To determine if the fuel pump is causing excessive white smoke, perform the following steps:
1. Insert a piece of wire through the fuel pump flange drain hole; see Figure 10-1.

2. Crank the engine momentarily and feel for wire vibration.
[a] If the wire did not vibrate; refer to section 10.2.1.
[b] If the wire did vibrate, check for aerated fuel; refer to section 10.3.

Drive Hubs and Coupling Replacement
Perform the following for drive hubs or coupling replacement:
1. Replace the drive hubs or coupling; refer to appropriate service manual, fuel system chapter.
2. Verify the drive hubs and coupling replacement; refer to section
Engine Test with Replaced Drive Hubs or Replaced Coupling
Perform the following to determine if replaced drive hubs and coupling resolved excessive white
1. Start and run the engine.
2. Run the engine at idle with a no-load for approximately 5 minutes, allowing the engine
coolant to reach normal operating range.
3. Visually inspect exhaust for excessive white smoke.
[a] If the engine exhaust emission appears normal, no further troubleshooting is required.
Shut down the engine.
[b] If the engine exhaust emission is excessively white, shut down the engine. Check
for aerated fuel; refer to section 10.3.

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