Diesel Pumps

Quick question regarding diesel pumps for pumping out barges in tow…

I have been told by one operator that killing the pump with the red lever - the one I initially push down before pulling the motor to start it and what I am understanding to be compression and priming fuel (is this incorrect?) - is wrong and can compromise and/or severely damage the pump. The throttle goes from rabbit to turtle to “Stop” and according to this operator this is the correct way to kill the motor - to lower the throttle to “Stop.”

I recently observed another operator kill the pump with the red lever. I asked about this versus the “throttle-to-stop” and he essentially suggested it didn’t matter and the way he did it posed no harm to the motor.

One of these operators has been on tugs for quite some time. The other has a lot of time plus being a mechanic. Both have significant experience but apparently disagree on this. So which is it?

Anyone here have a take on this? I will find the manufacturer of the pump and contact them as well.


The red lever is a decompression lever, essentially relieving the cylinder of pressure to allow you to pull start the engine. Otherwise the compression of the cylinder would prevent you from pulling hard enough to start the engine. Unless you’re a supreme badass like me.

The guy advocating for stopping the engine with the throttle is correct. While it’s unlikely, it’s possible for damage to the decompression mechanism to occur if it’s used to stop the engine and it isn’t a sound practice.

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There’s also the point that stopping with the decomp dumps unburned diesel in the combustion chamber. Due to the small amounts involved this doesn’t lead to significant lube oil dilution, but it does lead to destruction of the oil film on the cylinder wall.

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