Cleaning the Fuel System

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For your vehicle to run at its very best, or in some cases, for it to run at all, your fuel system absolutely must be clean. This article provides an overview of the fuel system, and discusses both preventive and corrective procedures to keep the system clean, with particular emphasis on cleaning the fuel tank.

Over time, the various components of a fuel system can collect residues that will choke the engine’s fuel supply and cause a variety of performance issues:

• The vehicle may run fine for a while, then mysteriously begin to stumble, stall, and die; only to inexplicably start again moments later as if nothing had happened…, right up until the moment when the whole cycle repeats.
• The vehicle may be hard to start or have a rough idle.
• You may notice a loss of power or poor fuel economy.
• In the worst cases, the fuel system can become completely blocked.

Quick starting, smooth idling and optimal performance cannot be achieved with a with a dirty fuel system. Many vehicles with driveability problems, particularly older or high-mileage vehicles, can benefit from a clean fuel tank, a new fuel filter and new or refurbished fuel pump.

Understanding the Fuel System

The sole purpose of the fuel system is to deliver fuel, on demand, to the vehicle’s engine. The Fuel system consists of the following main components (usually in this order):

• Fuel tank
• Fuel pump
• Fuel filter
• Fuel pressure regulator (some carbureted applications excepted)
• Carburetor(s) or fuel injectors

Fuel Tank

The fuel tank is nothing more than a reservoir for the vehicle’s fuel. However, in older vehicles, or vehicles that are driven infrequently, it is the primary source of fuel system contamination. Metal tanks -- common on older cars -- can be a big problem. Metal tanks rust because of condensation in the airspace of the tank. When a vehicle is driven regularly, the sloshing fuel keeps the tank sides clean. When the sits “idle” for long periods of time, water condensation has a chance to eat away at the metal. Then, when the vehicle is driven again, the sloshing fuel pulls the rust scale off the sides of the tank and send bits of this debris into your fuel system, where it clogs filters and pumps.

Fuel Pump

The fuel pump provides the means by which fuel is drawn from the fuel tank and supplied to the engine. On carbureted vehicles, the fuel pump, whether an electric or an engine-driven unit, can generally be rebuilt. Service parts and rebuild kits can be purchased from the manufacturer or from a variety of aftermarket sources. Fuel-injected models operate at much higher pressures and as a result, they are more complex, more expensive and unfortunately, are more often than not a “scrap and replace” type of part.

Fuel Filter

The fuel filter is the primary line of defense against fuel system contamination. Fuel filters are simple, effective and are generally considered “consumable” items.

• OEM- type filters are usually “one-time deals.” When the manufacturer’s replacement interval is reached, remove and discard the old filter, and install a new one.
• Aftermarket fuel filters are much more likely to have replaceable filter elements inside. Simply replace the element, reinstall the filter, and be on your way again.

Fuel Pressure Regulator

A fuel pressure regulator is present in almost all fuel-injected applications. In some applications, it also acts as a one-way valve that prevents the fuel from flowing back into the tank when the engine is turned off. Carbureted applications with a “stock” engine-driven fuel pump usually do without a fuel pressure regulator. They simply pump as much fuel as is needed at the appropriate pressure.

NOTE: If you upgrade to an electric fuel pump, you should add a pressure regulator at the same time.

Carburetor

The carburetor is a mechanical device that provides the correct mixture of air and fuel to the engine. The carburetor uses vacuum to draw fuel from the fuel system into the engine. Cleaning and rebuilding a carburetor can be a very complex task. Carburetors come in a wide variety of shapes and sizes, and each model is worthy of its own article on maintenance, servicing and repair. The service manual for your vehicle will normally have diagrams of the carburetor, and may include rebuild instructions.

NOTE: If the instructions in the vehicle’s service manual are not adequate, you can often purchase a manual covering a number of carburetor models for a particular manufacturer. Rebuild kits do not usually come with extensive instructions, so don’t expect much help there.

Fuel Injectors

Fuel injectors have replaced the carburetor on modern vehicles. Carburetors work best either at “idle” or at “full throttle.” Under other driving conditions, carburetors often respond to the engine’s changing air/fuel need too slowly. When catalytic converters were introduced, the shortcomings of the carburetor became more evident. Catalytic converters require precise control of the air/fuel mixture for proper operation. This level of control was not possible with the mechanically-controlled carburetor, and resulted in the incorporation of fuel injection systems in all vehicles manufactured today.

A fuel injector is an electronically-actuated electromagnetic valve mounted on the engine’s intake manifold. Its function is to “inject” (supply) fuel to the combustion chambers (cylinders) during vehicle operation. The fuel pump supplies pressurized fuel to the fuel injectors through the fuel rail. Operation of the fuel injectors is accomplished by the vehicles computer.

Fuel injectors are not one of the components that the DIYer can clean reliably “off vehicle.” Periodically cleaning the injectors “on vehicle” using a commercially available fuel injector cleaner should keep the injector in good shape. If a “deep cleaning” is needed, remove the injectors from the engine and take them to a professional fuel injector cleaning company. They will clean them and test them for flow and proper spray pattern.

NOTE: If you take your injectors to a professional company for cleaning, be sure they provide you with a report that shows the test results.

Determining why a bolt or stud has “seized”

Determining why a bolt or stud has “seized” is an important step in determining the most appropriate remedy. Check for the following:

• Is the bolt or stud rusted in place?
• Is adhesive or sealant applied to the threads?
• Is the stud or nut a structural component that has been intentionally welded in place, and is not intended to be removed?

Once you have a solid understanding of the situation, you’re ready to select the most appropriate strategy for removal.

Organize Your Arsenal

BE SURE you have the necessary tools and materials “on hand” before you begin. Depending on your specific situation, you’ll need some or all of the following:

• Penetrating oil
• Proper wrenches
• Stud puller
• Vise grips
• Propane torch
• Impact wrench
• “Canned air”
• Rotary cutter/grinder
• Wire brush
• Safety glasses
• “Painters” mask or respirator

Plan Your Attack

Hand Tools

Regardless of the reason that a bolt or stud has “seized”, proper hand tools are essential. Using the wrong tool, such as a “standard” wrench on a Metric bolt, will only add to your problems. While you may be able to remove some bolts this way, eventually you will “round” the head on a stubborn one. Using the proper tool for a fastener will increase your chances of removing the fastener successfully.

For stud removal, a collet-based tool is recommended. These tools tend to increase the chances of accomplishing the job without damaging the stud. When pulling studs from an engine case, a good vise grip is essential for applying the torque necessary for removal.

An impact wrench can be useful when removing a nut that rotates on a bearing (such as the steering wheel nut) or any fastener that is installed with a great amount of force.

Lubricants

In cases where a bolt or stud has “seized” due to rusting, a good quality lubricant or penetrating oil is often all that is needed. A wide variety of penetrating oils are available today, including brands such as “WD-40”, “Liquid Wrench” and “Kroil.” These oils are formulated to seep down into threads and joints, loosen rust, and reduce friction through lubrication. The downside? They take time to work. Your best bet is to apply the oil liberally around the entire circumference of the bolt, then let the oil “soak in” over night or, better yet, for 24 to 48 hours if time permits.

Depending on the location and position of the bolt, you can use modeling compound or silicone to build a “dam” around the bolt head. This will let you place a “reservoir” of oil around the bolt to maximize penetration. BE SURE to clean the area around the bolt before you “build your dam”, or the modeling compound won’t adhere properly, and the oil will seep out underneath.

Once the oil has done its work, try removing the bolt by alternately loosening and tightening it. Work slowly, loosening the bolt a bit further on each turn. This will help distribute the penetrating oil and break loose any remaining rusted areas while minimizing the possibility of stripped, crossed or broken threads.

Using Thermals

Rusted bolts that don’t respond to penetrating oil, or bolts that have been installed with an adhesive or sealant (such as red Loctite), can often be coaxed free by applying heat. A propane hand torch (or an oxy-acetylene torch may if you’re fortunate enough to have one on hand) is the tool of choice for these cases.

Use the torch to heat the metal surrounding the bolt or stud. This will help melt any sealant on the threads, and will also expand the metal around the stud. DO NOT apply heat directly to the bolt or stud. This will cause the stud to expand, making it even more difficult to remove.

Depending on the location of the bolt or stud, it may take some time for the surrounding metal to heat sufficiently. Aluminum and steel are very efficient thermal conductors. Heat applied to a local area will tend to be distributed evenly across the entire surface of the part. Be sure to heat the area surrounding the bolt or stud for a sufficient length of time to raise the local temperature around the fastener, then work quickly to loosen the bolt before the heat has time to dissipate.

BE SURE the area to be heated is free of oil or other combustible residue. NEVER use a torch near your vehicle’s gas tank.

BE SURE to use adequate eye and face protection when using a torch. Use a torch only in a well-ventilated area.

On the other side of the coin, “cooling” a stubborn bolt or stud can do the trick. One of the best methods for accomplishing this is by using one of the “canned air” products available at most office supply stores.

Hold the can over the bolt or stud, topside-down, and gently press the nozzle. The compressed “air” inside the can will drip out as a very cold liquid. Let the coolant sit for a few minutes, then work quickly to loosen the bolt before the area warms back up.

Alternately applying heat and cold can also be beneficial. The repeated expansion and contraction of the bolt or stud and the surrounding metal can help loosen rust and adhesives.

BE SURE to use adequate eye, face and hand protection when using coolants in this manner. Use coolants only in a well-ventilated area.

Use coolant sparingly. Frequent and repeated cooling may make the bolt or stud brittle and prone to breaking.

Grinding, Cutting and Drilling

When chemical and thermal methods have not achieved the desired results, grinding, cutting and drilling are your remaining options.

For most grinding and cutting procedures, a rotary hand tool (such as a Dremel) is usually sufficient. These types of tools are small, easy to maneuver, and offer a wide variety of cutting wheels and grinding discs. The high speed at which these tools operate (often up to 50,000) can usually make “short work” of a stubborn bolt or stud.

As a final resort, you can use a hand drill to bore out an embedded or broken stud. Begin with a small drill bit and gradually increase the diameter. BE SURE to keep the drill centered at all times, and use plenty of lubricant to aid the drilling process. BE CAREFUL not to damage the threads of the hole by using too large a drill bit, or by drilling at an angle. When the drilled hole is close to the size of the stud, remove the remaining material from with a pick. Once the stud has been removed, use a hand tap to “clean” the treads. If you suspect thread damage, you may be able to tap the hole to a slightly larger thread size

Special Considerations

Exhaust studs are generally difficult to remove, as they tend to rust and corrode very easily. Additionally, since these studs are subjected to extreme temperatures from the vehicle’s exhaust, they tend to become brittle over time. Before attempting to remove a rusty exhaust manifold, be sure to apply penetrating oil to all nuts, bolts and studs, and give the oil sufficient time to do its job. Make sure you lubricate the area heavily before even attempting to remove a rusty exhaust manifold. Unfortunately, if a stud snaps off, there really isn’t too much you can do. Since the studs are heated by the exhaust, they become very brittle over time. If you do snap a stud off, your only options are to drill out the stud, or have it removed professionally using an Electrical Discharge Machining (EDM) process.

In cases of steel studs, or those made of other ferrous materials, you may be able to weld a nut onto the stud. This will let you use a wrench to aid in remove the stud. Before welding, be sure to clean any rust, oil or other contamination from the threads with a wire brush.

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