Fuel Cooling the Fuel Pump Question

So there are plenty of examples of pumps that use the liquid they are pumping as a coolant/lubricant and those pumps should not be run dry. No question there.

I've seen the suggestion that the Tacoma pump relies on being submersed for proper cooling. Several suggest you should keep at least a 1/4 tank to properly cool the pump. I have no doubt the pump will run cooler submersed.

My question is how much of a difference this actually makes? Anybody have links to tests or test results of submersible fuel pumps being run not submersed? I would guess the pump has been engineered to withstand whatever increased temps from not being fully submersed.

Wouldn't the ambient temperature then also have an effect? We regularly drive our Tacomas where the ambient temp of the gas would range from less than 25 degrees to over 90. I would think that range should cover the range of the pump being submersed or not.

For my use, since I regularly take trips, I rely on having a 20 gallon tank and not an effective 15.

 

Look at this way something submerged in liquid is going to cool down. Once it’s not submerged it heats up. The heat is what kills the pump.

Truthfully I wouldn’t want to test that theory. Keep gas in the tank. In the 4 years owing my 15 the gas light has never came on.

 

I have been wondering the same. What the hell is the point of having the extra fuel, if using it is going to damage the pump?

 

It's bullshit.

If you're not running the truck out of gas often running to E isn't going to damage it.

 

Just my opinion but I don't believe running your tank low damages or overheats the pump. If that were the case there would be warnings in the manual. Driving your truck and the subsequent sloshing in the tank probably keeps the pump pretty wet.
With that said running out of gas is very hard on your fuel pump not to mention the high risk of sucking crud into it. I never run my tank under a quarter but that's just my preference not anything to do with the pump.

 

Sediment in the bottom of the tank is also bullshit.

Where is the fuel pump? At the bottom of the tank. If sediment was such a huge problem it would ALWAYS be sucking up the sediment.

 

Fuel flowing THROUGH the pump cools it.

 

I don’t know if second gens are the same, but the 3rd gen has a 21 gallon tank, and my light comes on at under 18 gallons. 3 gallon reserve is excessive, and I want to know if I can reliably use it.

 

In a pinch to get home- sure use it. But why would you want to use the last three gallons if there is a gas station nearby anyway? Just don’t run it dry. If you run it until the truck sputters and dies you are likely damaging the fuel pump.

 

Yes, that is an easy way to figure out how much is left, not a great way to know if it damages the fuel pump. I am sure it can do it once, but what about five times, or ten?

 

I usually fill up at around a quarter tank just because things happen, even at home. If you need your truck at home all the sudden, you don’t want the gas light to be on when you start it.

The problem is I spend a lot of time in the backcountry. Routinely several hundred miles between any possible fuel source, often in 4wd. Knowing if I can reliably use the last 2 or 3 gallons is huge when you have another 30 miles to a gas station.

 

Return style systems like in the Tacoma actually run hotter than most. The unused fuel returns and warms up the tank. Overall the fuel is cooler in the rails, but warmer as a whole.

Problem with running super low is surging while cornering, also means more likey pick up the bottom tank sediment.

 

Back in the late 90's, I used to work for SiemensVDO and we made fuel pump voltage controls. Yes, the fuel does cool the pump. Performing over voltage tests would make the voltage regulator very hot. You won't find scientific tests as the design tends to be company proprietary. Also, Toyota doesn't design individual components like those. They design the systems and have tier 1 suppliers design the components to meet a specification. Fuel pumps do fail. Not as often as vacuum type from yesteryear but the still do.

 

Good question. That extra 4-ish gallon reserve we have in the 2nd gens can make a huge difference when in remote areas far away from gas stations.

Unfortunately I doubt you'll ever find a 'study' about this, just people who happen to believe one way or the other and are very convinced of that

 

Bolded statement has been proven, original foam filter deteriorates due to moisture, gets caught in the high speed impeller, breaks vanes of the impeller, those get pushed to the SAI valves, causing them to stick open and throw a code causing truck to go into limp mode. Replacing that foam filter with a uni breather eliminates the original one breaking apart causing the issue described above.



Back to the topic at hand. The running low thing is not necessarily as much of a heat issue, as the taco fuel pump is in a lil "bucket" that is constantly filled with fuel submersing the pump regardless of fuel level. (though less fuel in the tank means less fuel to dissipate heat from this bucket, so pump does technically run a lil hotter as fuel level goes down). Its more of a sediment in the tank that could be sucked up by running low, clogging the filter making the pump work harder.

I try to keep my truck above half a tank in my weekly travels, but that is mainly just in case there is an emergency and i need to GTFO or drive somewhere, i dont want to be having to stop for gas.

 

I for one hate dropping tanks or pulling beds to change pumps. I usually don’t let my truck run below half a tank.

 

Throw an extra five gallon tank in the bed when off-roading to ease the mind.

 

I ran a fuel pump on the shop floor hooked up to a car battery for a few min and that thing got hot. (Wasn’t a Tacoma fuel pump)

 

I do lots of fuel pump replacements on various vehicles, I've never looked down in there and seen any sediment. As mentioned above, the pump is in the bottom, if there was sediment down there it would be getting sucked up in the pump regardless of where the fuel level is at.

I work at a gas station. There are filters below the dispensers that get changed every 6 months. Hundreds of thousands of gallons of fuel go through these filters in that period. When we take them off, the diesel filters will have a little varnish in them, the gas filters dont have anything in them

 

Shit, the old man aint giving anyone a discount, not even employees!

Im in seattle, ill bet our price is right up there with you guys!