Automotive Service Technology Section C/Automotive Special Problems
Course HS Title:
Automobile Service Technology/Special Problems
KCTCS Courses included in HS Title: (Lesson is prepared for course highlighted.)
KCTCS Course No.
KCTCS Course Title
This lesson will instruct the student on how to Differentiate between electrical and engine mechanical problems that cause a slow-crank or a no-crank condition. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in an Automotive Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Differentiate between electrical and engine mechanical problems that cause a slow-crank or a no-crank condition.
Given the proper tools and instruction, the student will be able to differentiate between electrical and engine mechanical problems that cause a slow-crank or a no-crank condition, and pass a written test covering the task with 100% accuracy.
Explain to students that customer complaints concerning the starting system generally fall into four categories: no crank, slow cranking, starter spins but does not turn engine, and excessive noise. This lesson will deal with No Crank/Slow Crank.
SAFETY TIP: Instruct Students to always wear eye protection during any operation. This would include operating power tools, working around a running car engine, carrying batteries, etc. Never work under a vehicle not supported by jack stands. It is not safe to work under a vehicle supported by only by a floor jack. Report unsafe conditions to your instructor. If you notice any type of hazard, let your instructor know about it.
Instruct Students that as with any electrical system complaint, a systematic approach to diagnosing the starting system will make the task easier. First, the battery must be in good condition and fully charged. Perform a complete battery test series to confirm the battery's condition. Many starting system complaints are actually attributable to battery problems. If the starting system tests are performed with a weak battery, the results can be misleading. Remind students that the conclusions may be erroneous and costly.
Before performing any tests on the starting system, inform students to first begin with a visual inspection of the circuit. Have them repair or replace any corroded or loose connections, frayed wires, or any other trouble sources. The battery terminals must be clean and the starter motor must be properly grounded. Instruct students that if the customer complains of a no-crank situation, attempt to rotate the engine by the crankshaft pulley nut. Rotate the crankshaft two full rotations in a clockwise direction, using a large socket wrench. Explain to students that if the engine does not rotate, it may be seized due to its being operated with no oil, hydrostatic lock, or broken engine components.
Inform students that a slow crank or no-crank complaint can be caused by several potential trouble spots in the circuit. Excessive voltage drops in these areas will cause the starter motor to operate slower than required to start the engine. The speed that the starter motor rotates the engine is important to engine starting. If the speed is too slow, compression is lost and the air/fuel mixture draw is impeded. Most manufacturers require a speed of approximately 250 rpm during engine cranking.
Instruct students that if the starter spins but the engine does not rotate, the most likely cause is a faulty starter drive. If the starter drive is at fault, the starter motor will have to be removed to install a new drive mechanism. Before faulting the starter drive, also check the starter ring gear teeth for wear or breakage, and for incorrect gear mesh of the ring gear and starter motor pinion gear.
Possible Causes of No Crank: 1. Dead battery. 2. Loose or dirty battery connections, 3. Defective starter switch. 4. Defective starter solenoid. 5. Defective or improperly adjusted Neutral Safety Switch 6. Starter terminal post shorted. 7. Defective starter.
Possible Engine Related Causes of No Crank: 8. Engine bearings seized. 9. Engine bearings too tight. 10. Piston-to-cylinder wall clearance too small. 11. Water pump frozen 12. Insufficient ring clearance. 13. Hydrostatic lock (water in combustion chamber)
Other Possible Causes: 14. Starter drive pinion jammed into flywheel teeth. 15. Starter armature seized.
Possible Repairs for Listed Causes of No Crank. Numbers correspond with the number listed above: 1. Charge or replace battery. 2. Clean and Tighten Connections. 3. Replace Starter Switch. 4. Replace Solenoid. 5. Replace or adjust switch. 6. Replace insulation. 7. Rebuild or replace starter. 8. Grind Crankshaft. Replace Bearings. 9. Install Correct Bearings. 10. Fit Pistons Correctly. 11. Thaw. Place antifreeze in cooling system. 12. Install correct rings. 13. Remove water and repair leak. 14. Remove starter. Install new pinion and replace starter ring gear if needed. 15. Rebuild or replace starter.
Possible Causes of Slow Crank: 1. Low battery state of charge. 2. Loose or dirty battery cable connections. 3. Battery capacity too small. 4. Dirty or burned switch contacts.
Possible Engine Related Causes: 5. Excessively heavy engine oil. 6. Starter motor defective. 7. Engine bearings, pistons, or rings fitted too close. 8. Cold, heavy oil in manual transmission. 9. Extreme cold weather.
Possible Repairs for listed Causes of Slow Crank. Numbers correspond with the numbers listed above.: 1. Charge battery. 2. Clean and tighten connections. 3. Install larger capacity battery. 4. Replace switch. 5. Drain and install lighter oil. 6. Rebuild or replace starter. 7. Provide proper clearance. 8. Hold clutch in while cranking. 9. Preheat engine prior to cranking.
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Evaluation and feedback Prior to Testing or Lab Work
Objective 1. / Formative assessment / Instructor will observe students as they practice the procedure to assure correct procedure and safety practices are being followed. A checklist will be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.
STUDENT ASSESSMENT: (Assess student progress with performance criteria.)
Objective 1 / Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)