Downloaded from www.Manualslib.com manuals search engine SERVICE DIAGNOSISÐGASOLINE ENGINES
PERFORMANCE DIAGNOSIS CHARTÐGASOLINE ENGINES
CONDITION POSSIBLE CAUSES CORRECTION
ENGINE WILL
NOT CRANK1. Weak or dead battery 1. Charge/Replace Battery. Refer to Group 8A,
Battery, for correct procedures. Check charging
system. Refer to Group 8C, Charging Systems, for
correct procedures.
2. Corroded or loose battery
connections2. Clean/tighten suspect battery/starter connections
3. Faulty starter or related circuit(s) 3. Check starting system. Refer to Group 8B,
Starting Systems, for correct diagnostics/procedures
4. Seized accessory drive
component4. Remove accessory drive belt and attempt to start
engine. If engine starts, repair/replace seized
component.
5. Engine internal mechanical
failure or hydro-static lock5. Refer to Group 9, Engine, for correct diagnostics/
procedures
ENGINE CRANKS
BUT WILL NOT
START1. No spark 1. Check for spark. Refer to Group 8D, Ignition
System, for correct procedures.
2. No fuel 2. Perform fuel pressure test, and if necessary,
inspect fuel injector(s) and driver circuits. Refer to
Group 14, Fuel System, for correct procedures.
3. Low or no engine compression 3. Perform cylinder compression pressure test. Refer
to Group 9, Engine, for correct procedures.
ENGINE LOSS OF
POWER1. Worn or burned distributor rotor 1. Install new distributor rotor
2. Worn distributor shaft 2. Remove and repair distributor (Refer to Group 8D,
Ignition System
3. Worn or incorrect gapped spark
plugs3. Clean plugs and set gap. (Refer to Group 8D,
Ignition System)
4. Dirt or water in fuel system 4. Clean system and replace fuel filter
5. Faulty fuel pump 5. Install new fuel pump
6. Incorrect valve timing 6. Correct valve timing
7. Blown cylinder head gasket 7. Install new cylinder head gasket
8. Low compression 8. Test cylinder compression
9. Burned, warped, or pitted valves 9. Install/Reface valves as necessary
10. Plugged or restricted exhaust
system10. Install new parts as necessary
11. Faulty ignition cables 11. Replace any cracked or shorted cables
12. Faulty ignition coil 12. Test and replace, as necessary (Refer to Group
8D, Ignition System)
ENGINE STALLS
OR ROUGH IDLE1. Carbon build-up on throttle plate 1. Remove throttle body and de-carbon. (Refer to
Group 14 for correct procedures)
2. Engine idle speed too low 2. Check Idle Air Control circuit. (Refer to Group 14,
Fuel System)
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DIAGNOSIS AND TESTING (Continued)
