ASE 8 - Engine Performance

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Gwen Simmons
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1 ASE 8 - Engine Performance Module 4 Fuel Systems Gasoline Student Exercises

2 Exercise 1-1: Fuel Quality Testing (With Special Tool) Objectives: Following completion of this worksheet, you will be able to: Perform fuel quality tests Use your knowledge and critical thinking skills to identify possible engine performance problems associated with poor fuel quality. Tools Required: Safety glasses Tech 2 J Fuel Composition Tester J A Fuel Pressure Gage or equivalent J A Fluke 87 or equivalent 1. Turn ON the J Fuel Composition Tester. 2. Verify the fuel composition tester is operational by measuring the AC frequency output with a DMM. Caution Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete. 3. Install the J A Fuel Pressure Gage, ensuring that all safety precautions are followed. IMPORTANT: You will need to bleed the J A a few times in order to obtain an accurate fuel sample.

3 4. Close the bleed valve on the fuel pressure gage. 5. Place the bleed hose (1) of the fuel pressure gage into the 100 ml beaker (2). 6. Command the fuel pump relay ON with a scan tool. 7. Slowly open the bleed valve on the fuel pressure gage, until an adequate fuel sample is obtained. 8. If water appears in the fuel sample, clean the fuel system and replace the fuel in the vehicle

4 IMPORTANT: Do not allow any substances other than gasoline, ethanol/gasoline blends, air, or acetone into the test ports of the fuel composition tester. Contaminants in the fuel composition tester could result in misdiagnosis. 9. Pour the fuel sample from the beaker (1) into the J 44175, until the level of the fuel is at the top of each fuel test port (2). 10. Observe the diagnostic LEDs on the fuel composition tester. If the red fuel diagnostic LED is illuminated, a fuel contamination condition exists. Refer to Fuel System Cleaning. 11. Measure the output frequency of the fuel composition tester. 12.Subtract 50 from the reading on the DMM to obtain the percentage of alcohol in the fuel sample. Refer to the examples in the following table. 13. If the fuel sample contains more than 10 percent ethanol, replace the fuel in the vehicle. Student Workbook ASE 8 - Engine Performance Module 4 - Fuel Systems Gasoline Fuel Composition Frequency (Hz) Subtract 50 Ethanol Percent Test Examples Example A 50 Hz Example B 65 Hz Example C 129 Hz General Motors Corporation All Rights Reserved 4-4

5 Exercise 1-2: Fuel Quality Testing (Without Special Tool) Tools Required: Safety glasses Tech 2 J A Fuel Pressure Gage or equivalent 100 ml graduated cylinder with stopper Student Workbook ASE 8 - Engine Performance Module 4 - Fuel Systems Gasoline Repeat steps 3-8 from the previous exercise. 1. Using a 100 ml specified cylinder with 1 ml graduation marks, fill the cylinder with fuel to the 90 ml mark. 2. Add 10 ml of water in order to bring the total fluid volume to 100 ml and install a stopper. 3. Shake the cylinder vigorously for seconds. 4. Carefully loosen the stopper in order to release the pressure. 5. Re-install the stopper and shake the cylinder vigorously again for seconds. 6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid separation. If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and water, will be more than 10 ml. For example, if the volume of the lower layer is increased to 15 ml, this indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because this procedure does not extract all of the alcohol from the fuel General Motors Corporation All Rights Reserved 4-5

6 Exercise 1-3: Fuel Quality 1. Using one of the 2 previous methods for testing fuel quality, perform an analysis of the fuel specimens provided by your instructor. Sample # OK BAD Student Workbook ASE 8 - Engine Performance Module 4 - Fuel Systems Gasoline 2. What symptoms for might you expect for: a. sample 1 b. sample 2 c. sample 3 3. Find a document on esi that describes the process to clean the fuel system. Describe the process in your own words. Doc id# 2002 General Motors Corporation All Rights Reserved 4-6

Fuel System Diagnosis

Page 1 of 6 2001 Chevrolet Express Express, Savana (VIN G) Service Manual Engine Engine Controls - 5.0L and 5.7L Diagnostic Information and Procedures Document ID: 720867 Fuel System Diagnosis Circuit