I have been reading the forum for a couple of months now and have learned a lot. I realize there are many of us running our gas tanks down to nearly empty. I have seen this in threads discussing hypermiling, x hundred mile/tank clubs, how far have you gone on a tank of gas, .... (you get the idea). Given all of this I have a question about the fuel pump in the HCHII. Does the fuel pump use gas for lubrication or for cooling? That is, if we continue to run our gas tanks nearly dry over and over again, are we damaging our fuel pumps in any way? I would find this information useful. If the fuel pump needs a certain amount of gas to function properly, I will stop running my tank below all bars going out on the fuel gauge.

 

Fuel pumps are self lubricated with synthetic parts, and do not need liquid for lubrication. They do not need to be cooled, and have thermal circuit protection.

Using all of the fuel in the tank will not have any issues for the fuel delivery system.

 

Except cavitation does damage to fuel pumps. So you really don't want to run them dry for that reason.

 

Not true. Modern pumps are designed to run dry or with partial liquid without any damage at all. Remember these parts are designed for AOW (all of world), and they have to operate in much more demanding environments than here in the US. Modern fuel systems do have no load and low pressure sensing, and the ECU will shut the pump off if it encounters a situation like that.

 

I think I err on the side of caution. Not sure what a HCH fuel pump costs but mine costs about a grand and it's NOT covered under warrantee by damage caused by running it dry.

 

Right. The low fluids warranty exclusion is intended to target claims from operating the car with no oil, not no fuel. The car tends not to work when no fuel is present.

Besides, the ECU shuts off the fuel pump if it runs dry. Same thing happens if the engine loses oil pressure, the fuel pump shuts off. In the end there are enough safeguards built into the car that this is a pointless discussion. It does not matter if you run the tank dry or if you fill it up every day, the fuel pump will not be harmed.

 

For what it's worth, the fuel pump is in fact cooled by the fuel around it. All in-tank electric fuel pumps are. I'm not so sure it's coincidence that some pumps last 200,000 miles plus and others only 60-100k...(all cars not just hybrids)...

That is all I have to offer for info on this subject.