Modern Automotive Technology PowerPoint for by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

Chapter 21 Fuel Tanks, Pumps, Lines, and Filters

Contents Fuel supply system Fuel supply system service

Fuel Supply System Draws fuel from the fuel tank and forces it into the fuel metering device Fuel metering devices fed by the fuel supply system include: gasoline injection system diesel injection system carburetor

Fuel Supply System Components The basic parts of a fuel supply system include: Fuel tank stores gasoline, diesel fuel, or alternate fuel Fuel lines carry fuel between the tank and the fuel metering system

Fuel Supply System Components Fuel pump draws fuel from the tank and pumps it to the fuel metering system Fuel filters remove contaminants in the fuel

Fuel System Types

Fuel System Types

Fuel System Types

Fuel System Types

Fuel Tank Must safely hold an adequate supply of fuel for prolonged engine operation Normally mounted in the rear of the vehicle under the trunk or backseat in a passenger car Fuel tank capacity varies from about 12 to 25 U.S. gallons (45-95 liters)

Fuel Tank Construction Fuel tanks are made of either thin sheet metal or plastic Metal tanks are made by soldering or welding two formed pieces of sheet metal together a zinc alloy is plated to the sheet metal to keep the tank from rusting

Fuel Tank Assembly Several components go together to make up the fuel tank assembly: Fuel tank filler neck extension tube on the tank for filling the tank with fuel Spillback ball large ball in the fuel tank filler neck to prevent fuel from leaking out of the vehicle during fillups

Fuel Tank Assembly Filler cap Fuel tank baffles Fuel tank straps sealed to prevent the escape of fuel and fuel vapors from the tank cap is not vented to atmosphere Fuel tank baffles placed inside the tank to keep fuel from sloshing Fuel tank straps used to secure the tank to the vehicle

Fuel Tank Assembly

Thick steel bands bolt around the fuel tank Fuel Tank Straps Thick steel bands bolt around the fuel tank

Tank Pickup-Sending Unit Extends down into the tank to draw fuel and operate the fuel gauge Sending unit is a variable resistor resistance changes with changes in the fuel level controls the amount of current reaching the fuel gauge

Tank Pickup-Sending Unit “Sock” filter strains out debris in tank

Fuel Gauge Operation

Fuel Tank Pressure Sensor Used to monitor the fuel tank pressure in late-model vehicles equipped with OBD II systems Aids in the operation of the evaporative emissions control system

Fuel Lines and Hoses Carry fuel from the tank to the engine Fuel lines are made of strong double-wall steel tubing Fuel hoses are made of synthetic rubber needed where movement occurs between parts, such as between the frame and the engine

Fuel and emission control lines Fuel Lines and Hoses Fuel and emission control lines

Fuel supply line, fuel return line, and fuel vapor line are shown Fuel Lines and Hoses Fuel supply line, fuel return line, and fuel vapor line are shown

Plastic Fuel Lines Made of high-strength nylon tubing Used instead of metal lines on some vehicles Inside diameter determines line size when ordering parts Quick-disconnect fittings are used to connect lines to injection components

Fuel Return System Most fuel injected vehicles use a fuel return system to cool fuel and prevent vapor lock Fuel return line carries excess fuel back to the tank keeps cool fuel constantly flowing through the system

Returnless Fuel Injection Systems Most late-model vehicles are equipped with returnless fuel injection systems Some systems use a pressure regulator mounted on the electric fuel pump assembly (in the fuel tank) When system pressure exceeds specifications, the regulator routes fuel back to the tank

Fuel Filters Used to stop contaminants such as rust, water, and dirt from entering the fuel lines, hoses, throttle body, injectors, pressure regulator or any other part that could be damaged “Sock” filter on the tank pickup tube is used to filter out debris Second filter is usually located in the main fuel line

Variations of Fuel Filters

Fuel Pumps There are two basic types of fuel pumps: mechanical fuel pump electric fuel pump

Mechanical Fuel Pump Powered by an eccentric on the engine camshaft Bolts to the side of the engine block Used on carbureted gasoline engines

Mechanical Pump Construction

Mechanical Pump Construction Rocker arm metal arm that pivots in the middle the outer end of the rocker arm rides on the eccentric; the inner end of the arm operates the diaphragm Return spring keeps the rocker arm in contact with the eccentric

Mechanical Pump Construction Diaphragm synthetic rubber disc clamped between the halves of the pump body metal pull rod connects the diaphragm to the rocker arm Diaphragm spring when compressed, the spring pushes on the diaphragm to produce fuel pressure and flow

Mechanical Pump Construction Check valves fuel flows easily through the valves in one direction but cannot flow through in the other direction valves are situated so that fuel can enter through one valve and exit through the other

Pump Operation (Intake Stroke) Eccentric lobe pushes on the rocker arm Diaphragm is pulled down, compressing the diaphragm spring Pumping chamber volume increases Vacuum created allows atmospheric pressure to force fuel through the inlet check valve

Pump Operation (Intake Stroke)

Pump Operation (Output Stroke) Eccentric lobe rotates away from the rocker arm Diaphragm spring pushes on the diaphragm and pressurizes the fuel in the pumping chamber Spring tension controls fuel pressure Fuel flows out through the outlet check valve

Pump Operation (Output Stroke)

Pump Operation (Idling) Occurs when the engine is running at slow speeds The rocker arm is free to slide through the pull rod when fuel pressure compresses the diaphragm spring The rocker arm moves up and down while the diaphragm remains stationary

Pump Operation (Idling)

Vapor Lock Problem created when bubbles in overheated fuel reduce or stop fuel flow Fuel boils, forming bubbles that displace liquid fuel Fuel bubbles reduce fuel pump output, causing engine performance problems Caused by high underhood temperatures and low fuel pressures

Vapor Lock

Electric Fuel Pump Produces fuel pressure and flow for the fuel metering section of a fuel system Located inside the fuel tank or in the fuel line between the tank and the engine A few systems use a pump in the tank and a second pump in the line to further increase fuel pressure

In-Tank Electric Fuel Pumps

Electric Fuel Pump Advantages Produces almost instant pressure Produces smoother flow than a mechanical pump Vapor lock is less likely because the pump is located away from the engine and pressurizes all the fuel lines that are near engine heat high pressure increases the boiling point of fuel

Rotary Fuel Pumps There are three basic types of rotary fuel pumps: impeller type roller vane type sliding vane type

Impeller Fuel Pump Uses centrifugal action to pump fuel Uses a small dc motor to spin the impeller Impeller blades cause the fuel to move outward due to centrifugal force Centrifugal force produces pressure to move the fuel through the fuel lines

In-Tank Impeller Pump

Fuel hoses, pump motor, and strainer can be removed and replaced In-Tank Impeller Pump Fuel hoses, pump motor, and strainer can be removed and replaced

Roller-Vane Fuel Pump Positive displacement pump that moves a specific amount of fuel with each rotation Small rollers and an offset-mounted rotor disc produce fuel pressure Positive displacement pumps require a pressure-relief valve to limit the output pressure of the pump

Roller-Vane Fuel Pump When the rotor and rollers spin, they pull fuel in on one side of the pump Fuel is trapped and pushed to a smaller area on the opposite side of the pump This squeezes the fuel between the rollers, and the fuel is forced out under pressure

Roller-Vane Fuel Pump

Electric Pump Circuit In this circuit, if the oil pressure drops too low, the switch shuts off the fuel pump

Fuel Supply System Service

Fuel Supply Systems Scanning Scan for diagnostic trouble codes before starting repairs Vehicles equipped with OBD II systems may monitor fuel tank pressure, fuel line pressure, fuel level, and other conditions Datastream operating values may be available for the circuit, which can speed troubleshooting

Fuel Tank Service Typical fuel tank problems include fuel leakage, physical damage, and contamination Vibration or rusting can cause a fuel tank to develop pinhole leaks

Fuel Tank Removal Empty the tank using the drain plug or by pumping the fuel out of the tank using an approved method Special pumping systems with catch tanks are available use extreme care because of the obvious fire hazard do not use an incandescent trouble light, which could drop and break, lighting a fire

Fuel Tank Removal A vehicle’s electric fuel pump may be used to empty the tank disconnect the fuel hose at the main fuel line and route it into an approved gas can turn the ignition key on and allow the fuel pump to force fuel from the tank to the can

Fuel Tank Removal Draining the tank

Fuel Tank Removal After draining, remove the tank from the vehicle Disconnect the filler neck, fuel lines, wires, and other components Remove the straps or bolts holding the tank to the body Slowly lower the tank without dropping or hitting it

Fuel Tank Installation When installing a tank, replace the rubber insulators Check that all fuel lines are properly secured Replace the fuel in the tank Check for leaks

Sending Unit Service When a fuel gauge does not work properly, use a gauge tester before condemning the sending unit If the gauge does not function with the tester installed, either the gauge or the circuit is faulty If the gauge functions with the tester installed, replace the sending unit

Gauge tester connected to the harness Sending Unit Service Gauge tester connected to the harness

Using a cam tool to remove the cam lock ring Sending Unit Service Using a cam tool to remove the cam lock ring

A long drift punch and light hammer blows will rotate the lock ring Sending Unit Service A long drift punch and light hammer blows will rotate the lock ring

With the sending unit removed, measure its resistance Sending Unit Service With the sending unit removed, measure its resistance

Fuel Line and Hose Service Faulty fuel lines and hoses are common sources of fuel leaks Fuel hoses can become hard and brittle from exposure to engine heat and the environment Engine oil softens and swells hoses Metal lines should be replaced when smashed, kinked, rusted, or leaking

Fuel Line and Hose Service Inspect fuel lines, hoses, and fittings for leakage and damage

Fuel Line and Hose Service To disconnect this fitting, press down on the locking tab while pulling apart

Fuel Line and Hose Service To reconnect this fitting, simply push the two halves of the fitting together

Fuel Line and Hose Service When installing fuel hoses, make sure they are pushed completely over raised areas on the fuel line

Fuel Line and Hose Service Rules Remember these rules when working with fuel lines and hoses: Place a shop rag around the fuel line fitting during removal Only use double-wall steel tubing Make smooth bends in tubing Form double-lap flares on the ends of the fuel line

Fuel Line and Hose Service Rules Basic steps for making a new fuel line

Fuel Line and Hose Service Rules Reinstall all fuel line hold-down clamps and brackets Route all lines in their original location Use a recommended tool to release clip-type fittings If a plastic line or fitting is damaged, replace it Use OEM plastic tubing to repair fuel systems

Fuel Line and Hose Service Rules Avoid bending or rerouting stiff, used plastic lines Cover plastic fuel lines with a wet towel when welding, cutting, or grinding nearby Use approved synthetic rubber fuel hose in a fuel system

Fuel Line and Hose Service Rules Make sure a fuel hose fully covers its fitting or line before installing the clamps When servicing press-fit line fittings, you may need to replace the O-ring seal to prevent fuel leakage Double-check all fittings for leaks

Fuel Filter Service Involves periodic replacement or cleaning of system filters Clogged fuel filter can restrict flow to the injectors, diesel injection system, or carburetor Clogged in-tank strainer when clogged, the strainer can collapse and stop fuel flow the strainer will open again after the engine stalls

Fuel Pump Service Fuel pump problems include: low fuel pressure high fuel pressure fuel pump noise inadequate fuel flow fuel leakage

Fuel Pump Service Low fuel pump pressure High fuel pump pressure caused by worn components, high resistance in the electric pump circuit, or leaking check valves High fuel pump pressure caused by a faulty pressure relief valve or fuel pressure regulator

Fuel Pump Service Fuel pump noise caused by bearing and part wear on electric pumps caused by faulty rocker arm spring or rocker arm wear on a mechanical pump

Fuel Pump Service Fuel pump leaks caused by diaphragm or gasket leaks on a mechanical pump inline electric fuel pumps often leak from inlet and outlet hoses leakage may contaminate the engine oil or leak externally

Fuel Pump Tests There are three common fuel pump tests available: fuel pump pressure test fuel pump volume test fuel pump vacuum test

Fuel Pump Tests Several other problems can produce symptoms similar to those caused by a faulty fuel pump: restricted fuel filters damaged fuel lines or hoses air leak in the vacuum side of the pump injection or carburetor problems ignition problems engine mechanical problems (low compression)

Fuel Pump Pressure Test Connect a pressure gauge to the output line of the fuel pump fuel injected engines often have a service fitting on the fuel rail To test a mechanical pump, start the engine and allow it to idle To test an electric pump, you may need to activate the pump motor or start the engine

Fuel Pump Pressure Test Compare gauge readings to specifications If fuel pressure is not within specs, check the pressure regulator, pump volume, fuel lines, and filters before replacing the pump Isolate the fuel pressure regulator from the pump by restricting the return line If pressure rises sufficiently, the problem may be in the regulator

Fuel Pump Pressure Test General fuel pressure specifications: Gasoline injection fuel pressure 15–40 psi (100–280 kPa) Diesel supply pump pressure 6–10 psi (40–70 kPa) Carbureted engine fuel pressure 4–6 psi (30–40 kPa)

Route the output line from the fuel pump into a graduated container Fuel Pump Volume Test Route the output line from the fuel pump into a graduated container

Fuel Pump Volume Test With the pump running, allow fuel to pour into the container for the prescribed amount of time Close off the valve Compare the volume to specifications General volume specification: minimum of one pint (0.47 liters) in 30 seconds

Connect a vacuum gauge to the inlet side of the pump Fuel Pump Vacuum Test Connect a vacuum gauge to the inlet side of the pump

Fuel Pump Vacuum Test Activate the pump With the pump running, compare the vacuum reading to specifications General vacuum specifications: 7–10 in. Hg. If the pump failed the pressure or volume tests but passed this test, the fuel supply lines or filters may be at fault

Electric Fuel Pump Circuit Tests Many electric fuel pump problems are caused by electrical circuit problems Broken wires, faulty relays, shorts, blown fuses, computer malfunctions, and other problems can affect electric pump operation

Electric Fuel Pump Circuit

Supply Voltage Test If a pump fails its performance tests, measure the supply voltage to the motor

Supply Voltage Test If supply voltage is low, use a service manual schematic to find problem areas

Testing the Fuel Pump Relay Energize the relay and check continuity

Inertia Switch Used to open the fuel pump circuit after a severe impact or collision Safety device that can prevent a serious fire by shutting off the pump in a collision Usually located in the trunk or near the electric fuel pump After a collision, a button on the switch must be pressed to reset the switch and enable the pump

Fuel Pump Removal and Replacement To remove a mechanical pump, disconnect the fuel lines and unbolt the pump Use a new gasket when installing a pump Torque the fasteners to specifications

Fuel Pump Removal and Replacement

Fuel Pump Removal and Replacement To remove an in-line electric pump, disconnect the fuel fittings and wires

Fuel Pump Removal and Replacement To remove an in-tank electric pump, the fuel tank must often be removed from the vehicle Some vehicles are equipped with a fuel pump access door in the trunk or under the rear seat the access door allows pump removal and replacement without tank removal

Fuel Pump Rebuilding Older mechanical fuel pumps are held together with screws and can be overhauled if parts are available Most mechanical and electric pumps are replaced, rather than rebuilt

Air Filter Service An air filter removes dirt and dust from the air entering the engine intake manifold Air filter service involves replacing or cleaning the filter element Paper elements are usually replaced with a new unit

When replacing a filter element, wipe out the filter housing Air Filter Service When replacing a filter element, wipe out the filter housing

Air Filter Assembly