4A 6 EMISSIUN C0llTll0LS EXllAl ST SYSTEMS VI Sorvlca Dlagnnsls lllonllnuadl Condition Possible Cause Correction INTAKE BACKFIRE 1 Improper ignition timing 1 Adjust timing 2 Faulty accelerator pump discharge 2 Repair as necessary 3 Improper choke operation 3 Repair as necessary 4 Defective EGR CTO 4 Replace EGR CTO 5 Defective TAC unit 5 Repair as necessary 6 Lean fuel mixture 6 Check float level or manifold vacuum for vacuum leak EXHAUST BACKFIRE 1 Vacuum leak 1 Check manifold vacuum and repair as necessary 2 Faulty diverter valve 2 Test diverter valve and replace as necessary 3 Faulty choke operation 3 Repair as necessary 4 Exhaust leak 4 Locate and eliminate leak PING OR 1 Incorrect ignition timing 1 Adjust timing SPARK KNOCK 2 Distributor centrifugal or vacuum 2 Check advance and repair as advance malfunction necessary 3 Excessive combustion chamber 3 Use combustion chamber cleaner deposits 4 Carburetor set too lean 4 Adjust carburetor 5 Vacuum leak 5 Check manifold vacuum and repair as necessary 6 Excessively high compression 6 Check compression and repair as necessary 7 Fuel octane rating excessively low 7 Try alternate fuel source 8 Heat riser stuck in heat on 8 Free up or replace heat riser position SURGING CRUISING 1 Low fuel level 1 Adjust fuel level SPEEDS TO TOP SPEEDS 2 Low fuel pump pressure or volume 2 Replace fuel pump 3 Metering rod s not adjusted 3 Adjust metering rod s properly YF Model Carburetor or 4350 Model Carburetor 4 Improper PCV valve air flow 4 Test PCV valve and replace as 5 Vacuum leak 5 Check manifold vacuum and repair as necessary 6 Clogged main jet s 6 Clean main jet s 7 Undersize main jets 7 Replaw maifl letlsl 8 Blocked air bleeds 8 Clean air bleeds 9 Clogged fuel filter screen 9 Replace fuel filter 10 Restricted air cleaner 10 Clean or replace air cleaner