How to prime a car engine?

This blog post will answer the question, ‘How to prime a car engine’, and cover topics like how to prime a car engine with oil, how to prime a car engine if it has been sitting for a long time, and how to prime a car engine using a priming bulb and a choke.

How to prime a car engine?

The following steps need to be followed in order to prime an engine:

  • We need to fill the oil pan with a high-quality primer oil
  • Next, we need to prime the particular system using a drilling and priming tool
  • The crankshaft needs to rotated manually during the priming process, to ensure the oil gets in and around all the bearings and critical parts.

How to prime a car engine with oil?

The oiling system of a car is very important to prime before the first start-up of the car. This is because priming lubricates the internal pathways and ensures oil flows through all the critical moving parts.

If a system is not primed before the first start-up, it can lead to excessive heat generation and wear and tear that can damage the engine severely.

The following steps can be followed to prime an engine using oil.

Oil funnel

The first step involves procuring an oil funnel. An oil funnel for the priming process can be of two types.

  • Triangular oil funnel with a spout like structure coming out at the top
  • A tubular oil funnel with an aperture at the top that can be directly attached to the dipstick port of the engine.

Adding oil to the car

Oil can either be added by removing the car’s radiator cap or by using one of the oil funnels to pour the oil into the engine. It is to be noted that the funnel spout should be positioned adjacent to the dipstick port of the car to avoid oil spillage.

Air bubbles

The presence of gas in oil causes the formation of air bubbles. This should be remedied immediately as it can affect the level of oil required by the car. The dipstick level can also be checked to determine if the oil level has gone down, which indicates that air bubbles are present.

Check the oil level again before start-up

The checking of the oil level needs to be repeated after the priming process has been completed just as a precautionary measure to ensure little to no air bubbles are present inside the oil.

Removing the gas

To perform this step, we need to turn off the car engine for a few minutes and just let it sit for a while after priming it. By the time of start-up, if there are gas bubbles inside the oil, they should rise up at the upper half of the lubrication system.

These gas bubbles once spotted can be scooped up from the surface using either an oil funnel or any other collecting medium.

These steps need to be repeated if necessary depending on the amount of air bubbles present in the oil.

How to prime a car engine if it has been sitting for a long time?

Engines face startup problems especially in winter as a cold car engine needs extra fuel to run. Hence, it is necessary to prime an engine before start-up, especially in cold weather.

The fuel can either be added to the engine via the injection pump or by adding it directly into the induction. The engine needs to be cranked a few times to let the fuel flow into cylinders and let the fuel vaporize.

These are some other ways to get the oil flowing inside the cylinders:

  • Make sure the car is parked
  • The gear should be in neutral 
  • Turn on the ignition key 
  • With the ignition turned on, press on both the clutch and the gas pedal so that the car does not start
  • This type of cranking can help move the oil in all the critical regions of the engine and aids in a quicker start-up

How to prime a car engine using a priming bulb and choke?

The carburetor in a car is responsible for providing the required air-fuel ratio to be combusted inside the combustion chamber. If a car is started up without priming it, the fuel in the carburetor vaporizes but it is not enough to be able to participate in combustion.

There are two ways to prime an engine in this case.

Using a priming bulb

It is a rubber material that is usually placed adjacent to the carburetor and acts as the checking valve to help add fuel to the carburetor to run the motor.

When the priming bulb is pressed, it creates a vacuum and draws fresh fuel into the intake line. This intake fuel line adds oil to the carburetor to prepare it for combustion.

Using a choke system

The choke system when used hinders the flow of air and the engine vacuum created helps to draw fuel to the carburetor faster, thus allowing a faster start-up.

Research shows the use of certain products that can help prime the engine better.


This blog post addressed the question, ‘How to prime a car engine’.

We came across the different steps used to prime a car engine with oil and the procedures to follow while priming the engine in case the car has been sitting for a while. Furthermore, engine priming using a priming bulb and a choke system has also been discussed. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): How to prime a car engine?

How do you Prelube a new engine?

The valve in the tank needs to be opened first to enable the air pressure direct the oil into the engine. The engine should be rotated manually to ensure the oil reaches all the critical regions of the engine.

What is a dry start car?

When we install a car motor right after getting it without priming the engine or lubricating the motor before start-up, it is known as dry starting a car.

How long do you have to wait after you flood an engine?

We should let the excess fuel evaporate by putting up the hood of the car for about 30 minutes. After this we can try starting the engine again without pressing the gas pedal, if it does not work, the problem is likely faulty spark plugs.