More Modern Fuel Woes

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
NickD
Posts: 83
Joined: Mon Jul 19, 2010 11:02 pm

More Modern Fuel Woes

Post by NickD »

I found today some other examples of the problems that can arise when using modern fuels in old minis. I noticed that the fuel tank had an area of bare metal below the sender unit and so removed the tank to investigate and repaint. Fuel had been leaking around the sender unit and had dissolved the paint from a large area around the bottom of the tank. I removed the locking ring and sender unit from the tank and found that the rubber seal had also been dissolved by the fuel, leaving only a few crumbled remains. Even worse, the fuel had also softened some of the two-pack paint around the lower tank mounting plate so that an area of this had peeled away too.

The car hasn’t been used recently due to a gearbox problem so the fuel is probably about 20 months old. Has anyone else noticed/suspected that these new fuels seem to become more corrosive with age? The fuel that I removed from the tank will dissolve the remaining paint from the tank in seconds, so that it just wipes off with a rag in a similar (but faster) fashion to brake fluid on cellulose paint.
All this is very worrying as there is no way to be sure that seals (or paint!) will survive long-term, even if they initially seem OK.

Polarsilver
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Joined: Fri Jan 15, 2016 1:22 pm

Re: More Modern Fuel Woes

Post by Polarsilver »

Best of luck with the solution ,
My biggest issue starts when this old useless fuel is drained off is how to dispose of this old dead Petrol .. no easy method that i have found :roll:

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Peter Laidler
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Location: Abingdon Oxfordshire

Re: More Modern Fuel Woes

Post by Peter Laidler »

I had the opposite happen to me with fuel. Laid up my 2000 RCSport500 for the spring of 2017 and didn't bring it out of hibernation until May 2019. Brought it home not expecting it to start but (battery kept on low trickle over lay-up) due to stale fuel but it kicked into life straight away. Took it to get MoT a few days later expecting it to fail emissions due to same stale fuel. Nope, sailed through. I was expecting the fuel to be as crap as the emissions usually are. But nope!

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Spider
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Location: Big Red, Australia

Re: More Modern Fuel Woes

Post by Spider »

Benzene is added to 'modern' fuels to increase the octane. Benzene is also one of the main components of Paint Thinners !

I know with some 'aged' fuels their paint dissolving abilities increase. Just why this is, I don't know (I'm no chemist) but yes, I've had very similar experiences as you have had Nick. It's cat's pee - dreadful stuff, but what we're stuck with.

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mab01uk
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Joined: Thu Jun 24, 2010 7:08 pm

Re: More Modern Fuel Woes

Post by mab01uk »

Peter Laidler wrote:I had the opposite happen to me with fuel. Laid up my 2000 RCSport500 for the spring of 2017 and didn't bring it out of hibernation until May 2019. Brought it home not expecting it to start but (battery kept on low trickle over lay-up) due to stale fuel but it kicked into life straight away. Took it to get MoT a few days later expecting it to fail emissions due to same stale fuel. Nope, sailed through. I was expecting the fuel to be as crap as the emissions usually are. But nope!
I have noticed that modern fuel does not go stale in injection Minis as quickly as it does in an older carb Mini, I have been told this is because the 'closed loop' fuel system of a modern fuel injection car is far better sealed from the atmosphere and therefore the fuel takes far longer to degrade over time.

The fuel in my carb Mini usually starts to go stale after about 6 months or so, the car will reluctantly start but misfire and run rough, after longer periods it won't start at all and the carb/float chamber often needs cleaning out......I have tried using the old fuel up in my Honda petrol lawn mower but it also ran badly on the old fuel or refused to start!

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mab01uk
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Re: More Modern Fuel Woes

Post by mab01uk »

Polarsilver wrote:Best of luck with the solution ,
My biggest issue starts when this old useless fuel is drained off is how to dispose of this old dead Petrol .. no easy method that i have found :roll:
My local council dump/recycling centre usually accept small quantities of dead petrol if it is poured into their tank for collecting old sump oil.....not sure if this is 'official policy' though.

carbon
Posts: 519
Joined: Fri Jan 07, 2011 9:26 pm
Location: Scotland

Re: More Modern Fuel Woes

Post by carbon »

Spider wrote:Benzene is added to 'modern' fuels to increase the octane. Benzene is also one of the main components of Paint Thinners !

I know with some 'aged' fuels their paint dissolving abilities increase. Just why this is, I don't know (I'm no chemist) but yes, I've had very similar experiences as you have had Nick. It's cat's pee - dreadful stuff, but what we're stuck with.
No benzene is added to UK fuel, it's nasty stuff (carcinogen) and permitted levels in UK fuel are very low.

There are other aromatics such as toluene and xylene which are in paint thinners and are still permitted in fuels.

But benzene does smell nice.

minibitz
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Joined: Fri Aug 08, 2014 11:06 pm

Re: More Modern Fuel Woes

Post by minibitz »

I recently had fuel issues during a track day. There was a unmanned fuel station at the track and one of the pumps was labeled as 100 octane. What I did not realise was the fuel was a blend with higher than usual Ethanol content. The mini being used is running an SPI motor with factory injection. During the course of the day I started to get a full throttle misfire. Nothing much to worry about but power was definitely down from normal. Go the car home and checked all the sensors, plugs, cap, rotor etc but nothing obvious. Engine would run but then stall when revved or eventually just stop running if left for a few minutes. Decided to drain the fuel and change the fuel filter. Cut the filter open and found it was chocker with crud. Filter has been changed previously so not particularly old. Looking into the gas tank though the fill neck the inside of the tank was gleaming bare steel so can only assume whatever was in the fuel had done a thorough job of stripping all the crud from the tank, fuel lines etc. Fitted and new filter and regular 98 unleaded and bingo, back to running perfectly!

NickD
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Joined: Mon Jul 19, 2010 11:02 pm

Re: More Modern Fuel Woes

Post by NickD »

Interesting point about the high ethanol content, as I noticed some years back when buying fuel at the Spa circuit that even fresh fuel had the ability to remove paint from areas such as the block and I think that these continental fuels also had an increased ethanol content. I could be wrong in attributing my problems purely to the age of the fuel, particularly as the car still started and ran OK on this fuel.

The real problem was that the sender seal in the tank was so short-lived and allowed the fuel to escape, so evidently at least some of the modern aftermarket seals are not being made from the correct rubber. There was only about a gallon of fuel in the tank so the sender and seal would not even have been in contact with the fuel while the car was unused, so I can’t be sure whether the fuel or the rubber or a combination of the two caused the problem.

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Spider
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Location: Big Red, Australia

Re: More Modern Fuel Woes

Post by Spider »

This is a bit dated now, but here's what BP had to say on this subject (and it's not too far different to what we've seen);-

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