What's getting in my carb?

[Greg Smith]

I inherited a barely used chainsaw that had been put up a while. Replaced all the fuel/oil lines and filter, put in fresh gas and seafoam and adjusted the carb and it runs like a scalded ape...for a short while (tank or two). After about a tank of gas, it would bog down and die. Decided to do a carb rebuild, and when I took it off, the carb was especially clean EXCEPT for for the screen inside the carb which was completely filled to the brim with fine almost white paste, which dries quickly when spooned on on a screwdriver...it is just fine dust. Took the carb apart completely and put it in an ultrasonic cleaner and came out spotless...put it back together with the original components, saving the rebuild kit for later. Anyhow, ran great again and put it up. Took it out a couple weeks later and started it up and it wasn't long before it was dying again. Fiddled with the carb screws a bit and then gave up and took the carb off and opened it up...again, completely clogged with the same white paste...blasted it out with carb cleaner and it's running great again. I checked the filter (which was new), and it is intact and passes fuel. I'm curious hw this paste is gatting past the filter and hanging up in the screen. Thanks in advance.

 

[TBS]

I'd replace the filter and fuel line again. What type of container is your fuel in?

 

[grizz55chev]

I'd replace the filter and fuel again. What type of container is your fuel in?

Could be your fuel filter material disentagrating, seen it before. Change the filter by reaching in the tank with a wire and pulling the filter through the opening.

 

[svk]

Sediment from your tank?

Dump the fuel out and let the tank dry. Is there a fine film dried up on the tank walls?

 

[pioneerguy600]

Am fuel filter? Some AM stuff dissolves in E laced gasoline.

 

[HarleyT]

What make and model saw is it?

 

[Greg Smith]

The saw is a Mac 3214...cheesy saw, I know, but it is small enough to fit in my truck tool box. I have a much bigger, better saw that is using the same gas from the same fuel can with no problems. I did use fresh gas, but one thing I didn't think about was the condition of the gas can mixed in...it is plastic and relatively new, but had been "empty" for a while. I did drain the saw tank through a coffee filter and the picture shows what filtered out...same stuff...took forever to get through the filter. So I guess it's in the tank, but I am surprised it's getting past the tank filter. I put straight gas from a different can into the saw, shook it up and dumped that fuel, then filtered mix back into the saw through a coffee filter & ran the saw...it runs fine now, but I'll drain it again, rinse with straight gas and then leave it open to dry. I'll do the same with the gascan I am using. I wondered about the tank filter deteriorating...but it seemed solid. I don't know what an AM filter is? Can you elaborate? I'm sure the gas I'm using has 10% ethanol...no place in Austin TX to get straight gas.

 

[grizz55chev]

The saw is a Mac 3214...cheesy saw, I know, but it is small enough to fit in my truck tool box. I have a much bigger, better saw that is using the same gas from the same fuel can with no problems. I did use fresh gas, but one thing I didn't think about was the condition of the gas can mixed in...it is plastic and relatively new, but had been "empty" for a while. I did drain the saw tank through a coffee filter and the picture shows what filtered out...same stuff...took forever to get through the filter. So I guess it's in the tank, but I am surprised it's getting past the tank filter. I put straight gas from a different can into the saw, shook it up and dumped that fuel, then filtered mix back into the saw through a coffee filter & ran the saw...it runs fine now, but I'll drain it again, rinse with straight gas and then leave it open to dry. I'll do the same with the gascan I am using. I wondered about the tank filter deteriorating...but it seemed solid. I don't know what an AM filter is? Can you elaborate? I'm sure the gas I'm using has 10% ethanol...no place in Austin TX to get straight gas. View attachment 556055

AM means aftermarket. If your filter is a simple screen type then it may not have a fine enough mesh to keep the fine particulate out. Since you know that the tank is contaminated, a good rinse job and new filter should do the trick.

 

[HarleyT]

I asked because I was curious about what the tank/saw was made of.
A metal tank has a white colored powder corrosion when it corrodes.
But your saw is black plastic, isn't it?

 

[grizz55chev]

He may need to check the can he's refilling, seen them cause headaches as well.

 

[Greg Smith]

The filter is after-market, but it's not a screen...it's one of those typical "stone-like" cylinders with a weight on the end, that you see on chainsaws, weed whackers, leaf blowers, etc. I thought those things are pretty tight, but apparently not. I'm gonna replace it after washing the tank out again. Thanks for everyone's help.

 

[Greg Smith]

and yes...both the saw tank and fuel can are plastic. I'm gonna rinse out the fuel can too...I'm actually betting that's the culprit.

 

[svk]

The saw is a Mac 3214...cheesy saw, I know, but it is small enough to fit in my truck tool box. I have a much bigger, better saw that is using the same gas from the same fuel can with no problems. I did use fresh gas, but one thing I didn't think about was the condition of the gas can mixed in...it is plastic and relatively new, but had been "empty" for a while. I did drain the saw tank through a coffee filter and the picture shows what filtered out...same stuff...took forever to get through the filter. So I guess it's in the tank, but I am surprised it's getting past the tank filter. I put straight gas from a different can into the saw, shook it up and dumped that fuel, then filtered mix back into the saw through a coffee filter & ran the saw...it runs fine now, but I'll drain it again, rinse with straight gas and then leave it open to dry. I'll do the same with the gascan I am using. I wondered about the tank filter deteriorating...but it seemed solid. I don't know what an AM filter is? Can you elaborate? I'm sure the gas I'm using has 10% ethanol...no place in Austin TX to get straight gas. View attachment 556055

The stuff is microscopic when dissolved which allows it to pass through the filter tank filter. When it gets into the carb the particles that stick together form the sludge you end up cleaning out.


As the others guys mentioned it's probably your external fuel tank that is contributing the gunk to your saw.

 

[astnmacgto]

The filter is after-market, but it's not a screen...it's one of those typical "stone-like" cylinders with a weight on the end, that you see on chainsaws, weed whackers, leaf blowers, etc. I thought those things are pretty tight, but apparently not. I'm gonna replace it after washing the tank out again. Thanks for everyone's help.

The filter your talking about is ceramic type and usually a very good choice... I like them for everything but a stihl, they get oem

 

[Okie]

I won't forget this one for awhile. Took some patience to figure it out.
I had similar problem with a chainsaw that was given to me and had been stored for several years.
Before even trying to run the saw I replaced all the fuel lines, fuel filter,, installed a carb kit, added some raw gas to tank and dumped tank gas into a funnel with a white paper strainer towel and noticed gunk from the tank, casually cleaned the gas tank and got the saw started and was running great. Few days later I took the saw to the woodlot and it acted like it was starving for gas, checked new tank fuel filter as ok, removed carb and not anything noticeable until I blowed some air thru the carb sintered filter while it was in a white paper tower and the carb inlet iron filter and small screen was clogged. Could see the small screen was clogged when looking at it thru a magnifying glass.
Poured gas out of the gas tank into a white paper towel in a funnel and seen it had very very fine mess coming from the tank. I cleaned the tank with lacquer thinner, but could still see some on the walls of the tank that looked like a hard mold when I looked carefully. Put the saw back together and few days later it happened again. Long story shortened, it took several tank cleanings and soaking to get the fine mold looking gunk removed.
It was fine enough that it would get past the in tank filter and into the carb inlet sintered iron filter and the carb's fine screen. Almost as fine as a stain.
This old saw had the old model Tillotson carb that used both the sintered iron type inlet filter and the small screen inside the carb. Some of the stuff would eventually get past the inlet sintered iron carb filter and eventually into the small screen and was not apparent until air was blown thru the filters into a white paper tower to see what was coming out of the filters. When the carb filters first started clogging the saw would not take throttle, but would sit and idle.
The sintered iron type filter in the carb would stop most of the fine stuff. Could not believe so much of it would get past the in tank filter. It was like the in tank filter was just a pre-filter for larger trash.

 

[Greg Smith]

Is lacquer thinner safe for a plastic tank/can? Did you soak the tank with lacquer thinner or just fill it up, shake it good, and dump it out? Sounds like my problem is the same one you had.

 

[pioneerguy600]

I see the AM abbreviation was explained, good, but the tank filters are too coarse to catch this fine material we are now finding trapped in the very fine carb screens. Seems the gasoline is now degrading plastic gas containers, especially when the containers are left out in sunlight. My own plastic tanks/containers hardly ever see the sun/ always kept indoors and covered when outside, they show no signs of this white degradation. I have seen many gas cans that are used around boats that are bleached nearly white due to sitting outside year round exposed to the elements and sun.

 

[Greg Smith]

Problem now solved...it was indeed the saw tank. I borescoped it and it was full of "gras deaux" (cajun technical term) and an old filter (I might have done that). Well after ~20 rinses through a paper towel (I lost count), a wipe out with a shotgun bore swab, and several compressed air blasts, it finally came clean. I pulled the carb again, and the screen showed a bit of the stuff as well so i knocked that out with carb cleaner. If I'd known it was going to take so many rinses, I would have hit it with my steam cleaner. I considered taking the tank off and putting in my ultrasonic cleaner, but it probably wouldn't have fit. There does't appear to be any degradation of the tank and I checked the fuel in the gas can and it is clean. Hopefully that solves it...thanks for all ya'lls help.

 

[svk]

Good work. It still may crud up one or two more times but you've done the lions share.

 

[Okie]

Is lacquer thinner safe for a plastic tank/can? Did you soak the tank with lacquer thinner or just fill it up, shake it good, and dump it out? Sounds like my problem is the same one you had.

Just shake it and dump it out. Have to be careful using lacquer thinner around plastic, some plastics will melt or get soft fast.
(and I always use chemical gloves and eye protection, some of that stuff coming out of gas tanks will melt your internals eventually)

I was into a really dirty tank awhile back and used a piece of old porch chain and some water in the tank and jacked up the rear tire on my tractor and securely tied the tank to the wheel and left the tractor idling in low gear so as the piece of porch chain was scrubbing the inside while it was slowly rotating and the chain scrubbing the inside, went back in few hours and rinsed the tank while the tank was still tied in place and all was very clean inside after a few rinses. The old style porch swing chain has sharp ends on the links and does a good job of cleaning the inside.

I've used this method on the larger old vintage auto gas tanks before using the red-kote epoxy liner. You can go on doing other things while the tractor tumbler is operating.

Cleaning gas tanks is not a fun job and takes lots of time. (would not do it for anyone else)