I've got a 92f250 diesel naturally aspired pickup truck. If I begin to run short on fuel (on one of the tanks, remember its a ford), the engine will surge for a short period of time. This is usually my indicator to change the fuel supply over to the other tank and start looking for a fuel station. However, this is not a long surge, usually on the order of 10 to 15 seconds. I'm guessing that small sips of air are making it into the fuel rail and the injectors are obtaining better spray distributions because of the air being mixed in with the fuel.

Good luck!

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1995 E320 -171k-km
1995 S420 -333k-km