Reminder about fuel going off

[david.g.chapman]

I know this has been mentioned before, but I thought it was worth bumping up as I was affected by this last night.

I had filled the tank of my +2 with 99 RON Tesco Momentum fuel in mid February after taking plugs out of my breather lines (keeping the fuel as fresh as possible over winter).

I then used the car on and off over the next few weeks but noticed an increasing tendency to cut out on overrun and splutter into life on acceleration.

Last night I had to drive home in the car at 11.30pm with the outside temperature at 1 degree C or so. I made it home but there was plenty of misfiring as if the mixture was too lean.

Today I spluttered my may to Tesco again and filled up with more Momentum fuel. It took about 1 mile to clear the carbs and the engine was fine again!

So it only took 1 month with clear fuel tank breathers for good fuel to go bad. Lummie!

P.S. Has anyone tried fuel stabilizer? Is it any good?

Dave Chapman.

[69S4]

Some vehicles seem to be more sensitive to this than others - or more likely, some carburettor designs let the volatiles evaporate more easily than others. The fuel currently in my Stromberg S4 is 'normal' 95 from last summer and it started and ran perfectly at the weekend. I have a couple of bikes like that - on the up side a little '70's 125 Suzuki that starts with anything of any age in it, while on the down side a few bikes that will not start at all if the fuel in the float bowl is more than a couple of weeks old. The carbs have to be drained and refilled to get them to go. That's not a recent 'blame it on ethanol' thing, they've been like this for many years.

[Andy8421]

Dave,

In the 'good old days', fuel seems to have lasted longer, but I guess many of the additives are no longer permissible, and the blends available now have a shorter shelf life. This is from the RAC website, but is a direct copy of a document put out by BP, so is probably correct:

"How long can I keep fuel for?
Probably not as long as you think. Once you’ve put fuel in a container you only have a few months before the quality starts to fall away – even less if the fuel is contaminated in any way.

Generally speaking, petrol has a shelf-life of six months if stored in a sealed container at 20 degrees – or just three months if kept at 30 degrees. The more it's exposed to heat, the more quickly it will go off.

If the container isn’t tightly sealed, you’ll be able to keep it for even less time and there’s increased fire risk due to flammable vapours escaping

As for diesel, it can remain usable for between six and 12 months before becoming ‘gummy’ which, if used, can clog up filters and cause you issues with your engine."

A number of things go wrong with petrol, but it is the evaporation of the volatiles that causes the short term problems - hence the temperature dependence and need for a sealed container. With all due respect to the glorious weather you have no doubt had in Essex this year, I doubt whether the temperature has led to a deterioration of the fuel in the time you have had it. More likely it was a duff batch from Tesco - they have form in this respect (with apologies for posting a link to 'The Mirror'):

https://www.mirror.co.uk/money/tesco-compensates-drivers-after-accidently-24792083

Edit: With respect to fuel stabilisers, I use this stuff in my garden equipment over the winter, but I wouldn't want to put it in a twinc.

https://www.amazon.co.uk/Briggs-Stratton-Additive-Stabiliser-992381/dp/B003374F9E/ref=asc_df_B003374F9E/?tag=googshopuk-21&linkCode=df0&hvadid=255577450279&hvpos=&hvnetw=g&hvrand=1049475446504347117&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9041123&hvtargid=pla-782268904997&th=1

[david.g.chapman]

Thanks for the illuminating replies.

I find my lawn mower seems to take fuel of any age (within reason), but my Stromberg twinc is far fussier.

Dave Chapman.

[The Veg]

Another data-point: Back around October I removed my Plus 2's fuel tank to get at the diff-mounts, and while I poured most of the drained fuel into my other car's tank, I reserved about 2 gallons in a jug to put back in once everything was buttoned-up, which should only have been a couple of weeks later at most, right? We all know how time-expectations go with these projects...the upshot being that I didn't have it all back together until three weeks ago! Those two gallons of fuel had been in the jug for four months but I can't recall how long in the car before that. It took a bit of cranking to get the system primed, but it did start and run. This is US fuel with 10% ethanol and Strombergs. During the intervening four months the fuel-jug was in a garage that got fairly cold a couple of nights but also usually has fairly high humidity.

[Emma-Knight]

I use Liqui Molly Marine fuel stabilizer. It has naphta added and Loti started fine after 5 years of sleep, fuel tank half full. And I use Shell V100 or Aral Ultimate102 only. No alcohol added
Also, there‘s no rust in the tank, though just original (no coating).
For storage, I use the Liqui Molly engine preserver. When spraying in the plug holes, the starter rpm is increasing noticably. It keeps things from rotting away...
I found these products at my local yat supplier...
Anna

[tonyabacus]

Have a chat with the technical guy at Millers Oils, I can’t recall his name, but he was very informative about additives and fuel stored in little used cars
Tony

[david.g.chapman]

Just a postscript on my "fuel problem".

Yesterday, with more fresh fuel in the car I started to have the same symptoms as before. The age of the fuel was having an effect but there was something else going on.

After replacing the coil and the powerspark ignition with spares and no success, I took the carbs off and had a look at the diaphragms. They has looked ok when I last adjusted the mixture (I have federal carbs so I have to move the needle carrier up and down). When I looked again splits had started to open up next to the thicker outer ring on the diaphragm. You have to pull the diaphragm to see them. Ah Ha!

I ordered some new ones from Burlen and in the meantime have temporarily sewed up the splits and superglued them to confirm the fault. Yes, the misfire has gone.

Cheers,

Dave Chapman.

[john.p.clegg]

Dave
" splits had started to open up " , would this be due to the ethanol?
Are the new gaskets Viton or FKM ?

John

[david.g.chapman]

The Burlen diaphragms are hydrin based. Contact with the fuel is limited, but some vapour would be around the bottom surface of the diaphragm.
The old diaphragms have lasted at least 5 years/ 12000 miles. I also use E5 fuel as a matter of course.
So for Stromberg owners any misfiring or low idle speed, the first port of call seems to be the diaphragms!

Dave Chapman.