Letting the fuel level get low in the tank...Bad?

[econ]

To be clear, I am NOT talking about running out of gas.

I understand that running out of gas would be detrimental to the health of the fuel pump as the fuel acts as a lubricant for the pump. The pump running without fuel flowing through it will damage it to some extent.

Moving on...

I am talking about letting the level get very low. Lets say low enough for the first fuel level indicator light come on and alert you to the fact that you need to add fuel to the tank.

This means there is about 3 gallons in the tank. Maybe a little more, maybe a little less.

I see two ideas tossed around on this subject:

1) Letting the level get that low will cause the pump to send debris onto the fuel lines. Not good! Keeping the tank fuller will eliminate this problem.

2) The pump relies on being fully submerged in fuel to stay cool. Letting the fuel level drop down to a very low level will result in a portion of the pump being out of the fuel thus taking away the pumps cooling system and causing the pump to run at elevated temperatures shortening it's life.



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Thinking this through....

The problem I see with #1 is that the fuel pump draws from the bottom of the gas tank anyways, regardless of how full it is so the notion that the pump will pick up more debris on a low tank than a full tank does not add up. Unless I am missing something.

As for #2, I can see some merit to argument. But, in the case of the 5th generation Camaro SS, how low exactly would the fuel level have to be in order for the cooling of the pump to become a problem? Does our fuel pump even run hot and need cooling?


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I understand that keeping the tank full enough to prevent this altogether would be a good way to go.

[CamaroCracka]

You have the right idea. Running fuel from the bottom of the tank increases the likelihood of picking up trash or even some water if it got in there. It would also cover less of the fuel pump providing less cooling.

I don't think running from a full tank down to the light regularly would be a problem. There are still three gallons when the light comes on. Running it continually below a quarter tank like a teenager could present problems, particularly if you accelerating/cornering hard and the fuel is moving around.

[11/SS/RS]

I guess a good question would be how many actual pump failures have there been from fuel pumps picking up debris? How many failures from being run low on fuel?

Id venture to say its hard to prove either way.... It would be interesting to know what the manufacturers of these pumps would have to say about how many hours or how many gallons of pumped fuel are they supposed to last. IOW, is there a predetermined life span to the pumps accounting for normal use in a daily driven car?

[ABM2SS]

Water is more dense than gasoline so it goes to the bottom of the tank where the pick-up is. Thus, you wouldn't pick-up more water on a low tank level.

I have run my tank down well below the low fuel warning without issue. Once, going by last miles-to-empty (once you get the low fuel warning it no longer gives you the count-down to empty on 5th Gen Camaros) I calculate that I had less than 1/2 gallon left when I filled-up.

[Chester]

Back in the 80's I had a friend with a new Monte Carlo, Seemed like his tank was always between empty and quarter. Remember he was changing fuel filters quit often. Running tank low more chance for condensation.

[FasNuf]

The question is what kind of pump is the OP talking about? OEM has a fuel bucket so the pumps are always submerged in fuel until the tank is empty. This applies also to the Deatschwerks pump like I'm running. If he's talking about a Fore system or something similar where the pumps aren't in the bucket, then they won't be getting cooled by the surrounding fuel, this is why they say to keep the tank at least half full. As far as pulling junk off the bottom, I don't know of a pump that doesn't have the pump sock on the bottom of the pump so it's going to be at the bottom anyway. Maybe I'm missing something here, let me know.

[0stones0]

Most fuel systems have a “sump” area on the very bottom of the tank that is the lowest part. The inlet on the pump is usually just above this, so that debris and water don’t enter the system.

[FasNuf]

Originally Posted by 0stones0

Most fuel systems have a “sump” area on the very bottom of the tank that is the lowest part. The inlet on the pump is usually just above this, so that debris and water don’t enter the system.

That’s not how my OEM pump and tank was but maybe the SS is different.

[Mouse330]

It doesn't matter if you have a 1 gallon tank or a 1000 gallon tank the water will be on the bottom sucked up by the pump

[0stones0]

Originally Posted by FasNuf

That’s not how my OEM pump and tank was but maybe the SS is different.

Have never had the tank out so, couldn’t say for sure. More than likely, it’s as you state. Seems really strange that they wouldn’t have such a “sump” area though. It’s very common in aircraft. I see it all the time.

[FasNuf]

Originally Posted by 0stones0

Have never had the tank out so, couldn’t say for sure. More than likely, it’s as you state. Seems really strange that they wouldn’t have such a “sump” area though. It’s very common in aircraft. I see it all the time.

Our tanks actually have two sides, one on each side of the driveshaft tunnel. Theres a tube that goes from the drivers side over to the passenger side where the fuel pump is located inside a bucket. As the engine runs the fuel gets pumped out of the bottom of the bucket that's always overflowing. This keeps the pumps cool and from starving of fuel when low on gas driving up a steep incline. If I'm not mistaken, the bucket gets filled by a venturi and I'm not exactly sure how all that works, but the fuel pump inlet is at the bottom of the pump itself and is covered with a sock prescreen. So running a pump not submerged creates heat and wouldn't be recommended for longevity.

[econ]

Originally Posted by FasNuf

The question is what kind of pump is the OP talking about? OEM has a fuel bucket so the pumps are always submerged in fuel until the tank is empty. This applies also to the Deatschwerks pump like I'm running. If he's talking about a Fore system or something similar where the pumps aren't in the bucket, then they won't be getting cooled by the surrounding fuel, this is why they say to keep the tank at least half full. As far as pulling junk off the bottom, I don't know of a pump that doesn't have the pump sock on the bottom of the pump so it's going to be at the bottom anyway. Maybe I'm missing something here, let me know.

OEM pump and tank for a 2013 Camaro SS

[econ]

Originally Posted by FasNuf

Our tanks actually have two sides, one on each side of the driveshaft tunnel. Theres a tube that goes from the drivers side over to the passenger side where the fuel pump is located inside a bucket. As the engine runs the fuel gets pumped out of the bottom of the bucket that's always overflowing. This keeps the pumps cool and from starving of fuel when low on gas driving up a steep incline. If I'm not mistaken, the bucket gets filled by a venturi and I'm not exactly sure how all that works, but the fuel pump inlet is at the bottom of the pump itself and is covered with a sock prescreen. So running a pump not submerged creates heat and wouldn't be recommended for longevity.

Having a hard time envisioning this "bucket" you speak of.

So as long as the "bucket" is full, cooling capacity for the pump would be at 100% then right? How big is the bucket and how much fuel would it hold?

[econ]

Originally Posted by CamaroCracka

You have the right idea. Running fuel from the bottom of the tank increases the likelihood of picking up trash or even some water if it got in there.

What would you say to the theory that since the fuel pump draws from the bottom of the fuel tank and debris/water being heavier than the gas causes the debris/water to settle towards the bottom, the fuel pump will pick up an equal amount of debris/water with a full tank as it would with a near empty tank?