| HOT STARTING SYMPTOM |
- Engine cranks but will not start
|
1) Engine flooded, fuel level too high |
1) Adjust float drop and setting; inspect needle and seat for proper seating; check for dirt |
| 2) Fuel vapors in carburetor bowl |
2) Inspect bowl vent operation and correct |
| 3) Fuel line hot, touching engine block or exhaust |
3) Inspect and reroute fuel line |
| COLD ENGINE DRIVEABILITY SYMPTOM |
- Engine stalls when put in gear
|
1) Incorrect choke vacuum kick setting |
1) Inspect and correct |
| 2) Fast idle RPM too low |
2) Adjust fast idle RPM |
| 3) Incorrect fast idle cam setting |
3) Correct cam positioning |
| 4) Improper choke adjustment |
4) Adjust choke |
- Hesitation, stalling during acceleration
|
1) Defective choke control switch |
1) Test, replace if needed |
| 2) Incorrect choke vacuum kick setting |
2) Adjust vacuum kick |
| Backfire |
3) Low fuel/float level |
3) Adjust float drop and setting; check fuel level |
| Stumble |
4) Faulty accelerator pump or blocked pump discharge |
4) Inspect, adjust pump stroke, plunger; test fuel discharge quantity; check pump spray direction |
| 5) Secondary throttle not closed, wrong lockout adjustment |
5) Adjust secondary throttles |
| 6) By-pass holes and ducts blocked |
6) Clean preheater assembly |
| 7) Incorrect intake air preheater setting |
7) Set to proper season |
| 8) Incorrect carburetor synchronization; on dual carburetor models |
8) Synchronize carburetors |
| 9) Main and/or air corrector jets blocked |
9) Inspect and clean |
| 10) Faulty power valve |
10) Replace |
| 11) Plugged heat crossover system |
11) Clean and test heat crossover valve; clean passages |
| WARM ENGINE DRIVEABILITY SYMPTOM |
- Low power, Surging high speed operation
|
1) Main jets clogged |
1) Clean |
| 2) Fuel filter dirty (restricted) |
2) Replace filter |
| 3) Pinched, blocked fuel line |
3) Inspect and repair |
| 4) Air cleaner dirty (restricted) |
4) Replace air cleaner |
| 5) Faulty power valve |
5) Adjust or replace |
| 6) Throttle linkage out of adjustment; not opening fully |
6) Inspect and adjust linkage |
| 7) Low fuel pump output |
7) Replace after testing |
| 8) Improper fuel level |
8) Adjust float/fuel level |
| 9) Carburetor seals leaking |
9) Replace seals, gaskets |
- Carburetors cannot be synchronized
|
1) Weak return springs |
1) Replace springs |
| 2) Linkage binding, needs adjusting |
2) Inspect, clean and adjust |
| 3) Blocked idler jets |
3) Clean jets |
| (Dual Carburetor models) |
4) Faulty mixture control screw(s) |
4) Replace screw(s) |
| 5) Faulty carburetor seals |
5) Replace seals as needed |
| 6) Vacuum leak(s); Check for leak at brake unit |
6) Locate and correct leak |
| 7) Carburetors not tightened to intake manifold properly |
7) Evenly tighten carburetor screws; check torque |
|
|
1) Fuel system leak |
1) Locate and repair leak |
| 2) Wrong size jets |
2) Install correct jets |
| 3) Faulty fuel inlet needle and/or seat |
3) Replace needle and seat |
| 4) Fuel mixture setting incorrect |
4) Adjust idle RPM and mixture |
| 5) Dirty air cleaner |
5) Clean or replace |
| 6) Excessive accelerator pump discharge |
6) Test and adjust fuel discharge quantity |
| 7) Intake air preheater not ON or OFF according to season |
7) Temperature above 50°F (10°C), preheater should be OFF |
| 8) Enrichment system does not switch off |
8) Free up vacuum plunger |
| 9) Choke valve not opening all the way |
9) Adjust choke valve |
| 10) Secondary throttle opens too early |
10) Inspect secondary throttle linkage, adjust or repair as needed |