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Symptoms of fuel pump O-ring problem?

165K views 167 replies 66 participants last post by  1 Lucky Texan 
#1 ·
Our '02 H-6 Outback suddenly started running poorly tonight - it runs fine at idle and up to 1/8 to 1/4 throttle, but as soon as you ask for more power it just falls on its face. If you can get it to rev up to around 5K, it perks up some but still isn't running like it should. I at first suspected a plugged cat, but after driving it some I don't think this is it, as the break point between running OK and not is very distinct.

I haven't had a chance to connect a fuel pressure gauge to the fuel rail yet but I suspect that this may be a case of low fuel pressure, possibly caused by the O-ring popping out of the cap beside the fuel pump as I have seen in a couple of threads here. Most of the descriptions seem to indicate that the car just quit running, though, not running but at reduced power.

http://www.subaruoutback.org/forums/66-problems-maintenance/26419-2001-subaru-just-shut-down-2.html

Has anybody seen the infamous O-ring cause symptoms such as the ones I'm seeing, or if not any ideas where to look next?
Also, what pressure should I be seeing on the fuel rail at idle? The manual I have isn't very complete as far as diagnosis but it does call out a pressure range from the pump of 54-98 psi.

Thanks!
 
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#2 ·
Sounds about right. Yours probably hasn't completely expelled the o-ring yet. Mine ran similar to that on the way back home from the gas station and wouldn't start after I parked it a few days back. Just fixed mine today by replacing my cracked cap (the thing that retains the o-ring) with one from a used 4-cyl pump. The good news is the fuel pump is pretty easy to access and remove to repair/replace.
 
#3 ·
Well, the car wouldn't start at all for my wife this morning so she used my daughter's car to go to work. I hit seven stores on the way home - auto parts, (Napa included) hardware stores, and Lowe's - and nobody had a -138 O-ring in stock. When I got home I ordered a pack of ten Viton O-rings off of Amazon and they will be here tomorrow. Shipping was one and a half times the cost of the O-rings, but what are you going to do? I was lucky to get them overnighted, I only had 20 minutes to spare before it would have been too late to get them by tomorrow.

Looks like I get to dig into it tomorrow after work. Hopefully that's all it is.
 
#4 ·
Got it apart - one of the tabs on the metal cap is cracked partway where they folded it vertical. Manufacturing defect! The O-ring did not appear to be swollen but I will replace it with a new one I got that is made of Viton so that shouldn't be a problem in the future.

Taking a break for supper now, will post some pictures I took of it later.

I am going to try to wrap a hose clamp around the tabs once I reassemble the cap, hopefully that will help it stay together.
 
#6 ·
Pretty poor pictures for the most part, but it was dark and cold. :) Click the picture for a large version.

Here you can see the O-ring popping out:



A couple of pictures of the bend and crack in the metal tab:









I ended up putting a hose clamp around the three tabs once it was installed on the pump assembly body. I tightened it up just enough to prevent it from slipping off. Hopefully the crack doesn't grow.

Car runs great now! This really wasn't that bad of a job. Beats crawling under the car and dropping the tank to get to the pump, like I had to do with the Bonneville my wife used to have. That was the pits.
 
#7 ·
So I take it the only way to get a replacement cap is to cannibalize another pump?

If so, is the cap on a 4-cylinder the same as the cap on the pump on an H6?
 
#9 ·
Just as a followup...

Car still runs great and has all the power it should, but does not start immediately if it has been sitting off for a while. I had my wife try turning the key on and off a couple of times before starting it after it had sat and it did fire right up then, so it appears that the fuel pressure is bleeding off over time.

My suspicion is that the replacement Viton #138 O-ring I put in is just a whisker smaller in cross-section than the (probably metric) original and it is allowing gas to weep past when the pump is off. The Viton is a slightly higher durometer than Buna, at 75 vs 70 and that may not be helping matters, especially with the cold temps we have been having.

I'm inclined to leave it alone for the time being and try to source a replacement cap. I kept the original O-ring and will probably put it back if I can find a cap - I really don't want to mess with the cracked one I have now if I can help it.

I searched car-part.com for a fuel pump and they didn't have any listings whatsoever.

Found a couple of pumps listed on eBay for $90 in a junkyard in VT, about a 2 hour drive from me. They did not have actual pictures of the pumps, and the listing was somewhat unclear so I sent them an E-mail asking if it was just the fuel pump itself or the entire assembly via their listed contact address the day before yesterday but have not heard any response back from them as of yet.

Next best choice I have found is from Advance Auto Parts, at $338.09. They currently have a 15% off promotion going on so that would bring it down to about $288. Free shipping, too.

Not sure what I'm going to do yet - waiting to see if I hear back from the junkyard. My wife relies on the car for work so uptime is very important.
 
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#10 ·
OK, I was gonna try to draw somthing in Paint, but I'm gonna try to just describe an 'approach' to a fix.

There are 3 molded tabs on the chamber right? A screw type 'hose' clamp, positioned above them, should be secure. Now, suppose 2 more screw clamps were prepared in such a way that they were were cut apart and secured behind/under the clamp on the chamber, at 90degree intervals, but extended under the cap and crossed in an X. Then they could be tightened to pull UP on the cap. Certainly some extremely secure ways to attach everything (maybe pop rivets?), positioned so the screw mechanisms clear each other, etc. is critical. And i can only suppose the screw clamps would stay secure. Unless there are some type that can be safety wired or otherwise 'locked', there's probably still some risk. Might be at least as secure as the original design!

kinda like garter belts hanging down, then passed under the cap in an X, tightened, to pull up on the cap.

does this make sense?
 
#11 ·
It does, and that might work! I think a single one would be sufficient.

I was also considering TIG welding up the crack, but I'd prefer not to since that's going to compromise the cad plating and introduce the possibility of corrosion, especially with all the alcohol in the fuel nowadays...

I believe they make metal versions of Nylon zip ties, where the metal strip is passed through a sort of a buckle and folded over. Something like that might work, as well.

I was also seriously considering the possibility of making a new cap from scratch. I have access to a lathe and mill at work - the only question would be what material to make it from.
 
#12 ·
oh yeah, like the bands on CV boots. But I guess you can use needlenose pliers to cinch them up?

yeah, I'd comfortable with stainless for the 'hose clamp/garter belt idea', but really, I'd be guessing even on that. there are several stainless alloys and they aren't necessarily corrosion free in all circumstances. But, we KNOW the factory solution seems to have a problem. (but, maybe some type of misplacement of the o-ring causes xtra stress? may be a small fraction of all the cars)

and, as for machining a replacement, I have no idea if Delrin or anything else would work in a gas environment either. Does that cap just snap on or does it 'bayonet' on?
 
#13 ·
Yeah, not sure on material compatibility. If I was the primary driver I would be a lot more open to experimentation but you know that when momma is unhappy, everybody is unhappy and not having her car makes her less than happy. :)

The junkyard finally got back to me, the entire assembly is what they are listing so I am going to go pick one up tomorrow. Then, I will have a spare I can experiment with.

The cap does push on and turn, like a bayonet. The tabs are not symmetrical, either - of the three, one is about twice as wide as the other two so you can only put it on one way for whatever reason. I don't see why that would matter because as I recall the rest of the cap is symmetrical.

One thing I have been wondering is what the purpose of this cap is in the first place. I didn't spend too long checking it out since it was really cold out when I was working on it, but my guess was that it was the bottom of an accumulator. Anybody know?
 
#14 ·
I swapped the cap off the junkyard pump today. While I had the original pump out and laying on a board before taking the broken cap off, I noticed that gas was dripping out from between the junction of the cap and plastic body it connects to.

When I got both of them apart, I put my calipers on the junkyard O-ring then on the Viton -138 O-ring I put in ours. The -138 measured .105" thick, while the junkyard O-ring measured a full .125" thick. I still had our original O-ring and while it was somewhat distorted from where it had popped out, I got an average of about .118" thick.
That's a huge difference!

I coated the OD of the junkyard O-ring plus the ID of the junkyard cap with a little clean motor oil to prevent the O-ring from rolling over and assembled them onto our original pump assembly since it was a whole lot cleaner than the junkyard one. Assembling the cap took a little more force than it did with the -138 O-ring, which is good as it shows that there is a bit more interference now. I put it all back together and we'll see how it works, but I feel confident that this will take are of the problems with restarting after it had been shut off.

Based on my findings, I would have to say that the -138 O-ring someone else specified is NOT the correct one for this application. From charts, the -138 has a cross-section of .103", ID of 2.112", and OD of 2.318".

The plastic section of the pump assembly that the O-ring slides over is ~54mm (2.126") and the ID of the metal cap where the O-ring rests is ~59mm (2.323").

I think it is actually supposed to be a #-928 metric O-ring with a cross-section of 3mm (.118"), ID of 53.09mm (2.090") and OD of (2.326"). This would seem to provide the necessary "squish" to seal it up.

Amazon currently has a 12-pack of 75 durometer Viton -928 O-rings listed for $12 or a 5-pack of 70 durometer nitrile (Buna) listed for a buck. They also list EPDM O-rings in that size, don't use them as EPDM is NOT compatible with gas!

Hope this thread helps someone who comes along later...
 
#20 ·
well, I got a reply from tech services at Airtex and individual parts from their assembly are not available for sale separately.


dunno if they would even be the right size/configuration - but if it was cheap enough, may have been worth try.

I might try to email Bosch. wonder if Denso makes the part for Subaru or ????

seems a shame someone might have to spend $200 - $400 when they just need a $19.95 part.
 
#22 ·
I do regular maintenance on the cars in April and Oct. so, one thing I did to day, was combine changing the fuel filter on the wife's 03 H6 OBW with installing a new , large-type cap and replacing the o-ring on the fuel pump.

here is another link to the youtube video with the best instructions;


I used a metric 928 viton (brown) o-ring , and the cap from a filter kit number W0133-1617990 (about $40- $60 online)


a coupla notes on the above video;

I used a vacuum cleaner to police the area I was working to limit debris possibly getting in the tank.

Lower the windows/open the doors to reduce breathing fumes.

Be prepared for about 2-4 oz. of gasoline to come out of a coupla those hoses. If possible, thread a rag or 3-4 layers of paper towels under the hoses/cable before removing the hoses.

I used some twine to bundle the hoses and cable then threaded the twine up thru the driver's headrest post and pulled them up so they would be out of the way. Sorta replaced the use of the video author's wife's hands. Made it a one-man operation.

His fuel pump gasket came off with the pump. I didn't notice this before and had a more difficult time getting the pump out thru the gasket. So, make sure to free the gasket if it is stuck and carefully bring it out with the pump. Go slowly and carefully as it may be possible to break or bend something if you just 'horse' it outta there.

My original cap appears in great shape, the tabs do not appear to be cracked or bent. The o-ring was quite swollen however. I replaced the o-ring (lubed with a little oil) with the metric 928 Viton unit sent to me (thanx Dave L) and installed the new cap (W0133-1617990). I had to use waterpump pliers to remove the old cap. I f you you any tool, be careful not to bend/break/force anything. I was careful not to rotate the new cap too far as I think the 'bump/dimple' on the large tab is meant to stop the cap at the correct point. Forcing it farther would cause the bump to ride on top of the plastic lug and put outward force on the large tab.


so, still not sure if all these units are quite the 'ticking time bombs' I originally thought. The o-ring was definitely swollen so......
 
#167 ·
I do regular maintenance on the cars in April and Oct. so, one thing I did to day, was combine changing the fuel filter on the wife's 03 H6 OBW with installing a new , large-type cap and replacing the o-ring on the fuel pump.

here is another link to the youtube video with the best instructions;
Hey Tex, the link is broken now, do you know what video that was, and can you link it back here as a reply, so I can put it back your post in 2013.

(seems like just yesterday,...and I thought this thread was newer).
 
#24 ·
^^^I think it's distinctly possible.

And, I;ll apologize here if the multiple posts are annoying, since there are several threads that were never combined, nor one made into a sticky, I thought posting to the larger threads would help someone in the future find info.
 
#25 ·
Outback 2000 Fuel pump o'ring and cracked cap

Hi, I just thought I would share my experience with you, the people from this forum, that ended up helping me alot in my troubleshooting and fixing of this problem!

As I was driving in the city, my Outback 2000 just stalled and would not start anymore. I got it towed at my house and started narrowing the causes of the failure. I checked the plugs : ok, fuses : ok, coil : ok, sensors : ok, diagnostic codes : ok, and strangely, fuel was flowing when I cranked the engine as I checked with the line disconnected from the fuel filter and flowing in a can. This is where it's strange because there was some fuel flowing but not enough! And at one point, it completely stopped flowing. I suspect there was enough pressure to push a bit in the line but not enough to feed the complete line.

Anyway, after reading about this o'ring problem, I decided to reach to the fuel pump to check it. Thanks to this video , it was an easy task, although I really did not like having my face above an open fuel tank... Be careful is all I got to say if you attempt this job!

So, I finally get the pump out and find the small reservoir cap to be cracked (see picture here http://hamsterdoremi.files.wordpress.com/2013/04/photo.jpg?w=240) and the o'ring just barely showing but oviously not doing its sealing job. I unscrew the cap and find that the o'ring is too big for the cap as it probably expanded from the fuel bath!

So I call the dealer to buy the part and, guess what, it's sold as a complete unit only and costs between 565$ and 800$! I check with the local auto parts shop and he tells me the pump assembly is worth 1500$! I inform him that it is twice the dealers price but he says it's a question of demand... No wonder there is no demand dude! Anyways I end up finding a «get the part yourself» scrap yard where the guy sells the complete assembly for 15$, I like the idea! So I get there, thinking I would just swap the pumps completely instead of fiddling with the cap and o'ring. I get to the scrapped car with my ratchet and, O horror, I see that someone already cannibalized the pump and it's lying on the back seat all torn... But the cap and o'ring are still there! And this one is in good shape! I unscrew the thing, tell the guy the pump was already gone, he apologizes and out I am with my free part!

I get back home and put the new used cap back (it's quite tricky but applying a bit of oil greatly helped). Note to future users, the o'ring goes around the pump plastic shaft and not inside the cap cover. You will never be able to screw it this way. I reinstall and voilà! My outback is on the road again. Such a small thing and it almost made me scrap the car... I encourage all of you to attempt this job as it is fairly easy and saves alot of money! Thanks to all!
 
#30 ·
I used a Viton 928 metric o-ring. brown in color. So far, it's working. While i think mine originally came from the internet (I traded for it - long story) you can probably get them from local industrial supply or perhaps a NAPA or carQuest. (try amazon too if buying on-line)

the cap and filter do NOT come with an o-ring (well, mine didn't) I did an internet search on part number W0133-1617990 and bought from partsgeek.

likely that other number would work at a soob-specific parts seller or dealer.
 
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