'Tired' petrol

[David Morris]

Hi there,

Has anyone experienced problems with petrol left in the tank from the previous year? Our Javelin did yesterday! It is not a problem starting from cold but she suffers from fuel vapourisation when using up 'old' fuel from last year and has been left standing for around 30 mins with a hot engine. Left until she is cold, and she bursts into life on the first touch of the button!

I have the same problem with lawn mowers and a portable generator. Modern unleaded seems to be the problem when it is left standing for a few months. Has anyone else had similar problems?

All the best,

David

[Forumadmin]

Always the same, every year! Any petrol over 3 months will have same symptoms. Also if left longer you may have the problems Heinz Kuntze(and others) where the sticky petrol gummed up the valves and bent them and push rods. The inlet ports were covered in a black sticky residue. Carbs may also gum up. Even new petrol in the tank may dislodge the sticky residue and get into the system.
My advice is to drain tank if planning to leave for more then 3 months.

[Tony Fearn]

Hello David,

Page 15 of Feb's Jowetteer has an article by Geoff McA about this problem.

Tony.

[Keith Andrews]

Issues with gumming , varnish is with the old leaded type fuels yrs ago...not with modern non leaded
The issue with modern fuel ids more the higher fractions of the fuel evapotae off or peminate out thru the container walls they are in.
Even so as mentioned above fuels ideally 'expire ' around 6 weeks

For storage of cars , mowers, chainsaws etc...there is no need to drain the fuel systems...doing so often/can cause even more issues.
Just dont keep the tank full, have less than 1/4 tank....before firing up, dilute the fuel already in the tank with fresh.
By the time the engine fires the new gas is thru...or close to.
Draining causes gaskets, seals , hoses etc to dry out, shrink, crack.

[David Morris]

Hi there,

Thanks for all the advice! Thinking back, I should have remembered that I have had the same problem over a couple of years! 'Old' fuel created exactly the same situation last year and the year before! It seems that using 'old' fuel when starting from cold is ok. It's when she has been standing for a more than 20 mins with a hot engine, she is impossible to start until cold again, or until she has 'new' fuel in the system. Several squirts of Easy-start down each carb intake will work though! I assume this is due to the fuel in the carb bowls losing its 'umph' due to the heat from the engine??

Anyway, I think the advice to keep as little fuel in the tank over the winter is a good idea and when going out in the spring, to top-up with fresh fuel asap.

Thanks guys!

All the best,

David

[Bronteboxer]

Hi David,

Interesting commentts on the petrol. I have three classics one Jowett and two other marques. One is an MGB and the fuel has been in since 2009 as it hasn't run much. I recently recommissioned for this season (to sell actually if anybody is interested!) and from cold it ran with intermiitent misfire and backfiring on its way for the MOT and it has never suffered anything like this before. Putting new fuel in has virtually cured the problem. I think it now needs a bit more fuel and a run to get everything back to rights. It's 95% improved instantly.

Move on to Jupiter. Not run since last August with very little fuel left in the tank, but still the best part of 7 months. On start up, guess what intermittent running and an odd backfire exactly like the MG. So its new fuel into this at the weekend and a run to check. I'm expecting it to clear with this action. The only car I haven't had any trouble with is my old Merc , but that has only had fuel in for 4 months and strangely they do not seem to suffer this fate for some reason. As this car has been laid up many times for lenghy period and as far as I am aware has not suffered and there seems to be very little in the way of problems when reading the club forum.

Good advice below.

Graham Austin.

[Keith Andrews]

It isnt a good idea to run on the old fuel, I dont know how much of the higher solvents are lost , or if enough to cause any wear or gumming ......But it does pay to get in the habit with lawn mowers, chain saws, cars etc to put away with nesr MT tanks, and fill up as one goes to use it.
eg I know my lawn mower uses not quite 1 funnel full of fuel about 1/4 to 1/3 of tank....So i dont fill any more than that.
I also keep the fuel in a steel full sealed tank..and give a shake before use.

[Bronteboxer]

Re the Lawn Mower use - I have a Honda petrol mower which I have had for 20 years and has had significant use. I changed the oil last year after 19 years for the first time (yes I know - shame) and mostly it has run on 'old fuel' drained from tanks or left for long periods. It runs sweetly, never fails to fire up on the pull starter even after long periods and uses no oil!

Graham Austin.