem seals functioning? (Oil leaking past seal = poor combustion)

The basic questions to ask for White Exhaust Smoke are:‪

Note: White Smoke is usually partially burned fuel that ends up as raw vaporized fuel in the exhaust. White Smoke can also be the result of a coolant leak that ends up as steam in the exhaust.

  • Is the fuel quality within DDC specification? (Cetane No. minimum: 45, Cetane Index, minimum: 40)
  • Is the air preheater installed and functioning properly? (Cold air = raw vaporized fuel in the exhaust)
  • Are there air bubbles in the coolant? (Suggests a head gasket failure = vaporized water in exhaust)
  • Are there air bubbles in the fuel? (Suggests a fuel line/pump leak = late fuel injection = raw vaporized fuel in exhaust)
  • Are the valve clearances correct? (Incorrect valve timing = incorrect combustion timing)
  • Is the charge air cooler cracked? (Reduced air flow = incomplete combustion and soot)

    Note: Refer to Service Information Letter 05 TS -01 for service information on cracked charge air coolers. See Figure "Service Information Letter 05 TS-01 (View 1 of 2)" and Figure "Service Information Letter 05 TS-01 (View 2 of 2)" .

  • Is the comparative cylinder compression test result correct/within specifications? (Low compression = incomplete/poor combustion)
  • Has a fuel nozzle failed causing excess fuel delivery? (Excess fuel = incomplete combustion and raw fuel in exhaust)
  • Is the IMP Sensor/TBS working correctly?

Section 1.3.6
COOLANT LOSS

The basic questions to ask for Coolant Loss are:‪

  • Has the oil level risen? (If so, it would suggest coolant in the oil and a head gasket failure.)
  • Have you noticed any coolant leaks or coolant puddles under the vehicle?
  • How often do you add coolant?
  • Is the radiator cap on tight and sealing properly?
  • What type of coolant is being used?
  • What type of inhibitor is being used?

Section 1.3.7
INTERMITTENT ISSUES

The basic questions to ask with Intermittent Concerns are:‪

  • When was the last time the intermittent concern occurred?
  • Does the Amber Warning Lamp (AWL) come on?
  • Does the concern only occur in damp or rainy conditions?
  • Does the concern occur when the vehicle hits a bump or rough road?
  • Does the engine miss, drop to idle, quit running, or exhibit hard starting?
  • Is there any pattern related to trip miles or engine temperature?


MBE 900 and MBE 4000 EGR Technician's Manual - 7SE940
Generated on 10-13-2008

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