by Richard Rowe
Motor – Hot Rod Image by Jeffrey Zalesny from Fotolia.com
Carburettors and mechanical pumps aren’t the most common fuel delivery systems these days, which may mean you’re unfamiliar with their quirks. Preparing one of these old-school systems is a fairly simple procedure, all the more so since most were designed from the ground up with the need for setup in mind. Priming is generally only necessary if the car has been stationary for a while and helps prevent excessive cranking on an engine with no oil pressure when starting.
Remove the engine air filter cap to expose the carburetor. Identify the carburetor fuel bowl vents; The fuel tank vents serve as a kind of “chimney” for the tanks, preventing pressure or vacuum damage. The bowl vents will be the hollow vertical tubes that come out of the top center of the carburetor or from both sides of your air intakes.
Fill a dropper with gasoline from the container.
Pour the gas-filled dropper into the fuel bowl vent and repeat this procedure at least 10 times per fuel bowl, for a total of 70 milliliters with a 7 mL dropper. The amount will vary by carburetor and engine, but 70ml should be sufficient for most carbohydrates.
Priming the fuel pump
Disconnect the hose that connects the fuel pump to the carburetor. In the case of rubber lines, this will usually involve removing a hose clamp; other engines will require you to remove the carburetor line with a wrench. Place a rag over the end of the open fuel line.
Spray a three second burst of starting fluid on the carburetor. Stay away from the engine and have an assistant turn the ignition key to start the car. The car should run for about five seconds and then die.
Repeat the spray and die procedure until you see fuel start to wet the rag in the fuel line.
Reconnect the fuel line to the carburetor.
- You don’t need to manually prime a mechanical fuel pump like you do with a carburetor. A fuel pump works with vacuum; At idle speed, a well-functioning fuel pump must generate enough vacuum to prime.
- Be careful when using starting fluid around a disconnected fuel line. Some engines have a tendency to fire against and burp flames when starting fluid is used, which is not a good thing around gas-soaked rags and gushing fuel hoses.
Articles will need
- Standard 7 milliliter dropper
- 1 liter of gasoline
- Key (optional)
- Shop rag
- Flat head screwdriver
- Ether based starting fluid can