Why Diesel Generator Fail to Start

by Generator D. Diesel Generator

After using a diesel generator for a long time, some malfunctions may occur that will cause the generator fail to start. What can you do when it happens?

If diesel generators fail to start, you can analyze the causes from fuel system failure, electric starting system failure, insufficient compression pressure in the cylinder and the low ambient temperature and other factors.

Fuel System Failure

1. Air in the fuel system

This is a common problem that a diesel generator fails to start normally.

Solution: Check whether the fuel oil pipe connector is loose or not, and ensure that the air is cleared from the fuel system. Loosen the bleed screw bolt on the diesel filter, and then use the manual oil pump to pump the fuel until the air bubble is gone.

2. Fuel Line Obstruction

Solution: Check whether the pipeline is smooth or not.

3. Fuel Filter Clogging

Solution: Clean the filter or replace the filter element

4. The Handle Position of Fuel Injection Pump Is Not Correct

Solution: The handle position should be pushed to no-load when starting the diesel generator set. Rotation speed is about 700-900r/min.

5. Fuel Injector Problem – Little fuel injection or fuel injection is not atomized

Solution: Remove the fuel injector, connect it to the high pressure oil pump, pry the fuel injection pump plunger spring and observe the spray condition. If necessary, wash the injection pump.

6. Oil Supply Problem – Oil transfer pump doesn’t supply oil or the oil supply is brokenly.

Solution: Check whether the oil inlet pipe is leaked or not and the filter screen on the oil inlet pipe connector is blocked or not.

Electric Starting System Failure

1. Battery Power Shortage

The most common failure for diesel generator is battery failure.

Solution: Use the battery with sufficient power, or increase the battery to use in parallel. Replace the new start-up battery if necessary.

2. Circuit Wiring Error or Poor Contact

Solution: Check whether the wiring is correct and reliable.

The compression pressure in the cylinder is insufficient; fuel injection is normal but does not catch fire; or fuel oil inside the exhaust pipe

1. Excessive wear of piston ring and cylinder liner

Solution: Replace the piston ring, and replace the cylinder liner according to the wear condition.

2. Valve leakage

Solution: Check the valve clearance, vlave spring, as well as the sealing of the valve guide and seat. If the seal is not good, you should make a repair.

3. Combustion chamber volume is too large

Solution: Check whether the piston belongs to the model, if necessary, measure the combustion chamber volume.

Ambient Temperature Is Low

Solution: According to the actual ambient temperature, the corresponding low temperature measures should be adopted.

A lack of diesel generator maintenance or operation knowledge will undoubtedly result in malfunction. To prevent the malfunction occurring again, it is obvious that daily maintenance of the generating set is very important, which not only helps prolong the service life of the machine, but also reduces the cost.

In the result of a power failure standby generators are there for us when we need them the most… at least that’s what we hope. As with any piece of machinery a generator cannot be 100% reliable, this blog will explore some of the common reasons why a diesel generator may fail to start and most importantly, how to reduce the risk of a failure.

Standby generators are often operated infrequently, meaning that monthly tests and service plans are vital to ensure problems are not occurring unknown to the operator. Let’s take a look at the most common reasons why a generator will fail to start and what you can do to prevent these happening in the future.

1. BATTERY FAILURE

Image of a battery connected to a diesel generator

One of the most common reasons a generator will not start is due to a battery failure. Often this could be caused by a loose connection or a sulfation build-up (a build-up of lead sulphate crystals on the plates of lead-acid batteries). When sulfate molecules in the electrolyte (battery acid) become so deeply discharged it causes a build-up covering the plate leading to the battery not being able to provide enough current.

A battery failure can also occur due to the charger breaker being open inoperable, usually by a fault within the battery charger unit itself or the AC supply being disconnected by a tripped circuit breaker. This can often happen after a service or maintenance has been carried out when the charger has been turned off and not turned back on again. It is always worth double checking the generator system after a service or maintenance has been carried out to ensure the charger supply circuit breaker is in the correct position.

Finally, a battery failure could be due to dirty or loose connections. Connections need to be regularly cleaned and tightened to prevent a potential for failure.

At Power Electrics we recommend you replace your batteries every three years to reduce the risk of failure.

2. LOW COOLANT LEVELS

Without radiator coolant, an engine would soon overheat, leading to mechanical breakdown and engine failure. Coolant levels should be checked on a regular basis by visually checking if there are any puddles of coolant. The coolant colour varies depending on the manufacturer although it most commonly will look red.

Internally plugged radiator cores can also lead to low coolant level shutdowns. When the generator is operating under load, the thermostats open completely when the engine reaches the optimum operation temperature, meaning the radiator cannot allow the proper amount of flow through the core. Because the coolant has to go somewhere, it escapes through the overflow line. When the engine cools off and the thermostat closes, the level drops and activates a low coolant level shutdown to your generator. Because this only happens when the generator has reached to optimum running temperature under load, it is suggested that you test your generator with an external load bank with sufficient load to reach the temperature value needed to open the thermostats.

3. BAD FUEL MIX

Often the reason your generator will not start is linked in some way to fuel. A bad fuel mix can occur in several ways:

When your fuel runs out the engine receives air but no fuel

The air intake gets clogged, meaning there is fuel but no air

The fuel system might be supplying too much or too little fuel to the mix. As a result, combustion does not occur properly within the engine.

Finally, there may be impurities in the fuel (i.e. water in the fuel tanks) which causes the fuel not to burn. This is often the case when fuel has been standing in a tank for long periods of time.

As part of a routine service of any standby generator, it is always best practice to test the fuel to ensure it does not cause a fault in the future.

4. CONTROLS NOT IN AUTO

When your control panel displays the “Not in auto” message this is a result of human Control panel error, normally due to the main control switch being left in the off/reset position. When it is in this position the generator may not start in the event of a power outage.

Regularly check the control panel of your generator to make sure the ‘not in auto’ message is not displaying. There are plenty of other faults which display upon the control panel that can result in your generator not starting.

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