How long before 'bio' petrol goes off? Misfire related?

[AndyPen]

It has been 10 -12 weeks since I last used the 970 and foolishly I filled it up, then the weather has been rubbish so it hasn't moved.

Had a weird slight misfire when I finally took it out yesterday. It was erratic and not like, for example, a plug going (they are new this summer). Its on H4s and runs rich at low revs where it was fine, but once under pressure (warmed up) it had this slight hesitancy.

It is a cammy little ex race engine so needs to rev a bit, but didn't overdo it in case of damage.

Any thoughts before I pump all the fuel out Folks?

Can it really go off that quickly as it just feels just like old fuel used to feel like to me?

[Catmint]

I found super market fuel would go off after about two weeks in the carb bowl

[irlmin]

It only has a life of a few weeks , have encountered several issues all solved by drain and refill . its not 'petrol ' as we knew it I am afraid . G

[Polarsilver]

3x Petrol weeks & gone off with about 2 gallons left in the Tank.. have tried most cures to try to stop the issue.. best i have found is some stuff called "Fuel Fit" from Briggs & Stratton (on ebay for about £6 )..so designed for Chainsaws/ Mowers stored through through the Winter .. i use this but its No proper fix in a Mini Tank the Petrol will still go off probably due to the large Air Gap above the Petrol... also use Fuel Fit in my spare Petrol Green Plastic carry can ..as that Mower Stuff does stop that stored in the Green Plastic Can Petrol from also going OFF
My solution is a spare US made Fuel Pump rigged up as a self priming Power Pump to remove Petrol out from the Tank Filler neck.. then I use this removed Vinegar that was E5 Petrol as Weed Killer .
Open to better suggestions as the best fix cos it will get worse when E10 Petrol comes along

Also this E5 Petrol wrecked my Rubber Petrol Pipes so designed for Unleaded in about 12 Months as they became rock Hard .. solution was DemonTweeks Fuel Pipe at about £18 per mtr;.. we will see if it lasts longer that one year.

[woodypup59]

I find my 1960's minis don't like petrol more than a few weeks old. They cough and splutter, to the extent that once the fuel is over 3 months old, I need to keep the choke out quite a bit. So I keep the tanks on them nearly empty. Also, the bio-ethanol is quite corrosive so I try to minimise the amount in the system.

Any excess fuel is siphoned out and put in the modern - EFI cars like my Focus and my mates Golf GTi seem to be able to burn anything.

BTW, modern petrol goes flat like lemonade - butane gas is bubbled into it to raise the calorific value and of course that evaporates away.

[AndyPen]

Thanks everyone - I have a spare pump or two here so I guess I can get it out easily enough, or even disconnect the carbs that end and link to a length of pipe and a container.

What a pain eh???

[AndyPen]

Anyone tried this ethanol remover kit??

https://www.classic-oils.net/Ethanil

[imack]

Have read that the fuel is past its best after two weeks, but I've just fired up my 649 cammed 1380 for the first time since September and it seems to be running cleanly once it cleared it's throat.
Always use shell super unleaded with millers lead additive and octane booster. Not sure if she'll super had ethenol when I last filled it up a few months ago, pretty certain it does now though

[AndyPen]

I think it may well have been in for a while - just not advertised until late last year by Shell.

So annoying when the car was running so nicely when I put it away... assuming it is the old petrol of course - but things definitely look that way!

[Catmint]

I second the use of Briggs and Stratton fuel preserver stuff - when we parked the car up in October 18 for the winter I put some in, when fired up in May for Blyton it started straight away and we are still running on that tank of fuel

[AndyPen]

Thanks Catmint, I will get some.

I'll also trial the ethanol removal kit, but probably when the winter weather turns to sunnier days. In the meantime, I will drain the tanks of the two cars that are running new fuel - the 850 SDL has it in as well.

[Polarsilver]

"Maybe" a solution to keep my Bio Petrol Fresh ?.. is to fit & plumb in a 3rd Fuel Tank of the small Race Type that can also have a Tank Vent shut off tap, given the issue seems to be E5 Petrol does not like fresh air & will turn bad in about few weeks ? .. reasoning my road cars do not get long runs and if i go out on a long Drive i can still fill the Original Tanks with Petrol... ( i would also need to fit shut off taps to the OE tank Lines to stop these empty Tanks allowing air to be drawn into the Fuel Pump as it feeds of the 3rd Tank )
Question ..does this E5 Petrol go off when stored overwinter in a Race Tank?

[mab01uk]

The later SPi and MPi Minis don't seem to suffer from this problem so much, I am guessing this is because the injection cars are sealed systems from the outside air/atmosphere?

[AndyPen]

"Maybe" a solution to keep my Bio Petrol Fresh ?.. is to fit & plumb in a 3rd Fuel Tank of the small Race Type that can also have a Tank Vent shut off tap, given the issue seems to be E5 Petrol does not like fresh air & will turn bad in about few weeks ? .. reasoning my road cars do not get long runs and if i go out on a long Drive i can still fill the Original Tanks with Petrol... ( i would also need to fit shut off taps to the OE tank Lines to stop these empty Tanks allowing air to be drawn into the Fuel Pump as it feeds of the 3rd Tank )
Question ..does this E5 Petrol go off when stored overwinter in a Race Tank?

Spent hours reading tech specs and counter claims etc. Rough estimate 3-6 months if sealed well.

[arnie]

https://www.bp.com/content/dam/bp-count ... -tanks.pdf

[AndyPen]

https://www.bp.com/content/dam/bp-count ... -tanks.pdf

Thanks Arnie, yes, that was one of the reports. Have now drained the tank pretty much and there was definitely an 'old' smell to it, and the tank is quite new!