Lets see, at full throttle, my truck (a little 4.6, and light) gets under 1 mpg. That's reported by instrument. The fuel system after the pump holds less than a pint. so in an 1/8 of a mile I would be out of gas. Last time I checked, every fuel injection system on the market required high pressure to operate. No more cheap thin plastic filters, right?
So even if your lines were full when you nailed it, there would be no pressure on the fuel in the line. They are pressurized guys. No immersion in fuel, no pressure. Not much fuel arriving.
Chris

 

maybe i am running out of gas. all i know is when i floor it, itll suddenly die like it has no fuel at all. and this happenes when the guage isnt all that low. i dunno how low it will go before u completely run out, but on my '01, itll go way lower and never pukes like this one does. and like i said this only happens when the fuel is low. as soon as i fill it up, i have no problems whatsoever at WOT.

 

Dude, your smarter than that. That instrument gets that number based on workload vs. speed. Do you think you consume a quarter or half gallon of gas on the race to 60mph? Using your logic I'd be able to burn though my full tank of gas in my driveway reving the engine in park in like 10 minutes!

 

dzervit, yes I am smarter than that. The system I use reads the flow from the metering system. Of course you get 0 mpg per gallon, at idle. You ain't a movin.

Another comparison, we used to use approximately 1 gallon of Avgas per run in a 525 hp Rat. That equates to about .6 miles to a gallon.
Running my 396 tripower Firebird (68 Bird, 69 375 horse Rat, with tripower from a 427) I made a long run of 14 miles, and used 12 gallons of gas. I was going rather fast....At WOT you aren't burning the gas, you are passing the gas. (sorry couldn't resist)

When you kick in nitrous (not my cup of tea) you use the gas as a coolant. try a few runs an check out the consumption. .

In my 'builder days' we used to use a tank on the firewall, or cowl to test and run Rats, and other evil breeds. A gallon goes through a pair a AFBs pretty fast. It's almost amazing. A single double pumper 850 can 'oversuck' two fuel pumps.

I have worked on tanks that had been 'imploded' that is, the gas feeding the duel quads pulled enough gas out to bow the tank from suction. Failed venting.
Suction in a non vented tank is one of the causes for starvation at high RPMs. Check any racing builders manual.


Also remember, I am not suggesting it uses up a whole pint, that was what's called a theoretic number. I rather doubt the system functions at all when the fuel is removed from the pickup point. You would lose functional pressure very quickly. I have done it on steep hills in LA, around Echo Park. One grade there, anything under an 1/8 of a tank and you might be rolling back down to the bottom.
Not news to off roaders.
Chris

Oh, addition Notice the gauge on my dashboard, if you ever happen to look at my gallery... I have been doing this junk a long time.. Just for fun, I floored the truck at 60. Both my gauges showed fuel consumpion at between 1 and 2mpg at WOT.

 

dezervit I'm with you these guys are smoking crack...What are they talking about!!

go ahead and tell em the days of fuel starved carburetors are over. A fuel injected engine would die immediately if the fuel pump ran dry for even just a couple of seconds.....

 

On hard launch with a an almost empty fuel tank perhaps it starves the fuel pump for maybe a second, maybe two. Tops. read your post. Read his. If the fuel surges away you are saying the engine would quit.

Not for seconds. it would lose power. It takes more than two seconds of fuel starvation to kill an engine. It's still turning from momentum. How many RPM's do you think it takes to maintain a running engine? Hint, you crank it by a starter, slow enough to see it turn and it takes off.

Read up on flashpoints.

Before they invented fuel shut offs, you couldn't kill some motors. Called dieseling. Motor would run at about 10-15 rpm for quite awhile after you shut it down. That's with electric fuel pumps.
It doesn't take a huge amount of fuel to keep er turnin.

When your fuel is starved, there is no magic cut off. It keeps trying to run, at lower RPMs, using the gas that does get through. I don't think this is rocket science.
Chris

 

Ok Chris, I get ya... but we are also assuming the 'drain' is at the front or middle of the tank. With the common knowledge of liquids shifting around constantly, don't they design tanks with a rear 'drain' (for lack of a better word) or bowl like bottom to contain and suck up the last bit-o-fuel.

Now, the orignal post said he lost power on the shifts... should he lose power shortly after that hard launch and not magically at the shift points? I just don't buy the whole gas-starving bit....

 

Yeah, dzervit, I have to wonder.
I wasn't presenting this as 'The way it is' Walter Crankcase style.

I was offering it as a theory.

I got the impression that he was failing at the top of the gear, which is sure the thing that would happen with starvation.

I'm thinking something like; Launch, the small amount of fuel surges back. Going up through the gear, he's running on the fuel already pressurized. maybe three(?) seconds worth at WOT. Fuel starts to run out, lowering RPM, while the PCM is correcting back to keep the mix as rich as it can. Sorta dropping back to idle, but not all the way. Then the fuel, which has been surging back, after launch, is sucked into the pickup. Suddenly more fuel than needed. Up through the next gear.

I don't know where the pickup is on this tank, shop manual doesn't cover it. Most tanks I've seen have a small area for moisture to collect under the pickup. Don't see that under my truck.

Heck we dun beat this un to death.

Have a great one,
Chris

 

Could it be that there's some computer "back-off" setting when the low-fuel light is on? As I think I read earlier, sort of a limp-home mode?

 

Darn, NukePooch I was going to let this one die.
I just looked at the logic loop for a drive by wire, not a ford, but I think it might be relevant.

If the system detects too lean a mix, it either increases the fuel mix, if at WOT, or decreases the air flow to attain a 'safe' mixture.
If it is at WOT, and is unable to increase the fuel mix (starvation?) it must reduce the air intake to maintain a safe mixture.

If it ain't getting enough gas, it's going to slow the motor down till it is getting enough gas.

You could call that a 'limp home' but it's not like the old Calpaks, gettum home circuit.
It's not even open loop.
It's more a simple loop thing. Mix too lean, increase gas, Not enough gas, decrease air.

On a cable drive truck, it would shudder, pop, and jerk, running out of gas thing.
On drive by wire, apparently, it just drops the throttle back to where it is safe.

Whoo hoo, too much like work (time consuming and no money in it)
Chris

 

I thought that I should just clarify a few things, I read through my post and saw how some people got confused. For my truck from the start in 1st gear the truck reved to about 4200rpm then seamed like it just shut down. Acceleration stoped rpm's droped to about 3700, this seamed like it lasted for 1/2 to 1 second, just enough time for me to decide to keep my foot to the floor or not, it grabbed 1st gear again and then continued to kick some Hemi ***.

Soory for the confusion.

 

it wouldnt surprise me if this feature is built in to the CPU

 

lets not forget that liquid is not as compessable as air, hence if fuel pick-up sucks air then you have just lost your fuel pressue (not fuel) to injectors..you dont like air in your brake lines for the same reason.....good point chris!!