My diesel lift pump on my old truck was frame mounted with the injection pump mounted on the engine. That pump got hot as hell.

 

A different application (gas station in tank pumps), but for a while I was an engineer at a pump company that made them and the flow of gas through the pump was what cooled it, not just being submersed.

I have also had external electric fuel pumps. Holley made them for a long time. Never had a problem with them either.

 

Well, I ran mine that low prior to installing a new fuel pump to support my blower set up. For normal day to day operation, I agree with you.

 

Let's leave the design of the equipment to the engineers. (I'm an engineer in the nuclear industry). The key issue is NPSH (net positive suction head) for the pump which is relationship of the level, specific gravity and temperature of the fluid. Last of the considerations is how hot the pump is going to operate at. Fuel filters are relied upon for any considerations of "crud" in the system. Pumping systems are typically designed well within any normal considerations >150 degF.

 

As a conclusion - when the low level light comes on head towards a gas station - or be ready to stand by on the side or the road.

 

True story. My son was always running the tank in his Camaro to E before filling up. And I kept telling him that wasn't a good thing to do, that his fuel pump was eventually going to fail if he kept doing that. Well, guess what? I had the (sort of) pleasure of telling him "I told you so." Of course, he didn't like hearing that. But he didn't like having to pay for the R&R even more. Lesson learned. The hard way.

 

I usually start looking for a Chevron station when the tank gets down to half-full. That gives me 1/4 tank to find Chevron specifically. Sometimes the price break can be significant on long (cross-country) trips--up to 30 cents per gallon difference in some places.

I think the 'half-tank practice' is good for keeping the pump cool and allowing me a better chance to shop prices. Locally, it's 12 cents a gallon merely for stopping at a different Chevron on the same route if I can wait that long.

 

Had a wife years ago who was seemingly incapable of putting gas in a car. Was always leaving me with a car with the guage on "E" or calling me 'cause she ran out of gas. I explained to her many, many times how hard on the fuel system and the engine this behavior was but, to no avail. Finally, one night she called me late at night to say I needed to come pick her up because my "stupid '55 Chevy (with the L88 spec 427 big block)" had the audacity to run out of gas on her. I picked her up, but it was too late to get gas anywhere (many years ago). I told her that it would have to sit there over night and woe be unto her if anything happened to it!!!!

The next morning, when she said let's go get your car.....I handed her a gas can and her coat and said, "You can't be bothered to put gas in the cars when they need it, here is what I have to do when you pull this stunt and I get stuck somewhere before I can get gas." She asked if I was going to drive her and I said, "No. You created this situation and you are going to walk your happy a$$ down there, fill up the can on the way and bring my hot rod home!!!"

It was hard for me to not fold and make her do it, but she never ran out of gas again!!!! She also didn't talk to me for about three days!! I guess between the two, some would call that a win/win situation.

She took me much more seriously about taking care of the cars after that as well.

DSTURBD

 

That was kind of my point: this whole meme of "don't let it get below X gallons or it'll hurt the fuel system/pump/whatever" is based on a bunch of hand-waving and zero actual evidence about how the critical bits were designed to work.

 

The economic argument for topping off actually makes sense, assuming there are large disparities in prices across your driving range. I normally only see 2-3 cents difference between the major brands in my area, which is usually less than the price jitter at the same station over the two weeks or so it takes me to go through a tank. YMMV, so to speak. (I could probably get no-name gas a bit cheaper but that opens up a completely different can of worms. )


But arguments based on equipment longevity are much less convincing. Seriously, does anyone here have any clue what temperature the pump actually operates at or how it varies with fuel level? Or any hard data showing how that variation correlates with pump life? Show me the numbers and I'll eat the crow.

 

That "suck dregs" argument get's me laughing every time. I hear it from those who haven't actually seen or worked on a C5 fuel tank pump. For those who don't know the fuel pump has a large white filter element that actually rests ON the VERY BOTTOM of the tank.... in essence pulling fuel from the bottom to start with... ALL THE TIME!

 

Not incompetent as I have noticed all makes and models have this same issue. If you are going to have an in tank pump, then no matter how you do it, the pump is going to become uncovered at some point.

Personally never having seen the insides of a C5 tank, I'm just asking what that level is. My ears tell me it is higher than 1/4 full. I also only see pumps failing after 10 years or more due to this, so who's to say it the pumps would last much longer anyways. I look at it as a preventive maintenance kind of thing.

 

They fail (or not) due to something, at wildly varying ages and usage patterns.


There's probably some critical internal part that gets corroded from being force-fed Techron.

 

The earlier comment about the tanks having internal "baffles" also gave me a chuckle.

 

I had a warranty claim denied on my 2001 when the pump failed because I only had a 1/4 tank of fuel when I brought it in.

 

The fuel pump in my son's Camaro failed way before the Camaro was 10 years old. If I remember correctly, it was probably no more than 5 years old at the time (but it's been some years since it happened so I don't remember exactly). At any rate, I'm 99% sure the pump failed because of the reason I stated in my previous post.

 

So there is no baffle to keep the sloshing to a minimum, and also to keep the fuel level float from jumpping around? I find that hard to believe. Every other tank I have actually seen in person had some sort of vertical baffling to prevent the float from swinging wildly. Not saying your wrong, but finding it odd that a vehicle designed to push the limits so to speak, wouldn't have baffles installed.

 

Those that wish top argue the benefits of not running your tank low are going to hate some of us when we give 'em the old "I told ya'"

The fact is we may be wrong, but then, why gamble when the odds pretty much suck?

 

That's odd: they usually don't show that much imagination when they're making up a bogus reason to deny a warranty claim.

 

OK then, don't believe it. No "baffles". BTDT.

Btw, the float arms move straight up or down, and any sudden changes can be compensated for in the pcm software.