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Gray sludge in gas tank / carb?

#1

L

LKB

I have a TroyBuilt power washer powered by a 4.5 B&S engine that uses the 795469 carb (the kind that has a priming bulb and mounts directly to the gas tank, which has a mounting plate with machined channels that forms the bottom of the carb).

I recently have had all manner of problems getting it to start. Removed and flushed out the gas tank (soaked with kerosene, then rinsed and completely dried), changed oil, replaced the carb, carb gasket/diaphragm, spark plug, air filter, etc. (kits with all that are less than $20 on Amazon). Ran fine once, but the next time I needed to use it, it would not start. Took it apart and the gas tank has a light gray sludge everywhere (even on the sides of the tank — they look almost like crystals), which needless to say had completely stopped up the carb.

I also had exactly the same thing happen recently with my gas weed eater. But my lawn tractor (Cub Cadet) is using the same gas and is running fine (knock wood).

What’s weird is that I’d been running all my stuff for years on standard regular gas (which almost certainly had some ethanol in it), but recently had found a place nearby that sells ethanol free regular gas (mostly for boaters) that I have started using in my small engines.

Any idea what this gray crud is and why it is forming? And what I can do to prevent it?

thanks,
LKB
Austin, Tx.


#2

S

slomo

Don't use gas additives that are not proven.

Flush out the fuel tank. Use bolts/screws shaken in Dawn or some solvent. Blow out with compressed air.

Clean and reinstall OEM carb.

Change all fuel lines and filters. Make the fuel system as clean as you just bought it.

Dump and clean your fuel can.


#3

L

LKB

No gas additives used. Fuel tank cleaned, flushed, dried. New carb, which includes new integral fuel lines (mounts atop the fuel tank).

Still getting this grey sludge, even with reasonably fresh ethanol free gas that's working fine in my lawn tractor. As indicated, same thing happened with my weed eater (brand new carb, fuel lines, fuel filter, and cleaned gas tank).

Anyone have any ideas what this sludge actually is?


#4

StarTech

StarTech

Once the cast starts to disintegrate due moisture it usually hard to stop and the items has to be replaced.

On handhelds it usually comes from the diecast fuel filter assembly. Again caused by water in the fuel. Cheap aftermarket are even worst at this disintegration over time.


#5

L

LKB

StarTech said:
Once the cast starts to disintegrate due moisture it usually hard to stop and the items has to be replaced.

On handhelds it usually comes from the diecast fuel filter assembly. Again caused by water in the fuel. Cheap aftermarket are even worst at this disintegration over time.
Click to expand...
Thank you sir.


#6

I

ILENGINE

StarTech said:
Once the cast starts to disintegrate due moisture it usually hard to stop and the items has to be replaced.

On handhelds it usually comes from the diecast fuel filter assembly. Again caused by water in the fuel. Cheap aftermarket are even worst at this disintegration over time.
Click to expand...
See it with the pressed powder metal fuel filters, and carbs.


#7

L

LKB

ILENGINE said:
See it with the pressed powder metal fuel filters, and carbs.
Click to expand...
Thanks. You are correct, on my weed eater, the fuel filter in the gas tank had pretty much dissolved. But where the vast amount of gunk in the pressure washer fuel tank came from is a mystery -- the carb is almost all plastic + brass parts -- very little pressed / diecast metal I can see.

May tear one of the failed ones open out of curiosity.


#8

I

ILENGINE

LKB said:
Thanks. You are correct, on my weed eater, the fuel filter in the gas tank had pretty much dissolved. But where the vast amount of gunk in the pressure washer fuel tank came from is a mystery -- the carb is almost all plastic + brass parts -- very little pressed / diecast metal I can see.

May tear one of the failed ones open out of curiosity.
Click to expand...
the top of the fuel tank is powdered metal or aluminum but the sides and bottom are steel


#9

shadetree#1

shadetree#1

I've seen similar happen to gas tanks that are of magnesium type.
Had a old chainsaw (had been stored for several years and the fuel dried out in the tank) that had a mold type stuff growing inside. It would get past the new in tank fuel filter and clog the carb inlet screen inside the carb.
I had to tie the tank to a tractor wheel and place nut and bolts inside with a cleaner and tumble the tank. New fresh mixed gas into the tank then stopped the growth.

Had a plastic tank on a lawn tractor that gas had evaporated and left a molasses layer inside. It would get through the inline fuel filter to the carb and cause the needle/float to stick, both open and closed.
I still have not got that one cleaned out yet.

Yep it can happen.


#10

L

LKB

ILENGINE said:
the top of the fuel tank is powdered metal or aluminum but the sides and bottom are steel
Click to expand...
Ah, that would make sense, especially given the "crystaline" look of the grey crap that appeared to be growing in the tank. Thanks.


#11

S

slomo

Wow, never seen this pot metal dissolving trick. Lot of wise people on this site.......


#12

VRR.DYNDNS>BIZ

VRR.DYNDNS>BIZ

When it comes to gas these days, we have all seen everything. algae, mold, metal forming oxides, plastics and rubber decay, and far more. Ethanol and additives and time are the enemy. If it runs on gas, in time problems will evolve unless it is dry. A few years back I had conversations with the R&D departments of both Walbro and Zama. Since 1985 they have researched materials to withstand these issues to no success.


#13

L

LKB

Thanks for chiming in.

OK, so my problem stems from water or something ethanol-related contaminants dissolving stuff. Ergo:

1. What solvent/cleaner do people recommend to clean out this dissolved pot metal grey crud from the gas tank? And once I have it clean, should I treat the inside surface with anything? Or should I just chuck it and replace with a cheap plastic aftermarket one?
2. Is it even worth trying to clean the cheap aftermarket carbs once they‘ve sucked up some of this crud?
3. Big picture, what’s the advice for the best way to deal with small engines that are used infrequently (quarterly or even less frequently)? I‘ve now found a source of ethanol free gas nearby, and I try to run the engines until they are completely out of gas, but for things like my chipper, tamper, and pressure washer that might go a year between uses, what are best practices?


#14

7394

7394

Test your gas to be sure it is 100%...

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#15

A

Alton R

LKB said:
I have a TroyBuilt power washer powered by a 4.5 B&S engine that uses the 795469 carb (the kind that has a priming bulb and mounts directly to the gas tank, which has a mounting plate with machined channels that forms the bottom of the carb).

I recently have had all manner of problems getting it to start. Removed and flushed out the gas tank (soaked with kerosene, then rinsed and completely dried), changed oil, replaced the carb, carb gasket/diaphragm, spark plug, air filter, etc. (kits with all that are less than $20 on Amazon). Ran fine once, but the next time I needed to use it, it would not start. Took it apart and the gas tank has a light gray sludge everywhere (even on the sides of the tank — they look almost like crystals), which needless to say had completely stopped up the carb.

I also had exactly the same thing happen recently with my gas weed eater. But my lawn tractor (Cub Cadet) is using the same gas and is running fine (knock wood).

What’s weird is that I’d been running all my stuff for years on standard regular gas (which almost certainly had some ethanol in it), but recently had found a place nearby that sells ethanol free regular gas (mostly for boaters) that I have started using in my small engines.

Any idea what this gray crud is and why it is forming? And what I can do to prevent it?

thanks,
LKB
Austin, Tx.
Click to expand...
I would flush out the gas tank. I would check my gas can also.
I would never trust what comes out of a gas station pump. Pore your fuel into a glass container first before you put it into your machines. I had to replace my wifes gas tank because of trash and water. A cars fuel tank has a baffle in it. You can't get that junk out.
Sounds like your places you buy fuel from is your problem.


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