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Author Topic: Here's a daft question!  (Read 1220 times)

TailUK

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Here's a daft question!
« on: August 16, 2013, 03:56:47 PM »

Does petrol go off!   I was embarrased last weekend by offering the use of my generator at a show and not being able to get it started.  Since then I've had it in pieces and tested the electrics, all fine.  The only thing i can think of is bad gas.  The petrol from my can is about 3-4 months old and if it's "gone orf" that would explain it. Help?
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essex2visuvesi

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Re: Here's a daft question!
« Reply #1 on: August 16, 2013, 04:09:31 PM »

I would say yes.... I have had the same problems with last summers petrol in the spring in the chainsaw and lawn tractor
what I tend to do is use the "old" petrol mixed with new once the device has been run a few times (60/40 new/old seems to work).  If the fuel is premixed with 2s oil then the starting issues are increased.
Whether this is truly the case I don't know but experience tells me that first run of the spring needs fresh petrol
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knoby

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Re: Here's a daft question!
« Reply #2 on: August 16, 2013, 06:24:23 PM »

yes, it does go off over time & how it is stored will affect how quickly it goes off. Also the refineries change the chemical composition of the petrol depending on the season. Petrol produced in summer is different to petrol produced in winter.
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Martin [Admin]

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Re: Here's a daft question!
« Reply #3 on: August 16, 2013, 07:40:59 PM »


Doesn't the Octane evaporate?
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Bob K

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Re: Here's a daft question!
« Reply #4 on: August 16, 2013, 07:57:47 PM »

The problem with petrol is that it tends to be hydroscopic, and over time will absorb water which will form out at the bottom of the tank and carb.  Water at the bottom of either will stop the works. 
I was going to suggest boiling it off using a blow torch underneath, but that may get me a red card?   {-)
 
Ooops, only 3999 members.  I hope someone wasn't daft enough to try that advice.  :embarrassed:
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Martin [Admin]

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Re: Here's a daft question!
« Reply #5 on: August 16, 2013, 08:09:42 PM »

Only 9 members left after someone tried that last time!   :o
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Steve J

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Re: Here's a daft question!
« Reply #6 on: August 16, 2013, 08:55:25 PM »

Does petrol go off !

Yes. Petrol fresh from the pump will have more butane in than petrol that has been stood in a can. Having said that, I've never had a problem starting the 2 strokes petrol engines in my model planes with oldish petrol.

Steve
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NFMike

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Re: Here's a daft question!
« Reply #7 on: August 16, 2013, 10:23:24 PM »

I keep a bit of spare petrol in a sealed jerry can and by an odd coincidence I've just in the last couple of days  'cycled' it into the car after about 18 months stored and will refill with fresh. After researching this matter originally I use a fuel preservative. (People with (eg.) little used vintage autos use it). Car seems fine with this old stuff but there was probably twice as much fresh fuel in the tank already, so not a serious change of mix.

That said I'd have thought 3 or 4 months in a properly sealed can wouldn't be much of a problem. If it isn't well sealed then that would be another matter of course.

Shipmate60

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Re: Here's a daft question!
« Reply #8 on: August 16, 2013, 10:28:07 PM »

The additives in the petrol can start to separate and sink to the bottom a good shake can assist rejuvenating and if you add some petrol injector cleaner and give a shake. The injector cleaner is an octane improver which helps starting and running.


Bob
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malcolmfrary

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Re: Here's a daft question!
« Reply #9 on: August 17, 2013, 10:30:58 AM »

A quick search for "petrol aging" came up with this link - http://floridasportfishing.com/magazine/service-repairs/fuel-stabilizers-revolutionary-or-rip-off.html -  a short way down the page was this comment "Some things, such as whiskey and wine, age gracefully, but gasoline and diesel fuel is not one of them. During the aging process, masses of carbon, gum and resin form in your fuel." So it would appear that there is more than one process at work.  Keeping it in a sealed can will stop volatiles wandering off, and should keep water vapour away, giving the can a shake should disperse any accumulated gunk at the bottom of the can, but there isn't a lot that can be done to restore the chemical changes.  So there has been very little research directed at de-aging whiskey and brandy.  Yippee!
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