Skip to main content

MBE 900 STARTING DIFFICULTY (ENGINE ROTATES)

There are several causes for the engine to have starting difficulty. These probable causes are: ‪

  • DDEC-ECU Control Unit Wiring Harness Damage
  • Empty Fuel Tank
  • Low Battery Voltage
  • Corroded or Damaged Battery Terminals
  • Defective Magnetic Switch
  • Defective Starter
  • Low Cranking Speed
  • Fuel Supply Valve
  • Plugged Fuel Filter(s)
  • Fuel Pump
  • Aerated Fuel
  • Restrictive Air Filter
  • Low Compression

Troubleshooting Procedure for DDEC-ECU Control Unit Wiring Harness

To determine if the DDEC-ECU Control Unit wire harness is causing starting difficulty, perform the following steps: ‪

  1. Turn the ignition switch to the ON position.
  2. Install the Diagnostic Data Link (DDL) adaptor to the data cable and plug the adaptor into the DDL connector in the vehicle; refer to OEMguidelines.
  3. Determine if DDEC-ECUdata is being received by the DDR; refer to OEMguidelines. If no data is being received by the DDR, check for intermittent code or a fault and no codes by doing the following:
    1. Check for poor mating of the connector halves or terminals not fully seated in the connector body (backed out terminals).
    2. Look for improperly formed or damaged terminals. All connector terminals in the problem circuit should be carefully inspected to determine proper contact tension. Use a mating terminal to test the contact tension.
    3. Electrical system interference may be caused by a defective relay, or a switch causing an electrical surge. Look for problems with the charging system (alternator, etc.). In certain cases, the problem can be made to occur when the faulty component is operated as in the case of a relay.
    4. Verify alternator grounds are clean and making good contact. Disconnect the alternator belt to test.
    5. Wiggle wires and harnesses to try to make the problem active, or to occur again.
  4. If data is being received by the DDR, check the vehicle circuit breakers or fuses; refer to section .

Vehicle Circuit Breakers or Fuses Check

To determine if the vehicle circuit breakers are causing starting difficulty, perform the following steps: ‪

  1. Visually check DDEC-ECU Control Unit circuit breakers or fuses to determine if circuit breaker(s) or fuse(s) are tripped or blown; refer to OEMguidelines.
    1. If circuit breakers tripped, determine cause and repair or replace as necessary; refer to OEM guidelines. Perform validation; refer to section .
    2. If circuit breakers are not tripped, measure the voltage at the DDEC-ECU Control Unit power harness. An Electronic Troubleshooting Guide is currently under development for this procedure. Contact DDCTechnical Service Group in the interim.

DDEC-ECU Control Unit Power Harness Voltage Test

An Electronic Troubleshooting Guide is currently under development. Contact DDCTechnical Service Group in the interim. ‪

Power Harness Repair

Perform the following steps to repair the power harness: ‪

  1. Repair the damage to the power harness.
  2. Verify repair of the power harness; refer to section .
Test Engine with Repaired Power Harness

Perform the following steps to determine if the repair resolved the starter difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check for an empty fuel tank; refer to section .

Troubleshooting Procedure for an Empty Fuel Tank

To determine if an empty fuel tank is causing starting difficulty, perform the following steps: ‪

  1. Determine the amount of fuel in fuel tank; refer to OEMguidelines.
    1. If fuel is at recommended level, check for a weak battery; refer to section .
    2. If fuel is below recommended level, refer to section .

Low Fuel Level Resolution

Perform the following steps in order to resolve low fuel level: ‪

  1. Fill fuel tank to full; refer to OEMguidelines.
  2. Verify fuel tank refill; refer to section .
Test Engine with Filled Tank

Perform the following steps to determine if a filled fuel tank resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the battery; refer to section .

Troubleshooting Procedure for Low Battery Voltage

To determine if a weak battery is causing starting difficulty, perform the following steps: ‪

  1. Measure the battery voltage; refer to OEMguidelines.
    1. If voltage is between 10.5 - 14 volts (21 - 26 volts for a 24-system), check the terminals for corrosion or damage; refer to section .
    2. If voltage is less than 10.5 volts (21 volts for a 24-volt system), battery replacement is necessary; refer to section .

Battery Replacement

Perform the following steps for battery repair: ‪

  1. Remove and replace the battery; refer to OEMguidelines.
  2. Verify battery replacement; refer to section .
Test Engine with Replaced Battery

Perform the following steps to determine if the battery replacement resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the terminals; refer to section .

Troubleshooting Procedure for Corroded or Damaged Battery Terminals

To determine if corroded or damaged terminals are causing starting difficulty: ‪

  1. Visually inspect terminals for corrosion or damage.
    1. If corrosion or damage are not found, check the magnetic switch; refer to section .
    2. If corrosion or damage are found, repair is necessary; refer to section .

Corroded or Damaged Battery Terminal Repair

Perform the following steps to repair corroded or damaged battery terminals: ‪

  1. Repair or replace any corroded or damaged terminals; refer to OEMguidelines.
  2. Verify repair of corroded or damaged terminals; refer to section .
Test with Repaired Battery Terminals

Perform the following steps to determine if the repair resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the magnetic switch; refer to section .

Troubleshooting Procedure for Defective Magnetic Switch

To determine if a defective magnetic switch is causing starting difficulty: ‪

  1. Start the engine.
  2. Clamp a heavy gauge battery jumper cable between the two large studs of the magnetic switch. See Figure 20538 .

    Basic Cranking Circuit

    1. If the engine cranked with the jumper cable in place, the magnetic switch must be replaced; refer to section .
    2. If the engine did not crank with the jumper cable in place, check the starter; refer to section .

Magnetic Switch Replacement

Perform the following steps for magnetic switch replacement: ‪

  1. Replace the magnetic switch; refer to OEMguidelines.
  2. Verify magnetic switch replacement; refer to section .
Test Engine with Replaced Magnetic Switch

Perform the following steps to determine if the magnetic switch replacement resolved the starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the starter; refer to section .

Troubleshooting Procedure for a Defective Starter

To determine if a defective starter is causing starting difficulty, perform the following steps: ‪

  1. Place the red lead of a voltmeter to the solenoid BATterminal; see Figure 20539 .

    1. Black Voltmeter Lead ‪

    4. Harness Tube ‪

    2. Starter Ground Terminal Lug ‪

    5. Volt Ohm Meter ‪

    3. Red Voltmeter Lead ‪

    Starting Motor Available Voltage Test

  2. Place the black voltmeter lead to the starter ground terminal; see Figure 20538 .
  3. Engage the starter switch.
  4. View the voltage reading on the meter.
    1. If the voltage is less than specification while cranking the engine, replacement is necessary; refer to section .
    2. If the voltage is to specification while cranking the engine, check the cranking speed; refer to section .

Starter Replacement

Perform the following steps for starter replacement: ‪

  1. Replace the starter. Refer to section .
  2. Verify replacement of starter; refer to section .
Test Engine with Replaced Starter

Perform the following steps to determine if the replaced starter resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the cranking speed; refer to section .

Troubleshooting Procedure for Low Cranking Speed

To determine if low cranking speed is causing starting difficulty, perform the following step: ‪

  1. Install a tachometer to the engine and record engine revolution while cranking the engine; refer to OEMguidelines.
    1. If the cranking speed is greater than 100 rpm, check the OEM fuel supply valve; refer to section .
    2. If the cranking speed is less than 100 rpm; refer to section .

Low Cranking Speed Repair

Perform the following steps for low cranking speed repair: ‪

  1. Drain the engine oil. Refer to section .
  2. Remove the oil filter(s).
  3. Install new oil filter(s). Refer to section .
  4. Refill the lubrication system with new oil.
  5. Verify low cranking speed repair; refer to section .
Test Engine with Replaced Oil

Perform the following steps to determine if the replaced oil resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the fuel supply valve; refer to section .

Troubleshooting Procedure for the Fuel Supply Valve

To determine if the fuel supply valve is causing starting difficulty, perform the following steps: ‪

  1. Check that the fuel supply valve is open; refer to OEMguidelines.
    1. If the fuel supply valve is open, check the fuel filters; refer to section .
    2. If the fuel supply valve is closed, repair is necessary; refer to section .

Fuel Supply Valve Repair

Perform the following steps for fuel supply valve repair: ‪

  1. Correct valve operation or replace valve.
  2. Prime the fuel system; refer to section .
  3. Verify fuel supply valve repair; refer to section .
Test Engine with Fuel Supply Valve Open

Perform the following steps to determine if opening the fuel supply valve resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the fuel filters; refer to section .

Troubleshooting Procedure for Plugged Fuel Filter(s)

To determine if a plugged fuel filter(s) is causing starting difficulty, perform the following steps: ‪

  1. Disconnect the fuel line return hose from the fitting located at the fuel tank.
  2. Place the opened end of the fuel line into a five gallon container.
  3. Start the engine.
  4. Run the engine at 1000 rpm.
  5. Clock fuel rate for one minute.
  6. Measure the amount of fuel delivered into the container.
    1. If the fuel flow is greater than 1.7 L/min. (0.5 gal/min.) and aerated (small bubbles), check for air in fuel; refer to section .
    2. If the fuel flow is less than 1.7 L/min. (0.5 gal/min.), replace the fuel filters; refer to section .

Plugged Fuel Filter(s) Replacement

Perform the following steps to replace the fuel filter(s): ‪

  1. Replace the fuel filter; refer to section .
  2. Test the engine to determine if starting has been improved; refer to section .
Test Engine with Replaced Fuel Filters

Perform the following steps to determine if the replaced fuel filters resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check the fuel pump; refer to section .

Troubleshooting Procedure for Fuel Pump

To determine if the fuel pump is causing starting difficulty, perform the following steps: ‪

  1. Check fuel intake pressure upstream of fuel pump.
    1. If pressure at idle speed (600650 rpm) is -0.09 to -0.12 bar (-1.3 to -1.7), check for a restricted air filter.
    2. If pressure at idle speed (600650 rpm) is greater than -0.09 to -0.12 bar (-1.3 to -1.7), check for aerated fuel.

Drive Coupling Replacement

Perform the following steps for drive coupling replacement: ‪

  1. Replace the drive coupling.
  2. Test the engine to determine if starting has been improved; refer to section .
Engine Test with Replaced Drive Hubs or Replaced Coupling

Perform the following steps to determine if replaced drive coupling resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check for aerated fuel; refer to section .

Troubleshooting Procedure for Aerated Fuel

To determine if aerated fuel is causing starting difficulty, perform the following steps: ‪

  1. Disconnect the fuel line return hose from the fitting located at the fuel tank; refer to OEMguidelines.
  2. Place the opened end of the fuel line into a suitable container.
  3. Start the engine.
  4. Run the engine at 1000 rpm.
  5. Visually check to see if air bubbles are rising to the surface of the fuel within the container.
    1. If air bubbles are present, repair is necessary; refer to section .
    2. If air bubbles are not present, check for a restrictive air filter. Shut down the engine; refer to section .

Aerated Fuel Resolution

Perform the following steps for aerated fuel resolution: ‪

  1. Shut down the engine.
  2. Tighten all fuel line connections between fuel tank and fuel pump; refer to OEMguidelines.
  3. Visually inspect all fuel lines between fuel tank and fuel pump for leaks.
  4. Replace damaged components as required; refer to OEMguidelines.
  5. Verify aerated fuel resolution; refer to section .
Test Engine with Aerated Fuel Resolution

Perform the following steps to determine if aerated fuel resolution resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check for a restrictive air filter; refer to section .

Troubleshooting Procedure for Restrictive Air Filter

To determine if a restrictive air filter is causing starting difficulty, perform the following steps: ‪

  1. Remove the air filter element; refer to OEMguidelines.
  2. Attempt to start and run the engine.
    1. If the engine starts and runs, no further engine troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, refer to section .

Air Filter Replacement

Perform the following steps for air filter replacement: ‪

  1. Visually inspect the air filter for clogging and replace as necessary; refer to OEMguidelines.
  2. Visually inspect gaskets for deterioration and replace as necessary; refer to OEM guidelines.
  3. Visually inspect air inlets for restrictions and clean as necessary; refer to OEMguidelines.
  4. Verify air filter replacement; refer to section .
Test Engine with Replaced Air Filter

Perform the following steps to determine if the replaced air filter resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, check compression; refer to section .

Troubleshooting Procedure for Low Compression

To determine if low compression is causing starting difficulty, perform the following steps: ‪

  1. Perform a cylinder compression test.
  2. Compare cylinder compression test results to specifications aslisted in Table .

    Description ‪

    Pressure in kPa (psi) ‪

    Compression Pressure at Starter Speed ‪

    2800 (406) ‪

    Permissible Difference between Individual Cylinders ‪

    400 (58) ‪

    Compression Testing Specifications
    1. If cylinder pressure is below specifications, refer to section .
    2. If cylinder pressure is within specifications, call Detroit Diesel Technical Service Group.

Low Compression Repair

Perform the following steps for low compression repair: ‪

  1. Remove cylinder head; refer to section .
  2. Inspect the cylinder head for worn or damaged valves; Refer to section .
  3. Replace damaged valves; Refer to section .
  4. Inspect the cylinder kit components for worn or damaged liners; pistons or piston rings.
  5. Verify repairs made to cylinder head valve(s) or cylinder kit components; refer to section .
Test Engine with Repaired Cylinder Head Valve(s), and Cylinder Kit

Perform the following steps to determine if the cylinder head valve and cylinder kit repair resolved starting difficulty: ‪

  1. Attempt to start and run the engine.
    1. If the engine starts and runs, no further troubleshooting is required. Shut down the engine.
    2. If the engine fails to start and run, call the Detroit Diesel Technical Service Dept.