What engines do school buses have? (how it works)

In this blog post, we will answer the following question: What engines do school buses have? We will explain how a school bus engine works, how to identify possible issues with it and how to maintain a school bus for many miles and safe journeys. 

What engines do school buses have?

Most American school buses have a diesel engine. Currently, Skoolies and Skoolies mostly use diesel as fuel, although there are quite a few initiatives to switch to Gas, less to electricity and occasionally to hydrogen. 

The motor ranges for American School Buses

F3.8 105125 kW 500600 Nm
B4.5 112157 kW 650850 Nm
B6.7 164224 kW 9001200 Nm
L9 264276 kW 15001600 Nm
L9N 209239 kW 12201356 Nm

Is a diesel or gasoline engine better for a Skoolie?

Historically, diesel engines have long been considered more enduring than their gasoline counterparts. One of the reasons for this is that a diesel engine runs slower than a gasoline vehicle. In addition, until the 1980s, diesel vehicles benefited from a simpler design, which promoted high reliability.

Later, however, these engines were made more complex. They are now equipped with turbo and high-pressure injectors. These additions have improved the performance of each car, but also undermined their reliability: these parts are now responsible for many breakdowns.

Today’s diesel vehicles no longer correspond to the opinion still anchored in many minds, who consider that this type of fuel is synonymous with an indestructible engine.

But if the diesel models have seen their robustness decline in recent decades, they remain on average more enduring than the petrol versions. If thermal engines (diesel as gasoline) would have a similar lifespan, a diesel model would travel on average 16,000 miles per year, compared to 9,300 annually for gasoline. 

In terms of mileage, the average lifespan of diesel would therefore be 155,000 miles, compared to 60,000 miles less for gasoline.

How does a school bus engine work?

A school bus diesel engine works by igniting (igniting) the fuel by being injected with a high-pressure spray into a combustion chamber (or pre-chamber, in the case of indirect injection) containing air at a temperature higher than the self-combustion temperature, with no need for a spark. 

The main components of a fuel system include the following:

  •  Tank: It is the tank for the fuel of your bus.
  • Fuel filter: Attaches to both ends of fuel pumps to separate impurities, ensuring optimum engine performance.
  • Fuel pump: Its main function is to extract the fuel from the tank and pump it to the internal combustion engine.
  • Fuel injectors: It is an electronic valve that opens and closes at regular intervals to deliver the correct amount of fuel to the engine.

How exactly does the fuel system of a school bus work?

As you already know, the fuel is stored in a special tank that is filled from the outside through a small hole that is sealed with a lid. Before being converted into energy, this fluid must first pass through a pump.

The fuel pump is what physically pumps this fluid and allows it to travel through metal lines. In this way, the fuel can reach the filter, where any impurities or dirt is removed before it enters the engine.

This last component is very important, therefore it is necessary to keep it clean. It is the only way to ensure that your Skoolie’s engine works properly and has a long service life.

As the fuel flows, the final conditions to provide complete combustion is atomization and spray pattern. The former is achieved as a result of injection pressure, due in part to the diameter of the holes in the injector. On the other hand, the space, angle and number of holes in the injector tip will determine the spray pattern.

How do you know if the school bus engine is failing?

The basic symptoms that your Skoolie’s fuel system is failing or already worn out are as follows:

• Difficult engine starting

• Noise in the fuel tank

• Slow acceleration

• Unintentional stopping while driving, especially in high temperatures

• Loss of energy or power

• The “check engine” light is on

• Engine idling is unstable

• Excessive smoke coming from the engine

• Noticeable fuel odours

• Decrease in fuel economy

Drivers who ignore the warning signs above will eventually end up with an engine that will have a lot of trouble starting. For example, when a fuel pump does not work, the diesel will not be able to reach the engine after starting your Skoolie.

If you notice any of these symptoms, we recommend that you take your Skoolie to a maintenance service to have it checked before something goes wrong. The pressure, flow and operation of the fuel system components should be examined to diagnose any problems.

How should you maintain a school bus engine?

The maintenance of the fuel system and school bus engine is quite simple. The main point is to keep the diesel in your Skoolie clean and fresh. Pollution and debris are the number one cause of failure in this system.

It is recommended to replace your Skoolie’s fuel filter annually or every 15,000 miles. approximately. Additionally, the entire system should be cleaned through a professional decarbonization service to minimize the build-up of fuel by-products.

How to extend the life of a Skoolie diesel engine

Diesel engines are always more sophisticated, so it is more difficult for them to be damaged, even if it is more expensive to repair them. These days, saving on repair and maintenance of the car and extending its lifespan is essential. 

To do this, we give you some very useful and economical tips: you just need a little time and patience. Here’s how to extend the life of a diesel engine.

Steps to follow:

  1. First of all, remember to follow the maintenance plan specified by the manufacturer in the maintenance book at all times. Carry out regular technical checks and pay attention to the oil and the parts to be changed.
  1. Do not stop the engine suddenly immediately after driving on a freeway or on a mountain road. It is necessary to wait, at least, a minute, because the hot oil in the turbine can burn itself and you can break the turbo.
  1. It is highly recommended to use the reserve as little as possible. Always try to fill the tank when the indicator shows that there is a quarter full left as, in the case of diesel, impurities from the fuel collect at the bottom and can pass into the fuel system, damaging it enormously.
  1. If a tanker is refilling the tanks at a gas station, never take gasoline as dirt and moisture may enter. In all cases, it is necessary to wait at least one hour after recharging.
  1. You should periodically check the oil level. A very low level can seriously damage the engine, and an excessively high level can damage the hoses. To overhaul it, it is necessary that the car is not running and the engine is cold.
  1. Before starting, wait 10 seconds for the engine to warm up. Thus, the oil pump has enough time to lubricate the whole engine. 
  1. Draining the fuel filter regularly is also very important. This prevents moisture in the fuel from affecting the injection system. When you bring the car to technical control, ask that it be purged.
  1. The fuel filter should be changed approximately every 60,000 km. This will prevent impurities from entering the injection system and becoming damaged.
  1. Check the revs, because by travelling with the engine below 2000 rpm and accelerating without changing gears, you can cause several problems in a short period of time. During combustion, more carbon particles are produced, which shortens the life of the catalyst EGR valve, further damaging the engine and causing wear and vibration.
  1. Finally, you must avoid the use of biodiesel because it is more humid than diesel and can therefore cause problems in the injection system.

The bottom line

Despite their dimensions, school buses are more fuel-efficient than trucks and semi-trucks. On average, a school bus or a Skoolie has a 30% fuel consumption, with 10  mpg! 

Besides, diesel Skoolies are more fuel-efficient than gas buses. On average, a diesel school bus can travel about 510 miles on a diesel tank versus just 270 miles on gasoline, based on the same standard size gasoline tank.

If you have any questions or comments on the content, please let us know!

FAQ on What engines do school buses have?

Do school buses get good gas mileage?

Yes, school buses get good gas mileage. A Skollie can get an average of 10 miles per gallon, which is pretty good for a bus. 

How long do diesel school bus engines last?

Diesel school bus engines last 15 to 20 years or 250,000 miles if properly maintained and treated with care. In rare cases, the Skoolie engines will not even get to seven years, as the causes of wear and breakdowns are plenty. 

What is the best diesel engine for an RV?

If your budget allows it, the best diesel engine for a motorhome is an engine greater than 100 hp. You will have more comfort with a more powerful and more torquey engine, especially if you are travelling with a large payload. 

How to make the best of your diesel engine?

The following tips should help you reduce your fuel consumption and take the best from your diesel engine. A motorhome consumes between 12 and 30 litres per 100 kilometres depending on the engine and the size, we assume that if you take the road in a motorhome, it is certain that you are going on vacation or for the weekend.

Other FAQs about Skoolie that you may be interested in.

How long do diesel school bus engines last?

How much does it cost to get a bus painted?

Can you tow a car behind a Skoolie?


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