We recently attended a vessel to investigate a hot start issue on one of their Caterpillar 3408 engines.
The operator reported that the engine started fine from cold but reported issues when the engine reached optimum operating temperatures.
To allow the hot start investigation to begin, the engine was started and run for approximately 15 minutes off load and brought to its normal operating temperatures.
During this time, our engineer noted the oil temperature reached 62°C and oil pressure just under 60 psi.
The action of the governor and fuel pump were observed as the engine was shut down. Upon restart attempt, our engineer found the governor linkage would not move.
On the 3rd start attempt, he manually assisted the governor and the engine started and ran, with the governor then operating as expected.
After disconnecting the fuel pump linkage, he tested the travel angles on the fuel pump and governor.
The governor had 40° of rotation as expected and the fuel pump had approximately 60°, though during operation only travelled 10°, (also as expected.)
It was found that the fuel pump arm had approximately 10mm of ‘dead rack’ which has not been correctly compensated for in the set-up of the linkage.
The usual cause for this is the governor not receiving enough oil pressure to operate it during cranking when the oil is warmer and therefore thinner.
This is because the fuel pump and governor are not correctly set up for each other so the fuel pump does not supply fuel during cranking when it should.