: When to Refuel?



300:29:1
04-04-13, 08:51 PM
So there was a thread discussing fuel pump failures and the stress that running the fuel tank low places on the fuel pump. I've looked in the owner's manual and can't find anything with regard to letting the fuel level get below a certain point. I'm wondering if there's anything in writing, as opposed to speculation and conjecture, with regard to this issue. Some here have said that half a tank is the threshold for refueling. I have always let my fuel level drop to at least 1/4 before refueling on all of my vehicles without any adverse effects, and I've never seen anything from an auto manufacturer that stated this may cause problems. I know we have some mechanics in here as well. So please tell me how low is too low,why, and cite a source. I don't want to hurt my SRX, but don't feel like running to the gas station all the time.

redvett94
04-05-13, 11:55 AM
First of all the intank pump is lubricated by the fuel and no fuel no lub and cooling. Second the tank pump only pumps fuel to the secondary hi pressurepump and if it goes dry you going to be replacing both pumps. Can you spell EXPENSIVE.

300:29:1
04-05-13, 12:47 PM
First of all the intank pump is lubricated by the fuel and no fuel no lub and cooling. Second the tank pump only pumps fuel to the secondary hi pressurepump and if it goes dry you going to be replacing both pumps. Can you spell EXPENSIVE.

But at what point should you refuel to a sound costly repairs? Why is this not mentioned anywhere in the manual? No need to insult me.

redvett94
04-05-13, 02:03 PM
I was not insulting you or anyone else i was educating you on what happens with all vehicles with electric pumps. You are best to not go below 1/4 tank if possible.

beachcad
04-05-13, 02:05 PM
But at what point should you refuel to a sound costly repairs? Why is this not mentioned anywhere in the manual? No need to insult me.

Hello 300:29:1,
I don't think there was any intention by anyone of insulting you. The 1/4 mark is a good indication that it's time to refuel. If you consistently allow the fuel level to get low enough to cause the low fuel indicator to display, then you will be flirting with the afore-mentioned expensive repairs.

300:29:1
04-05-13, 02:06 PM
Hello 300:29:1,
I don't think there was any intention by anyone of insulting you. The 1/4 mark is a good indication that it's time to refuel. If you consistently allow the fuel level to get low enough to cause the low fuel indicator to display, then you will be flirting with the afore-mentioned expensive repairs.

So 1/4 is reasonable then? Some have said 1/2. 1/4 seems reasonable.

beachcad
04-05-13, 02:33 PM
So 1/4 is reasonable then? Some have said 1/2. 1/4 seems reasonable.

Needing to refuel at 1/2 tank is absurd. The in-tank pump is on the bottom and will still be submersed even below an 1/8, typically. We all know that different vehicles have varying degrees of how the fuel level is displayed. The first 1/2 may "last" a lot longer than the second 1/2! This is a primary reason that the 1/4 level is used as a "safe" measure. My daughter used to consistently wait for the low fuel indicator before refueling, and consequently, ended up having to replace the fuel pump. I have normally refueled anywhere between a 1/8 and 1/4 level without any problems.

P.S - I have seen the low fuel warning light on occasions too!

redvett94
04-05-13, 02:37 PM
All you need is to keep the pump cool and lubricated. What happens is when the vehicle runs out of gas and you try to start it or turn on the Ign. the pump will run dry.

Huey Driver
04-05-13, 02:40 PM
Agreed with most here, its probably a preference thing, but the tank design probably allows that 1/8-1/4 is fine. Also, just as some food for thought, if you are constantly driving around topping off your tank, you're carrying around 75 pounds of useless weight. In my old trailblazer, I swore I was getting 2 mpg better when nearly empty than when topped off. Probably all in my head.

beachcad
04-05-13, 02:46 PM
Precisely! But I also intended to mention another factor that we usually don't consider, and that is whether the vehicle is being driven on an incline or decline, or sharp curves. These factors can cause the fuel to be slanted away from the pump, if the fuel is at a low level.

stevec5375
04-05-13, 04:51 PM
Just imagine if we weren't still stuck on fossil fuels this would not even be a problem. (Nor would the high price of gas.)

redvett94
04-05-13, 05:04 PM
What do think we should use? If CNG catches on and it will, NG is going to be expensive. Plug in cars still use fuel to power the power generating plants.
Diesel fuel is projected to incresase 300% by 2016 and thats why new Long Haul Semis 39% are now being built to use CNG.
If you want to drive your going to pay regardless.


Just imagine if we weren't still stuck on fossil fuels this would not even be a problem. (Nor would the high price of gas.)

RippyPartsDept
04-05-13, 05:09 PM
letting the tank run low on fuel isn't necessarily that big of a problem
but never filling it all the way up and always running low on fuel is

for instance if you only put $10-$20 in at a time and just fill up the tank a little bit (and consequently visit the pump more often)
you run a much higher risk of pump failure than if you always let it get to the 'low fuel' message but then fill it up all the way

packardv8
04-05-13, 07:06 PM
Yes, running out of fuel can damage a fuel pump. However, I've never seen any reputable, reliable source which substantiates, running down to the low warning light is a cause of failure.

I know a guy who is a fleet service manager and the fuel tank of every vehicle is filled every morning. They still regularly have to replace GM fuel pumps.

jack vines

stevec5375
04-05-13, 07:07 PM
What do think we should use? If CNG catches on and it will, NG is going to be expensive. Plug in cars still use fuel to power the power generating plants.
Diesel fuel is projected to incresase 300% by 2016 and thats why new Long Haul Semis 39% are now being built to use CNG.
If you want to drive your going to pay regardless.

What about hydrogen fuel cells? Water vapor is the byproduct. California had some refuel stations going for that tech but I haven't heard much about it lately.

http://edition.cnn.com/2012/11/25/business/eco-hydrogen-fuel-cell-cars

redvett94
04-05-13, 09:00 PM
Not in our life time. Too advanced.GM had FI on Corvettes in 1957 and very few people bought them. Too advanced for the mind set. Think about Air bags GM offered them in 1974 and they were not accepted along with Power windows and locks in the 50"s My new GM vehicles all had PW,PL and AC most people said it was crazy. Guess what we have FI, AC, PW & PL.:confused:
Give the new power sources 25years.

Terry Judkins
04-05-13, 09:55 PM
There is a good discussion of fuel pump failure modes here. http://www.agcoauto.com/content/news/p2_articleid/195

redvett94
04-06-13, 02:05 PM
Without refuling stations you cant go anywhere. Probably will be 15-20 years from now.

NotMine
04-06-13, 03:55 PM
I'll just reply to some on topic discussion......

I have heard (I believe it was from a Chev. Service Manager on another GM forum), the fuel pump sits in a bit of a molded well of the fuel tank. The intake sock is outside the well. So, the pump never really goes absolutely dry. The tank, because again the intake is outside the well, can.

It would be nice for someone to confirm this. This rumor/myth or truth has been circulating on all the GM forums. However, when looking at replacement parts in on line catalogs, the pictures appear to illustrate the pump "draws" from the bottom. That should confirm the running draw hypothesis.

And for what it is worth.......when traveling, and on a number of occasions around town, I do not fill my vehicles until under an 1/8Th of a tank. Never had any fuel pump problems....all (always) GM products.

redvett94
04-06-13, 05:36 PM
The pump will run dry when the tank is empty and will still damage the pump.