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Guest Message by DevFuse
 

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Erratic fuel readings?


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17 replies to this topic

#1 Guest_mtsmiths_*

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Posted 09 June 2003 - 10:29 AM

Drove Whitefish > Spokane > Whitefish yesterday, '00 Legacy ran fine, but on return trip started getting faulty gas readings. Needle would drop slowly from 1/2 to E, wander back up to 1/4, drop back to E w/low fuel warning light, then back up to 1/2.

Consumption is normal, readings are normal until it gets to 1/2 tank. If you shut it off it reads normal for awahile then starts getting erratic.

Other than that, the CEL (which seems to come and go) had been off for two weeks straight and IT came back on when all this cr@p started.

Clueless on this end.

Yes, the cap was on tight.

Any help appreciated.

#2 Guest_mtsmiths_*

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Posted 09 June 2003 - 10:34 AM

No I DON"T top off!

Yes I DO turn cap for six clicks.

Where are the sending units and how do you get to them ... and how much $$$$ do you have to shell out to SOA for the parts?

#3 Guest_mattocs_*

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Posted 09 June 2003 - 12:28 PM

Ok. what is topping off? If it when you have almost a full tank and you fill it up the rest of the way? or is it when you fill it up and then keep fillling it up until it is all the way full?

#4 Guest_mtsmiths_*

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Posted 09 June 2003 - 02:15 PM

When the auto shut-off engages and cuts off the fuel flow, and you grab the nozzle and pull it out a few inches and hit it again to fill it right up to the filler neck ... that's 'topping off'.

Don't do it. Leave it at the auto shut-off.

#5 Guest_Bulsi_*

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Posted 10 June 2003 - 08:40 AM

I just responded to the same problem under the "Check engine light, 2000 Forester. " post.
I had the EXACT same issue with my 98 OB, the fuel gauge drops to 1/2 tank or empty momentary and you get the CEL.... it was the fuel level sending unit. There are actually two in my OB. It is not possible to visually tell which one is bad, you'd have to use some testing equipment. For good measure, I replaced both myself and the problem was solved. Apparently this is not an uncommon Subaru issue. I had this mysterious condition for over a year... the dealer just kept giving me the "don't top it off" and "gas cap" solution, but trust me, it's your fuel level sending unit(s). Replace them and your troubles will be over.
If you are mechanically inclined, it's not very difficult to do yourself and it is covered in the Haynes Manual.

#6 Guest_TDOG67_*

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Posted 10 June 2003 - 09:51 AM

How much did the sending units cost?

#7 Guest_mtsmiths_*

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Posted 10 June 2003 - 09:52 AM

Can I trouble you for a quick description of the process (which I hopetogawd doesn't involve removing the fuel tank). I'm fairly wrench savvy, but am leaving Montana for DC Thurs. at 0'dark:thirty and don't have access to a Haynes.

I'm not gonna worry about it on the trip out, now that I know there's no fundamental problem. But I'll be back there all summer, and would like to fix it.

I checked fuel consumption for the leg we were exhibiting the problem and it was 27.7mpg. Best the d@mn car has ever gotten, must be the RS205/15s and alloys I just put on it.

#8 Guest_93leg_*

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Posted 10 June 2003 - 02:36 PM

Re: Fuel guage probs on 1990 Legacy

I copied this from somewhere. Maybe the Archives. I have just done this over the weekend with success on my 93 Legacy. I took my time...around two hours. Saved a lot of cash. I would check the fuel pump side first.Here it is.

Could be of some help.
«Since I have seen lots of complaints posted about the fuel gauge senders for '95 Legacys of all types failing (check out how many at dejanews!) and have not seen any posts about how easy it is to fix, I thought I would post my experience. I had to get a car last weekend (broke my left foot, can't use the clutch in my usual car...) and got a '95 Outback wagon, in part because it is very similar to my wife's '97 so anything I learn from it has double application... The only thing really wrong with the car, I got it pretty cheaply, was that the fuel gauge was not working right.
First of all, kudos to Subaru for making it so easy to get to the senders! On most cars I would have to drop the fuel tank, but this has plates screwed down in the luggage space that open to uncover ports in the top of the tank. (There is one sender on each side of the car for the AWD cars, where the tank goes up over the drive shaft so has a low spot on each side, just one on the right side for the FWD models. The one on the right has both the in-tank pump and a sender, the other just a sender. The two senders connect to an electronic box that averages their output.)
After you open one of the ports you can take out the sender pretty easily: The one on the same side as the pump has to be unscrewed from the pump to get it through the port: Don't drop the screws in the tank!
Once the sender (the two are almost identical) is out on a bench you see a standard float on an arm, moving a contact along a resistor pack on a ceramic printed circuit. The problem turns out to be the The connection between the moving contact and the wire off to the outside world. The wire connects to a thin brass piece, that has a phosphor-bronze spring pushing against it, the other end of the spring pushes against the moving contact piece. Between the brass piece and the moving contact should be less than 1 ohm, was infinite on both of my senders no matter how I wiggled the float arm around. The metals had just gotten oxidized. The float is held in by a push-on nut. It might be possible to get that off peacefully, but I was afraid of damaging the mechanism so I hit it with a Dremel and took it off. It is then pretty easy to disassemble the float and contact assembly: Look out for a small plastic pivot piece that the float arm goes through, you not only need to be sure not to lose it you also have to either keep it in position in the plastic body or else later on you will have to rotate it to drop exactly in to place. I used fine silicon carbide paper to clean the surfaces of the two brass pieces (moving contact's arm and connection to outside world) and also the two ends of the spring, put it back together, good connection in all positions of float. The only remaining problem is to hold it together: If you were able to remove the push-on nut you may be able to reuse it. I got a roll pin at the hardware store, one of those little pieces of steel that is not quite a tube because it has a slot down one side, designed to be driven into a hole. It has a 5/32" outside diameter, was about an inch long, and the inside diameter was just too small to fit over the float arm which is about 0.1" diameter. I cut a little ring off of it with the Dremel, forced the ring over the float arm just like the original push-on nut had been, and it was all done but reinstallation. I did both sides, the gauge works perfectly.
This car has 90K miles on it. If I need to do this every 90K miles that will be OK. A more permanent fix would be to take some very flexible wire, e.g. litz wire, and connect it between the two sides so that it flexes with motion of the float. It will have to live in gasoline, so don't use wire with much insulation but rather route the wire so it can't hit anything it should not connect to. I think this would be pretty easy, should last longer than the resistance element would.»
Bob Wilson
Gilles (Montreal)

1992 Loyale wagon, 5spd, 4WD, 192,000 klms (june 99 - stolen oct 00)
2.2L 96 Legacy Brighton wagon, 5spd, AWD, 160,000 Kilometers

#9 Guest_Bulsi_*

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Posted 11 June 2003 - 04:38 PM

Regarding the price, I believe the dealer quoted me about $100+ for each sending unit. I ordered them online for around $65 each from www.subaruparts.com
The above post is accurate, however, it makes it sound more difficult than it really is. If you are NOT trying to fix the existing sending units, but want to replace them with new parts... it's pretty straightforward.
The only tricky parts are pulling the assemblies out through the small openings... it's really very easy, just take your time, play with the rotation and angle a little and they will come out easily. The second trick is that the driver side unit has the Low Fuel Level sensor attached. This is easy too, just cut the old wire and solder on the new wire lead from the new sending unit.
Once you see the assembly and have your new parts in hand, it will all make sense.
Check your email, I'll send some helpful pictures.

#10 Guest_mtsmiths_*

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Posted 11 June 2003 - 05:54 PM

I'm battery dancing right now. See if it all goes away on it's own.

If it comes back, I'll do it sometime this summer and the PIX will help a LOT!

#11 Guest_subekit_*

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Posted 25 June 2003 - 05:21 PM

was wondering if the repair process would be the same for the sending units on my 99 legacy L wagon ? dealer told me this year has the fuel pump/sending unit that cannot be separated..great ! so instead of getting a new sender for $65 , i'd have to get the whole unit for $250+....so i'd like to fix it if possible before forking over the $...the car has 88k.

#12 Guest_mtsmiths_*

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Posted 25 June 2003 - 06:59 PM

Two battery dances, and 2,400 miles of driving and no more bogus fuel readings, the low fuel light now comes on between 1/16th and empty.

Cruising at a steady 70 - 75mph we averaged 27.2 or so for the whole trip. One leg from Janestown, WI to Columbus, OH we got 30.1. I'm getting 26.7 running around in Maryland traffic ... and belive me, after six years in Montana this is TRAFFIC!

I'm cinvinced the CEL (O2 sensor) is a poor connection. Every time I erease it, it comes on after driving on a rough stretch of road.

#13 Guest_Drquasievil_*

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Posted 26 June 2003 - 01:10 PM

I had a similar problem on my 95 legacy. It was less than 3 years old and the dealer replaced the two fuel sending units for free. As soon as the warranty expired, one or both of the sending units went bad again. The gage registers 3/4 when the tank is full. I left it alone after that. A notorious Subaru problem. Or it could be the float inside of the tank. Try to get it repaired for free.

#14 Guest_subekit_*

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Posted 26 June 2003 - 01:56 PM

damn sending units huh ?! thanks to mtsmiths for telling me about free code reading at autozone...they did it in 5 minutes...got a po463 " voltage signal from the fuel level sensor is too high for the current engine operating conditions." can anyone tell me if it can be fixed as in 93leg's posting a few above this one ? fuel level sender is luckily only $52+ at 1stsubaruparts...so i dont know if it's worth it to spend the time trying to fix it ? but i love the challenge. does anyone make high quality aftermarket :rolleyes: sending units for these subarus ? seems like if i get new oem, it's just gonna happen again down the road...as in the posting above ? anyone ?

#15 Guest_Drquasievil_*

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Posted 26 June 2003 - 02:16 PM

Why would you go through the trouble of pulling parts out and fix a sending unit that it will fail again or you may not be able to fix. If you have to go through all that might as well get the new sending units. remember there are two.

#16 Guest_subekit_*

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Posted 27 June 2003 - 07:41 AM

why try to fix it ? why not ? did you read leg777 ? i'd rather spend a couple hours learning something new about my car ..then just shelling out $ for a part i potentially don't need..and if it happens down the line , so be it ..i'll know how to work on it. and i'll know the work was done correctly...it seems like the problem in these units lies in the resistance of the arm, the contacts and wire developing an oxidation...an ohm meter will show if the resistance is correct for the full..around 50...empty..around 1ohm..and it should be an even, gradual resitance between the two extremes.:P

#17 Guest_Drquasievil_*

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Posted 27 June 2003 - 12:52 PM

I hear you. Please let us know your experience and if the fix worked. We can learn something from your experience

#18 Guest_subekit_*

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Posted 27 June 2003 - 05:25 PM

let you know how it turns out Doc .




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