Trouble Shooting

For Diesel and Petrol Generators

BLACK SMOKE
Black Smoke when starting a generator is NORMAL.

Probable Causes are as follows:

  • Some or all injectors are bad
  • Air inlet is restricted
  • Engine timing incorrect
  • Internal engine problems

Please note this information is related to a generator which runs continuously emitting Black smoke, not just on start up.

WHITE SMOKE
White Smoke when starting a generator is NORMAL.

Probable Causes are as follows:

  • Some or all glow plugs are bad
  • Plugged or restricted return
  • Some or all injectors are bad
  • Incorrect Pump to Engine Timing
  • Low compression
  • Bad injection pump
  • Incorrect engine timing

Please note this information is related to a generator which runs continuously emitting white smoke.

GENERATOR WILL NOT START

Probable Causes are as follows:

  • Low cranking speed
  • Incorrect starting procedure
  • Some or all glow plugs are bad
  • No fuel to cylinders
  • Plugged or restricted return
  • Insufficient fuel supply
  • No voltage to shut off solenoid
  • Shutoff solenoid bad
  • Poor fuel quality
  • Some or all injectors are bad
  • Incorrect pump to engine timing
  • Low compression
  • Bad injection pump
  • Incorrect engine timing
  • Internal engine problems

NO / VERY LITTLE POWER

Probable Causes:

  • Plugged or restricted return
  • Poor fuel quality
  • Incorrect pump to engine timing
  • Air inlet restricted
  • Internal engine problems

GENERATOR RUNS ROUGH

Probable Causes are as follows:

  • Some or all glow plugs bad
  • Plugged or restricted return
  • Insufficient fuel supply
  • Poor fuel quality
  • Some or all injectors bad
  • Bad injection pump
  • Idle speed too low
  • Air in fuel
  • Fuel leaks at injection lines

GENERATOR KEEPS STALLING

Probable Causes are as follows:

  • Plugged or restricted return
  • Insufficient fuel supply
  • Shut off solenoid is bad
  • Poor fuel quality
  • Bad injection pump
  • Incorrect engine timing
  • Internal engine problems
  • Idle speed too low
  • Fast idle solenoid is bad
  • Air in fuel

General Troubleshooting tips

Rusted or corroded connections

An oxidized connection will prevent the circuit from being completed. This applies not only to the major cables externally, but also to the electronic control devices internally.

Carbon flash deposits around the 110-vac and 120-vac receptacles

This will indicate whether the device that was plugged into the generator shorted out the receptacle. The device may have shorted the generator to ground and caused a carbon flash when the plug prongs touched the receptacle. Also, check for carbon flash where the brushes touch the rotor’s slip rings. A broken spring will allow the brush to bounce and flash.

Signs of overheating

Discoloration of the slip rings and a burnt smell should be noticeable inside the generator. Look to see if the windings turned black. The insulative sprays that manufacturers use to insulate the windings may vary in colour from shades of reddish brown to light brown to dark brown, so try to compare the colour to that of a new unit.

Wire insulation that is heat-hardened

Fabric and plastic insulation hardens over time due to heat exposure and overheating. Long-term heating should be more uniform. A short, excessive heat cycle may have less hardening and burning at the unit’s outer perimeters and excessive heat signs toward the centre or heat source.

Insects that have developed a community inside the generator

Their nests and debris can cause electrical shorts. Generators left out in the elements, such as for running water wells, provide a nice home for critters such as spiders, wasps, and mice.

Loose bolts, screws, and fasteners

This condition will either prevent full-time service or give intermittent service depending on the situation.

Crimp connections

These connections have several problems. Even though they’re widely used, they represent the least professional fix. First, they come loose as the machine vibrates, and lose consistent, quality contact. Second, because dissimilar metals are in contact, a galvanic cell is set up that result in corrosion when moisture is present.

Solder joints that have cracked or broken loose

This condition occurs much less frequently than crimped connections and basically results from poor-quality workmanship.

Worn insulation allowing wires to short

Insulation deteriorates from physical contact when wires rub together due to vibrations. Eventually, the internal wires can short to each other or to ground.

Oil or grease on slip rings

This isn’t a common problem, but it occurs when engines start smoking or oil leaks develop.

Crossed wires

Mistakes happen, especially if someone else worked on the generator before you.

Fuses, circuit breakers, and ground fault interrupts
These can easily be tested with a volt-ohm-meter.

Brushes making poor contact

This occurs when springs deteriorate or the slip rings need cleaning, and can easily be checked with an ohm meter. There should be zero ohms resistance across the brushes. Be sure to isolate the brushes from the controller before measuring.