Troubleshooting Engine Runs Rough If At Slow Speed - Check: If Fuel Injected, see EFI Di- agnostic Manual ‰ Idle speed and idle mixture. ‰ Engine timing and spark plugs. ‰ Fuel pump pressure. ‰ Water or contaminants in fuel. ‰ Carburetor or manifold vacuum leak. ‰ Internal carburetor fuel leak. ‰ See Electrical/Ignition/Fuel Service Manual . If At High Speed - Check: ‰ Air leak on suction side of fuel system. ‰ Too low octane fuel. ‰ Ignition system secondary circuit. ‰ Engine timing. ‰ Wrong model or size carburetor, improper main jets or power valve, defective secondary fuel circuit, or secondary vacuum diaphragm failure.
7743722 - Downloaded from www.volvopenta.com 13/05/2008 20:17:06 ‰ External canister and carburetor fuel filters. ‰ Fuel pump pressure. ‰ Engine compression. ‰ Water or contaminants in fuel, or water in cylinders. ‰ See General Information on page 17 and the Electrical/Ignition/Fuel System Service Manual . Engine Noises and Vibrations Valves - Hydraulic Lifters ‰ Rapping only when starting–oil too heavy for prevailing weather, var- nish on lifter, oil needs to be changed. ‰ Intermittent rapping–leakage at lifter check ball. ‰ Idle noise–excessive leak down rate, faulty check ball seat. ‰ Generally noisy–excessive oil in crankcase, stuck lifter plunger.
‰ Loud noise at operating temperature–scored lifter plunger, fast leak down rate, oil viscosity too light for prevailing weather or operating temperatures. ‰ See appropriate Engine section. Ignition System (Ping or Knock) ‰ Improper tuning. ‰ Incorrect spark plug wire routing. ‰ Use higher octane fuel. ‰ See Electrical/Ignition/Fuel Service Manual . VPA 7743722 English 10-2004 107