fuel fill cap spare o-ring not fit

[paulga]

The existing o-ring has developed some cracks so I bought some spares that seem to fit the cap size. I bought 1 1/2" (38mm) o-rings. but the spare is a tiny bit larger than the existing o-ring. As a result, it runs a bit too loose when it goes onto the fill cap. since it cannot seal, i had to reuse the existing o-ring. is there a smaller deck fill o-ring than 1 1/2"?

in this photo, the one on top is the existing o-ring, the other one is the spare

 

[fgutierrez10]

The existing o-ring has developed some cracks so I bought some spares that seem to fit the cap size. I bought 1 1/2" (38mm) o-rings. but the spare is a tiny bit larger than the existing o-ring. As a result, it runs a bit too loose when it goes onto the fill cap. since it cannot seal, i had to reuse the existing o-ring. is there a smaller deck fill o-ring than 1 1/2"?

in this photo, the one on top is the existing o-ring, the other one is the spare

View attachment 155253

Take your old o-ring to a NAPA store and they'll match it for you

 

[paulga]

Take your old o-ring to a NAPA store and they'll match it for you

Thanks.
I thought 1 1/2" is the norm.
actually i just saw o-rings are sold at every sizes
I will buy some 36 and 37mm and match if NAPA does not have it

 

[Nick F]

actually i just saw o-rings are sold at every sizes
I will buy some 36 and 37mm and match if NAPA does not have it

Yes - O-rings have an enormous range of standard sizes. Buy a ring that is one or two sizes smaller, but the same thickness. Where I live there is a store that specialises on O-rings. If possible, take the cap to the store and get a ring that is just a bit of a stretch fit on the cap. You will have to stretch it more to get it past the threads of the cap but, when in place, it should still be slightly tight (ie, not loose).

Here is the listing of O-ring sizes

https://www.parker.com/Literature/O-Ring%20Division%20Literature/2-sizes.pdf

 

[Marco Flamingo]

I have three different sizes of o-rings on my deck fittings. They all look superficially the same, but not the case. Most plates are secured with a chain. If you can disconnect that, take the plate with you when shopping. Much easier than trying to use a caliper and ruler to guesstimate.

A few years ago I needed a big o-ring for a different project. I took it to an "O-rings-R-Us" type of business in a strip mall north of Seattle. Just o-rings (who knew?) They had special measuring gadgets and a durometer to get it right. Probably not necessary for a simple water-tight deck fitting, but make sure that you get something that is fuel rated even if not for fuel. You might even spend the extra pennies for Viton.

 

[paulga]

Yes - O-rings have an enormous range of standard sizes. Buy a ring that is one or two sizes smaller, but the same thickness. Where I live there is a store that specialises on O-rings. If possible, take the cap to the store and get a ring that is just a bit of a stretch fit on the cap. You will have to stretch it more to get it past the threads of the cap but, when in place, it should still be slightly tight (ie, not loose).

Here is the listing of O-ring sizes

https://www.parker.com/Literature/O-Ring%20Division%20Literature/2-sizes.pdf

Which store is the oring outlet?

I just checked the local Napa store, they don't have orings in store

 

[Bmarler]

The deck fill o ring is a bit unusual in that it has a smaller cross section for the diameter.
I use the two pack from Perko on mine. https://marinepartssource.com/spare...MI98Pl-IK7hgMV187CBB13JQAmEAQYDSABEgIDyPD_BwE

 

[Nick F]

I use Fluidseal Inc, but they are in Canada. Google for O-ring supplier.

As regards the O-ring material, I prefer Buna-N (also called Nitrile). Both Buna and Viton are rated excellent for diesel, but in my opinion Buna is a bit more elastic and easier to stretch into place. Buna is also less money and more readily available - it is the basic material for O-rings.

As also mentioned, you have a choice of hardness. The most common is 70 Durometer and this I recommend. You dont want 90 which is used for very high pressure sealing, and also harder stretch into place.

 

[C lectric]

O rings are available in a HUGE range of sizes, from small where you almost need a magnifying glass to see it is an O ring to huge which are many feet across. They are also available in various shapes such a square O rings and others.

Also in Metric sizes.

They are numbered also to identify them rather than using the measured sizes.

Always take your old ring with you or the odds are you will not measure it correctly.

Keep a note of which ring goes where and the size needed including that number.

THat's what I do and then I only need to look it up in the future. Saves a large amount of time.

 

[paulga]

I use Fluidseal Inc, but they are in Canada. Google for O-ring supplier.

As regards the O-ring material, I prefer Buna-N (also called Nitrile). Both Buna and Viton are rated excellent for diesel, but in my opinion Buna is a bit more elastic and easier to stretch into place. Buna is also less money and more readily available - it is the basic material for O-rings.

As also mentioned, you have a choice of hardness. The most common is 70 Durometer and this I recommend. You dont want 90 which is used for very high pressure sealing, and also harder stretch into place.

The main purpose of the oring is to keep water out. I thought diesel does not usually get to the oring. Nitrile orings should be rated for fuel, even though it does not say so explicitly? Also immune to the ethanol additive?

 

[paulga]

The deck fill o ring is a bit unusual in that it has a smaller cross section for the diameter.
I use the two pack from Perko on mine. https://marinepartssource.com/spare...MI98Pl-IK7hgMV187CBB13JQAmEAQYDSABEgIDyPD_BwE

I didn't focus on the thickness. The spare part is 3.5mm "wire size". There are also 4mm and even 5mm size. Is a thicker oring preferred because it seals more effectively?

 

[JDCAVE]

I go to a place called “Fluidseal”. They have EVERYTHING. I bring in a sample and they put callipers on it and measure it every which way but Sunday. I change my filler cap “O” rings nearly every year and I have two sizes. I bought about 20 total for $20. Sometimes when I go to Fluidseal they give what I need and they send me away, no charge.

They even found me the seal for my “Speed Seal” on my raw water pump, and you won’t find those many places.

So try and find a place that just sells seals.

Jim

 

[paulga]

I go to a place called “Fluidseal”. They have EVERYTHING. I bring in a sample and they put callipers on it and measure it every which way but Sunday. I change my filler cap “O” rings nearly every year and I have two sizes. I bought about 20 total for $20. Sometimes when I go to Fluidseal they give what I need and they send me away, no charge.

They even found me the seal for my “Speed Seal” on my raw water pump, and you won’t find those many places.

So try and find a place that just sells seals.

Jim

Thanks. That store is only available in Canada. I saw the shipping options are greyed out.
Having a local oring store would be better than buying lots of potential matching sizes.

 

[JDCAVE]

Ask around locally with mechanics, oil industry, or others. I googled “O” rings and Vancouver or Richmond and Fluidseal came up. I am sure there are others. I’m sure that any big US city will have some similar business. I see that Greenline Hose also stocks seals. Seals are a pretty important item with many needs. Gotta be something near you.

Jim

 

[Bmarler]

I didn't focus on the thickness. The spare part is 3.5mm "wire size". There are also 4mm and even 5mm size. Is a thicker oring preferred because it seals more effectively?

It’s better to use the correct thickness. Then the cap seats in the deck fitting properly. If the o ring is too thick the cap won’t screw down flush.

 

[hmason]

Surprisingly there is an app to measure o rings. It's called "Olypsys"and it's available in the App Store and google play. It claims to measure both the diameter and thickness of the O-ring. I've never used it but it sure looks interesting.

 

[JDCAVE]

Well…I’m off to Fluidseal tomorrow! American Diesel sent me a couple of fuel line seals for installation of my new on-engine fuel filters. They are quite stiff. I says to myself “Be careful not to drop these, you’ll never find them around the engine!” Sure enough Flip! Never to be found! Installation paused while I take the other new seal to Fluid seal tomorrow for sizing.

 

[Nick F]

A bit more info on O-rings:

- There are not separate metric and inch sizes – the table lists the dimensions in both units.

- The bible is the Parker O-ring table as listed in my previous post. I repeat it again:
https://www.parker.com/Literature/O-Ring Division Literature/2-sizes.pdf

- There is a standard numbering system, which includes a digit for the thickness (cross-section or cord size). The numbering system is as follows:

Number _______Cross-section, inch (mm) _______Nominal cross-section

2-0xx ______________0.070 (1.78)______________________1/16

2-1xx ______________0.103 (2.62)______________________ 3/32

2-2xx_______________0.139 (3.53)_______________________1/8

2-3xx ______________0.210 (5.33)_______________________ 5/32


- As Bmarler says, you should use the correct (original) thickness.

- Stick with 70 Durometer Nitrile

- Once again, Google for O-ring suppliers in your area to find the local best place. If you have to buy online, buy a range of sizes either side of what you think is right. They are so inexpensive that this is a no-brainer!

 

[Comodave]

The main purpose of the oring is to keep water out. I thought diesel does not usually get to the oring. Nitrile orings should be rated for fuel, even though it does not say so explicitly? Also immune to the ethanol additive?

You want diesel rated O rings if it to be used on a diesel fill. You may get diesel on the filler when fueling. The

 

[Nick F]

See Parker compatibility chart

https://www.parker.com/literature/O-Ring%20Division%20Literature/Section%20VII.pdf

 

[koliver]

I have a box of assorted O rings from Harbor Freight. Cheap and will get you by if not exactly the size or material you are looking for.

 

[C lectric]

I too have boxes but they only cover a limited range of sizes.

As you find you need an O ring get the number for it

O rings are available in a HUGE range of sizes, from small where you almost need a magnifying glass to see it is an O ring to huge which are many feet across. They are also available in various shapes such a square O rings and others.

Also in Metric sizes.

They are numbered also to identify them rather than using the measured sizes.

Always take your old ring with you or the odds are you will not measure it correctly.

Keep a note of which ring goes where and the size needed including that number.

THat's what I do and then I only need to look it up in the future. Saves a large amount of time.

If you have the parts books for you equipment find that part and not the O ring number as part of the parts book.

 

[paulga]

Ask around locally with mechanics, oil industry, or others. I googled “O” rings and Vancouver or Richmond and Fluidseal came up. I am sure there are others. I’m sure that any big US city will have some similar business. I see that Greenline Hose also stocks seals. Seals are a pretty important item with many needs. Gotta be something near you.

Jim

curious what did that store use to take a measure of the oring

i solved my puzzle by digging into the PO's spare parts. I found a bag labeled as "Deck Fill Caps". It includes 4 orings that fit the fuel cap snugly, so I changed for both fuel caps.

with a caliper, i got the size is 36.5 x 3.5mm

 

[Flatswing]

this is one time where i used West Marine. -a box of assorted O rings in useful sizes and lots of them for $20. lots to fit my various 1 1/2" deck fills and everything else aboard.

 

[paulga]

this is one time where i used West Marine. -a box of assorted O rings in useful sizes and lots of them for $20. lots to fit my various 1 1/2" deck fills and everything else aboard.

their goods look ok.
but the price of some stuff only sounds correct when the store runs 20% off programs

 

[johnma]

orings come in many different cross sections and sizes. Depending where it was made. Japan cross sections are on the .2 and .8 mm ( ex. 1.2, 1.8, 2.2, etc.) Europe, especially Germany are on .5 mm ( example, 1.5mm, 2.0mm, 2.5mm, etc.) American are all over the place with cross sections and work with what they call dash numbers, which are 4 digit number that begin with a 2 or 3 (example 2-001, 2-002 etc

so, try to measure the cross section and the id. As you can see from the details above, you need to be exact or you're going to keep getting it wrong. See if there is a hydraulic component repair shop near where you live and bring them the sample unless you want to spring for a digital caliper to make your measurements.

 

[paulga]

orings come in many different cross sections and sizes. Depending where it was made. Japan cross sections are on the .2 and .8 mm ( ex. 1.2, 1.8, 2.2, etc.) Europe, especially Germany are on .5 mm ( example, 1.5mm, 2.0mm, 2.5mm, etc.) American are all over the place with cross sections and work with what they call dash numbers, which are 4 digit number that begin with a 2 or 3 (example 2-001, 2-002 etc

so, try to measure the cross section and the id. As you can see from the details above, you need to be exact or you're going to keep getting it wrong. See if there is a hydraulic component repair shop near where you live and bring them the sample unless you want to spring for a digital caliper to make your measurements.

Thanks for the insights.

 

[Delta Riverat]

No need for expensive calipers for this sort of work, the cheap ones will do fine. Get a 6 pack. One for the engine room, one for the saloon and one for the fly. Have 3 leftovers for those that fall in the drink -

 

[BruceK]

I have a box of assorted O rings from Harbor Freight. Cheap and will get you by if not exactly the size or material you are looking for.

I`ve got a box of those too, hundreds of them in lots of sizes in one box. Hard not to find the one you want, though query quality considering the cheap price.
When replacing the O ring, or reclosing after refueling etc, you can add to the seal with a good smear of grease over the seal,extending to the fitting edges.

 

[dhays]

their goods look ok.
but the price of some stuff only sounds correct when the store runs 20% off programs

At West Marine you pay for the convenience of having their products available to see, touch, and pick up on site. There are plenty of times when that is worth the premium.