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How do you know when your fuel is too old?

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Old 04-21-2012, 01:39 AM
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Rendegade
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Default How do you know when your fuel is too old?

As above. I'm having a dog of a time trying to keep my PAW happy.

I think the fuel is cactus, but I don't know how to tell.

How do you know when it's stuffed?
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Old 04-21-2012, 01:49 AM
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Default RE: How do you know when your fuel is too old?

Renegade,

Take a measured amount of your fuel, say 100ml. Put it in a graduated cylinder and let the ether gas off. Over a day or so, the oil & kero will separate. This will give you the non ether components of your current blend.

From this you'll be able to see what you fuel mix was before the ether evaporated. Then you can compare it to the desired mix.

regards


Greg
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Old 04-21-2012, 03:31 AM
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Default RE: How do you know when your fuel is too old?

If your fuel was in a factory sealed metal can before you opened it for use - it can last for years and years. I have many gallons of DDD fuel that are over 15 years old and work flawlessly. If the can has been opened before and sat for awhile, do what the last poster suggested. It wll tell you quickly whether you still have adequate Ether, Kerosine, and Oil content.
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Old 04-21-2012, 06:16 AM
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Default RE: How do you know when your fuel is too old?

If the fuel is in a decent container and sealed off OK, the fuel will last indefinitely. I am still using a 10 or 12 year old container of model diesel fuel myself.
But if you are one of those guys who leave the cap off of the fuel can a lot when fueling up engines or planes, then a lot of the ether will evaporate on you causing the fuel to get old and stale much faster.


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Old 04-21-2012, 08:05 AM
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Default RE: How do you know when your fuel is too old?

Renagade....with the ether loss hard to start, if you get it going requires as you found out I am sure quite compression increase , it will run hotter transition poorly
and puts quite a stress on the engine due to overcompression to get ignition of the fuel mix martin

you could try a quick and dirty fix add an oz of ether to a pint of your fuel thats 6% it might go off and run ok with compression reduced back where it should be
if better but if not there yet add an other 1/2 oz of ether that brings you up to about a 10% increase in ether if still does not sound and run right just get some fresh fuel
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Old 04-21-2012, 08:56 AM
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Default RE: How do you know when your fuel is too old?

Once you seal up your can of fuel, there should be no odor. If you can smell it, it is leaking.
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Old 04-21-2012, 04:11 PM
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Default RE: How do you know when your fuel is too old?

Thanks guys, The fuel can I use is an old acetone can with two bras tubes soldered into the top, one has a clunk and the other does not, When stored I run a peice of tygon over the top tubes to seal it all off.

Unsure as to whether it leaks, but it lives in my workshop and haven't ever noticed that sweet smell.

I'll try the evaporation method to determine if my fuel is weak on ether.
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Old 04-21-2012, 04:28 PM
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Default RE: How do you know when your fuel is too old?

Before you blame your fuel, does the engine fire from an exhaust prime? does the engine have a perfect piston seal? if there is any leakage when you turn the engine over very slowly up to TDC , if the compression slowly leaks off, you have an engine, not a fuel problem.
If you have a good engine, you know your fuel is a problem when you flick until your arm drop off!
If in doubt top up the ether. Or use a small prime of a drop or two of straight ether.
If your engine runs on a prime and won't continue to run, there are a whole load of other issues to check, crankcase seal, leaky back plate, hole in the needle assembly in the wrong place etc etc
Cheers JG
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Old 04-22-2012, 03:04 PM
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Default RE: How do you know when your fuel is too old?

It'll run out a prime, but I'm chasing the compression to keep it going, and it sags and labours. I just cant get it to burp along under compressed which makes me think the ether's gone.

I'll check the other things too, I've set the spray bar as I've always done for C/L glow motors, which is rotated until you can't see the hole and then nipped up. Correct?
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Old 04-22-2012, 05:23 PM
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Default RE: How do you know when your fuel is too old?


Quote:
ORIGINAL: Rendegade
....... I've set the spray bar as I've always done for C/L glow motors, which is rotated until you can't see the hole and then nipped up. Correct?
Yep theoretically correct and I think that the lab rat tested angle is 15º below the horizon.

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Old 04-22-2012, 06:24 PM
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Default RE: How do you know when your fuel is too old?


Quote:
ORIGINAL: Rendegade
It'll run out a prime, but I'm chasing the compression to keep it going, and it sags and labours. I just cant get it to burp along under compressed which makes me think the ether's gone.
If it runs out a prime, chances are that the fuel is not the problem.

Are you sure it's burning the prime correctly? If it is over-compressed, sometimes an engine will pre-ignite and just bounce the prop back and forth instead of a full rotation. In that case, usually it will start running correctly if you just lower compression a bit.

Lots of stuff to try...good luck with it.

George
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Old 04-22-2012, 07:14 PM
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Default RE: How do you know when your fuel is too old?

I flew today with diesel fuel at least four years old, in a can similar to what you describe.
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