OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Bright Yellow fuel???

Hi all,

I was doing a service job for a bloke today and when I removed the carby and fuel tank to flush and service I noticed the fuel was bright yellow.

I removed the carby and pressed the primer bulb and it was like it hadn't had a drink for a LOOOOOONG time and was very dehydrated!

In the photo below you will see the yellow stain on the box is the last little bit of fuel that I squeezed out of the carb.

This mower would start on start ya bastard and run perfectly fine but it would not start on the fuel alone.

The fuel also smelled off but by no means the worst I have wiffed.

My guess is there was crappy old fuel in the tank that had started to break down and gum up and when I put fresh fuel in it started to dissolve the varnish but has anyone seen this before? Is there an additive that turns fuel yellow?

After I cleaned out the carb and tank the mower started and ran like new.

I don't remember ever seeing yellow fuel before. clear, black, purple yes but not yellow...

Curious to know what caused this.

Thanks,
Pete.

it must be getting around here somewhere pete , had one this week too bright yellow and smelled different , turned out it was 98 premium just killed the s/plug was all .
have seen it yellow but normally it stinks

In theory, if it smells badly and is yellow, it contained ethanol when it was new. The ethanol is hygroscopic (it absorbs water), and the hydrated material, probably mixed with some of the constituents of petrol, decomposes. It is not related to gum formation, but it does make a claggy mess that won't go through the jet, and clogs the float bowl.

I don't like ethanol in fuel for several reasons, but if the fuel is going to be kept for a long time without airtight sealing to keep the moisture out, it is just a bad idea to use it.

I totally concur with grumpy, that seems as it has had ethanol as a mix from sale or post mix. The yellow colour is the begining of oxidition (due to water content) but the oil beased fuel has stopped it hence the yellowing colour.
ethanol is good when fresh, if left for a time (6 months plus, you need to get a fuel additive or drain all the fuel.
for long term storage use the bare bones all oil based fuel as the more you refine it the more extras are just going to break down and casue problems.

Peter

hmmm fair enough.

The same bloke brought around a GMC with a chonda motor that wouldn't run a couple of weeks ago. Opened up the fuel cap WOW the fuel was RANCID.

Adjusted the engine brake/kill switch cable, fresh fuel and vrooooom. Some people just don't understand what fresh fuel is...

Vccomm; that's strange that you saw it a week ago too ... mind you petrol has been very expensive here lately. Maybe more people are using the E10 stuff for lawnmowers???

Grumpy/Vibexr8; that's interesting. Never new ethanol turns yellow with water and age. Learn something new every day!

I'll have to ask what fuel he used - mind you he'll probably say "dunno - BP? Mobil? Shell?" It's hard to get straight answers sometimes. Once had a bloke bring me a brand new sanli and tell me his son filled the petrol tank with oil and the sump with petrol. Yeah riiiiiggggghhhhhhttttt. Your son is maybe 6 month old buddy ...

Thanks guys.

Pete.

he was from eliz' too , i know of one station had a bad rep' a while ago close to there , from personal experiance too !! made a nice mess of the cooks car just lucky w=its duel fuel or we have been hmmmmmmmm . stuck at moonta

Pete, Good question and a comprehensive answer from Grumpy as usual. Thanks for putting up the thread. I learnt something new as well.

I have encountered a fair new mowers with similar problems to yours one but never actually asked the question.

Jaffa.

Also here is a simple easy way to check ethanol (alcohol) present and its percentage.

Using a 250ml container fill will 50 ml of water and 200 ml fuel.

Cap and shake to mix water with the fuel.

Set aside and wait a few minutes.

Now if ethanol is present you would get a reading of over 50ml of water at the down of the container.

Divide this overage reading by 200 to get percentage of ethanol. Be done in 125 ml container but the 250ml makes readings easier since everything is doubled.

Example: reading of 70ml minus the original 50ml water equal net reading of 20ml of ethanol which is 0.10 or 10 percent.

As Grumpy said ethanol attract moisture from the air quite easily. I have seen clear fuel become cloudy with a within a minutes on high humidity days if left open to air.

Btw the way our here in the was yellow at first when unleaded was introduced it look like lemonade. Now it much paler in color. As far as I know there was no change in the dying system here in the US.