Gen 2 H6 fuel pump O-ring failure- Ethanol? - Subaru Outback - Subaru Outback Forums

SubaruOutback.org is the premier Subaru Outback Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Rate Thread
Old 06-22-2012, 10:47 AM   #1 (permalink)
Registered User
 
Join Date: Nov 2007
Location: central NY USA
Car: 2003 LLBean H6 Outback
Posts: 4,385
Feedback Score: 0 reviews
Default Gen 2 H6 fuel pump O-ring failure- Ethanol?

Just hit me, forgive me if this was mentioned in the individual threads- could the O-ring failure (swelling) be because this o-ring in this pump (or maybe just some lots) is susceptible to swelling from ethanol?

The swelling might even be the cause of the tab cracking.

Dave
CNY_Dave is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 06-22-2012, 12:01 PM   #2 (permalink)
Registered User
 
1 Lucky Texan's Avatar
 
Join Date: Jan 2004
Location: behind the Krell Metal door
Car: 03 H6 OBW & 06 WRX Sportwagon
Posts: 7,475
Feedback Score: 0 reviews
Default

At first, I thought, 'hey, we just need to correlate where folks with the problem live and use of ethanol.' But, I think something like 90% of metro areas use it right?

interesting detail for sure but....i dunno.

I suppose, if there were zero reports from areas known to never have ethanol, that could be a damning piece of evidence. problem is, I'd bet for every report we've seen, there are several that were just repaired at a dealer and the car's owner was just told - "you had a bad fuel pump"
__________________
Time Flies Like an Arrow,
Fruit Flies Like a Banana!
1 Lucky Texan is online now   Reply With Quote Quick reply to this message
Old 06-22-2012, 12:45 PM   #3 (permalink)
Registered User
 
Seabass's Avatar
 
Join Date: Aug 2010
Location: At a bar.
Car: 05 OBXT 5eat stg1.2
Posts: 2,105
Feedback Score: 0 reviews
Default

I doubt it. Fuel systems have been ethanol safe since the 80's.
Seabass is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 01:24 PM   #4 (permalink)
Registered User
 
Join Date: May 2009
Location: WV
Car: OBW H6 VDC, H6 OB Sed, XT6's
Posts: 5,322
Feedback Score: 1 reviews
Default

Quote:
Originally Posted by CNY_Dave View Post
Just hit me, forgive me if this was mentioned in the individual threads- could the O-ring failure (swelling) be because this o-ring in this pump (or maybe just some lots) is susceptible to swelling from ethanol?

The swelling might even be the cause of the tab cracking.

Dave
i was wondering the same thing. I think I can answer this and give us a test that would prove one way or the other.

Mine failed, one partially cracked tab and the oring squished out. I fitted a new oring with the cap that had broken tabs. It lasted a bit over 200 miles and failed again. i had an extra oring and hose clamps to hold the cap on just in case so i got it back on the road easily until I located a good used cap. here's the key:

***when i removed the "new" oring (one day old and 200 miles) it looked exactly like the old one that had failed - waaaay stretched out. it was not even close to reusable.

so this tells us that whatever is causing it can happen very quickly.
but i don't think it's ethanol.

given that it happened so fast on mine that gives us a very easy test. simply place an oring in ethanol gasoline and see how it does after one day. you can even stretch it over a can or something to give it some tension (easier than trying to find compression).

but i think that's highly unlikely to be the case so i'm not doing the test.

i just got a cap from a board member and he happened to include the original old oring and it looks perfectly sized - though aged, not stretched at all. i highly doubt it avoided ethanol gasoline the past 10 years and who knows how many miles before hitting the junk heap.

based on my experience i think the tabs crack and then the ensuing pressure relief from the cap sealing surface and fuel pressure is enough to slowly push the oring out from under the cap...a little bit, then some more, etc. until it's hanging out and the car won't run.

the key is the orings are *really* stretched out....

i'd be curious to know why the caps are cracking....
__________________
H6 VDC OBW, H6 OB Sedan, XT6's, castrated LSi - FWD EJ18
grossgary is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 01:47 PM   #5 (permalink)
Registered User
 
Join Date: Nov 2007
Location: central NY USA
Car: 2003 LLBean H6 Outback
Posts: 4,385
Feedback Score: 0 reviews
Default

Yeah, and why aren't the H4 caps cracking?

Are the pressure specs a lot higher on the H6?
CNY_Dave is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 02:13 PM   #6 (permalink)
Registered User
 
Join Date: May 2009
Location: WV
Car: OBW H6 VDC, H6 OB Sed, XT6's
Posts: 5,322
Feedback Score: 1 reviews
Default

Quote:
Originally Posted by CNY_Dave View Post
Yeah, and why aren't the H4 caps cracking?

Are the pressure specs a lot higher on the H6?
oh wow - this isn't happening on the H4's? i didn't know that.

the H6 and H4 fuel pumps are "different" - though i'm not sure what that means.
__________________
H6 VDC OBW, H6 OB Sedan, XT6's, castrated LSi - FWD EJ18
grossgary is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 02:26 PM   #7 (permalink)
Registered User
 
1 Lucky Texan's Avatar
 
Join Date: Jan 2004
Location: behind the Krell Metal door
Car: 03 H6 OBW & 06 WRX Sportwagon
Posts: 7,475
Feedback Score: 0 reviews
Default

is it always the tab with the ground wire? maybe it's just shock/vibration on that tab from the xtra mass of the wire?

Wonder if failure is more likely on cars driven off-pavement? Or cars driven around mostly empty?( less buoyancy/dampening from the fuel.)


also, check this out; http://www.ultimatesubaru.org/forum/...64#post1117764
__________________
Time Flies Like an Arrow,
Fruit Flies Like a Banana!
1 Lucky Texan is online now   Reply With Quote Quick reply to this message
Old 06-22-2012, 02:45 PM   #8 (permalink)
Registered User
 
Euchre's Avatar
 
Join Date: Jun 2011
Location: Back home again, near where it was made
Car: 2002 Outback Wagon 2.5L Auto Weather Package
Posts: 1,582
Feedback Score: 1 reviews
Default

Ethanol isn't suddenly there in our gas when it wasn't at all before. Ethanol has been added to gas for decades, just in smaller amounts. The permitted ratio of ethanol to gasoline has risen over time, and thus fuel systems have been made to cope with it for quite a while. If your car was made in the 70s or earlier and still has all the original fuel system parts, it might be an issue - but most of those used mechanical fuel pumps and not so many rubber or synthetic O-rings.

The engines that are being hurt by recent jumps in ethanol content are the ones not on the street - boats and small engines. Small engines from as recently as 6 years ago just weren't made with 10-20% ethanol fuel in mind. If you look around, you'll notice many marina gas stations say 'ethanol free'.
__________________
My car warms the rear window, mirrors, wipers, my butt, and my heart - because I WILL get there!
Euchre is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 04:42 PM   #9 (permalink)
Registered User
 
Join Date: Apr 2011
Posts: 16
Feedback Score: 0 reviews
Default

It's definitely also a problem with the 4 cylinders. My 2000 2.5L had a tab crack and the resulting problems. I ended up getting a junkyard fuel pump assembly but had some problems that seem to have been caused by that O-ring not sealing properly. I replaced it with a viton o-ring in the correct metric size and it's worked perfectly every since.

A lot of the o-rings sold at parts stores seem to just be butyl rubber which, I believe, breaks down quickly in gasoline/ethanol. It's also not easy to find the correct size.

The crack on mine looked like a fatigue thing. Possibly due to the wire, or possibly due to cyclic loading on the cap. With a new o-ring the fit is very tight and the fuel pressure should remain fairly high and constant even when the car off. With a looser fit the pressure can leak down while parked and I could possibly see the cyclical pressurization-depressurization eventually causing a problem, especially if there was a rough edge on the cap for the crack to start from.

For posterity, although it's mentioned in another thread on the subject, I used a -928 metric o-ring with a 3mm thickness x 53.09mm ID (not sure if the -928 is standardized - the shop I got it from just used the dimensions).
andykane is offline   Reply With Quote Quick reply to this message
Old 06-22-2012, 04:54 PM   #10 (permalink)
Registered User
 
Join Date: Nov 2007
Location: central NY USA
Car: 2003 LLBean H6 Outback
Posts: 4,385
Feedback Score: 0 reviews
Default

I do see this mentioned a lot more for H6s than H4s- previous post is first H4 mention I recall.
CNY_Dave is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply


Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Subaru Outback - Subaru Outback Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 01:52 PM.



Powered by vBulletin®
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.3.2
Copyright 2009-2010 SubaruOutback.org. All Rights Reserved.