blue sediment in carbs

[txninak@arctic.net]

I have a 1999 Yamaha F50 4-stroke, which I have used for three seasons with no problems whatsoever. To winterize, I have added a gas additive and run the engine dry prior to putting it up for the winter. I did not until this year realize I could drain the remainder of the fuel from the carbs, so likely a small amount of fuel has remained in them over each winter. New gas has been used at the beginning of each season. <br /><br />This year, the motor has performed inconsistently, sometimes running well (usually at high RPMS, above 3000), but at both high and low speeds it will sometimes miss and lug. I have cleaned all the fuel tanks, lines and filters and replaced all the gas, again. Upon draining the carbs, I discovered a blue crystalline substance that breaks into a powder when you press it. It does not dissolve in gas or in carb cleaners, but repeated application of carb cleaner directly into the carb seems to flush it to the bottom of the bowl. I'm assuming this sediment is what is causing the performance problems; however, what is it? where did it come from? how do I get rid of it? and how do I keep it from coming back?

 

[Bco128]

Re: blue sediment in carbs

i would guess you ave an aluminum fuel tank.it was run out of fuel and this allowed it to oxidize,which you are now pulling into your carbs.im not a guru but had something like this in a mower with an aluminum tank.the corosion in the tank turned a blueish color when it was wet and crumbled easily.

 

[Bco128]

Re: blue sediment in carbs

just bumping this to get you attention.

 

[txninak@arctic.net]

Re: blue sediment in carbs

We've never used aluminum - or any metal - tanks with this motor, just the plastic 6-gallon ones that came with the motor. Also, all extra fuel we've carried with us has been in plastic containers. We did wonder if the sediment was due to some type of oxidation, but no idea where it would come from!

 

[Bco128]

Re: blue sediment in carbs

just a thought.have you strained the fuel from the plastic tanks to see if it is coming from the fuel pumps?

 

[txninak@arctic.net]

Re: blue sediment in carbs

We've changed out all the fuel in the tanks, and drained the lines, filters, etc before starting with fresh fuel. I didn't strain the fuel as it came out of the tanks or lines, but there was nothing like this in the fuel filters.

 

[grandx]

Re: blue sediment in carbs

Complete stab in the dark, but any chance fuel has alchohol in it? Maybe deteriating some gaskets or hose material.

 

[txninak@arctic.net]

Re: blue sediment in carbs

How do I determine if the gas has alcohol in it? I don't think I'd recognize it even if it did.

 

[jimowen]

Re: blue sediment in carbs

Another stab in the dark...<br /><br />It does sound like oxidation of aluminum, so where could it be coming from? My guess would be that since you run it dry, there is air in the fuel system. Dutch Harbor was kinda wet last time I was there, so there is salty air around. I think I would disassemble the fuel pump and just see if anything similar was growing on the walls of the fuel pump housing (Either that, or the carb bowls themselves - these are essentially the only aluminum metal past the fuel filter)

 

[txninak@arctic.net]

Re: blue sediment in carbs

Well, I guess we'll be checking the interiors of the fuel pump and carbs next. We will post again after looking at them. Thanks to everyone for their suggestions.

 

[suzuki40]

Re: blue sediment in carbs

That is a common problem, if the fuel is left sitting in the bowls for a long period of time, the additive they use in the gas to clean your engine is what does it. over time it evaporates and clings to mostly the gasket material and crystlizes into a white chaulky substance, kind of like the crap that formes on battery post. Exxon gas seems to be the worst for this. they put so much stuff in there gas it unbelievable.<br /><br />Suzuki40