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Old 12-21-2005, 12:12 AM   #1
hilfiger4you
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Default Is running out of fuel in STI bad for the engine

Hi guys,
I got a 05 STI. My fuel gauges is broken since the sensors in the tank were not working. Dealer will fix it on monday but today as I was driving, I had 220 on the trip meter and normall in the winter i get 250 to for a full tank of gas. However, as I was driving on the highway about to go and fill up, and I was cruising in 6th gear at 65-70miles an hour, the rpms started to surge and drop a few hundred. I give it some gas and the speed is back up, but a few seconds later it does it again, I knew I was about to run out of gas so I pulled to the shoulder on the highway. I tried to give it some gas a few more times as the rpm surged 2-3 more times, finally I just put it in neutral and let it roll. The car died eventually.

Tow truck came and filled me up. My questions is this, is running out of gas bad for the engine. I take care of my STI and I don't want it to have leaned out and have a bent valve or piston. The tow mechanic said it is okay no biggie because the ECU fuel map is the same regardless if you are low on fuel so by having low fuel, the engine was just cut off.
PLease advise.
thanks
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Old 12-21-2005, 01:23 AM   #2
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Well you get a fuel cut from too much boost and a fuel cut from too high RPM's and a fuel cut, I guess, at 155 mph I'm told. So fuel cut offs are in the plan of things. I think the reason to not run out of fuel aside from being stranded is the possibility of backfiring which could damage the turbo. Seems I read this in the Manual, but I could have read it somewhere else.

I think Subaru would have a hard time selling cars if running out of fuel easily damaged the engine. Hwy61
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Old 12-21-2005, 01:43 AM   #3
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Quote:
Originally Posted by hwy61
I think the reason to not run out of fuel aside from being stranded is the possibility of backfiring which could damage the turbo. Seems I read this in the Manual, but I could have read it somewhere else.

I think Subaru would have a hard time selling cars if running out of fuel easily damaged the engine. Hwy61
^

'fuel cut' does not equal 'running out of fuel'

'running out of fuel' is bad, 'fuel cut' is a safety feature.....

'running out of fuel' can cause a lean condition that could result in engine damage....it can also destroy your fuel pump (although they are cheap & easy to replace)

'fuel cut' cuts ALL fuel going to the engine....so no combustion will take place...

ALL CARS RUNNING OUT OF FUEL COULD RESULT IN ENGINE DAMAGE....

if you 'run out of fuel' during a full boost pull...I can almost guarantee you will need a new motor...
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Old 12-21-2005, 02:05 AM   #4
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run out of gas is always bad , which that there are more " dirt" and "werid stuff" at the bottom of the tank, which is not good to run those in your car for sure..
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Old 12-21-2005, 03:06 PM   #5
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so what am I going to do? Should I replace the fuel filter and if so where is that located at?
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Old 12-22-2005, 12:22 AM   #6
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running out of fuel results in lean mixture and misfires. both of which tend to be bad for the engine. it happened once so shouldn't damage anything but definitely recommend not making a habit of it
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Old 12-22-2005, 12:24 AM   #7
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My car would run out of fuel when I did cyclones, but only once...
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Old 12-22-2005, 12:32 AM   #8
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You should be ok. Just make sure that I keep an eye (ear) out for any rough idle or performance drop.
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Old 12-22-2005, 12:53 AM   #9
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Quote:
Originally Posted by NaVaWRX
run out of gas is always bad , which that there are more " dirt" and "werid stuff" at the bottom of the tank, which is not good to run those in your car for sure..
There shouldn't be any bad stuff at the bottom of your tank. Regardless, the system is well protected with filters. All stock automobile fuel systems I'm familiar with remove fuel from the "bottom" of the tank. That way you can use all the fuel in the tank.

Years ago when I worked at a gas station we had to pump water out of the underground tanks regularly and it was always advisable to avoid filling up when a tanker was discharging into the tanks stirring up whatever. We checked several times after tanker refills and never found anything in the fuel.
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Old 12-22-2005, 03:01 AM   #10
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Quote:
Originally Posted by hwy61
I think the reason to not run out of fuel aside from being stranded is the possibility of backfiring which could damage the turbo. Seems I read this in the Manual, but I could have read it somewhere else.
Cars backfire because they're running rich....
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Old 12-22-2005, 03:03 AM   #11
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Quote:
Originally Posted by mnavarro
Cars backfire because they're running rich....
cars afterfire because they run rich, but yes everyone calls it backfire....
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Old 12-22-2005, 08:05 PM   #12
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I appeciate all the info guys, however, i know it is bad for the fuel filter since it should be submerged in fuel at all times to keep cool. However, i talked to 2 subaru techs from separate dealerships and they say when I was low on fuel, the reason the engine bogged was cause the ecu sensed low fuel pressure so the rpms dropped in power to maximaze the air/fuel ratio or whatever in accordance with the fuel. they also said that it is no different than if you were to turn off the car. The only thing to worry is the fuel pump and the fuel filter that might gather more gunk.
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Old 12-22-2005, 09:00 PM   #13
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Quote:
Originally Posted by hilfiger4you
However, i talked to 2 subaru techs from separate dealerships and they say when I was low on fuel, the reason the engine bogged was cause the ecu sensed low fuel pressure so the rpms dropped in power to maximaze the air/fuel ratio or whatever in accordance with the fuel. they also said that it is no different than if you were to turn off the car. The only thing to worry is the fuel pump and the fuel filter that might gather more gunk.
Too bad the STi doesn't have a fuel line pressure sensor. And, as far as I know, the STi's only fuel filter is integrated into the fuel pump, so you don't have to worry about replacing it.
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Old 12-22-2005, 09:17 PM   #14
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Running out of fuel isnt going to really hurt the engine to much, but you will starve and eventually destroy your fuel pump.
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Old 12-23-2005, 01:03 PM   #15
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Quote:
Originally Posted by testes1010
^

'fuel cut' does not equal 'running out of fuel'

'running out of fuel' is bad, 'fuel cut' is a safety feature.....

'running out of fuel' can cause a lean condition that could result in engine damage....it can also destroy your fuel pump (although they are cheap & easy to replace)

'fuel cut' cuts ALL fuel going to the engine....so no combustion will take place...

ALL CARS RUNNING OUT OF FUEL COULD RESULT IN ENGINE DAMAGE....

if you 'run out of fuel' during a full boost pull...I can almost guarantee you will need a new motor...
Not to disagree but I don't expect we know more than the Subaru technicians. The following pages are right out of "the manual" A fuel cut is a fuel cut, yes the fuel cuts are for the reasons I listed are to help protect the engine but the engine doesn't know one from the other. No fuel is no fuel. Yes I know the difference between an instant fuel cut and an instant fuel cut from running out of gas versus possibly the fuel pump picking up a little, engine runs, no fuel, then a little etc. And yes you don't want to run an engine at high RPM with a lean A/F ratio for any reason if you can help it.

Damaging anything has not been my experience with running out of fuel and while aggravating and an inconvenience, it won't ruin your engine. If it did, auto manufactures would make even more efforts to eliminate this common occurrence. Cruising along at 65 and 3000 rpm as the OP stated, equals no engine damage. A fuel cut at 7500 RPM or due to sustained boost way over the tune limit would likely do more damage but I've never experienced any. Remember Subaru warrants these engines for a lot of miles and if they fell apart that easily they would be out of business. Engine management is very sophisticated on these engines so is the fuel pump. I recently had mine out and it has stuff on it I don't even know what it does.

BTW, the bottom of the fuel pump intake is well baffled regarding sloshing fuel, the fuel pump sits in an internal baffled area within the tank to further reduce fuel sloshing/fuel pickup problems. This is especially important for Rally or racing cars and mine is a "racin" car. There is a several stage fuel filter located here filtering fuel before it even gets in the fuel pump and an in -line filter between the engine and fuel pump. I believe there is a pressure regulator on the fuel line once it passes the fuel rails for surplus fuel returning to the tank.

I'll also state that it is my opinion running out of fuel won't damage the fuel pump but I will have to do a little more research to show the validity of my opinion. Merry Christmas everyone, Hwy61




Last edited by hwy61; 12-23-2005 at 01:15 PM.
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Old 12-23-2005, 01:19 PM   #16
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And to proove it's a racin car, here I am passing one of all the Lotuses I could find on the Barber racetrack recently including the Exige. About 120 mph here and 18 lb boost. What a beautiful track. Want to take a visual ride around the track on your computer, go to Porsche driving experience, Barber Racetrack and there is a two lap ride in real time in a 911. The video laps are 2 min 6 sec I believe, I was turning 1 min 53 sec laps. Naw, not even close to a track record. http://www.porschedriving.com/the_track_detail.asp# Hwy61


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Old 12-23-2005, 01:32 PM   #17
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BTW Testes1010 I worked for years trying to get recreation areas and a nice hiking/bicycling trail along the top of the Evansville, Vanderburg County, Levee Authority District earthen flood levee, to get you guys a nice recreation facility going. Anything ever happen? Hwy61
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Old 12-23-2005, 02:59 PM   #18
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Quote:
Originally Posted by hwy61
Not to disagree but I don't expect we know more than the Subaru technicians. The following pages are right out of "the manual" A fuel cut is a fuel cut, yes the fuel cuts are for the reasons I listed are to help protect the engine but the engine doesn't know one from the other. No fuel is no fuel. Yes I know the difference between an instant fuel cut and an instant fuel cut from running out of gas versus possibly the fuel pump picking up a little, engine runs, no fuel, then a little etc. And yes you don't want to run an engine at high RPM with a lean A/F ratio for any reason if you can help it.
the only thing the manual is stating that a misfire will potentially destroy your cat, repeatedly doing so will break apart the cat, then destroy your turbo....this is a known issue especially when running higher boost(higher EGTs) on a catted uppipe....

I definately do not know more about my car than the ones that wrote the manual, sadly I probably do know more than the local Subaru dealers' service department....

again, ECU-induced Fuel Cut is NO Fuel going into the combustion chamber, & yes it is Instant, if you've ever overboosted you will know this....Injector IDC = 0%

Running out fuel is Not a Fuel Cut, definately not Instant....Injector IDCs stay on target, from my understanding there is no precautionary controls in place to prevent otherwise. I did just dig through the service manual & found nothing to support a precautionary system or anything allowing the ECU to cause an induced fuel Cut due to low line pressure or an empty tank. Not saying it doesn't exist, I just found nothing to support it.

Some types of fuel pumps running out of fuel is bad(not sure if ours is one or not) many fuel pumps are actually cooled by the gasoliune that surrounds them. No fuel, no cooling capacity equals overheated fuel pump.

Eville does have a bike/walking trail around part of the city.
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Old 12-23-2005, 03:53 PM   #19
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[quote=testes1010]the only thing the manual is stating that a misfire will potentially destroy your cat, repeatedly doing so will break apart the cat, then destroy your turbo....this is a known issue especially when running higher boost(higher EGTs) on a catted uppipe....

I definately do not know more about my car than the ones that wrote the manual, sadly I probably do know more than the local Subaru dealers' service department....

again, ECU-induced Fuel Cut is NO Fuel going into the combustion chamber, & yes it is Instant, if you've ever overboosted you will know this....Injector IDC = 0%

Running out fuel is Not a Fuel Cut, definately not Instant....Injector IDCs stay on target, from my understanding there is no precautionary controls in place to prevent otherwise. I did just dig through the service manual & found nothing to support a precautionary system or anything allowing the ECU to cause an induced fuel Cut due to low line pressure or an empty tank. Not saying it doesn't exist, I just found nothing to support it.

Some types of fuel pumps running out of fuel is bad(not sure if ours is one or not) many fuel pumps are actually cooled by the gasoliune that surrounds them. No fuel, no cooling capacity equals overheated fuel pump.

Eville does have a bike/walking trail around part of the city.[/QUOTE

You know it's really irritating that accurate detailed information is so hard to come by. Subaru has a new "technical information site" that really has promise, they seem to have everything including the factory service manual. Only problem is they charge a ridiculous fee to access it for a few hours.

I think our local Subaru technician actually knows something but his attitude is so bad I don't want to talk to him. e.g.
Good morning, I just bought this new STI, are you guys having any problems with them or are they pretty much bullet proof. Says he "the only problem they have is what guys like you screw up." now I'd never even met this guy before and there were no mods on the car, I was being friendly. So I said, really, where's your boss. In that room says he, so I had a little talk with him about his mechanic's attitude. I'm 56 and a local professional, no reason to give me that kind of crap.

The parts guy on the other hand is very helpful and a hot rodder himself. We need more Scott Siegels and dealerships with people like him. I can assure you I won't ever buy a car from this dealership with an employee with that attitude that I might have to deal with.

Hey, if you've got a service manual I've got two questions. 1. How about a picture of that fuel pump assembly and what all those buttons etc are on it, especially the small round cylinder that is about an inch long and near the bottom. I'd like to know more about it's operation and if you are out of fuel does the EM cut the power to the fuel pump, I don't remember mine running on...... and 2. My TMIC when blocked and filled with regulated air pressure attempting for an internal pressure of 18psi with all holes blocked, leaks air at the BOV. Now the compressor won't flow enough air to really be pumping a huge volume at any instant but should the BOV be leaking air at 2 psi. The STI bov does not have a hole in the valve like the WRX 2.0 apparently has. The Green overcomes this leak and will hit 18/19 psi but is not holding it. The boost was dropping to 14 psi at 6000 rpm or so when dynoing at TopSpeed in Atlanta. We locked down the waste-gate, but still couldn't keep the boost up. Perhaps this is normal BOV operation, perhaps not. TopSpeed recommends a GFB BOV. Thanks. Hwy61
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Old 12-23-2005, 04:16 PM   #20
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2004 WRX/STI manuals...

'02-'03 Impreza Lineup manuals...

we all need to thank ride5000 for hosting them for us....

btw, I've had good luck with my APS Dualvent...
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Old 12-23-2005, 08:59 PM   #21
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TESTES thank you for all your long information. I appreicate that. So to sum this up, running out of fuel on a turbo car such as the STI can be bad for the fuel pump and bad for the CAT if done many times when it misfires. I know that when you misfire the engine light comes on. I did not get any engine light.


My only question is this, 2minute before the car died, rpm bogged and surged and i gave it some gas to stabalize the rpm back, but eventually it died. During that period of time, would I have LEANED OUT???

thanks
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Old 12-23-2005, 11:04 PM   #22
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Quote:
Originally Posted by testes1010
the only thing the manual is stating that a misfire will potentially destroy your cat, repeatedly doing so will break apart the cat, then destroy your turbo....this is a known issue especially when running higher boost(higher EGTs) on a catted uppipe....
Photoed manual quote is from an STI manual and there is no cat in the STI up-pipe.
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Old 12-24-2005, 08:53 AM   #23
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Quote:
Originally Posted by hilfiger4you
During that period of time, would I have LEANED OUT???

thanks
It probably did lean out BUT at idle or low rpm I highly doubt any damage would occur, very worse case your plugs are white, but I even doubt that. If it had done it during a high boost pull, damage would more likely occur.
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Old 12-24-2005, 08:56 AM   #24
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Quote:
Originally Posted by hwy61
Photoed manual quote is from an STI manual and there is no cat in the STI up-pipe.
^ agreed, but the picture says catalytic damage could occur. My guess is most of the manuals are 'generic' with a few specific parts. Not unlike MY02-03 service manual including the Outback, 2.5RS, etc....

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Old 12-24-2005, 11:29 AM   #25
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I'm figuring the cat behind the turbo, don't want that one crumbling and stopping up the works either. Ralph "the green" Nader would be upset but that won't be happening on my STI either. It's nice and safe sitting on a shelf.

Why can't those guys put some nice photos in the service manual. I find the drawings all but worthless.
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