Old petrol - starting and running problems

Robert Wilson

Robert Wilson

Well-Known Member
Joined
23 May 2012
Messages
8,053
Location
Second Coast, Ross-shire, overlooking Gruinard Bay
Visit site
Further to my earlier thread about my two outboards (4HP 2strk & 2.3HP 4strk) which would run only with chokes out and were "pigs" to start.
After faffing about with plugs, carbs, linkages etc etc., in final resignation I changed the petrol yesterday.
BINGO!!

I bought the petrol three months ago, stored it in the usual plastic can, in the yard. I'm amazed it deteriorated so quickly.
Usually I've kept petrol for up to a year without problems. Has the chemical make-up of petrol recently been changed?

Lesson learnt.
 
Last edited:
The Clean Air Act in the US, resulted, as from 1996, in different oxidants being added to petrol between summer and winter formulations.
I've been unable to find out if this has been repeated in the EC and, specifically, in the UK.
I suspect that the fuel you bought was purchased from stock sourced during the summer, but the summer formulation does appear to have a lower stability than the winter one.
 
I had the same thing yesterday - my Suzuki 2-stroke wasn't a happy bunny. Fresh plugs and fresh fuel and it started first pull! Still a little rough at low revs so I think the old stuff's still gumming it up a bit but it's a huge improvement. The engine has oil injection rather than premix so the old petrol went into the car which won't care two hoots if it's a little stale especially after being diluted in a big tank.
 
Normal unleaded soon looses it's umph, best to buy super unleaded, it will last most of the season, probably 4p more per litre but better than throwing it away.

Unleaded has had this unfortunate quality for quite some time, if you buy from a small village garage they may have had it in stock for a couple of weeks before you purchased . Use a high volume petrol station, they will have at least two deliveries per week but super unleaded is best if keeping for some time.
 
I have found that it pays huge dividends to drain ALL fuel from carburettor and fuel line as well as tank before layup anywhere, any season. Leftover is put in a jerry and tossed into the car as per josephmore, above
 
Thanks folks,
That's interesting to hear. And reassuring.
I'll not make the same mistake again - I hope!

Snow here today; big shock as it's the first we've had all winter that has actually lain. Ah well, all jobs done on Khamsin, stores and gear aboard next week and then get some sailing in.

Big SORRY to all Northern sailors, this means that our fantastic winter weather will come to an end on Friday and all of us up here are going to get "Esh-Aitch-One-Tee" weather for the rest of the year.
 
fliti said:
I have found that it pays huge dividends to drain ALL fuel from carburettor and fuel line as well as tank before layup anywhere, any season. Leftover is put in a jerry and tossed into the car as per josephmore, above
Click to expand...

That's good advice, but in my case both engines have been in commission all winter. If the fuel had been many months old I could more easily accept the fact.
Ah well, all's well etc etc.
 
Robert Wilson said:
That's good advice, but in my case both engines have been in commission all winter. If the fuel had been many months old I could more easily accept the fact.
Ah well, all's well etc etc.
Click to expand...

I reckon that plastic cans may not be a good idea for long term storage. Polythene is permeable to oxygen...whether significantly so in the thickness used in petrol cans I could not say though.
In the past i have regularly stored 2 stroke petrol from one year to the next but I only ever do so in metal cans that are full ( ie minimal air space)

Looks like I may also have to use a stabiliser in the future.

Your experiences my explain why my Flymo was difficult to start this year ....... its never easy but it was particularly difficult this time.
 
Another possible cause of the problem is the hygroscopic nature of modern alcohol containing petrol. When old fuel, which may have absorbed some water, evaporates over a winter layup the water may be left behind at the bottom of the float chamber. When you try to start it is that water which is sucked in first and prevents starting.

I was told this years ago by an outboard engineer when leaded petrol - containing no alcohol - was still available. His advice was to use leaded in outboards. This transformed the starting of my outboard.
 
I have a fairly old Honda 2hp 4 Stroke.
Initially it was a real pig to start.
I did two things.
Always used fresh petrol (over each season)
Always turned the fuel off and allowed it to run dry when not being used for a bit.

My theory is that the jets in the carb are so small they are easily blocked with gum or other residues from fuel.

It also took a while to dawn on me that on first use after a 'drain' you have to leave it about 2 or 3 minutes for the float chamber to fill up again. It would not start before this time and caused me much worry.

Now I know the above it's reliable and usually starts on the 2 pull
 
Interesting thread, especially around fuel cans. I seem to have temporarily misplaced mine so was just going to go to the local garage and buy a new one, especially as I use relatively little 2 stroke. Might have to buy a proper metal one and buy stabiliser. Any make that is especially recommended?
 
Seatrout said:
Just out of interest, does the same apply to diesel fuel?
Click to expand...

Not certain on diesel fuel, but after my experiences with petrol I now add additive to boats diesel to be sure...

RE petrol, after no end of trouble I bought some fuel additive. Not had an issue with old petrol since, 15 quid a bottle but still on first bottle...

So my advise even with relatively hi fuel consumption use an additive...
 
I have a handbook for a 70's Italian motorbike which warns of these problems: 'the fuel may go sour after a few months'.
It's normally best to whip the float bowl off any small carb that has been idle for a few months, clean it out and blow through the jets.
Alcohol in petrol may have made it a little bit worse, but it's the same old song and dance.
 
All very strange.

So many people having problems with old petrol. I have run my Yamaha 2 stroke outboard on petrol that in some instances has been 2 years old. In my experience it has had no effect on starting or running even after a winter layup.
 
theoldsalt said:
All very strange.

So many people having problems with old petrol. I have run my Yamaha 2 stroke outboard on petrol that in some instances has been 2 years old. In my experience it has had no effect on starting or running even after a winter layup.
Click to expand...

That's a very tolerant outboard. Hang onto it!

My lawnmower gave me plenty of (fruitless) exercise on the starter cord until I finally relented and changed the fuel for new stuff. Started first time afterwards (yes, really!) and the fuel I replaced was less than 6 months old.
 
You must log in or register to reply here.

Share this page

Top