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MG MGB Technical - Water in the fuel

How does water get in the fuel if the car's kept in a garage with a tight fuel cap?
J.F.G. Brown

Condensation
David DuBois

This is why I always fill my tank before putting the car in the garage after a drive. If you have half a tank of fuel, when the temperature drops at night condensation will form on the inside walls of your fuel tank and then mix with your fuel. My B is 45 years old, with the original fuel tank. Filling it each time has kept water out of the fuel system. RAY
rjm RAY

Well I think I may have solved the problem! I pumped the tank out into several bottles and tins and guess what - it was about 50% petrol and the rest something that looked like cloudy water and tasted like water! Lires of it! The first bottle I filled was an empty Old Speckled Hen bottle. When the mixture settled and eventually separated, only the neck contained petrol all the rest was this watery liquid!

I recall that having sorted my ignition problem, I 3/4 filled the tank with fuel on the day after the Shell service station opened after having been converted from a BP one. I am left wondering if the cloudy watery liquid is the remains of a flushing treatment? I can't believe I had so much water in the tank before refuelling.

The AA man who rescued my stranded car last night told me that contaminated fuel from service stations was not unknown. I am proposing to contact the AA to give them a sample for analysis.

Meantime, I have removed the filler tube and swabbed out the tank internally with absorbant cloths wrapped around a 12mm pipe bending spring and left it to evaporate overnight.

JB
J.F.G. Brown

Put some isopropyl alcohol in, sold here as "Drigas" or "fuel line antifreeze" or similar. Puts the remaining water into solution with the gas and burns it. Doubt it would have helped before you drained though! And change any filters you may have, although if the car will run, it will suck the Drigas through and dry the filters.

And go tell them you want a free tankful, at minimum. If the station was closed a while, they either also had condensate from empty tanks, or they have a leak letting groundwater in, which won't happen when the tank is full, but might interest the environmental authorities. Could cost them a substantial amount in lost fuel and cleanup/penalties.

FRM
FR Millmore

When I worked in a service station, the first thing we did every morning was to "stick" the fuel tanks. We used a 20' wooden stick, with a small amount of dye on the end, that would turn purple if it came in contact with water. This happened more often than you would expect. The next thing we had to do was to call in a special service that would pump the water from the bottom of the offending fuel tank. I would pay a return visit to where you purchased the fuel and ask for compensation. RAY
rjm RAY

A little habit I've got into is steering away from a servo if there happens to be a tanker there filling the tanks
I got caught big time once filling up while the tanks were getting filled, thinking, nice fresh fuel, but all I got was the same as you JB , half a tank of rubish from the bottom of the tank that the tanker had stirred up.
Cheers Willy
William Revit

Thanks for you your comments guys.

Well, I disconnected the fuel supply pipe at the carbs and pumped out the tank.

Eventually, the pump was clicking so fast that I stopped it to avoid potential damage and prepared to dry out the tank. Firstly, I removed the rubber hose connection between the filler and the tank entry. Then I wrapped some absorbent rags (old tee shirts and vests) around a 12mm pipe bending spring which I could manipulate around the inside of the tank from the entry hole. I did this some dozen or so times with new rags each time until they no longer came out soaked in fluid but were merely damp. then I left the boot lid open in the garage for 3 days to allow any remaining fluid in the tank to evaporate and dry out.

Today, I reconnected the hose from the filler to the tank and poured in about a litre of new petrol. With a glass jar placed under the disconnected fuel pipe to the carbs again, I switched on the pump for a few seconds until the jar (about 1/4 pint) was full, recovering it again to wait to see the results as some water would probably still be left in the fuel pipe. About 1/2 in of water eventually appeared in the bottom of the jar. I replaced the jar with a fresh empty one and started pumping again. This time there was no water in the jar.

I then reassembled the carb float chambers, replaced the fuel line and replaced the air filters. I then cranked the engine which started as soon as the carbs had filled up.

Boyed up with success, I poured in the remainder of the 15 litres of new fuel I had bought and took the car for a test drive. Needless to say the problem had gone. I think the ignition timing may need checking (I had replaced the distributor for a '123' electronic type) but otherwise it ran fine.

Given the amount of contamination, I find it difficult to believe that it could have been introduced by anything other than through the fuel dispenser at a service station and I am following this up.

I hope this helps any other driver perplexed by this problem.

Joe B
J.F.G. Brown

This thread was discussed between 26/07/2012 and 31/07/2012

MG MGB Technical index

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