As mentioned in a previous post, fuel was leaking from the carburettor pump assembly, something it shouldn’t really do. The company that did the restoration of the carb were quite surprised at the level of degradation of the diaphragm and queried if I had been using bio fuel… which I haven’t.

Ethanol, (the active component in bio fuel) will eat through any nitrile rubber components in the fuel system. Don’t use it unless your vehicle manufacturer states its OK in the hand book.

Some research on whether or not petrol is cut with ethanol in Switzerland, yielded little results until I went to fill the Defender with diesel last week. Right next to the diesel pump was E85 (85% ethanol). Will steer clear of this.

After some back and forth email exchange with Dave from Carb-Exchange, we concluded the damage was probably down to old fuel damaging the diaphragm. Dave kindly popped a couple in the post to get me back on the road as it were.

Off the engine again. The carb pump assembly lives behind the 6 brass screws. The small split pin, washer and spring also needs to come off. There are 3 locations for the split pin. The carb has been set up using the middle hole.


It’s obvious which one is the new one. The nitrile rubber on the old one was literally coming off on my fingers.


Everything cleaned up a bit and ready for reassembly


Gasket, pump body and pump spring back on. (make sure the locating stud is engaged bottom left hand side)


New diaphragm offered up


Top pump cover screwed down. Return spring, washer and split pin fitted back in the correct location.


With this little task complete, I was able to run the motor up to temperature, set the timing correctly and adjust the mixture.

Whilst i was at it, I cured the coolant leak from the Smiths heater. I had used replica wire clips on all of the coolant hoses, which look the part but really don’t make a very good seal as about 5% of the circumference is not compressed fully. As soon as the engine starts and the coolant system is pressuring, water drips out from this small uncompressed portion. I replaced everything with stainless steel jubilee clips and the problem is solved. The little Smiths heater kicks out a good amount of heat. I think it’ll be quite cosy inside 🙂

Wire clip vs jubilee clip