Fuel Pumps,submersible type

Can anyone validate some info concerning the modern day fuel pump in the fuel tank.
I have been told that its unwise to run the fuel level less than 1/2 a tank ,especially in
very hot weather. The reason is, the fuel is supposed to help cool the fuel pump. When
there is less than approx 1/2 tank ,the fuel pump begins to run hot and often times will
fail prematurely. This usually dosent happen the first or second time running low on fuel,
but over extended periods it will often happen. What I would like to know ,is there any truth to this matter.
Has anyone ever had it happen to them or know of it happening. ed

To the best of my knowledge, I have never had a pump failure because of low fuel. It is true that the fuel cools the pump, but the fuel flowing through the pump should do a good job of that. Some pumps are better than others, and you should stick with the AC Delco pumps if possible. There are some other good ones. I put a Bosch pump in my car, and the first one lasted about 30 days. The second one about 2 years. I will never install a Bosch pump in my car again.

Story 1: My 94 RMW was bought with 135k, pump went around 180k. Wife drives it until the fuel light goes on. Original pump. So on one hand you can say it burned out after 45k of abuse, but then again it went 180k in the first place. Zero warning on the failure

Story 2: I bought a 91 Olds (different pump) from a forum membr. He replaced the pump with an aftermarket one. 40K later it died on me with zero warning

Aftermarket is hit or miss. I buy Delco for these kind of parts or Delphi. That said the 91 got whatever autozone had at 9pm on a Friday night. I went Chinese over Bosch (have had quality issues like Fred's story with other parts of theirs. )

it's hearsay evidence,.
fuel pump failure seems to quite similar to the game of craps,..sort of like 4l60e failures,.sort of like waterpump leaks,. etc,. etc,. yada yada ,. ad infinitum,.

I don't think running low has anything to do with it. Even when it's very low, fuel is still flowing through the pump, cooling it.

Any fuel running through the pump is running through the pump part, not through the electric motor part. So, yeah, immersing the pump probably provides superior cooling to a certain extent. Does cooling necessarily equate to extended life? That I'm not so sure about, particularly if it is a quality built part with adequately sized components that can handle the generated heat. This is a sealed motor. Unlike an open frame motor that relies on cooling air flow through the motor by design, a sealed motor is supposed to be able to handle any internally generated heat. How many fuel pumps fail because of cooked internal insulation vs how many fail due to mechanical issues like worn bearings or brushes? It certainly wouldn't hurt anything to keep the tank above 1/4 full, but I don't think it will make a huge difference overall.

All that said, there's a few other good reasons to keep the tank closer to full than empty. Like moisture -- the more air above the fuel, the more water an ethanol blend fuel will absorb.  

I don't think keeping the fuel pump completely submerged helps in preventing it's demise. Personally everytime I've had one quit working was after I filled up. That's right fuel pump says "Oh the tank is full time to quit working now. BLAH! Have fun replacing the pump with 33 gallons of gas Jack@$$" rasafrasin. . .son of a. . .stupid. . .effin pump.

Maybe the pump being completely submerged in fuel and then sitting all night made it too cold? So cold it quit working?

scoffman wrote:

Personally everytime I've had one quit working was after I filled up.

You may be on to something Shawn. I had the same thing happen, just after I filled up. To make it worse, I was 200 miles from home.

Tom