This website uses cookies to improve navigation. No personal data is held. Do you agree to the use of these cookies?    
Classic Engines, Modern Fuel

Comments on Topic: blocked fuel filters on rubber bumper Bs

Share this topic item by email
Submitted by Anonymous

In the last week, I have come across two 1977 BGTs with fuel starvation both caused by blocked filters just before the carbs. See below.

However I noticed on the return the B spluttered every now and then- long story short fuel filter full of what appeared to be chocolate powder.

The quandary I have is the tank is new and should in theory be sludge free, and hopefully rust free too,

but I do use Castrol Lead additive and was wondering if maybe this was reacting with the 99 Octane E5 fuel?

On my way home, I stopped at Oxford services for a rest from the heat and found two broken down MGs. A twin cam MGA coupe with a fuel leak. It turned out to be a loose bajo union on the front carb. Once tightened up they were good and on their way. It had been his dad’s car so he was less familiar with it. The second, a 1977 BGT with fuel starvation/vaporisation. It had a completely blocked fuel filter, either debris in the tank or degrading fuel hose from E10 petrol. It looked like coffee granules. He took the filter out and by passed it. It was his son’s MG so he was not familiar with it.

Do you have any thoughts on the cause. My 77 B runs fine on E5 and E10. My pump is original but the fuel hoses E5 resistant.

MGV8 Ian

Share this topic item by email
Submitted by The Author

Thanks for this comment.

I am not aware of any reports of additives reacting with ethanol to produce residue.

My thoughts are that any chocolate or coffee coloured deposits are rust. As this was found in the petrol filter, this is most probably from the petrol tank.

The book describes how corrosive water becomes after being in contact with ethanol blended petrol. It can cause severe rusting in just a few months. On this basis, the deposits seen in these filters are probably due to water getting into the petrol tank, settling in one place while the car was not being used and rusting the tank. In the case of the second BGT, the trip to Silverstone could have stirred up the deposits which were then pumped into the filter.

Some people have suggested that as ethanol absorbs moisture from the atmosphere when stored, this is the source of the water. This is probably not correct. Ethanol blended petrol would have to be stored for a very long time in a humid atmosphere before the water / ethanol mix came out of solution. The most probably cause is rain water or water when the car is washed getting into the petrol tank. This will sit at the bottom of the tank or float chamber absorbing ethanol from the petrol, regardless if it is E5 or E10.

I suggest people should be very carful when filling their tank in wet conditions. Also it would be worth checking the seals on the filler cap, etc.


Please wait .....