Gas in Diesel Engine Symptoms & What to Do

Gas in Diesel Engine: Symptoms, Causes & Fixes

If gas makes its way into a diesel engine, several complications can arise that impact its performance. There’s a reason why there is fuel specific to these big rig engines!

The issue arises when gas, which has different combustion properties than diesel fuel, is added to a diesel engine. Gasoline is less lubricating and combusts differently, leading to incomplete and inefficient combustion in a diesel engine.

Understanding the symptoms, causes and fixes for the issue is important so that you can minimize potential damage to one of the most important parts of your vehicle.

READ MORE: DIESEL VS. GAS ENGINES

Gas in Diesel Engine Symptoms

Diesel engines are known to be dependable, but if gas gets into the fuel system, there can be various symptoms that negatively affect the engine. These include:

• Rough running engine: Gasoline doesn’t combust efficiently in a diesel engine, causing irregular firing cycles. This results in a rough-running engine, noticeable through shaking, vibrations or a lack of smooth operation.
• Decreased power and acceleration: Gas contamination affects the combustion process, leading to reduced engine power. Acceleration may become sluggish or less responsive than usual.
• Excessive smoke from exhaust: When gas mixes with diesel, incomplete combustion occurs, leading to increased smoke emissions. The exhaust may emit black or blue smoke more prominently than normal.
• Unusual noises: Gasoline in a diesel engine can cause abnormal knocking or clattering sounds. These noises often indicate fuel combustion issues and can be alarming to vehicle owners.
• Stalling or difficulty starting: Gas contamination can interfere with the engine's starting process or cause stalling during operation. It may take more attempts to start the engine, or the vehicle might stall unexpectedly.

The impact of these symptoms on engine performance can include reduced efficiency, potential damage to engine components and increased emissions.

Causes of Gas in Diesel Engine

So, what can cause gas contamination in a diesel engine? There are a few main ways this can happen:

• Misfuelling at the pump: One of the most common causes is accidental misfuelling, where gasoline is mistakenly pumped into a diesel tank. This error can occur due to distractions, confusion or inattentiveness while refueling the vehicle.
• Contaminated fuel supply: Sometimes, gas contamination can occur due to issues within the fuel supply chain. This can include contaminated diesel fuel at the gas station due to improper storage, transportation or handling practices.
• Shared fueling equipment: Shared fueling nozzles or pumps at gas stations might contain residue from gasoline, especially if not properly cleaned between uses. Even a small amount of gasoline left in the nozzle can contaminate the diesel fuel being dispensed.

Sometimes, there are similar nozzle sizes and colors for the diesel and gas fuel pumps at a gas station. This can cause user errors or mistakes when choosing the fuel for a vehicle. Being distracted, tired or in an unfamiliar vehicle can result in this happening as well.

What Happens if You Put Gas in a Diesel Engine

Using gasoline in a diesel engine can lead to a range of detrimental consequences, impacting both the immediate operation and long-term health of the engine and its components.

The incompatible nature of gasoline in a diesel system triggers a chain of adverse effects that can result in severe damage if not addressed promptly:

• Reduced engine performance.

Damage to Engine Components

Engine components can become damaged as a result of using the incorrect fuel.

• Fuel injectors: Gasoline's chemical properties can damage fuel injectors, affecting their precision and ability to deliver fuel in the correct manner.
• Cylinder walls and pistons: Incomplete combustion can cause hot spots, leading to overheating and potential damage to cylinder walls and pistons.
• Valves and valve seats: Gas contamination can lead to valve sticking or damage to valve seats due to carbon buildup, affecting engine compression and performance.
• Filters and fuel lines: Gasoline can clog fuel filters and lines due to the formation of varnish-like deposits, hindering the proper flow of fuel and potentially causing fuel starvation.

READ MORE: HOW DIESEL ENGINES WORK

Gas in Diesel Engine Repair Cost

Repair costs associated with gas contamination in a diesel engine depend on various factors, including the extent of contamination, affected components, labor rates, vehicle model complexity and required replacement parts.

Addressing the issue sooner versus later can help lower repair expenses by preventing further damage. Seeking professional assistance from experienced mechanics or technicians is essential.

You can also learn how to fix these problems yourself by training as an automotive or diesel technician. A trade school like Universal Technical Institute (UTI) offers hands-on programs that can teach you the ins and outs of repairing vehicles.^1,18 With Automotive Technology or Diesel Technology program options, as well as a combined Auto/Diesel program, there are several training options for those interested!

Gas in Diesel Engine Fixes

As stated above, it’s important to bring your vehicle to a trained automotive or diesel technician so they’re able to fix the problem – unless you have the right training to do so yourself!
Some steps that a technician may take to help fix the problem of gas in a diesel engine include draining the fuel tank or flushing the fuel system. They might also choose to clean the fuel injectors and lines, so the fuel delivery process works smoothly.

Depending on the extent of the issue, they may need to replace these components, as well as change out the fuel filters.

READ MORE: HOW TO BECOME A DIESEL MECHANIC

What to Do if You Put Gas in a Diesel Engine

If you realize you put the wrong fuel into your diesel engine, don’t panic. Acting right away can help you prevent further damage to your vehicle.

• Do not start the engine if you suspect or know that gas has been added to the diesel tank.
• Avoid driving the vehicle to prevent the spread of contaminated fuel.
• Contact a professional mechanic or technician to schedule service.
• Take notes of details, including the amount of gas added if known.

Taking these steps is important and will help ensure that you get your vehicle running properly as soon as possible!

FAQs

What are the consequences of putting gas in a diesel engine?

From engine performance issues like reduced efficiency to incomplete combustion, engine misfires and damage to fuel system components, there are a range of negative side effects that can occur from putting gas into a diesel engine.

What happens if there’s a small amount of gas in a diesel engine?

Even a small amount of gasoline in a diesel engine can cause significant problems due to the differences in the combustion properties of these fuels.

The consequences might vary based on the quantity of gasoline introduced and the engine's sensitivity, but even a small amount can lead to issues.

Are there any immediate signs or symptoms if gas is added to a diesel engine?

Some of the main symptoms that can occur after gasoline is added to a diesel engine may include a vibrating or shaking engine, excessive smoke coming from the exhaust, unusual noises and difficulty starting. Sometimes a warning light might come on in your vehicle.

Get Trained as an Automotive or Diesel Technician at UTI

If you’re interested in learning how to make repairs and perform maintenance on vehicles, consider our automotive or diesel technology program options at UTI. You can gain skills needed to pursue a hands-on career and the knowledge to make repairs on your own vehicles, including ones related to putting gas in a diesel engine.¹

Request more info to get in touch with an Admissions Representative who can help you get started toward an exciting future!