Stihl 066 won't start no gas from carb?

[Derrick Sawyer]

Hey all,
Got an older Stihl 066 driving me crazy, couldn't start the saw so checked everything out- Vacuum and Pressure tested fine, piston looks fine, compression is good, fuel line and filter are new. Figured it just needed a carb rebuild, got a carb kit, cleaned out the old carb as I have done on dozens of other occasions (sonic bath) dried passages with air compressor, put back together, DOES NOT START.

Checked the inlet needle adjustment again, was fine, but dry. There is gas on fuel pump side but none getting to the needle side?? I raised the metering lever to give more fuel, still no start. I put in a carb off a newer 660, started and ran fine. Then I figured carb might be bad, recently got a bunch of stihl 660 parts from someone else, so I tried my rebuild kit on 2 other carbs after cleaning those as well, still no start due to no gas, driving me crazy spending all day rebuilding and cleaning carbs.

I guess its possible all these carbs are not fixable, what would cause some to not be rebuildable?

I sprayed carb cleaned thru and they seemed ok. Even brought the L screw way out to give more gas, still no gas on needle side. Note: the carb on my newer 660 that worked I had also rebuilt a while ago and its fine. Out of dozen of other carbs I have rebuilt, had one that could not stop from flooding, rest were fine.

 

[hotshot]

Pressure test the "bad" carb off the saw w/o the metering cover on.

Put some light machine oil or premix in the tubing before you connect the tester, then pump it up to 6 psig.

The oil should spurt out of the inlet needle port (around the needle) when you tap or quickly depress the metering lever.

If not, there's a plug at the inlet needle orifice. This assumes you have a squeaky clean inlet screen & no debris in the pump side.

Is your pump diaphragm and gasket the correct ones?

"I have a potty mouth"!

 

[Chainsaw Jim]

You can ruin check valves with compressed air. You don't want to let carb cleaner or anything other than the fuel you burn come in contact with carb diaphragms because it can stiffen and wrinkle them.

You can check the valve by closing off both jet screws just tight enough to be air tight and then using a piece of fuel line to hold over the little brass jet to draw a vacuum with. You can use a special tool or your lips. A good check valve on this model carb will hold tight.

 

[Derrick Sawyer]

Thanks for the replies guys.
Hotshot, the inlet need orifice is not clogged, i can see thru to the where the screen would be on the other side, and i put in a new screen I took a pic. The rebuild kit came with 2 diaphragms, one has an extra hole, i took a pic of the old diaphram (has dirt on it) and the 2 newer ones, it looks like i was probably using the wrong one....there is an extra hole close to where the fuel come in....would this not allow the pressure from the impulse line to build and allow fuel to overcome the pressure on the inlet needle from the spring?

I also took a pic of two carbs i tried to rebuild, one had a fixed jet, the other did not. So the check valve is the other bronze round thing that has a hole? If the check valve was bad, there would still be fuel entering the the needle side, but not enter the check valve or enter too much? Where in the circuit does the low and high screws go into in relation to the check valve and the jet? , Does the fuel then go into the other bronze thing pressed into the carb passage where the air goes thru and the venturi effect causes fuel to be drawn out due to low pressure?

 

[hotshot]

That's a lot of questions, but if the needle hole is clear & the metering chamber is dry, you now need to look upstream at the fuel pump side.

Pull the carb off & pressure test it.

What are the carb numbers?, they both look like Walbro WJs

 

[Wood Doctor]

So far you have been working entirely with fuel-related issues. What if it's all related to electricity? You have a good spark, right? How do you know this for sure?

 

[Derrick Sawyer]

pressure test was fine for both the fuel and the impulse inlets, and the pressure from inpulse is release when I depress the metering lever...looking at the fuel pump diaphragms the one with extra hole looks like it would not allow fuel to flow properly towards the screen over the inlet needle port, this must be the problem, too late to test tonight but i'll find out tomorrow.

thanks for the help. Carb with fixed jet (.72) is a WJ35A and the one with adjustable jet (.64) is a WJ51, i had also tested a WJ69 and it didn't work with the wrong diaphragm pump, but a previously built WJ69 worked fine.

Chainsaw Jim, i'll do the check valve tip as well, HOW do you propose cleaning the carb? Should i just sonicate in water/dish soap, then with only water, and use air pressure for all passages except the checkvalve?

thanks

 

[Derrick Sawyer]

Hey Wood Doc,
Yes, saw ran fine with carb from good running 660, and I did check with a spark tester and saw good spark, off course not under compression though. And the spark plug was dry...not flooded.

 

[Chainsaw Jim]

pressure test was fine for both the fuel and the impulse inlets, and the pressure from inpulse is release when I depress the metering lever...looking at the fuel pump diaphragms the one with extra hole looks like it would not allow fuel to flow properly towards the screen over the inlet needle port, this must be the problem, too late to test tonight but i'll find out tomorrow.

thanks for the help. Carb with fixed jet (.72) is a WJ35A and the one with adjustable jet (.64) is a WJ51, i had also tested a WJ69 and it didn't work with the wrong diaphragm pump, but a previously built WJ69 worked fine.

Chainsaw Jim, i'll do the check valve tip as well, HOW do you propose cleaning the carb? Should i just sonicate in water/dish soap, then with only water, and use air pressure for all passages except the checkvalve?

thanks

You don't need to clean either of those two carbs in the pics. They look as clean as they do new.

 

[Chainsaw Jim]

The main check valve is the brass one with no hole. The high jet screw lines up with the threaded brass jet nozzle with the flat head slot...which the carb pictured on the left appears to be missing.

 

[hotshot]

pressure test was fine for both the fuel and the impulse inlets, and the pressure from inpulse is release when I depress the metering lever...looking at the fuel pump diaphragms the one with extra hole looks like it would not allow fuel to flow properly towards the screen over the inlet needle port, this must be the problem, too late to test tonight but i'll find out tomorrow.

thanks for the help. Carb with fixed jet (.72) is a WJ35A and the one with adjustable jet (.64) is a WJ51, i had also tested a WJ69 and it didn't work with the wrong diaphragm pump, but a previously built WJ69 worked fine.

Chainsaw Jim, i'll do the check valve tip as well, HOW do you propose cleaning the carb? Should i just sonicate in water/dish soap, then with only water, and use air pressure for all passages except the checkvalve?

thanks

Now it sounds like you have the fuel line hooked to the impulse nipple, as FUEL should always be released when you depress the metering lever.

The impulse pressure does not change when you "pressure test it", but I've never done an impulse pressure check LOL.

 

[Chainsaw Jim]

Now it sounds like you have the fuel line hooked to the impulse nipple

How is that possible?

 

[alderman]

I have had some carbs that took several trips through the sonic bath before they worked. Just a cheap harbor freight unit here but just saying.


Sent from my iPhone using Tapatalk

 

[Wood Doctor]

How is that possible?

Good question. Now I've heard everything. Seems like you'd have to work pretty hard to get those connected up.

 

[hotshot]

How is that possible?

Anything is possible when you're bench testing. The OP had the impulse & fuel connections reversed
in his pressure test description.

If the carb's mounted on the saw, you could not reverse them. I'm bowing out of this thread, you've
got it covered.

 

[Derrick Sawyer]

Thanks guys, the saw starts fine now, the kit K10-WJ rebuild kit has two fuel pump diaphragms and I somehow used the wrong one, even though I usually save the old parts and make sure I replace them with ones that look the same, but its a small difference (see pic, its tough to tell), and that extra hole did not allow the build up of fuel pressure.

Hotshot is right, when I bench tested I pressurized the fuel line barb with the metering cover off and it held pressure till I depressed the metering lever. The carbs are all clean since I sonicated all of them already, the question is what solution do you use for sonicating? I add a drop of dawn dish soap for 15min, then rinse and use just water for the next 15min, then dry with compressed air.

Now i'll post the saw for sale, if you're interested take a look for an 066 from me

peace out

 

[Chainsaw Jim]

I'm bowing out of this thread, you've
got it covered it.

Every members input is important to this environment. It's all about learning. You don't learn if you don't ask questions and when information get corrected it allows better learning for many.