[Kip-on-truckin]

This week in (like an idiot) ran the pm out of gas. I think theres some useful knowledge to be had. Heres the poop:

Driving fast into headwinds and got it down to right near the empty line. Pulled into a station and parked about 30 feet from the pump. I was on the phone with a buddy, and wanted to finish the call so i just sat there idling, jawing away. 10 minutes later the van just shut off. No cough, no sputter, no warning other than the text message and low fuel light. Would not restart.

Sheepishly, i pushed the van up to the pump. Surprisingly easy to push on flat ground (3500 ext w/ 600# load). Fueled and it started first crank, no warnings or messages.

Whats odd is that it only too 23.53 gallons. There was an instance a while back where i ran it low and pumped 23.75 into it. Conclusion: i suspect the van shut ITSELF down with .5g in the tank, but had i been moving and not in park it would have kept running right up to 24g. Why? Is it possible that a low duty cycle the PCM fuel pump draws less fuel at idle so it cant cool itself with fuel flow, and if the tank is low it cant use the tank fuel as coolant? Or maybe the engine killed itself because it calculates its remaining fuel by duty cycle and miles driven, instead of relying on the float gauge? Is it possible it does this to not lose its prime, but when driving it asumes youd rather try to make it to a gas station than risk your prime?

Dunno, but you would assume the tank is the full 24 plus an undocumented reserve. Anybody gotvany ideas? You need NOT call me stupid for running it dry, i already know i AM stupid. Weird; last time i ran out of gas was 1989.

 

[RDinNHandAZ]

Nothing stupid about it. With gas prices falling almost daily i'd wait to the very last moment too. I have no idea why you couldn't pump the last .5 gal. I doubt the computer monitors the pump temp but you never know. I'd sooner think the movement moves about the fuel enough to keep the pressure up even though there may be times the pick up is sucking fumes thus more can be used? I know its a stretch.

 

[Brian P]

Actual nominal capacity is 90 litres ... this is a metric-design vehicle. 90 litres = 23.78 US gallons.

The slightest bit of slope will affect whether the pump can pick up the last little bit ...

 

[MsNomer]

Puts that 23.75 in a new light.

 

[Powderman]

You guys are really trying Hard to find something wrong..... .5 gallon spread out over..... say probably 2.5 sq.ft.is probably an 1/8"of depth.....if you didn't pinch off that extra turd this morning, it would probably make the difference of where the fuel lays in the tank......good god, get a life...

 

[Chris]

When you put in 23.75 gallons and later 23.53 gallons, did you do so at the same fuel station AND at that same pump?

Where I am going with this question is that there are probably variations between the internal flow meters of different fuel pumps. As a percentage, the difference you observed is small, so probably within the allowable tolerance of fuel-pump flow meters.

On the bright side, these pumps appear to be "honest." I once put 19 gallons (as reported by the pump) in an 18.4 gallon tank, and the car was still running!

 

[keeponvaning]

I always fill up at half full, why suck sh it from the bottom of the tank into your filter?

 

[Domitype]

Are you serious, keeponvaning?

 

[GapRunr]

I always fill up at half full, why suck sh it from the bottom of the tank into your filter?

Wow... sounds like you need to start buying your gas at better stations!

 

[keeponvaning]

Are you serious, keeponvaning?

100%! The worst thing you could do is let your engine run on fumes. Gas is cheap why would anyone want to try and beat the gauge!

 

[RDinNHandAZ]

100%! The worst thing you could do is let your engine run on fumes. Gas is cheap why would anyone want to try and beat the gauge!

It is true that running on fumes is a bad thing but as for sucking the bottom of the tank.... modern fuel systems with high pressure pumps have a pressure relief return line and circulate the fuel all the time and their pick up rests very near or on the bottom of the tank. More gas and they will start right up. There is going to be no difference between the first gas used after a fill up and the last gas as the van comes to a halt -empty. Relax about the dirt, as it should all be in the filter.:laugh:
For those with diesel the issue is a bit different. It may take several tries to purge the lines from the super high pressure lines to their injectors.

 

[jhrodd]

When you put in 23.75 gallons and later 23.53 gallons, did you do so at the same fuel station AND at that same pump?

Where I am going with this question is that there are probably variations between the internal flow meters of different fuel pumps. As a percentage, the difference you observed is small, so probably within the allowable tolerance of fuel-pump flow meters.

On the bright side, these pumps appear to be "honest." I once put 19 gallons (as reported by the pump) in an 18.4 gallon tank, and the car was still running!

Keep in mind that although few fuel pumps in this Country are "temperature compensated" at the retail level, if you did pump hot fuel through an ATC pump you would get more actual volume than indicated at the pump. Or vise-versa.

 

[keeponvaning]

It is true that running on fumes is a bad thing but as for sucking the bottom of the tank.... modern fuel systems with high pressure pumps have a pressure relief return line and circulate the fuel all the time and their pick up rests very near or on the bottom of the tank. More gas and they will start right up. There is going to be no difference between the first gas used after a fill up and the last gas as the van comes to a halt -empty. Relax about the dirt, as it should all be in the filter.:laugh:
For those with diesel the issue is a bit different. It may take several tries to purge the lines from the super high pressure lines to their injectors.

I'm talking about getting a clogged filter as I wouldn't expect any dirty fuel to get past the filter (unless it has a bypass). But the real point isn't dirty fuel, it's why take the chance of running out or having to pay rip off prices if you're desperate because you are almost out when you can fill up anywhere you like and whatever price point you choose if you fill up when the gauge reads ½ full instead of waiting for the light to come on?

I say this as someone whom has run out of gas on more than one occassion and unfortunately, had to not only walk but listen to my wife say "I told you to get gas back there". The only time I ever run on fumes now is driving through either CT or NY because of their extra high gas prices:laugh:

 

[RDinNHandAZ]

I hear you. We almost never try to cheap out on fuel when we travel as it ruins your whole day. I can tolerate 1/4 tank though. New York is the worst for price in the US in our opinion, Oklahoma seems cheapest.

 

[MsNomer]

Some parts of Oklahoma. Our city is not among the cheapest and we have a local refinery.

 

[rbisch]

All fuel tanks are designed with an expansion chamber.
On my 35 US gallon diesel it is possible to add an additional 3 gallons after the tank appears full (total 38 gallons). This is only if you are very very patient. Because of this expansion chamber one time fuel mileage calculations can be less then accurate.


Despite any opinions of safety it seems that gas tanks are manufactured to not accept more than 95% of their total volume because of regulations. Here is a quote from the US Department of Transportation Federal Motor Carry Safety Administration Regulation 393.67 Subpart E.

(12) Overfill restriction. A liquid fuel tank manufactured on or after January 1, 1973, must be designed and constructed so that—

(i) The tank cannot be filled, in a normal filling operation, with a quantity of fuel that exceeds 95 percent of the tank's liquid capacity; and
(ii) When the tank is filled, normal expansion of the fuel will not cause fuel spillage.
C

 

[RDinNHandAZ]

Despite any opinions of safety it seems that gas tanks are manufactured to not accept more than 95% of their total volume because of regulations. Here is a quote from the US Department of Transportation Federal Motor Carry Safety Administration Regulation 393.67 Subpart E.

(12) Overfill restriction. A liquid fuel tank manufactured on or after January 1, 1973, must be designed and constructed so that—

(i) The tank cannot be filled, in a normal filling operation, with a quantity of fuel that exceeds 95 percent of the tank's liquid capacity; and
(ii) When the tank is filled, normal expansion of the fuel will not cause fuel spillage.
C

Another Nanny State rule to protect us from ruining the charcoal canister, bulging the fuel tank, fuel spurting from the gas cap, Fires, etc. Probably we should protest those sorts of rules and find a way to circumvent them, being smarter than the engineers they hire.

 

[DavidMFear]

I ran out of gas this past week too! There is something wrong with my display and I can't get my DTE to show. I took a chance and lost. I believe I got about 25 miles from warning light and low fuel message, to W. My old E-250 gave me 50+ miles in such situations so I have become lackadaisical about it.

 

[mlts22]

I have always avoided running on fumes because of driving Ford F-150s, and the fact that running low on gas causes the fuel pump to run hot and wear out faster... and replacing those is a PITA, as it requires a driveshaft and fuel tank drop to get at it.

 

[Todd]

I've learned through paying for new fuel pumps that fill up is when the gauge is on 1/4. I had a guy who drove one of my GMC cube vans wreak two fuel pumps because he was too lazy to fill up until he was on fumes. Now I take the van away if I see it below a 1/4 tank.

I tell my children you always pay for education. The school of hard knocks hurts the most when it extracts its tuition straight from your wallet. Todd