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E36 Fuel Tank

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M3 Jambo View Drop Down
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    Posted: 01 Aug 2020 at 4:29pm
Hi There. Has anyone experienced issues with GRP fuel tanks contaminating fuel. My E36 wouldn't start, I thought it was the fuel pump, changed it, the car started then wouldn't start a few weeks later (it doesn't get used much!). Transpired the pump was covered in petrol gum. Emptied the tank, cleaned it out and put 1/2 a gallon of new fuel in it. Planned to empty it again, fit a new pump and fill with new fuel. After two weeks I've emptied the tank again to discover more gum in the bottom of the tank! I assume therefore it's the tank?
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Paul.S View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Paul.S Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2020 at 8:18pm
I believe that modern fuels with a higher ethanol content can degrade GRP fuel tanks. Best to avoid fuels lower than e95 if possible. Some fuels in europe now have a very high ethanol content these days, around 15%. It is also an issue for the pipework and seals in older vehicles.
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M3 Jambo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M3 Jambo Quote  Post ReplyReply Direct Link To This Post Posted: 02 Aug 2020 at 4:42pm
Hi Paul. Thanks for the response. I believe unleaded currently has 5% Ethanol in it which is going up to 10% sometime next year. Would really be very surprised if I'm the only one experiencing this issue, especially when the results seem so extreme. Would like the comfort of knowing it's a common problem before I change the tank. My car is one of the last E36's and has done less than 40K miles. Cheers A
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Mike Fishwick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike Fishwick Quote  Post ReplyReply Direct Link To This Post Posted: 03 Aug 2020 at 9:16am
Your E36 does not have a GRP fuel tank - it is made of plastic, like most fuel tanks from about 1984 onwards. BMW have stated that any vehicle made after 1986 is 'suitable' for use on e10 fuel . . . but at the expense of performance and fuel economy.  This means that a problem with a plastic fuel tank due to the use of an ethanol fuel is very unlikely.  The roads are not littered with dead E36 or other cars with plastic tanks!

UK 95 octane petrol must have at least 5% ethanol content, but there is no upper limit.  As ethanol is a cheap anti-knock agent, its proportion varies with different fuel makes and batches. Like all alcohols, ethanol is a poor fuel, this is why some 'high octane' fuels do not provide very good fuel consumption or performance.

Fuels can vary considerably - in some cases the new 85% ethanol fuels have been found to approach 100%.

You do not tell us the types of fuel you have used, and for how long, if have you mixed types, and if you buy fuel from different places.  It is possible that your problem may be due to mixing different fuel with different types of additives, or even a poor batch of fuel.

If your car is a 'garage queen' the problem may even be caused by evaporation, as most 95 octane types can evaporate quite quickly, leaving a brown residue which is not condusive to easy starting, particularly in low-compression engines such as lawnmowers.

If you have been using 95 octane filth, fill the tank with a decent 97 octane, such as Esso Supreme (avoid Shell V-Power) and see what happens.  Depending on where you live it may be difficult to find such decent fuel, but it is worth the trouble to find it.




Edited by Mike Fishwick - 03 Aug 2020 at 12:31pm
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M3 Jambo View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M3 Jambo Quote  Post ReplyReply Direct Link To This Post Posted: 03 Aug 2020 at 1:18pm
Hi Mike
Thanks for your reply. It would have been a major surprise if the problems only affected myself because as you point out, the country isn't littered with E36's with this problem. The car is a bit of a garage queen, but I do only use BP regular unleaded. The problem has arisen after two different batches of fuel have been used, the latter after only a couple of weeks of inserting fresh petrol. I've left fuel from both batches to evaporate in separate containers and no residue was present. I'll get some premium fuel and give that a try. Many thanks for the response, appreciated.
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