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How do I start a semi-truck?

Charley Helvy
Automotive Expert
Charley Helvy is an Automotive & Diesel Expert based in Avondale, Arizona. He is the founder of Charley’s Garage, an educational YouTube channel focusing on simple videos for automotive and truck enthusiasts. He has over 31 years of experience in the automotive world. He is a Diesel Instructor at the Universal Technical Institute and is a certified ASE Master Heavy Truck Technician. He offers training on gas and diesel engines on his YouTube channel, along with other DIY and explanation videos for beginners and enthusiasts alike. In 2024, he published a complete guide on Emissions Systems in Automotive and Diesel Vehicles.

Charley Helvy

Automotive Expert

Expert Answer

Starting a semi-truck is similar to starting a regular manual-transmission vehicle. First, ensure the transmission is set in neutral, depress the clutch pedal, and set the parking brake. Then, turn the key to start the engine. After starting, release the parking brake while keeping your foot on the brake pedal and the clutch pedal depressed. Next, select a gear gradually, release the clutch pedal, and you're ready to drive. The starting process resembles starting a standard automobile but on a larger scale.

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Question

What can I do if the truck will not start after filling it with diesel?

Community Answer

Make sure there's no air in the system. With diesel trucks, you can not have any air running through the fuel lines. Crack and bleed it and pump on the fuel pump (located usually on the side of the engine or on top of the fuel filter, depending on the truck) and keep pumping that out until there are no longer air bubbles coming out through where you've cracked it and there's just fuel coming out. Tighten where you've cracked it and bled it from, and try again.

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Question

What are the different methods for starting a diesel engine?

Community Answer

There are several different options for starting diesels, and the best option for any particular engine depends on the design of the engine and any 'starting aids' it has. For a particular vehicle, your best option is to refer to the owner's manual for starting in various (hot/cold) conditions. If you have problems starting, it may be that the starting aids aren't working properly.

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Question

I have a 92 C8.3 Cummins 300 hp motor that will start but won't stay running for more than 10 seconds. How do I fix it?

Community Answer

This could be any number if things. Combustion is starting the truck, but then it's being inhibited by something, fuel line or battery issues, perhaps. Take it to a diesel mechanic.

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Question

How do I start the engine when I bleed air from the system?

Community Answer

More often than not you would cycle the ignition key until the fuel pump quits running, but you need to do this several times. Now that the air is gone from your system, you need to reprime the fuel filters and pumps. By cycling the key, you'll get it primed.

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Question

Are the three-pronged plugs also used for diesel, and if so, what model years?

Community Answer

Three-pronged plugs are for grounding. They should always be used to plug in any and all cars during winter or cold months.

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Question

What should I do with a diesel truck that starts but the petals and gauges don't function?

Community Answer

The truck may have internal problems. To be safe, do not operate the truck and hire a professional to see what is wrong.

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Question

What could be wrong if my diesel van has new glow plugs, but will only start on a small push?

Community Answer

Push, as in physically pushing the truck? If so, your starter has teeth missing on the gear actuator or your flywheel has missing or broken/cracked teeth.

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Question

How long should I leave it plugged in for?

Community Answer

Plugging in your truck is only good if it is a cold season. Plugging it in keeps the spark plugs/ coils warm overnight and makes it easier to start in the morning.

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Question

Can I start the truck while it's plugged into an electrical outlet?

Community Answer

Yes, you can.

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Question

How do I engage my diesel truck?

Community Answer

After getting pushed and getting the right momentum, disengage the clutch (while in 1st gear or reverse depending on the direction) while simultaneously turning the ignition to start.

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Question

At what temperature do I need to plug the three prongs into the electric on a diesel engine?

Community Answer

20 degrees F and below is always a good rule of thumb. Some people plug their trucks in as soon as the temps dip to freezing (32 degrees). This is all dependent on a couple of factors that can affect cold weather starting: the condition of your batteries, glow plugs, starter and injectors, for example. The quality of fuel and cetane level in your tank also matter, as well as whether you are still running a high-viscosity conventional oil or you have switched to a wintertime lower-viscosity synthetic oil.

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Question

Brand new truck. Start diesel truck. Two check engine lights come on. 1 minute later another red check engine light comes on with stop on it. Shortly after that the motor turns off. What should I do?

Community Answer

Take it back to the dealer. If it’s brand new, it’s the dealer's problem to fix it, not yours. They should cover it under warranty.

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