This is pretty bizarre. I thought I knew a whole lot about fuel tanks, but this one has me stumped. I'm working on a 2003 Suzuki SV1000S motorcycle. Vehicle has fuel injection. The vehicle was garaged and NOT run approximately two years. Note I'm in Las Vegas and it gets pretty hot here in the Summer.

I went to start it up, and I couldn't hear fuel pump. Chased down a blown 10amp fuse. Replace fuse, repeat, blown fuse. I suspected perhaps fuel varnish sticking in the fuel pump impeller... That would definitely cause a blown fuse.

The fuel pump is inside the tank, mounted from the bottom. I went to open the tank up to drain it. I had one heck of time opening the gas cap. Total no go. I very carefully applied some low viscosity lubricant to the key lock there, turn key, attempt to open. No force, be nice! Add a drop of oil, turn the key, test. Do this 15 or 20 times. Finally I was able to get the gas cap open, and whoa...

what the heck is this?

White Dust on Gas Cap

No wonder I couldn't open the gas cap. I've never ever seen this before, even though this bike had been garaged for a long period before. What the heck?

One thing odd about that photo. The part that has the dust on it is not steel, nor do I think it is aluminum. It definitely does not stick to a magnet. The small ring just above the dust covered piece is steel. Absolutely no white dust on the steel ring. If I had to guess, the piece with all the dust on it is a zinc diecast part.

I will say, there is a whole lot of white / gray dust there. The photo doesn't do it justice. It wipes off easily, but there is a WHOLE lot of the stuff there (and in the tank, sigh). My guess is the stuff is 1/8" or more thick everywhere. I think I now know what is jamming the fuel pump. I'll know more when I get there.

Anybody know what it is? My tendency is to:

  1. remove the fuel pump, clean that up very carefully. Ensure the fuel pump motor impeller can be rotated freely.
  2. remove the gas cap filler and lock assembly take everything apart, clean it up carefully, perhaps with WD-40?
  3. remove the entire fuel tank from the bike, and clean it up? What method? Solvent? I use a lot of kerosine and acetone as solvents for other projects here. Perhaps soap and water? Followed by compressor blow out and dry in the sun for X hours?

Any ideas what this might be? My guess is this has something to do with the fuel. I know they use heavy amounts of ethanol in the gasoline here. Perhaps that is why we never saw this after long storage in another state. Could ethanol fumes react with zinc to cause this?

2 Answers 2


I'm not a chemistry expert, but it probably is the result of phase separation in ethanol blended gasoline.

You don't have to disassemble anything to correct this problem. Many old time classic car owners have restored gummed tanks and parts with Marvel Mystery Oil. Drain the tank and use it full strength. Allow to soak for days, if not weeks. Often, the oil is allowed to penetrate for months during a cold winter. If you'd like to accelerate the process, warm the fluid as much as possible (I clean warm combustion chambers in ten minutes). You can combine MMO with acetone 50-50 (or carburetor cleaner, or Berryman's B12) for a super penetrating fluid that frees everything from clogged injectors, stuck piston rings to rusted bolts frozen solid.

Once started, you can run the engine with up to 25% MMO mixed with gasoline without having to change spark plugs. A more reasonable amount, however, still very strong is 2 oz. per gallon, which will clean varnish from the fuel pump, gas lines & injectors. Acetone mixed with MMO in the gas greatly enhances the removal of deposits at a treat rate of .3 to 1.0 ounces per gallon.

  • Awesome advice. I'll let you know how well it works after I pick up MMO and perhaps carb cleaner. Note I did completely dissemble the fuel pump components last night. Old fuel varnish is everywhere.
    – zipzit
    Commented Sep 24, 2017 at 15:32

As you pointed out, this part is probably zine die cast. I've never owned the SV1000, but I have owned several SV650s. What you are seeing is likely "zinc rot". Here is the wikipedia page on it. It is a well known problem. If I had to guess, somehow the climate you are in or the fuel used accelerated the problem.

Here is an image of zinc rot.

enter image description here

The other possibility is the part is aluminum and you're just seeing "normal" corrosion of aluminum from ethanol. For whatever reason, ethanol can cause almost immediate corrosion of aluminum parts. This usually happens under high concentrations but can happen with gasoline like E10 as well. Here is a picture of what that looks like.

enter image description here

My suggestion for fixing this is removal of the fuel pump and gas cap. You can clean the tank out by putting abrasive material such as sheet metal screws inside and shaking the tank violently. Then just flush it with soap and water.

Replace with fuel pump with a known good one. Then replace the fuel cap as well with a new one. You can get an aftermarket keyless unit for much less money than the OEM one.

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