4-4
Table 4-1. Fuel System Troubleshooting (cont.)
Table 4-2. Vacuum Piston Assembly Troubleshooting
POOR PERFORMANCE ON ROAD
Check for:
1. Idle speed improperly adjusted.
2. Inlet system air leak.
3. Restricted fuel tank vent system.
4. Dirty or damaged air cleaner element.
5. Enrichener valve not seated or leaking.
6. Restricted fuel supply tract.
7. Plugged bowl vent or overflow.
8. Loose or plugged fuel and air jets or passages.
9. Worn or damaged needle or needle jet.
10. Vacuum piston assembly malfunction.
11. Accelerator pump inoperative.
Remedy:
1. Adjust operating idle speed.
2. Correct as required.
3. Correct restricted hose. Replace vapor vent valve.
4. Clean or replace.
5. Adjust, clean or replace.
6. Correct and clear restriction.
7. Clean and clear passages.
8. Clean, clear and correct as required.
9. Replace assembly.
10. See Vacuum Piston Troubleshooting below.
11. Repair as required.
POOR HIGH-SPEED PERFORMANCE
Check for:
1. Inlet system air leak.
2. Enrichener valve not seated or leaking.
3. Restricted fuel tank vent system.
4. Restricted fuel supply tract.
5. Dirty or damaged air cleaner element.
6. Plugged bowl, vent or overflow.
7. Worn or damaged needle or needle jet.
8. Vacuum piston assembly malfunction.
9. Loose or plugged main jets or passages.
10. Improper fuel level.
11. Accelerator pump inoperative.
Remedy:
1. Clean or replace.
2. Adjust, clean or replace.
3. Correct restricted hose. Replace vapor vent valve.
4. Correct and clean restriction.
5. Clean or replace.
6. Clean and clear passages.
7. Replace assembly.
8. See Vacuum Piston Troubleshooting below.
9. Clean, clear and correct as required.
10. Adjust float level.
11. Repair as required.
PISTON DOES NOT RISE PROPERLY
Check for:
1. Piston atmosphere vent blocked.
2. Diaphragm cap loose, damaged or leaking.
3. Spring binding.
4. Diaphragm pinched at lip groove.
5. Torn diaphragm.
6. Piston binding.
7. Piston vacuum passage plugged.
Remedy:
1. Clear vent.
2. Tighten or replace cap.
3. Correct or replace spring.
4. Reposition diaphragm lip.
5. Replace piston diaphragm assembly.
6. Clean piston slides and body or replace piston.
7. Clean and clear passage.
PISTON DOES NOT CLOSE PROPERLY
Check for:
1. Spring damaged.
2. Piston binding.
3. Piston diaphragm ring dirty or damaged.
Remedy:
1. Replace spring.
2. Clean piston slides and body or replace piston.
3. Clean or replace piston.
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