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Tii Kf Pump O-Rings


TR

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Yes there is plenty of discussion on FAQ going back a decade or more.  I searched and read a ton of it so don't yell at me.... :ph34r:

 

Some people say any fuel rated O-ring that is the same size will work.  Others say stick with the BMW O-rings.  My big concern is how long have the BMW O-rings been "drying out" while sitting in the factory parts warehouse in Germany and are they really up to 2014 fuel mixtures?

 

As mentioned in FAQ posts Buna material O-rings are an option.  What is the current thinking from the tii experts?

 

The supplier listed below has a 385 piece kit that includes 20 of the size 012 rings. 

 

70D Buna-N Black O-Ring Kits
$10.00 Order Online Special

http://www.allorings.com/oring_kits.htm

 

TR

'71 MGB - sold   '74 2002 - sold

'89 XR4Ti - sold  '94 Miata R Package - sold

'73 tii - restoration project - sold

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I'm no expert on the topic, so I tend to take the practical approach:  buy new.  If it works, then the FAQ will have a data point that "an o-ring is an o-ring."

 

Besides, they can't be any worse than "Genuine BMW Parts" which are made in China ...... and even a "lazy purist" such as myself won't know the difference anyway.

 

Cheers,

 

Carl

Edited by OriginalOwner
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Carl - thanks for commenting.  I'm hoping to update the somewhat old FAQ info and see if the tii experts have come to a conclusion about these o-rings (under the suction valve caps, the pressure regulator valve and other locations?).  

 

My concern was also that the BMW o-rings have flat sides vs. the curved sides of generic o-rings.  Does the small difference in shape matter?  Is newer material (Buna or other) better able to handle modern fuel mixtures (ethanol, etc.)?

 

TR

'71 MGB - sold   '74 2002 - sold

'89 XR4Ti - sold  '94 Miata R Package - sold

'73 tii - restoration project - sold

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Well that shows ya what I don't know:  never heard of a flat-sided o-ring ..... extrapolating into the nit-picky grammatical sense, BMW thus does not make an "o"-ring.

 

You'd have to Google "buna" for its suitability in gasoline/ethanol/whatever, I don't know.  Or call an o-ring manufacturing company and chat with their expert.

 

As for shape, if I correctly visualize what a BMW flat-ring looks like ..... with a full-cross-section O-ring you'll get more down-squish and therefore better sealing.  However, the o-ring will also squish out to the side, which means you'll have a smaller passage for fuel flow.  How much smaller ??  I'm not sure I can do the math on that, there are a lot of variables.  Or maybe these o-rings are not sealing a space related to fuel flow, and thus more squish doesn't matter ??  I don't know, never had a KF apart.

 

Perhaps the best idea is to chat with one (or more) of the people who rebuild the KF.  I have every confidence they are the best source of "what works" 40 years after the fact, since they are doing it now.

--  Gus Pfister in the San Fran bay area.

--  JF Pro in Van Nuys, CA.

 

Cheers,

 

Carl

Edited by OriginalOwner
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The only flat o-rings I've seen are used o-rings that need replacing. I'm not an expert, but when my car sits for awhile, the o-rings will sometimes leak. I bought a bulk bag of o-rings recently instead of buying the BMW o-rings for about the same price. I'll see if I can find the info if you're interested. They've worked well for a year or so and ive got plenty of spares.

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O2Tom and anyone else with a tii –

 

As I move forward getting my tii back on the road a big concern is getting fuel system parts (hoses, o-rings, etc.) that can handle current fuel mixtures.  I would like to avoid a fuel leak fire caused by:

 

  1. The official BMW part being not suitable for today’s fuel mixtures or having sat on a shelf so long that it fails prematurely or is no longer the same quality BMW offered 40 years ago.
  2. A non BMW part that is not correct for the application.

 

Note: I’m happy to buy the official BMW parts if they are the best solution.

 

I was hoping to get a clear answer if the official BMW “o-rings” under the 4 suction caps and the pressure regulating valve have a shape unique to the KF injection pump or if they are typical o-rings.  Also if someone can confirm the correct size for these to o-rings that would be helpful.

 

I looked at my 40 year old o-ring from the pressure reg valve and it appears to have a tapered side but this could be due to decades of compression.

 

Searching the FAQ there was info about http://www.allorings.com/  which has info on various materials and seems like a reputable source.  Materials they stock in ready to ship sizes:  Buna-N and Vitron.  Fluorosilicone might be a better material but this is a custom product.

 

FYI - I am not sure but if the 012 size o-ring is the correct size……

Viton o-rings, bag of 50 is $6.50

Buna-N o-rings, bag of 250 is $5.75

 

TR

'71 MGB - sold   '74 2002 - sold

'89 XR4Ti - sold  '94 Miata R Package - sold

'73 tii - restoration project - sold

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All i can offer is my experience, if this is of interest to you. The BMW o-rings I had bought seemed rather short lived to my memory. I had bought some around 2006 and by 2010 theyd already leaked after a long winter of not driving the car. After messaging someone on the FAQ, I bought some of the Buna-N o-rings that he had posted about. Like he had found, they work and if they start to leak, I've got extras. The item number was B1000-012 thru marcorubber.com with a description of 2-012 Buna-N O-rings. Maybe it would be a good idea to just replace them every two years in my case.

I've used the BMW fuel hose without issues for over 15 years on one car with gas with a 10 percent max ethanol content. Hope this helps.

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02Tom,  Thanks and my plan was/is to use the Buna-N o-rings because I don't have confidence that BMW's o-rings will be newer/better.  If anyone needs some I should have plenty of extras.  TR

'71 MGB - sold   '74 2002 - sold

'89 XR4Ti - sold  '94 Miata R Package - sold

'73 tii - restoration project - sold

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These o-rings seem to be the right size to be used to keep tension on the fuses like some of the e28 crowd is doing. I tried it on my 528e just for kicks. They seem a little tighter than what I'd want personally, bur i don't know what size they're using. I don't have any real interest in doing this to my car, though Ive had a lot of problem with them recently, but it may be a way to unload a few of the o-rings.

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These o-rings seem to be the right size to be used to keep tension on the fuses like some of the e28 crowd is doing. I tried it on my 528e just for kicks.

Rod used 7/16-inch I.D. silicone rubber O-rings to apply tension across the arms on the fuse box:

0-ring_fuse.jpg

John in VA

'74 tii "Juanita"  '85 535i "Goldie"  '86 535i "M-POSSTR"  

'03 530i "Titan"  '06 330ci "ZHPY"

bmw_spin.gif

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These o-rings seem to be the right size to be used to keep tension on the fuses like some of the e28 crowd is doing. I tried it on my 528e just for kicks.

Rod used 7/16-inch I.D. silicone rubber O-rings to apply tension across the arms on the fuse box:

0-ring_fuse.jpg

John in VA

'74 tii "Juanita"  '85 535i "Goldie"  '86 535i "M-POSSTR"  

'03 530i "Titan"  '06 330ci "ZHPY"

bmw_spin.gif

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...and to close this thread: 

 

The o-ring kit arrived and appears to be very good quality.  Kit was marked: Cure date=4Q2012 and Expiration date=4Q2027 so I know how old the rubber is.

 

I used the 110 size on the pressure regulation valve - the 012 size was smaller than the o-ring I pulled out.  I'll replace the suction cap o-rings and check for leaks the next time I start the tii.

 

Kit was on sale for $10.  Shipping was $11.

Marcorubber.com

 

TR

 

post-43366-0-89369500-1401922478_thumb.j

'71 MGB - sold   '74 2002 - sold

'89 XR4Ti - sold  '94 Miata R Package - sold

'73 tii - restoration project - sold

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