I wouldn't worry about the hissing noise just yet, or that you have a serious problem. There is no pump other than the lift pump and the IP. I would check your GP system. In cold weather the GP's are always the first thing to check out. Even one bad plug can cause hard starting issues. I'd make sure each plug is getting 12 volts. If on isn't check the resistance of the wire going to that plug to see if you have a bad wire. if the are all getting 12v, I'd pull each one out and give them 12 volts and see if they glow bright orange. If not you have a bad plug.

Also if you are running biodiesel and it's cold you may have clogged filters.

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