Why wont diesel start on cold mornings? - Power Genius (2023)

FAQs

Why won't my diesel car start in the cold morning? ›

If your diesel doesn't start in cold weather and you remembered to plug in the block heater, your battery may be the culprit. Batteries can lose 35 percent of their power at 32°F and as much as 60 percent at 0°F.

If your diesel engine won't start, the problem could be the amount of pressure in the fuel system. The engine may not start if the fuel pressure is too low. Fuel pressure that is too high can cause damage to the exhaust system while also increasing soot pollution in the exhaust.

Glow Plugs and Block Heaters: The use of glow plugs or block heaters will start the vast majority of diesel engines on a cold day. Glow plugs work by heating the internal combustion chamber so that conditions are suitable for compression and ultimately ignition.

Reasons A Diesel Engine Won't Start After It's Been Sitting

The most common are interrupted fuel delivery, problems with injectors, or a contaminated fuel line.

How cold is too cold for a diesel truck? The diesel fuel in your fuel tank will become like gel at a temperature of 15ºF or -9.5ºC and you will have trouble starting your engine. Anything below 15ºF / -9.5ºC can and will cause problems for your diesel vehicle.

Using the glow plugs is the most common method of starting a diesel in cold weather. The glow plug heating method raises the temperature of the air in the combustion chamber. The air in the combustion chamber must be compressed to 1/16 of its original volume.

If the vehicle won't start at all, listen for a clicking noise when you turn the ignition switch on. If the click is missing, the likely problem is the solenoid. On the other hand, if you hear a click but no fuel is pushed through the injector lines, and nothing is clogging the lines, it's time to replace the pump.

Fully depress the clutch pedal (manual transmission) or brake pedal (automatic transmission). Start the engine. Note: Do not touch the accelerator pedal.

A generator will begin to face difficulties starting when the temperatures dip, especially when it drops below 40°F. This occurs due to the engine and its components being too cold to function properly.

Why is my diesel engine hard to start when warm? ›

Also the most common reason of the difficult diesel engine warm start - wear-out of the plunger and barrel of the fuel pump. If plunger and barrel are worn out - cold fuel can be transported; however, as soon as the fuel warms up - it becomes more watery and cannot be transported by plunger and barrel easily.

Diesel engines depend on high temperatures created by compression to ignite the injected fuel and that makes them harder to start in cold weather than a gasoline engine. In fact, starting a diesel engine at 0°F (-17°C) is five times harder than starting one at 80°F (26°C).

As a general rule of thumb, if it is below zero degrees Fahrenheit, you should allow your engine up to seven minutes to warm up. If the temperature is between zero and fifty degrees, the warm-up period should be three to five minutes. Over fifty degrees will only require one or two minutes to warm up.

A general rule of thumb is to plug it in for at least 2-3 hours, and if it's especially cold outside, possibly even longer. A lot of people will say that simply starting the vehicle and letting it idle is a good enough way to warm up the oil and the engine.

Unnecessary idling wastes fuel, causes air pollution and increases engine wear. An idling diesel engine produces much higher emissions than it would while using the same amount of fuel under load. Extended idling causes a build-up of soot inside the engine and results in a puff of black smoke when the engine revs.

The only warm-up time you really need is about 30 seconds, just to get the oil circulating. In fact, diesels won't reach operating temperature unless they're under load, so warming an engine up prior to driving is actually just prolonging the process.

Diesels are durable engines anyway, and a semi driver who lets his engine idle overnight to keep warm can still expect to get hundreds of thousands of miles out of his engine. Even so, idling for extended periods of time isn't good for your engine.

The reality is, diesel fuel additives are a necessary part of winter driving. The upside is that you'll only need to use them for a few months out of the year. Make sure you get your additives before the winter starts so you'll never have problems starting your engine in the cold again.

Diesel 911 does not prevent fuel gelling – use Diesel Fuel Supplement +Cetane Boost (in the white bottle) as a preventive measure to keep fuel from gelling. Diesel 911 and Diesel Fuel Supplement +Cetane Boost are compatible in diesel fuel and may be used at the same time.

Gelling occurs when paraffin wax within diesel fuel solidifies and bonds together at extremely low temperatures. This is known as the fuel's cloud point, which for No. 2 diesel is typically around 14°F.

Should you idle a cold diesel? ›

If you are caught in an unseasonably cold weather situation, consider leaving the engine idling when possible. While this will limit your fuel efficiency, because idling does burn fuel, it will keep the fuel warm and prevents it from gelling.

When you rev your engine, you place additional and unnecessary stress on your car and its engine. This is imperative when it's cold outside—revving your engine before it has had time to warm up is especially damaging, as the engine's oil hasn't had sufficient time to circulate and properly lubricate your car.

You can easily add too much of a high-quality diesel fuel additive. What happens when you over-treat your diesel fuel? Overdosing can lead to a whole new list of fuel and engine issues from clogged filters to overall decreased engine performance and efficiency. If you're losing lubricity, don't over-treat.

Myth: Diesel engines need to warm up at idle for 5 to 10 minutes or more especially on cold days before driving them. Fact: This is one of the most common myths about diesel engines. Most engine manufacturers recommend that newer diesel engines idle for no more than 3 minutes before driving.

Block heaters and help diesel engines start on cold days by heating the internal combustion chamber. The block heater heats the coolant to circulate through the block and engine, keeping it warmer and making it easier to start.

Diesel Engines Blowing White Smoke from Exhaust

When white smoke occurs at cold start, and then disappears as the engine warms up, the most common causes are fouling deposits around piston rings and/or cylinder glazing. Use of our Flushing Oil Concentrate and FTC Decarbonizer address these respective problems.

Types of operation, such as excessive idling, short run time, light work and city type driving, all contribute to deposit formation which can result in poor cold start. All these operating conditions do not allow efficient diesel combustion.

For optimal performance, a diesel engine's primary need is a continuous supply of clean fuel. A symptom known as “airlock” occurs when this flow is interrupted by an air bubble, causing the engine to shut down and refuse to start.

When air bubbles or vapor are present in your diesel fuel delivery system, fuel injection is delayed. This delay happens because the fuel cannot be injected until the air and vapor are compressed to the correct fuel injection pressure.

When you change a diesel fuel filter, run out of fuel or disturb the fuel system, air is trapped. When you try to start the engine this air acts as a lock, preventing the normal supply of fuel into the cylinder.

Why is my crank weak when cold? ›

It's a common occurrence as low temperatures can cause your car battery to produce less current, making it that much harder for your engine to turn over in the morning. The cold can also stop your engine oil from flowing as well as it should, which puts even more strain on the battery.

• Cold Smart Start. If the ambient temperature is cold, allows the engine to warm up before load is applied.

Just like your car, if your generator won't start, it could be due to a dead battery or faulty connections. Try charging the battery via a 12-volt DC outlet or give it a jump courtesy of your car battery. If that doesn't work, then the battery is not likely the problem.

Prime the fuel system by turning the ignition on (Run position) for 30 seconds, but do not start the engine. This allows the pump to prime the system. Turn the ignition off, and then crank it for 15 seconds. If it does not start, repeat the first task and this one until it starts (cycle the key).

If your diesel doesn't start in cold weather and you remembered to plug in the block heater, your battery may be the culprit. Batteries can lose 35 percent of their power at 32°F and as much as 60 percent at 0°F.

There are a lot of factors that can affect the way a diesel engine starts in the cold. The “gelling” of diesel fuel, weak batteries and failed glow plugs are just a few of the things that can cause your truck to have difficulties starting in cold weather.

If your diesel engine has been sitting a long time and still won't start after following our recommended steps, there are several possible causes. The most common are interrupted fuel delivery, problems with injectors, or a contaminated fuel line.

The more cold-starts your diesel is subjected to, the shorter its lifespan will be. Inconsistent metal expansion and poor-flowing (thick) lubricants don't provide protection from moving parts. Another thing to worry about is fuel washing the cylinder walls before compression ignition can occur.

Diesel fuel does not fare well in cold temperatures – it can start to form crystals that clog fuel filters and fuel lines. Prolonged freezing temperatures can cause engines to not operate properly or not start at all.

Myth #2: Diesel engines won't start in the winter.

​“Modern diesel engines start in cold weather with very little effort.” The problem is that diesel jells at low temperatures. Below about 40°F, certain hydrocarbons in diesel turn gelatinous.

What diesel additive should I use for winter? ›

Opti-Lube Winter Anti-Gel

This additive protects during freezing temperatures of up to -40 °F, making it one of the best fuel additives for winter use. In addition, the Opti-Lube Winter Anti-Gel formula does not contain harmful chemicals, unlike standard fuel additives.

As a general rule of thumb, if it is below zero degrees Fahrenheit, you should allow your engine up to seven minutes to warm up. If the temperature is between zero and fifty degrees, the warm-up period should be three to five minutes. Over fifty degrees will only require one or two minutes to warm up.

When temperatures drop, diesel forms crystals that clog fuel fuel filters and fuel lines. Not only does this cause engines not to start, it can also lead to costly repairs if engines get damaged. To prevent diesel fuel from gelling (or crystallizing) you should use an anti-gel fuel supplement.

Just 0.4 percent coolant containing glycol in diesel engine oil is enough to coagulate soot and cause a dump-out condition leading to sludge, deposits, oil flow restrictions and filter blockage. According to one study, glycol contamination results in wear rates 10 times greater than water contamination alone.

Unnecessary idling wastes fuel, causes air pollution and increases engine wear. An idling diesel engine produces much higher emissions than it would while using the same amount of fuel under load. Extended idling causes a build-up of soot inside the engine and results in a puff of black smoke when the engine revs.

The best thing you can do to warm up your diesel engine—after letting it idle for no longer than two minutes—is to start driving it. Heading off at a steady pace will heat up the engine and get the oil circulating.

Cutting Diesel with Kerosene

In the winter time, kerosene is extremely useful for changing the cold weather handling temperatures of diesel fuel. The rule of thumb is that mixing in ten percent kerosene will lower the cold filter plugging point of a diesel fuel blend by five degrees.

Fuel heaters are the most effective way to keep diesel fuel from gelling, as it constantly monitors the temperature of the fuel and makes heating element temperature adjustments accordingly.