72 350 sl - leaking fuel pump

[jdcoving]

I have what appears to be a Beck/Arnlel fuel pump that is leaking. Just purchased car and put in 10 gallons of fresh gas to find about 2 tablespoons of of gas in catch pan over night. Can this pump be rebuilt?

[Graham]

Originally Posted by jdcoving

I have what appears to be a Beck/Arnlel fuel pump that is leaking. Just purchased car and put in 10 gallons of fresh gas to find about 2 tablespoons of of gas in catch pan over night. Can this pump be rebuilt?

Beck/Arnley pumps are likely rebuilt OE Bosch pumps. The head of the pump can be dismantled and it does have two 0-ring seals that could possible be leaking. (see pictures below) Sometime there is an internal leak and gas comes out around the electrical connectors. Probably more difficult to repair.

I would first maybe remove the cover so you can get at pump, then wipe everything dry and see if you can see just where fuel is leaking from. Perhaps it is from one of the hose connections.

It is possible to get replacement pumps these days, for under $200. I think we have discussed this here in SL or Vintage forums. There is more over on Benzworld.



By the way, I also own a 1972 350SL. There is a good MB107 forum over at Benzworld where many of us 107 SL owners hang out. Check out the EGV107 section in the stickies over there.

[jdcoving]

I have previously removed the cover and wiped the area down. It did appear there was fuel around the electrical connections. All hose clams were tight. Is it a internal fix around the electrical connections and if so how hard is it? At what point do I just get a new pump? I checked out the benzworld egv107 site and it was almost overwhelming. Thanks for the tip I'll continue to study it.

[ejboyd5]

Without more information or pictures it's difficult to supply a definitive answer. Sometimes leaks around electrical connections can be slowed or cured with an application of Loctite 290 (green) which has an amazing ability to wick into and seal small spaces.

[Graham]

There was a similar discussion earlier on that covers the replacement pumps currently available. MB, Bosch & Nissan all OK.
1975 R107 450SL Leaking Fuel Pump Replacement - Mercedes-Benz Forum

The attached pic shows the electrical connections on a new pump (my spare). Canister of pump is crimped on, so any fix would have to be from outside. You could try, but now that replacement pumps are more reasonably priced, maybe a new one would be best choice?

But I would suggest first making sure that that is where the leak is.

[97 SL320]

Something to be aware of. Most electric fuel pumps have a fuel submerged motor, this keeps the motor cool and prevents sparking brushes from ignition fuel vapor. This is where a wire terminal leak would come from not a shaft seal as they don't use one.

[jdcoving]

Here are more pic. It appears the hoses and fuel filter have been replaced. The hose clamps are tight. Am I missing any fittings such as back flow preventer etc. When I parked it last I clamped off the hose directly below the tank. I still got a small amount of seepage from the pump. Could this have been drainage from the fuel lines after the pump? What is the black canister (correct name not known) just before the pump used for? Sorry not a good picture of electrical terminals but they were damp.

[Graham]

Originally Posted by jdcoving

Here are more pic. It appears the hoses and fuel filter have been replaced. The hose clamps are tight. Am I missing any fittings such as back flow preventer etc. When I parked it last I clamped off the hose directly below the tank. I still got a small amount of seepage from the pump. Could this have been drainage from the fuel lines after the pump? What is the black canister (correct name not known) just before the pump used for? Sorry not a good picture of electrical terminals but they were damp.

Some of the worm gear hose clamps are not ideal so even if tight, could leak. Especially if the hose is not exactly the right size.

The pump has (or at least should have) a check valve built into the side nozzle. See diagram below.

The black canister is called a damper cage. Germans don't know why it has that name in English! Apparently a poor translation! It has no internal parts. Just flexes very slightly and this apparently helps provide smoother fuel flow as well as reduce pump noise.

The number of the original Bosch pump was 0580464005.

You may have to remove the pump, block the exit and pressurize the inlet to find out where the leak is. That would give you a chance to check the hoses.

Another check would be to remove coil wire so engine won't start and block the return line from the fuel pressure regulator under hood. Then turn key on and off a few times. This will/should build up about 50psi pressure in fuel system between pump and If there are leaks they may now be easier to locate. While about it, check for under hood leaks at injectors and in fuel rails.

[jdcoving]

Adsit has a updated direct replacement pump for $110 with hardware. One year warranty. It is a Adsit brand.
Price seems decent. What is the history of Adsit brand parts? I have seen there catalog and viewed their web sit and they look reputable. Any thoughts.

[Graham]

Originally Posted by jdcoving

Adsit has a updated direct replacement pump for $110 with hardware. One year warranty. It is a Adsit brand.
Price seems decent. What is the history of Adsit brand parts? I have seen there catalog and viewed their web sit and they look reputable. Any thoughts.

They don't have a good reputation among Benz owners. They are just a reseller of products. The pump they list is an Airtex pump. Others have learned the hard way not to buy that pump for their Djets.

Buy a decent pump. That would be the Bosch pump. You can buy it right on this site. Either as the Mercedes kit, or the Bosch pump plus some parts that are listed. You would also need a clamping sleeve of some type because new pump is smaller in diameter. More info in this Benzworld post: http://www.benzworld.org/forums/r-c107-sl-slc-class/2663738-new-djet-pump-now-available-mb.html

Have you determined that your pump is leaking from the electrical connections? If so, you may find this thread interesting even although fix is not that easy.

[jdcoving]

Thanks for all the feed back. I am going to try and rebuild my pump before purchasing a new one. I have ordered the o-rings from Napa. Found some fuel injected hose clamps and hoses. After disassembly I could see where possible leakage might have occurred around them. I also see some slight pitting in the o-ring grove. I would like to put some sealant on before reassembly. So far I have only found gas resistant products. Any suggestions for this product? Again thanks for the input.

[Graham]

Originally Posted by jdcoving

I would like to put some sealant on before reassembly. So far I have only found gas resistant products. Any suggestions for this product? Again thanks for the input.

Usually not a good idea, but you do have the filter downstream to catch sealant if it comes away.

I have used Permatex MotoSeal on diesel fuel, but not on gasoline. But that is what they recommend for gasoline.

Would it be possible to clean out the corrosion with a solvent like acetone and then fill any cavities with JB-WEld? It is apparently resistant to gasoline but you need to make sure it cures fully first.

[97 SL320]

resistant = stands up to occasional contact

proof = stands up to continuous contact

There really are not any sealers that stand up to gasoline.

New O rings are more pliable so they might seal even with pits.

[jdcoving]

Thanks - will check out these products.