Injection Pump Oil Leak

[ctaylor738]

My four-year 280SL project-in-a-kit is finally "almost" finished.  I took it for its 20 mile first drive a couple of days ago and when I put it back in the garage I noticed a serious puddle of oil where it had been sitting.  I checked it out and found that oil was dripping off the idle mixture adjusting knob on the back of the injection pump.  I took the adjuster assembly off and found that half of the o-ring that seals the adjuster shaft had gone missing.

This o-ring sits in a recess on the inside of the plate that holds the adjuster and is held in place by the tension of the spring.  I replaced it with a 4 x 1.6 mm o-ring, and no more leak.

I highly recommend replacing this piece if you have the adjuster off the pump or if you are installing a pump.

Cheers,

CT

[Rolf-Dieter ✝︎]

Thanks for the tip CT!

[wwheeler]

You are so right Chuck. Mine was leaking as well and had to replace it. Easy to do once you have it apart. I went a little further and used a Viton o-ring. The standard Nitrile (buna-N) o-ring is OK and resists oil, but has a limited temperature of 225-250*F. So over time, it hardens and will leak. Viton is highly chemical resistant and resists heat to 400*F. Yes it is more expensive, but on that small of a part, its only pennies.

If this was a static o-ring (meaning it never moves), Nitrile is OK. But it does become unseated everytime you make an adjustment.

One more tip along this line. Everytime you press the adjuster in, a little bit of oil drips out. I always take an oil rag and wipe the bottom side of the adjuster when I make an adjustment. A little over-the-top I know.