Stale petrol?

I have been busy getting my Austin 7 jacked up, all 4 wheels off the ground and the axles supported by home made "skates". The car can now be moved in any direction in the garage by just me. As I was doing this I noticed a smell from the rear mounted fuel tank. Stale petrol. The car has been sitting for at lest 6 years, maybe 7. Should I remove the tank and flush it out? I do have a syphon that is supposed to be for getting oil out of something with no drain plug. What should I expect?

Definitely lee I had the same with a bike laid up for 8 years, did fuel lines and carb. It took a lot of cleaning using gunk and fresh petrol.

I only put super unleaded in my old car after I found a creamy cheese like gunk in the carb and tank. I took the tank off and flushed it out through the level sensor hole. I have also had problems with a chainsaw and quad bike running on the new E10. So when you do flush it out I would definitely find some E5 to use and only use that.

Depends. Ethanol in fuel will attract water and may cause rusting. More recent petrol has contained more light ‘anes’ so will evaporate/disperse faster, leaving behind more of longer chain hydrocarbons (ie less volatile).

Our mini actually started on (mostly?) old fuel from about ten (perhaps longer) years ago. I doubt it would have done that with three year old fuel. May have had a sniff of ‘easy-start’ to help it fire initially, but once started it ran OK.

Modern fuels can encourage unwanted flora? (well not fauna).

Most certainly safest to clear it out - whether used later (diluted with fresh fuel) is up to you, after evaluation.

Petrol is a blend of different compounds and there will always be something that will evaporate faster than whatever is left from the original blend. This is why old petrol is dodgy whatever the quantity of ethanol it starts off with.

Martin C

Hows this for a plan?

I will syphon off some petrol to see if it is rusty, the tank was slosh sealed during restoration 20 years ago. If it isnt rusty I will just drain the tank, and refill with a few gallons of fresh petrol. I can take the float chamber off the carb, the petrol would have evaporated years ago, and swill out the jets. If the car starts and runs, that should be enough. If it doesn't, then a full strip down of the fuel system is in order. Can anyone reccomend a carb cleaner to spray into the jets?

Unfortunately, I can't recommend a carb cleaner, although I've used a few. I have a 4-stroke petrol generator - needed because the mains supply is vulnerable here in rural NZ. In the past, every time it was needed, or even tested, the wretched thing would not start, or wouldn't run cleanly until I had taken off the carb and removed and cleaned the jets. The trouble seemed to be salt formation on/in the brass (?) jets, which was not touched by carb cleaners. There was also gum and 'varnish' in the float chamber, which any tried carb cleaner dissolved.

This jet corrosion is the result of water in the fuel. It's a much greater problem now that there is alcohol in fuel. Thankfully, there is one (but only one) fuel mix, available in NZ, (NPD 100+), that is alcohol-free. I now use this in all my small engines that are intermittently used, and have had no similar problems. That's tempting fate, isn't it?

Does anyone know whether - and how - fuel 'stabilizers' work?

Edited By Kiwi Bloke on 21/06/2023 23:10:55

Car hasn't been run in 6 or 7 years? If you are planning on leaving it that long until the next time it runs, you would be better off to drain the system completely and store it dry. If the tank has been sealed it should not rust inside. Or you can put a cup or two of oil into the current petrol and slosh it around before draining. Seems to leave enough oil to inhibit rust on motorbike tanks. You can also spray WD40 in the filler neck and fog the tank to deposit a layer of anti corrosive on the inside of the tank.

If leaving it for some time with fresh petrol, you can buy fuel stabiliser at the car parts shop that stops it going too nasty in storage, if added while the petrol is still fresh. I find using premium grade petrol helps too. The low octane cheap petrol seems to gunge up quicker.

I found this out from having two sheds full of old motorbikes that sometimes go for years at a time without being used. Modern petrol really sucks.

Jet/carb cleaner I use whatever they have at the auto parts store. CRC brand is particularly good. It is all nasty stuff that you don't want to get on your hands, so it must be good!