Gas leak

[thelews]

small puddle of gas near inside of LR tire.  Coming from the long pump(67 250SL) through the canister.  REmoved the long canister and it appears gas was exiting what looks like a small nipple, maybe a relief?  This is a replacement fuel pump from 9-10 years ago, but not that many miles, when the one in the car failed.  This leak occurred after parking from the first drive of this year after climate controlled garage for 4 months.

Any thoughts?  Thanks

[thelews]

In researching, it appears my leak should be coming from the small O ring that seals the "bellows seal" on the inside.  As a testament to the previous owner's fine care of the car for 37 years, and the babied lifestyle it's had with me the last 13, everything came apart easily and looks great.  Attached are pics with no cleaning done.  I did remove the gas inlet housing cover this morning and the filter was surprisingly clean, maybe 2% of dirt particles.  I blew it clean.

Waiting for small O ring for shaft/bellows and large O ring for cover.  Carter P4601HP fuel pump ordered as back up in case my efforts fail.

Kind of surprised there wasn't one response to this query.

[mrfatboy]

Where did you source the o-rings?  When my long pump was rebuilt I bought a full rebuild kit from Authentic Classics.

BTW,  the small O-ring for the bellows shaft was my problem also.

[thelews]

McMaster Carr.  9263K285  With shipping, $10 for a bag of 25.  I'll have 24 left over.  Need any?

[mrfatboy]

I could use a couple for back up. 

Thanks. Pm Sent. 👍

[thelews]

Success.  Got my 25 Viton O-Rings for $11, $6 of which was postage/handling, 5mm ID X 1mm  Different profile than what came out, but fits and works.  As seen above, dug in and removed impeller, C clip, tabbed washer and bellows.  Cleaned as needed (very little), replaced O-ring on shaft sealing upper bellows and reassembled.  Club member was kind enough to send me a Viton O-Ring for the cover for a short pump (mine is long).  $29 from sources for just that O-ring. Different spec, about 1/2 mm larger in diameter and thickness, as I recall.  Interestingly, it was smaller than the one I removed, lubed it very slightly with Vaseline, stretched it just enough that it would sit in the groove long enough for me to get the cover on and keep it aligned and sealed.  Back together, hooked up, purrs like a kitten, no leaks, car runs as splendidly as ever.

Total cost, $13, $11 for O-rings, $2 to return the favor I got by sending off a couple of shaft O-rings to a couple of other club members.  Place out east wanted $450 to repair!

[ja17]

Sounds great John, and on your car, I know you barely got your hands dirty because it is spotless from top and bottom.

[thelews]

That is true.  It's the way it was when I got the car 13 years ago and still is now.  I think I've put about 7K miles on it, car has 156K miles.

[prefervintage]

I had the same leak on my car...a '69 with the long pump. I replaced it with the short pump and an open shroud. Seeing the price for a new old stock or rebuilt long pump, I want to rebuild the long pump 'spare'. Aside from an o-ring kit, does anyone know of  rebuild kit that includes the impeller and any other hardware? I see these for the short pump but not the long...thanks...Joe

[mrfatboy]

I had the same issue.  This kit was used to rebuild it.

https://www.authenticclassics.com/Fuel-Pump-Repair-Kit-Early-type-fits-230SL-p/auth-007292.htm

[prefervintage]

Thanks...that link helps...strange though why many short pump kits include the impeller but long repair kits don't...can't imagine an impeller failing unless you screw up taking it apart and bend a blade! I see brushes are included...that's good. A motor design lasts far longer than some other electric fuel pumps of yesteryear. I remember working on prewar Rolls-Royces that have SU electric fuel pumps...double acting metal bellows, there are two solenoids with breaker points that make-break with each compression cycle...even with a capacitor (or condenser - to 'condense' the electric field between plates), they pit and get stuck...similar thing in solenoid auto wining old car clocks...great until they stick and cook the coil!

[mauro12]

Hi guys ,
I know that this topic is quite old but I’m
Trying to figure out the leak of my long style pump .
I noticed some fuel when the car was parked , so it is not something that occurs when the pump is under power . According to your experience what can be the source of this kind of leak ? The hoses are new.
Maybe the bottom seal ?
Thank you

[Pawel66]

From my experience - perhaps the leak occurs all the time, you just spot it when the car is in park.

Do you have the fuel on the bottom of the fuel pump cover? If yes, it would suggest the leak is from the pump and fuel just flows down on the cover bottom. Checking is easy, just put your finger there. Then you probably need to inspect the pump carefully - every joint and connection. if it is difficult to spot the leak, you may want to clean the pump with brake cleaner and wait to see the leak.

If you replaced the hoses, chances are it is one of the connections that started leaking - see if any of them is wet and smells gasoline.

[Roberto M]

I have a 1969 280SL and I have the same problem with the long pump, I think the pump has never been touched, it is original, and it recently started to leak very little from the overflow tube. I ordered a complete kit to change the oring, bellows, brush. Hoping it turns out well.