Fuel Tank and Fuel Line Repairs

Fuel Tank and Fuel Line Repairs

A fuel tank is simply a reservoir for your car's fuel. Fuel tanks typically hold from 10 to 20 gallons of fuel, depending on the car's fuel efficiency. (My 40-year-old Continental has a 25-gallon fuel tank, accurately suggesting a low number of miles to the gallon. My Honda acts very smug about its small tank and efficient mileage.) Cars are designed to travel 300 to 400 miles before running out of gas. Unfortunately, human bladders are smaller and need more frequent pit stops. What can go wrong with fuel tanks and fuel lines? They can spring a leak. A small point of rust can become a hole in a few years. If the hole is in a tank or line housing fuel, the fuel can leak out and cause more problems than just low fuel efficiency. If you find puddles of fuel under your car, you know that the tank or line needs repair. Do it before the leak becomes a fire hazard. The best insurance against such leaks is a full undercoating of the underside of your car to minimize rust. Depending on the size of your car, undercoating can cost about $25 in materials plus your labor, or about $100 to $150 if a shop does it for you. Make sure a rust inhibitor is applied first. Fuel tanks and fuel lines can be repaired following these steps:

1. Visually inspect your car's fuel tank and fuel lines, looking for small wet spots. 

Touch the spot with a finger and then sniff it to see whether the liquid is gasoline. If so, look for other leaks and repair or replace the part as needed. 

2. To repair a fuel tank, purchase and apply an internal or external fuel tank sealer. 

Internal sealers are poured into the fuel; external sealers are applied to the holes on the outside of the tank. Internal sealers find and seal all holes, seen and unseen, but might not be recommended by the car's manufacturer because they can clog a system. External sealers are easy to apply, but can't ensure that unseen holes are sealed. 

3. To replace a fuel tank on a fuel-injected car, first depressurize it, as described in the preceding section. This isn't necessary on a carbureted car. Then drain or siphon the fuel from the tank into one or more large gas cans. Detach the fuel tank from the inlet pipe and the output fuel line. Find and remove the straps or hangers that attach the fuel tank to the car. Carefully lower the tank to the ground and remove it from underneath the car. Replace it with a new or rebuilt replacement tank. Don't try to make one fit that doesn't. 

4. To repair a fuel line, first determine whether the entire line or only one spot needs replacement. A damaged line can be repaired, but a rusted fuel line will soon spring another hole and should be replaced. A rubber fuel line that has developed a leak is probably old and needs to be replaced entirely. If your car is fuel-injected, depressurize the fuel system before working on it. Larger auto parts stores have fuel lines cut to length and bent for many newer cars. Otherwise, you might need to buy a straight fuel line along with some bending and flaring tools to make it fit your car. 

5. Realize that, once done with this job, you're a better person for the experience...

Fuel Pump Repair

Fuel pumps use suction to pull fuel from the tank and deliver it to the carburetor or fuel-injection system. Older cars used mechanical fuel pumps that were operated by 

the engine's camshaft. Newer cars use electromechanical or solid state fuel pumps. An electromechanical pump uses electricity to power the mechanical suction diaphragm. Solid state fuel pumps rely on electronics to do the job and have no mechanical parts. One more time: If your car has a fuel-injection system, make sure you depressurize the fuel system before working on it.

See the instructions provided earlier in this Section. To replace a fuel pump, follow these steps:

1. First, find the dam thing. Your car's fuel pump could be mounted on the side of the engine, somewhere in the engine compartment, near the fuel tank, or even inside the fuel tank. Your car's service manual helps you pinpoint it. 

2. Test the fuel pump. Some fuel pumps can be tested without taking them off the car, but others must be removed (see step 3). To test the pump, you first need to remove the fuel lines from the pump. Before disconnecting the input line, find a way of blocking it so that fuel from the tank doesn't spurt out. For a rubber input line, use Vise-Grip pliers to clamp the line. For a metal line, use a cap or a wad of putty to block flow after the input line is disconnected. Check input vacuum pressure with your finger or a vacuum gauge over the input. The car's service manual tells you what the input vacuum should be, but your finger over the input can give you a good idea as to whether the fuel pump is working. Check the fuel pump output pressure and volume in the same way. 

3. To remove the fuel pump, remove the mounting bolts that attach it to the engine block, frame, or tank. Fuel pumps inside a fuel tank typically can be accessed through a cover underneath a back seat or a trunk mat. Disconnect any electrical wiring. Drain any gas in the fuel pump or bowl into a gas can. Remember: Smoking while you're working on the fuel system can really be hazardous to your health and to those within a wide range of your location! 

4. Replace the fuel pump with one of the same output. Your car's specifications tell you what pressure and volume the fuel pump should be able to produce.