|05-23-2008, 08:19 PM||#1|
Join Date: Sep 2005
Chapter/Region: South East
Location: South FLVehicle:
2006 LGT Stg2 5MT
97 LegacyGT Wagon 4EAT
97 LGT - Fuel delivery problem - possibly related to gas fillup problem?
Car: 1997 Subaru Legacy GT wagon; automatic; 212K miles
Car details: Motor rebuilt around 173K. Assuming original injectors & fuel system still. Full 30K tuneup done @ dealership at 205K miles: PCV, fuel filter, air filter, thermostat, plugs & wires, tranny fluid change, coolant flush/change, brake fluid change, tire rotate/balance. New struts, brakes, brake hoses, brake pads, front CV axles, throttle position sensor, front O2 sensor around 205-206K miles.
Symptoms: Over time, fuel economy has worsened. At first with all city driving, achieved a max of 21 MPG. Over time this has degraded to 18MPG or worse. Also noticed that after filling up gas tank, acceleration seemed markedly improved compared to low tank. Over time, appears vacuum leak has developed. Rough, semi-erratic idle; high-pitched whistling noise coming engine bay when >3K RPM's with moderate or greater throttle; noted loss of engine power above 3K RPM's.
Note 1: Since I received the car around 200K miles, I have noted that at every gas station the pump will stop fuel delivery as if the tank is full - but it is not. Some pumps seem better/worse than others, but every fillup I can recall I have to re-start the fuel flow multiple times during the fillup. I don't know enough about the fuel evaporator neck/hose & a gas pump to figure what this issue could be, but thought it to be pertinent to the issue.
Note 2: Not long after receiving the car, I attempted to remove the throttle body to see if there was any carbon buildup. Unfortunately the coolant hoses running through it are glued on and I could not remove them - so I just re-attached the throttle body without replacing the gasket. This could be the source of the vacuum leak, yes? I will be diagnosing that soon.
I've been figuring for a while that I had a fuel delivery problem. Between what should be original injectors and a possibly failing fuel pump (re: poor engine power on low tank), I figured that was part of my acceleration & poor fuel economy issues. But just thinking a moment ago, I wonder if there is some issue with the evaporator neck in the fuel tank that could be causing fuel pressure or other fuel delivery issues? Again I don't know how that systems works, so I figured I'd throw it out here and see what the collective genius thinks.
Given I've replaced most every other component that could effect engine performance/economy (plugs, wires, front O2, PCV, etc), I'm narrowing it down to fuel delivery. Am I missing anything?
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|05-25-2008, 12:00 AM||#2|
Join Date: Jul 1999
Location: Where the Navy sends me...Vehicle:
1997 Legacy 2.5GT
The hoses that are "glued" in place aren't, really, they've just never been removed in 11 years and 200,000 miles so they're stuck on there pretty good. Use a set of pliers to grip the hose and rotate it about the pipe - that will break the seal, after which you should be able to pull the hose off pretty easily. Works every time for me on old, stuck hoses like that.
As for your potential fuel feed issues, you could very well be right. I wonder if the filter "sock" that's on the pump itself in the fuel tank is gunked up. With a higher fuel level in the tank, there's more net positive suction head to overcome the restriction in that filter sock, but as the tank draws down you lose some of that head.
I don't really know how the fuel vapor system works, either, but that is another potential culprit based on the symptoms you're describing. The vapor canister is the black plastic guy bolted to the frame rail on the passenger side front corner of the engine bay (below the ABS unit). Looking at that section of the FSM, the purge control solenoid valve is the brown solenoid on the front of the passenger side strut tower (I think - the line drawing is kind of crappy, and I don't have my car here to refer to). Check all the vacuum and vapor hoses are connected to those guys and not kinked. I think there's a check valve in one of the vapor lines to the vapor cannister - maybe pull off the line and be sure you can blow through that one way but not the other? (Of course, I don't know which way is right. ) Maybe try a new purge control solenoid? Looks like they're $48 through www.rockauto.com, and it says it's a Subaru part. Same part number on 1stsubaruparts.com is $65, so Rock Auto's got a good deal going. Still, I'd probably try to scavenge one for $2 at a junkyard first.
|05-25-2008, 11:07 PM||#3|
Join Date: Jul 2004
98 RWD BG Outback
...with R200 and ITBs ;)
I'm with Patrick on the hoses and the pump sock.
Check to make sure that the gas tank vent tube isn't kinked or crimped. This causes a lot of problems on BD/BGs since it travels through the frame of the car. You should be able to spot a spring-clamped rubber hose just above your rear subframe on the fuel door side. Make sure that guy isn't rotted or pinched. Also, the vent tube travels back out of the frame and up the rear fender well to the top of the filler neck.
DOes the fillup speed improve if you don't put the nozzle in all the way or rotate it a little?
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