2016 carrier 7500

Pump shouldn't be a problem remove the inlet line from the pump it's a 3/4 inch bolt there is a fuel filter screen that threads into it unthread and make sure it's not clogged with sludge if so blow it out with solvent or air reassemble with new copper washers thermo king part number 55-2208 pressurize fuel tank through tank vent prime and check for any leaks

 

It happens on all models tighten all the brass fuel fitting you could pull the pick up line out of the tank as well and make sure its cut on an angle and isn't forced against bottom of tank seen that many times but pressurize tank and look for any small leaks for sure

 

Buy a spare fuel tank cap. Drill a hole in the center-7/16" bit if I remember-and buy a 1/4" NPT tap from a hardware store, and tap away. The size of the drill bit to use will be on the package of the pipe thread tap. Screw in an air line quick connect with and pressure away with a cheap air pressure regulator from Harbor Freight set at 40 lbs. You might see fuel at leaking at the ends of the supply and return lines. If not visible, I would just tighten down on all of the ferrels around all of the line's ends. If it still loses a little prime sometimes-particularly in cold temps-cut the ends of the fuel lines back some and put new ferrels on at the same time. The cap and the pressure regulator (for pressurizing while out on the road with air from your truck that is governed at approx 120 lbs) is good to keep in the truck. Then you don't have to hassle with the little primer pump.

 

Keep in mind, a leak anywhere in the fuel delivery system (including return line) can cause it to lose prime. I learned this the hard way as my trucks engine kept increasingly losing prime, and I eventually figured out there was a small crack in the return line coming from the head, going to the fuel tanks. It wasn't until I put pressure to the fuel system with the truck engine off that I saw fuel spraying from that line. I would simply just change lines, starting with the one between the filter housing and the pump, one at a time and see if the problem goes away.

 

@reeferwrencher
Why Thermo King Whisper Units are priced lower? What kind of problems these get along the way?

 

Because they're old units and not nearly as good as the sb210/230 or sb310/330