Generators are not items that are used every day. Portable generators usually sit forgotten in garages, sheds, or basements between tailgate parties or camping trips, and standby generators are sometimes idle for years before answering the call during a storm or natural disaster. We switch generators on when we need power right away, but getting these machines up and running is not always easy. If you ever get frustrated because a generator that has been sitting idle for weeks or months refuses to start, it could be because you have either forgotten or never learned some basic skills that people once took for granted.
The machines we use each day have become easier to use and more capable over the years. Internal combustion engines work by burning a mixture of air and fuel, and the ratio has to be just right, or the engine will not start. Modern car engines have sophisticated electronic fuel injection systems to ensure the mix of fuel and air is not too lean or rich, and starting them is as easy as turning a key or pressing a button. Older vehicles used carburetors to mix fuel and air, and getting them started was more of a procedure.
Cars with carburetors cannot be started right up. Instead, the driver must pull out a choke to restrict the flow of air, then pump the gas pedal a couple of times before turning the ignition key. This pumping of the gas pedal delivers a tiny amount of fuel to the carburetor, which gives the spark plug something to ignite. Drivers did this without really thinking about it for almost a hundred years, but it is a skill that few people have to use today. The vast majority of gas and diesel generators still use carburetors, so you may have to do the equivalent of pumping the gas pedal a few times to get one running.
Priming a Generator’s Fuel System
Engaging the choke and pumping the accelerator prime the fuel system of a carbureted engine. This is necessary because fuel is not pumped into generator carburetors directly. Instead, the carburetor draws the fuel it needs from a float tank or float bowl. Priming ensures that this tank or bowl will contain enough fuel to get the engine running. If the fuel system is not primed, the engine will turn over but not fire.
Gas, Diesel, and Propane Generators
The kind of fuel your generator uses will determine the steps you will need to go through to prime its fuel system. Let’s take a look at how priming differs between gasoline, diesel, and propane generators:
- Gas generators: Priming the fuel system of a gasoline generator delivers a small amount of fuel to the carburetor. However, too much priming can flood the carburetor and make starting even more difficult.
- Diesel generators: Diesel engines are extremely durable and robust, but they can become sluggish and unresponsive if even a tiny amount of air enters the fuel system. Priming a diesel engine purges air from the fuel lines to prevent this from happening.
- Propane generators: Generators powered by propane work a little differently. Propane is delivered at constant pressure, so the fuel system only has to be primed during installation or when the propane supply runs out, and air enters the system. Despite this, many propane generators have a button marked “prime.” Instead of delivering fuel to the engine, these buttons control vacuum switches. Propane engines have solenoid valves that interrupt fuel flow to prevent accidents. These valves are controlled by switches that are closed by a vacuum, but that vacuum takes a little time to develop. When you press the prime button on a propane generator, the vacuum switch is bypassed to ensure the solenoid valve remains open.
How to Prime a Diesel Engine
A little fuel system priming should be enough to get just about any generator up and running, but you may have to go through the procedure two or three times if it has been a while since you last used your generator. Let’s take a look at the process step by step:
- Read your owner’s manual: Not all generators have a prime button. Some models have a valve that must be turned to begin fuel delivery, and machines with electronic fuel injection take care of everything automatically. The owner’s manuals for most generators have a quick start guide that can take a lot of the frustration out of starting a generator.
- Conduct a visual inspection: Before you prime a generator, you should conduct a brief visual inspection. Make sure that all wires and cables are connected, and check fuel hoses for cracks and leaks. This is especially important if you have not used your generator for some time.
- Take your generator outside: Running generators produce carbon monoxide, which is a colorless and odorless gas that can be deadly. This is why generators should never be operated in an enclosed environment.
- Use fresh fuel: Diesel and gasoline are carbon-based compounds that begin to oxidize as soon as the refining process is complete. This oxidation can damage fuel lines and engine components, so fresh fuel is essential if you want your generator to provide years of reliable service. If you have a propane generator, spoiled fuel is one problem that you won’t have to worry about.
- Prime the generator: You will probably have to press the prime button for about 10 seconds to deliver the needed amount of fuel to the carburetor and clear air from the fuel lines. If you listen carefully, you will hear an electric hum as the fuel pump starts up when you press the button. You should check your owner’s manual to find out how long the button should be pressed for. If your generator is fitted to a vehicle and the dashboard button does not work, you will probably find a second button on the generator’s control panel that does the same thing.
- Start your generator: Once the fuel system has been sufficiently primed, the generator should start right up. If it does not, repeat the above process another two or three times. If your generator still refuses to run after several attempts, you could have a different type of starting problem.
- Stop priming: Priming buttons only work when they are pressed, but fuel valves remain open. If your generator has a fuel valve, it should be set to the “run” position once the startup procedure is completed.
Other Generator Starting Issues
Generators are not particularly complex machines, but they can be extremely reluctant to start if they have not been maintained properly. There are also things that can prevent a generator in perfect working condition from starting. Here are a few of the most common causes of generator starting problems:
- Gravity: If your generator is located inside a vehicle that is parked on a steep incline, gravity could prevent it from starting. This is because generators have oil sensors that shut engines off to prevent catastrophic damage when lubrication levels fall. Parking on a hill could cause a generator’s oil to pool in a place this sensor cannot reach, which would initiate a shutdown and prevent starting. This problem can be caused by gradients as gentle as 5 degrees.
- No fuel: Checking the fuel level of a portable or standby generator is a logical first step to take when pressing the start button or pulling the power cord does not produce the desired result, but what about RV generators that are supplied by a vehicle fuel tank? If you have an RV generator that does not start, you should take a quick look at the fuel gauge. If the dial shows that the vehicle has less than a quarter of a tank of fuel left, the generator may be refusing to start to prevent you from running out of gas.
- Dirt and grime: Generators are often used in environments where the air is thick with dust and debris. When basic generator maintenance is neglected, this dirt can foul spark plugs and clog carburetors, fuel valves, and air filters. You will only need basic hand tools to remove and either clean or replace these components, and you should grab a can of WD40 spray to loosen the nuts and screws.
- Dead battery: Generators create power, but they also need power to work. If your generator does not start, its battery may be depleted or not properly connected. Generator batteries can be plugged into a standard electrical outlet to recharge, or you could use your car to provide a jump start if you have cables and are in a hurry.
- Plugs: Generators can be used to power all kinds of electrical appliances, but nothing should be plugged into them until they are running. If you are having starting problems, take a look to make sure that nothing is plugged in, and remove any cables, even if they are not connected to an appliance.
- Contaminated fuel: If you have a gas or diesel generator that has not been used in over a month, you should drain the tank and add fresh fuel. Contaminated fuel can prevent your generator from starting and damage its engine.
Fuel Injection to the Rescue
Modern technology has made fuel system priming a relic of the past for car drivers, and it could soon do the same thing for generator owners. Fuel injection systems eliminate the need for carburetors, and they use electronic systems to monitor and control the fuel and air mixture. This added sophistication increases costs, so electronic fuel injection tends to only be available on top-of-the-line generator models.
Fuel injection was once reserved for high-performance and luxury cars, but now even economy models have this feature as it does far more than eliminate starting hassles. Fuel injection makes engines run more smoothly and efficiently, which can reduce carbon dioxide emissions dramatically. Fuel injection systems also require far less maintenance than carburetors.
Maintenance Tips and Generator Deals
Generator manufacturers will likely take the same path as automobile makers, which means fuel injection will eventually become an industry standard. There will come a day when priming a generator will seem as odd as pumping the gas pedal before starting a car, but it may be years before that day arrives. In the meantime, you can rely on GeneratorTools to bring you up-to-the-minute information about new generators and improvements made to existing models. Our product roundups and reviews can save you money and help you to avoid expensive mistakes, while our recall and press release pages deliver news about rebates, incentives, and safety issues in a concise and easy-to-read format.