Most vehicles have a mechanical fuel pump with a latex diaphragm that moves in and out through a level. These cars sometimes fail to start after they have been sitting for long in winter. While you try to start the vehicle, it keeps cranking over and over and fails to start meaning; your fuel pump has a priming issue. But for the electric pump cars, they start on immediately the moment you crank the key to ignition. The priming issue may result due to several reasons like less fuel pressure created, low vacuum while sucking the oil, and more. So, which are the mechanical fuel pump priming steps?
Priming a Mechanical Fuel Pump
- Open the hood’s vehicle and find the fuel pump somewhere between the fuel tank and the first fuel filter.
- Detach the pipe that links the fuel pump and carburetor. The rubber lines will require you to remove a hose fastener. Others will remove the connection from the carburetor with a wrench. Position some rags on the end of the open fuel line in case of any leakage.
- You can still put a little air pressure in the fuel tank to force the fuel up to the pump.
- Sprinkle a three-second burst of starting fluid into the carburetor. After have someone turn the ignition key to start the car, which runs for some five seconds then fails.
- Repeat the spray and fail procedure until you notice the fuel begin to wet the rag over the fuel line.
- Later connect your fuel line to the carburetor.
When Should You Prime Your Mechanical Fuel Pump?
Your mechanical fuel pump primes itself almost every time you start the car unless you just turned it off. When you allow it to sit for a while, then turn the ignition on, it will prime. But there are those moments your car lies idle for a long time, especially in winter, and the engine becomes cold. When you turn on the ignition, the pump won’t prime, and thus you have to do it.
You can know when to prime a fuel pump, but there are things that you should check or consider first ;
- Your pump is drawing a vacuum to ensure you get fuel into the pump and the carb. That is, there are no leaks that could prevent the creation of a vacuum.
- Have a decent amount of gas in the tank
- Have no leaks at all in the lines or any potential for leaks. The leaks draw air into the system.
- Fuel in the line up to the fuel pump or as close you can get
- Enough fuel in the tank itself for it to hold enough pressure and prevent the motor from overheating
What Happens if You Don’t Prime a Mechanical Fuel Pump?
A functioning pump will prime itself more quickly on a running machine than at cranking speed. An incapacitated pump may start the engine well enough and is unable to prime. Any leakage at valves will significantly handicap things, as will wear at several points that can reduce stroke. Other more consequences will occur.
If you don’t prime a mechanical fuel pump, you will lead to extensive operation and driving issues with your vehicle. When the fuel-to-air ratio is low, and the cylinders aren’t receiving enough fuel, then the pistons won’t fire, and your motor will struggle to locomote the car forward. You will not just suffer from lower gas mileage or inefficiencies, but if your fuel pump isn’t priming, your car won’t start.
How Long Does It Take Prime a Mechanical Fuel Pump?
Your vehicle should have 43.5 psi following a pump run cycle. Then keep track of the fuel pressure for 20 minutes to check if fuel leaks out of the supply side. Sometimes the mechanical pump takes a little while for the fuel to flow. If you crank it for more than a minute and do not hear any fuel flowing, your pump might be faulty. There could be a hole somewhere in the fuel line or a loose-fitting that sucks in the air. You can test if your pump is okay using a 5-gallon container of gas. Plumb it into the container of gas and crank the engine over and check if there are leaks. The activity can still help to prime it.
Check this too: What Are The Signs Of A Weak Fuel Pump?
Conclusion
A mechanical fuel pump works on a vacuum; at idle speed, and the operating fuel pump should pull out enough of a vacuum to prime itself. But in a situation, you have stored it for some time, it may fail, especially in the winter season. Therefore, it’s best to prime it using the process above for you to start the car. But if you notice any delays in priming, check if your fuel pump is in good condition.