start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 58, the reader should be able to: • • Prepare for ASE Engine Performance (A8) certification test content area “C” (Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair) Describe how to check an electric fuel pump for proper pressure and volume delivery Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 58, the reader should be able to: • • • Explain how to check a fuel-pressure regulator Describe how to test fuel injectors Explain how to diagnose electronic fuelinjection problems Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: accumulator • baffle • check valve • delivery system filter basket • gerotor • hydrokinetic pump • inertia switch onboard refueling vapor recovery (ORVR) peripheral pump residual or rest pressure • roller cell • rotary vane pump side-channel pump • turbine pump vacuum lock • vapor lock • volatile organic compound (VOC) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FUEL DELIVERY SYSTEM Creating and maintaining a correct air–fuel mixture requires a  properly functioning fuel and air delivery system. Fuel delivery  (and return) systems use many if not all of the following  components to make certain that fuel is available under the right  conditions to the fuel­injection system: Fuel storage tank, filler neck, and gas cap Fuel tank pressure sensor Fuel pump Fuel filter(s) Fuel delivery lines and fuel rail Fuel­pressure regulator Fuel return line Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FUEL TANK A vehicle fuel tank is made of steel or polyethylene plastic. Some  SUVs and light trucks have an auxiliary fuel tank Tank design and capacity are a compromise between available  space, filler location, fuel expansion room, and fuel movement Some later­model tanks deliberately limit tank capacity by  extending the filler tube neck into the tank low enough to prevent  complete filling, or by providing for expansion room A vertical baffle in this same tank limits fuel sloshing as the vehicle  moves See Figure 58–1.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 58–1 A typical fuel tank installation Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Regardless of size and shape, all fuel tanks incorporate most if not  all of the following features: Inlet or filler tube through which fuel enters the tank Filler cap with pressure holding and relief features An outlet to the fuel line leading to the fuel pump or fuel  injector Fuel pump mounted within the tank Tank vent system Fuel pickup tube and fuel level sending unit Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Tank Location and Mounting  Most vehicles use a horizontally  suspended fuel tank, usually mounted below the rear of the floor  pan, just ahead of or behind the rear axle Fuel tanks are located there so that frame rails and body  components protect the tank in the event of a crash. Fuel inlet  location depends on the tank design and filler tube placement. It  is located behind a filler cap and often a hinged door in the outer  side of either rear fender panel Generally, a pair of metal retaining straps holds a fuel tank in  place. Underbody brackets or support panels hold the strap ends  using bolts. To prevent squeaks, some models have insulated  strips cemented on the top or sides of the tank wherever it  contacts the underbody Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Filler Tubes  Large tube extending from the tank to an opening on  the outside of the vehicle.  Figure 58–2 A three-piece filler tube assembly Federal authorities recognized methanol as a poison, and methanol  used in gasoline is a definite health hazard. Additionally, gasoline  is a suspected carcinogen (cancer­causing agent).  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 When the engine speed is increased, the pressure reading should  remain within the specifications Some engines do not use a  vacuum­referenced regulator The running pressure remains constant, which is typical for a  mechanical returnless­type fuel system. On these systems, the  pressure is higher than on return­type systems to help reduce the  formation of fuel vapors in the system Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Continued ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The Fuel Pressure Stethoscope Trick When the fuel pump is energized and the engine is not running, fuel should be heard flowing back to the fuel tank at the outlet of the fuel-pressure regulator If fuel is heard flowing through the return line, the fuel-pump pressure is higher than the regulator pressure If no sound of fuel is heard, either the fuel pump or the fuel-pressure regulator is at fault Figure 58–25 Fuel should be heard returning to the fuel tank at the fuel return line if the fuel pump and fuel-pressure regulator are functioning correctly Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Testing Fuel­Pump Volume  Fuel pressure alone is not enough for  proper engine operation.  Sufficient fuel capacity (flow)  should be at least 2 pints (1 liter)  every 30 seconds Fuel flow specifications are usually  expressed in gallons per minute.  A typical specification would be  0.5 gallons per minute or more.  Volume testing is shown in Figure 58­27 Figure 58–26 A fuel-pressure reading does not confirm that there is enough fuel volume for the engine to operate correctly Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 58–27 A fuel system tester connected in series in the fuel system so all of the fuel used flows through the meter which displays the rate-of-flow and the fuel pressure For long engine and fuel­system life and optimum performance, the fuel  filter should be replaced every year or every 15,000 miles or 24,000  kilometers (km). (Check the vehicle manufacturers’ recommendations for  exact time and mileage intervals.) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The first filter is inside the gas tank and is usually not replaceable  separately but is attached to the fuel pump (if the pump is electric)  and/or fuel gauge sending unit. The replaceable fuel filter is usually  located between the fuel tank and the fuel rail or inlet to the fuel­ injection system.  If the fuel filter becomes partially clogged, the following are likely: There will be low power at higher engine speeds. The  vehicle usually will not go faster than a certain speed  (engine acts as if it has a built­in speed governor) The engine will cut out or miss on acceleration, especially  when climbing hills or during heavy­load acceleration Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 A weak or defective fuel pump can also be the cause of the symptoms  just listed. If an electric fuel pump for a fuel­injected engine becomes  weak, additional problems include the following: The engine may be hard to start There may be a rough idle and stalling There may be erratic shifting of the automatic transmission  as a result of engine missing due to lack of fuel­pump  pressure and/or volume CAUTION: Be certain to consult the manufacturers’ recommended  service and testing procedures before attempting to test or replace any  component of a high­pressure electronic fuel­injection system Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Quick and Easy Fuel Volume Test Testing for pump volume involves using a specialized tester or a fuel-pressure gauge equipped with a hose to allow fuel to be drawn from the system into a container with markings to allow for a volume measurement This can be hazardous because of expanding gasoline An alternative test involves connecting a fuel-pressure gauge to the system using these steps: Step #1 Start the engine and observe the fuel-pressure gauge The reading should be within factory specs (typically between 35 and 45 psi) Step #2 Remove the hose from the fuel-pressure regulator The pressure should increase if the system uses a demand-type regulator Step #3 Rapidly accelerate the engine while watching the fuel-pressure gauge If fuel volume is OK, fuel pressure should not drop more than psi If the fuel pressure drops more than psi, replace the fuel filter and retest Step #4 After replacing the fuel filter, accelerate the engine and observe the pressure gauge If pressure drops more than psi, replace the pump Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Remove the Bed to Save Time? The electric fuel pump is easier to replace on many General Motors pickup trucks if the bed is removed Access to the top of the fuel tank, where the access hole is located, for the removal of the fuel tank sender unit and pump is restricted by the bottom of the pickup truck bed Rather than drop the tank, it is often much easier to use an engine hoist or a couple of other techs to lift the bed from the frame after removing just a few fasteners Be sure to clean around the fuel pump opening so that dirt or debris does not enter the tank when the fuel pump is removed Figure 58–28 Removing the bed from a pickup truck makes gaining access to the fuel pump a lot easier Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FUEL PUMP CURRENT DRAW TEST Another test to perform on a fuel pump  is to measure current draw in amperes This is often performed by connecting  a digital multimeter set to read DC  amperes and testing the current draw.  Figure 58–29 Hookup for vehicles equipped with a fuel pump relay Compare the reading to factory specs.  See the chart following for examples of typical fuel­pump current draw  readings Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: Testing current draw of an electric fuel pump may  not indicate whether the  pump is good. A pump not  rotating may draw normal  current See the chart on  Page 704 of your  textbook.  Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FUEL PUMP REPLACEMENT The following recommendations should be followed whenever  replacing an electric fuel pump: The fuel­pump strainer (sock) should be replaced with  the new pump If the original pump had a defector shield, it should  always be used to prevent fuel return bubbles from  blocking the inlet to the pump Always check the interior of the fuel tank for evidence  of contamination or dirt Double­check that the replacement pump is correct for  the application Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY The fuel delivery system includes the following items: • Fuel tank • Fuel pump • Fuel filter(s) • Fuel lines A fuel tank is either constructed of steel with a tin plating for corrosion resistance or polyethylene plastic Fuel tank filler tubes contain an anti­siphoning device Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Accident and rollover protection devices include check valves and inertia switches Most fuel lines are made of nylon plastic Electric fuel­pump types include: roller cell, gerotor, and  turbine Fuel filters remove particles that are 10 to 20 microns or  larger in size and should be replaced regularly Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Fuel pumps can be tested by checking: • Pressure • Volume • Specified current draw Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458