Ameer Randolph
Mechanical fuel pumps work on a vacuum and therefore do not need to be primed. However, some automotive diaphragm-type pumps do need to be primed to get going. Electric fuel pumps, for example, need to be mounted at the same level or below the level of the fuel in the gas tank or fuel cell as they require gravity to first prime and then deliver the fuel.
Does an inline fuel pump need to be primed?
| Characteristics | Values |
|---|---|
| Need for priming | Mechanical fuel pumps do not need to be primed as they work on a vacuum. However, some non-automotive diaphragm-type pumps do need to be primed. |
| Installation | Electric fuel pumps need to be mounted at the same level or below the level of the fuel in the tank or fuel cell as they require gravity to function. |
| Cooling | Electric fuel pumps can overheat with constant use and eventually fail. |
| Current draw | Electric fuel pumps can require 20+ amps of electricity at full bark. |
| Lubrication | For Chevy designs, it is recommended to pack the spring area with moly lube to prevent the spring from overheating and failing early. |
| Testing | To test the pump, plumb it into a 5-gallon container of gas, then crank the engine over. |
| Priming methods | To prime the pump, you can fill the carb manually through the vents, pressurize the fuel tank with compressed air, or pull a vacuum on the line until you have fuel. |
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What You'll Learn
- Mechanical fuel pumps work on a vacuum and don't need to be primed
- Electric fuel pumps need gravity to prime and deliver fuel
- A moly lube is needed to prevent the spring from overheating and failing
- A separate fuel line from a gas can can be used to prime the pump
- Some electric fuel pumps can self-prime
Mechanical fuel pumps work on a vacuum and don't need to be primed
If you want to prime the pump, there are a few ways to do so. One way is to take the pump out with the lines on and pump it by hand. Another way is to pressurize the fuel tank with compressed air. A third option is to take the line out of the carb and pull a vacuum on the line until you have fuel. Alternatively, you can fill the carb manually through the vents, so you don't have to do anything.
If the pump is new, it is a good idea to pack the spring area with a moly lube, as Chevy's design doesn't feed oil directly into this area. Without lube, the spring will overheat and fail early or cause the diaphragm to fail.
If you are still having trouble getting fuel to flow, you can try the following: pull the inlet hose off the pump and stick it in a fuel jug. Then, take your air blower and stick it in the fuel neck going into the tank, using a shop towel to seal it. A couple of "poofs" should get the gas flowing.
In contrast, electric fuel pumps create a constant fuel pressure and push more than they suck. This is why mechanical fuel pumps are mounted on the engine, while electric fuel pumps are often mounted in the gas tank itself.
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Electric fuel pumps need gravity to prime and deliver fuel
An electric fuel pump is an essential component of a car. It is used to ensure the gas travels from the fuel tank to the engine. The fuel must travel through a hose, also known as a fuel line, and it is the job of the fuel pump to ensure the gas reaches its proper location. The fuel pump is used in any car where gravity cannot be used to pump fuel into the system.
The fuel injected engine, in most cases, will use an electric fuel pump. You may need to prime it to boost the gas flowing through the system. Before you start priming, make sure the car is off and has been sitting for at least a couple of hours. You will be working around the fuel injection components of your car, and you can easily get burnt if the car is still warm. Put on protective gloves before you work inside and around the car. You may need to lift the car to access it from underneath. In many models, you will need to drain and pull the gas tank. In some models, the fuel pump is easy to access under the back seat or through the floor of the trunk. If you are unsure about the location of the fuel tank, refer to the manufacturer's directions. Once you have located the fuel tank, locate the electric fuel pump. The pump is usually located inside the tank.
There should be a prime switch located on the fuel pump line. Flip the switch to prime the fuel pump. You can prime the fuel pump a couple of times but do not leave it in the "on" position. Close the hood of the car and clean up your work area. Clean your hands completely with a cleaning agent that will remove any remnants of the fuel on your hands. Test out the car. Re-prime the electric fuel pump if necessary.
It is important to note that not all electric fuel pumps need to be primed by hand. Some models have a self-priming feature built-in. Be sure to check the information in the manufacturer's book to find out what type of priming system your car has. If you are unsure, consult the help of a certified automotive mechanic.
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A moly lube is needed to prevent the spring from overheating and failing
In-line fuel pumps work on a vacuum and do not need to be primed. However, if the pump is new, it is recommended to pack the spring area with a moly lube as Chevy's design doesn't feed oil directly into this area. Without lubrication, the spring will usually overheat and fail early or cause the diaphragm to fail. Moly lube is a proven and tested lubricant that is ideal for high-pressure metal-to-metal contact, such as the sliding bearing surfaces inside the compression tube of a piston. It also dampens the spring's natural harmonics when fired.
Moly lube is a type of molybdenum lubricant that contains heat-resistant molybdenum disulphide (MoS2) and graphite, in various combinations. It is used to lubricate and prevent the seizing of machine parts during repair or reassembly, even with repeated exposure to high temperatures. Moly lube is also suitable for lubricating parts consisting of materials that are not resistant to mineral oils. It is ideal for applications where the presence of copper is not desirable due to the risk of electrolytic corrosion or in the presence of chemicals that react with copper.
To prime an electric fuel pump, first, put on protective gloves and locate the fuel tank and pump. The pump is usually located inside the tank. There should be a prime switch located on the fuel pump line. Flip the switch to prime the pump. You can prime the pump a couple of times but do not leave it in the "on" position. Close the hood of the car and clean up your work area, including your hands. Test out the car and re-prime the pump if necessary.
Priming the pump can be done when you want to bleed your line. It is also used for safety reasons, such as when the engine starts to die or when the filters in the car become clogged. Some models of electric fuel pumps do not need to be primed by hand as they have a self-priming feature.
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A separate fuel line from a gas can can be used to prime the pump
A fuel pump is used to ensure gas travels from the fuel tank to the engine. The fuel must travel through a hose, also known as a fuel line, and it is the job of the fuel pump to ensure the gas reaches the proper location. There are two types of engines: carbureted and fuel-injected. The fuel-injected engine, in most cases, will use an electric fuel pump.
Priming a fuel pump is the act of filling the pump with liquid and forcing any trapped air out. When a pump is new, it will often be full of air, so it needs to be primed to work effectively when it is first used. It is essential to wear gloves and PPE when priming a fuel pump, as fuel may be spilled during this process.
One way to prime the pump is to run a separate fuel line to the pump suction from a gas can. Seal the hose in the opening of the gas can with duct tape, and then supply a low air pressure to the can to push fuel through the line. This should push fuel through the pump's check valves and prime your lines and carb.
Another method is to plumb the pump into a 5-gallon container of gas and crank the engine over. This will help prime the pump to some extent. It is also worth noting that some fuel pumps do not need to be primed as they have a self-priming feature.
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Some electric fuel pumps can self-prime
Some fuel pumps are mechanical and work on a vacuum, so they do not need to be primed. However, electric fuel pumps are essential components in most fuel-injected engines, and they may need to be primed to boost the gas flowing through the system.
Not all electric fuel pumps are created equal, and some can self-prime. For example, the Weldon A600-A fuel pump can self-prime. This is because it is mounted at the same level or below the fuel in the gas tank or fuel cell, and it needs gravity to first prime and then deliver the fuel. It pushes fuel rather than pulling it, unlike a mechanical fuel pump.
The mounting location of the electric pump is important. If it is in the engine bay instead of back by the tank, the pump may run dry and overheat, causing the car to shut down. A good fix is to use an electric fuel pump that can self-prime, but not all can do this.
If you are installing an electric fuel pump, you may need to prime it. To do this, make sure the car is off and has been sitting for at least a couple of hours. Put on protective gloves and drain and pull the gas tank. In some models, the fuel pump is easy to access under the back seat or through the floor of the trunk.
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Frequently asked questions
No, not all in-line fuel pumps need to be primed. Mechanical fuel pumps, for example, work on a vacuum and do not need to be primed.
If your in-line fuel pump is new and not feeding oil directly into the spring area, lubrication is needed to prevent the spring from overheating and failing early. Non-automotive diaphragm-type pumps also need to be primed to get going.
There are several ways to prime your in-line fuel pump. One way is to plumb it into a 5-gallon container of gas and then crank the engine over. You can also pull the inlet hose off the pump, stick it in a fuel jug, and use an air blower to blow into the fuel neck going into the tank.
If you are installing an electric fuel pump in a street application, cooling will be a huge obstacle as the large electric motors tend to heat up with constant use and eventually fail.
Yes, there are self-priming electric fuel pumps available, such as the Weldon A600-A fuel pump.
