Running Fuel Level to Near Empty ?

[Ejs4029]

Is there any truth to this ? And if so does it also apply to diesel engines ?


That the gas in your car “acts like a coolant for the electric fuel-pump motor, so when you run very low, this allows the pump to suck in air, which creates heat and can cause the fuel pump to wear prematurely and potentially fail.”

I’ve read where you should never go below a ¼ tank…I’ll admit on both my gas engine and diesel vehicles on occasion I have let the level get down to the low fuel light before re-fueling if so maybe it’s habit that should be avoided curious to know other opinions on the subject.

[spock123]

That’s the first time heard that.

[A32Deuce]

I replaced the fuel pump in two used vehicles. We generally refill at a quarter tank. If running on fairly level interstates getting down to the light coming on may not be bad. But around town, turns and bumps can move fuel from the pickup and run the pump dry. Fuel is for cooling and lubricating the pump.

[Kaadk]

I've never run right down to empty that I can tell. In the old truck there were a few times that I've run it right down to the point the DTE quit calculating and just displayed "Fuel Up NOW!", and even at that, I still probably had about 4 gallons left in the tank, based on the truck having a 32 gallon tank and it only taking 28 gallons on that fill up.

But those were rare occasions. I try to start thinking about fuel if I'm ever below 1/2 a tank. And when I'm towing, I check for fuel options whenever we take a bathroom break. If I'm off the highway and I see a gas station I think I can get in and out of with the trailer attached, I'm gonna top off, even if it's still got over 3/4 of a tank left, because you never know what the next stop is going to be like.

Especially with this current setup. I'm getting worse MPG towing this fiver with this super duty than I did towing the TT with with my 1/2 ton. Not by much maybe 9.x then to 8.x now, but it's enough of a difference that heading to some campgrounds I did last year where I knew I could make it on a tank of gas if needed, this time, I'm not sure.

[ScottBrownstein]

There is some truth to this as the pump sits in a "can" surrounded by fuel. The fuel does help to cool the pump. F-53 pumps from 1990 to at least 1998 0r 1999 experienced these failures and they are not easy to fix (drop the tank to get at the top.) I worried about this on my 1997 Bounder all the time but never experienced it personally. Sold it in 2015 in trade for a Georgetown 335DS. When the weather is very hot I would always try to run above 1/4 tank for this reason anyway.

[Scrapper]

Originally Posted by Ejs4029

Is there any truth to this ? And if so does it also apply to diesel engines ?

That the gas in your car “acts like a coolant for the electric fuel-pump motor, so when you run very low, this allows the pump to suck in air, which creates heat and can cause the fuel pump to wear prematurely and potentially fail.”

I’ve read where you should never go below a ¼ tank…I’ll admit on both my gas engine and diesel vehicles on occasion I have let the level get down to the low fuel light before re-fueling if so maybe it’s habit that should be avoided curious to know other opinions on the subject.

I have heard that ever since car makers started putting the fuel pump in the tanks.

Now the question is do the diesel engines still have the fuel pump/injector pump on the side of the engine or have they placed the fuel pump in the fuel tank? I believe diesels still have a injector pump. It takes a lot of pressure to vaporize diesel fuel. Many diesels need to be primed by either a electric pump (in the tank?) or a small hand pump on the side of the injector pump if you run out of fuel. I remember a IH 1466 tractor that you would crank the engine with the starter for 5 to 10 minutes to prime the fuel system.

[007matman]

In the two that I've ever replaced, I will confirm that both times they failed they were both low on fuel when they did.

No, it wasn't the same vehicles.. :-)

[elchilero53]

I always refuel at 1/4 tank never below. Not only does this avoid problems with the pump, but it keeps me with enough fuel that if I have to leave the house in a hurry, I am not short. If it gets that low, I head straight to the gas station. While pulling a trailer, I start looking at 1/2. That gives me breathing room in case there isn't a gas station immediately ahead.

[Paulie1138]

Yes, I remember tech bulletins recommending to avoid running low on gas engines with the pump in the tank. Depends on the design of just where the pump is located as to just how low you can go. Typically, between 1/4 and 1/8 tank. The gas does act as a coolant for the pump.

Diesels, it depends. My 7.3 has the pump outside the tank. But Ford suggests not to run it dry.

[Splitshaft]

Most, but not all fuel tanks have a “sump” to keep air out of the fuel pickup when accelerating, stopping, and turning corners, even when there is much less than a quarter tank of fuel, that includes virtually until the fuel tank is empty. That said, allowing air to enter a diesel fuel injector or injection pump can reduce power or even stall a diesel engine making it difficult or impossible to restart without bleeding the fuel system of air. Gasoline is a totally different beast from diesel fuel. Gasoline is very volatile and boils easily, especially now that it contains alcohol. Early gasoline engines suffered from “vapor lock” (vaporized gas in the fuel line before the fuel pump) even when the fuel tank was full due to gasoline’s volatility and heat. Fuel return lines on the early gasoline engines helped reduce vapor lock. When fuel injection became popular on gasoline engines, they required higher pressure electric fuel pumps in or outside the fuel tank, a fuel pressure regulator on the engine returned fuel form the fuel injector or injector rails to the fuel tank. This system added a lot of heat to the fuel in the fuel tank. So much so, these fuel systems could actually boil the gasoline in the fuel tank, even when the fuel tank was half full. Boiling fuel in the fuel rails supplying the gasoline fuel injectors can cause engine roughness, loss of power, and engine stalling. As fuel injection systems on gasoline system become more advanced, the fuel return was eliminated along with engine heat being added to the fuel in the fuel tank resulting in fewer fuel heat related problems for gasoline engines. The only real risk of running a fuel tank low on fuel, is running out of fuel between fuel stops. A lot has gone into the engineering and design of fuel systems to allow all the fuel in the tank to be used when required.

[TitanMike]

When on the highway I always make sure to fuel up when the gauge hits 1/4 tank. Not so much to protect the fuel pump but to avoid the likelihood I might have to walk because I misjudged how far it was to the next station.

There were a lot of problematic in tank fuel pumps in the early through mid 90's. When the tank fuel level was low they often vapor locked. A combination of the fuel blend and heat in the pump. Keeping the tank well above the 1/4 tank level helped but didn't eliminate the problem.

[Wolverine 1945]

I remember years ago they always said if you bough a older vehicle never run it to empty because you did not know what was down there !!!

[Paulie1138]

Last year, my daughter ran over some road debris that put a gouge into her 2014 fuel tank. There was a very slight seep that evaporated before it would even drip. I removed the tank to repair. Drained out the gas. Pulled the pump. Decided to test it. Yes, it got quite warm-almost too hot to touch after less than 10 seconds of run time. Current draw was within spec. Yea, I know, the pump seldom runs that long while in service. Car had 28,000 miles. I will still suggest to keep 1/8to 14 full to make it last. I do that anyway, so I am never in the position to HAVE to get fuel. One thing I was never able to find was what the normal run temp of the pump. But hot as tested cannot be good for long term use.

[spock123]

When on the road pulling the camper I stop when the gauge says half. I have a auxiliary tank but you never know and if the tank should not work as it should then I want to have enough diesel to find a station

[Wolverine 1945]

Damm near ran out this Spring,,, pulled out of a Campgrounds in WI on south bound I90,
I was sure there would be Gas stations down the road shortly,,, there was not !!!
I had to get off the HWY and head for a small town,,, 3 or 4 miles down the road I found a Gas station,,, put 54 gallons in our 55 gallon tank !!!
NEVER AGAIN !!!

[Oaklevel]

I was told by several Ford mechanics several years ago that if you run the 7.3 diesel dry the injector pump would go and back then a automatic $800 replacement.

So never wan't to take the chance.

[twdenman]

Most Class A generators won’t start when fuel is less than 1/4 tank.

[A32Deuce]

Class C also.

[Paulie1138]

Agree on the 7.3. Never go low is the way to go.

[wanderingbob]

Click and Clack say that the fuel cools and protects the pump!