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Discussion Starter #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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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.
 

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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.
 

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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.
 

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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.
That worked for me for a few months, but overtime the crack grew and the o-ring pushed out again despite the hoseclamp. I would definitely plan on replacing the cap sometime soon before it leaves ya' stranded.
 

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Discussion Starter #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.
 

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Discussion Starter #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?
 

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Yep, gotta take one off of a pump assembly, unless you can find a source selling replacement caps (Lemme know if you do!). Assuming the used pump I bought on ebay was correctly described as a 2.5L pump, then yeah, the caps are the same.
 

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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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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?
 

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Discussion Starter #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.
 

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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.
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?
 

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Discussion Starter #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?
 

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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...
 

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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...
brilliant investigation!
 

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Discussion Starter #16
Thanks!

Car is back to normal now, starts up immediately after sitting overnight, even.
 

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what years/models are likely to have caps compatible with -say- an 03 H6 Outback?
 

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I also wonder if individual PARTS for the aftermarket Airtex or Bosch (other?) units might be available and if they'd fit/work on OEM?
 

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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.
 
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