If your Cummins won t start, the problem may be lying with its fuel pump or air filter, its fuel line or oil sensor, its spark plugs, or fuel level. Regardless of the underlying issue, there’s almost always a fix that you can implement.

Power outages can prove costly for your personal as well as commercial property as they can not only damage your household electronic items but disrupt your production and other commercial activities. The impact of a power outage in commercial units can be devastating as it directly impacts the business output.

This is why investing in a power generator that can keep your units up and running even during a power outage is a good idea.

However, it is imperative to choose a reliable, technologically superior generator that functions even in harsh weather.

If this is what you are looking for then opt for a Cummins generator. Considered one the most trusted brands across the world, Cummins generators are known for their robust performance and lasting lifespan.

A Cummins generator comes with several benefits including high-quality design, ease of installation, enhance noise reduction, several options in power and price range, and high return on investment.

However, all machines are susceptible to damage and wear and tear. No matter how good a product is, it is bound to give away after a certain period of time and stop performing at the top of its capability.

The same is true for a Cummins generator. If your generator is not used for a long period of time, it might start experiencing starting trouble. However, there are several ways of checking and troubleshooting the starting trouble that will allow you to fix the issue at your end. If things don’t go back to normal, you can call in for a professional technician from Cummins to further inspect and fix the issues.

Common Generator Issue and How You Can Fix It

Cummins Generator

The choke is not performing properly

In an ideal situation, the choke valve must be kept closed when you try to start your generator. It must be turned on only once the engine has warmed up.

The choke valves are placed differently in different generators based on their brand and model. Wherever they are placed, they should always be in the closed position when you start the generator.

The generator’s oil level has gone down

Oil is an important component in ensuring that the engine performs smoothly, and if the oil levels go below the required amount, the engine might not start.

Usually, most generators come with pre-installed low oil sensors that will indicate if the oil level is low, despite that you must check the level with a oil dipstick every once in a while.

If the oil level is low, you must refill for better performance. You might also want to replace the oil if the generator hasn’t been used for a while or the oil hasn’t been replaced for some time.

Timely replacing the oil will ensure that your generator runs seamlessly, and the engine performs to the best of its capability. This practice will also ensure a longer lifespan of your engine.

There isn’t enough fuel

Cummins generator won't start

You might feel that not having enough fuel in the engine is not a possibility as that is the most basic requirement of starting any engine and people do tend to keep that in mind.

However, when it comes to generators, these machines are not used on a daily basis, increasing the possibility of the users forgetting about the last fuel refill. As you may guess, in case of low fuel, the engine will not start.

Keeping the RV fuel tank empty is never a good idea as it can damage the engine if repeated several times.

Did You Know?

There are numerous issues with the fuel that can lead to the generator not starting! Right from impurities in the fuel to seeping of water inside the fuel tank from bad quality fuel to stale fuel – all of these issues can give way to a blocked fuel filter and fuel pipe – which in turn can cause starting issues with your Cummins Generator!

Cummins Generator Repair

The spark plug is not functioning

The spark plug is responsible for initiating the ignition process as it is the spark plug that generates a strong enough spark for the engine to start. Over time, there could be depositions on its electrodes due to carbon accumulation.

This will result in weaker or no sparks from the plug. Use a small knife to clean the plug before reinstalling it. You can also check the plug by placing it close to the tester’s terminal while the engine cranks. If you see that the sparks are strong enough, and blue in color, the plug is performing fine. If the sparks are not strong enough, you might want to replace them.

There is an issue with the carburetor

Cummins Diesel Generators

The main function of a carburetor is to send a mix of air and fuel to the engine, and when there is some kind of clogging in the carburetor, the engine will not start. If an engine isn’t functional for a long period of time, the fuel might get contaminated.

The evaporation of the fuel sometimes leaves a thick black substance that accumulates on the carburetor disrupting the air and fuel supply to the engine.

Once you clean the carburetor, the engine will start normally. If the engine still doesn’t start, you might want to change the carburetor. One way of ensuring that this issue doesn’t arise is to use a fuel stabilizer. It will make sure that the fuel doesn’t unnecessarily evaporate. Such a fuel stabilizer is really helpful in generators are these machines are only used in case of a power outage. Unless any engine is used regularly, the chances of a clogged carburetor are high.

The generator is attached to other electronic items

If the Onan generator is plugged into other electronic devices, chances are that it won’t start.

Moreover, it can even damage the internal components of the generator. This can happen even if the electronic item is not switched on.

So, unplug the generator from all electronic devices before starting it.

You have a dead battery

Cummins Generator

The battery draining off is one of the most common issues that engines face. When a machine is not used for a prolonged period of time, the battery can drain on its own. A dead battery won’t enable ignition.

So, keep the battery in good shape to ensure that you face no starting trouble. Use your generator at least once every month so that the battery doesn’t drain. If in case the battery is an issue, you can jump-start it for instant charging.

A clogged fuel valve

The fuel valve is responsible for sending the fuel to the carburetor. If this valve is clogged, the fuel will not reach the carburetor and the engine will not start. In case of a clogged fuel valve, you can either check if the vacuum relief valve is open. Or unplug the outlet hose. Check the inlet pipes. If they are clogged, you can clean them for better performance.

Our Take


Cummins generators are regarded as one of the best products available in the market. They are known for their quality manufacturing, robust design, efficient performance, and long-lasting life. Still, any machine can give you trouble at different times of its life cycle. The best way to ensure that you don’t face any issues is to maintain them well.

When it comes to a generator, here are some steps that you can take to ensire the semaless running of the equipment –

  • Switch it on at least once in the month so that the battery remains charged
  • Regualar usage will ensure that the different valves don’t get clogged
  • Make sure to take readings of the oil and fuel levels at regular intervals
  • Replace spark plugs and fuel filters as and when required
  • Run the carb cleaner through the system to avoid any carb issue
  • Keep an eye on the circuit breaker on the back of the unit

This not only ensures that the engine remains in good working condition, but untimely malfunction will also help you save up on costly repair work.

However, if you still face starting trouble in a Cummins generator, you can try the above-mentioned steps If things don’t get resolved even then, call in for a technician from Cummins to get to the root of the issue and repair it in time. If not, you can always rely on our team of experienced technicians at CS Diesel to do the job for you!

FAQs About Cummins Generator Starting Problems

Can a Faulty Gas Solenoid Lead to Generator Starting Issues?

Yes, it can! The gas solenoid controls the flow of gas to a machine by using electric impulses. If your solenoid is faulty, your engine will only crank and not start because there isn’t enough electric impulse. In most cases, the fault in the gas solenoid occurs due to some loose wiring.

All you need to do is check the wires and if you find any loose connections, you can plug them again for the gas solenoid to start functioning again. And while you are at it, don’t forget to look for a bad ground connection, which might be contributing to the problem at hand.

What is the importance of Control Board in Cummins Generator?

The control panel of the Cummins Onan Generators are meant to control and protect the generator. together, the varied components of these RV Generators monitor the diesel engine as well as the AC alternator, and offer readings regarding voltage, frequency, and other important parameters.