Joined: Nov 2017 Posts: 31 Threads: 10
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Must admit I too have been very sceptical about stale fuel but this exercise has proved it to me except for the compression issue. I have just done a compression test with a hot engine and throttle wide open and it's giving around from 80 to a max of almost 90. As I have previously said Ibelieve that maximum compression is the cars compression ratio times atmospheric pressure so the maximum I can expect with 6/1 ratio which my big seven is is 6x14.7 equals 88.7. Is their correct or not? If it is then no way can you get any higher readings than this so I am either wrong or there are some incorrect testers out there.
I recently bought a brand new compression tester and that gives a reading of 50 ish but an old one I borrowed gives my the 85 ish. Interesting!
Joined: Dec 2017 Posts: 1,160 Threads: 68
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Location: Nottinghamshire. Robin Hood County
Car type: Austin Ruby Mk1 1935
My ruby has always had starting problems with fuel over 6 weeks old. It will usually run on the old fuel once started on new and warmed up but this spring I started it up on fresh fuel but it would not run at all on the old stale fuel even when warm. Had to drain the tank and just use it for washing parts etc.
John Mason.
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
Joined: Aug 2017 Posts: 780 Threads: 26
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Location: On a hill in Wiltshire
I too am sceptical about the "stale fuel" statement. I think it must be stale fuel plus something (more than time) else.
My little outboard - 2 stroke, used one week a year, so the fuel is 51 weeks old - starts second pull.
My big outboard, ditto, wouldn't go unless everything dried the previous year and fresh fuel put in.
The Cambridge lives in an unheated garage, is used maybe every three months at present, always starts.
By the time it has come up the village, there is more water than fuel in the carb due to condensation in the slab tank.
So far, the Tourer, kept in the home garage, starts and runs ok at irregular intervals. Using a torch, there is a layer of flaky rust over the bottom of the tank, the product of which accumulates as a fine dust in the pump and float bowl which need cleaning from time to time.
The lawnmower (4 stroke) which lives outside and hasn't been used since November, started second pull.
So that is 1 to 4 against the stale fuel. What is Factor X that we are missing?
Simon
Joined: Aug 2017 Posts: 68 Threads: 8
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Bacteria is a recognised problem for stored diesel in boats.
One thing that does deteriorate is an old rubber fuel pump diaphragm in 'new' fuel. I wonder if the OP's is black or red?
Another thing that doesn't last is a modern sub standard condenser etc etc
Joined: Dec 2017 Posts: 1,160 Threads: 68
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Location: Nottinghamshire. Robin Hood County
Car type: Austin Ruby Mk1 1935
For what it is worth I find with my Ruby it maybe something to do with how well the tank is vented. When I put petrol in ( I never put in more than 3 gallons) the car runs fine. I leave it in the garage and soon the whole garage has that lovely smell of petrol. Over the next few weeks this petrol aroma diminishes and with it the starting efficiency of the car. It would appear to me that with age the petrol has evaporated off the spirit element that vapourizes easily without warming. The car normally will run on old stale petrol okay once I have got it going on new fuel. I put this down to the engine and manifold being warm and thus enabling the petrol to vapourize more easily.
Could it be that some cars have more than necessarily over vented petrol tanks.
Has anyone else got views on this.
John Mason
Would you believe it "Her who must be obeyed" refers to my Ruby as the toy.
Joined: Aug 2017 Posts: 1,187 Threads: 71
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Some of you may remember the thread i started 'SU Woes' about my Riley running problems. After many weeks of ripping the carbs apart and replacing the Mag with my spare etc etc, I finally drained the tank and replaced it with a gallon of fresh petrol. The problem went away. Now I know there are plenty of people who can return to a car after some weeks and it will fire up perfectly, but for me, ageing petrol was the root cause of my trouble..
