stale petrol - exactly what is it?

I have had 2 fuel pumps die. The local workshop said this was due to stale petrol (a vehicle not used much). Just what is stale petrol? I presume the pentane put in for cold starts evaporates first, and some of the aromatics with low boiling points. So you are left with mostly octane and heptane, but those are chemically rather intert and would not do much damage. Or does something react with air in the fuel tank (lets say 30 litres if half full)?

Reply to
bruce56
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On Thursday 16 January 2014 09:41 snipped-for-privacy@topmail.co.nz wrote in uk.rec.cars.maintenance:

How stale exactly? Months? Year(s).

And what vehicle?

I've not personally come across this - at least with old and/or simple engines.

eg my 2 stroke lawnmower starts quite happily on year old petrol. I've had cars that have sat around in bits for quite long periods without trouble.

Reply to
Tim Watts

A quick google found this...

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as well as many other threads and articles.

What pumps? Electric, mechanical? Old car? Old stock or non-brand pumps? I'm wondering if it might be down to non-ethanol-friendly rubbers in them. I bought some petrol hose from a back-street car spares shop in Belgrade a few years ago - it lasted several hours before just collapsing and splitting.

Reply to
Adrian

water in the fuel would be a more likely cause.

Reply to
Mrcheerful

Presumably from condensation, assuming that fuel tanks are vented.

Reply to
Gordon H

even modern fuel systems have to be vented or no fuel could get out and the air that comes in has moisture. the only commercially available car that I know of that has a bag for the fuel inside the tank, that should avoid condensation in the fuel, is the Prius

Reply to
Mrcheerful

My chainsaw (American) and brush cutter (Japanese) start perfectly well (at least, as well as they ever do - the chainsaw is always a pig to start) but my hedge trimmers (Chinese) died when left all winter with fuel in them. The mender said the carb needs stripping and ultrasonic cleaning, which leads me to the conclusion that the fuel in the carb evaporates and leaves a residue that gums it up.

It may also be the case that the ethanol now added to fuel, being hygroscopic, adsorbs water from the air, degrading the fuel. Add to that the condensation inside a vented tank and I can understand why it may be the case that fuel left in a tool may degrade.

Reply to
Huge

Thanks for that link. The fuel pump in question is electrical, inside the tank. The first pump that died was OEM GM Delco part. It is no longer available, but fortunately a copycat pump is sold. That was the second failure. The car runs on RON 91; E10 was never put in it.

Reply to
bruce56

The original pump lasted how long with this "(a vehicle not used much)"? And the no name replacement failed after how long?

See where I'm coming from? ;-)

Reply to
Dave Plowman (News)

Huge wrote: [snip]

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!!!!!!!!!!

Reply to
Graham J

Typo, innit.

Reply to
Huge

My Alfa 75 never complains about stale fuel, even though it can be several months between start-ups.

Reply to
SteveH

91?

That's a Merkin standard, isn't it?

Reply to
SteveH

On what...?

Ah... We don't see 91 in Europe at all. It used to be available in Germany for a while, but not for many years.

Reply to
Adrian

Nah, RON is the same measure we use. The 'merkins use RON+MON/2.

Their "premium" 91 is about the same as our 97, "midrange" 89 a bit shy of our 95. Their 87 pikey is about the 91 he's referring to.

Reply to
Adrian

I was expecting a "Did you mean..."

:-)

Reply to
Gordon H

My Guzzi hasn't been on the road for three years and despite the petrol smelling like gloss paint it still starts.

Reply to
sweller

Three years and I'd say you're verging on problems with modern fuel. The Shite Old GS stood with a half-tankful for nearly a decade and it was still burnable fuel in there (as evinced by the same fuel actually firing well enough, later), but there was a varnish deposit on the pick-up/drain, petcock, float, floatbowl, everything.

Reply to
Grimly Curmudgeon

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