carb not getting fuel

[singinwoodwackr]

This ones got me stumped.
OE still carb, no primer bulb
I picked up a couple older, non-Mtronic 261 carcasses a while back and scrounged enough pts to get one ready to fire today. Problem is the carb doesn't seem to be getting any fuel inside...dry as a bone after multiple attempts to start the saw. Fuel line is clear, new filter and gas is getting to the carb pickup tube. Tank gets pressure from pull-starts. No leaks in the tank or anywhere else that I can see. Saw has good compression. New spark plug. I can get it to 'pop' with a little gas in the spark plug hole so it has spark.
I rebuilt the carb with the usual kit.
I disassembled the carb as I usually do and cleaned everything with carb cleaner and blew it all out with compressed air.
After taking it apart again to look for any blockage like crud in the screen, etc I made sure the pickup line was clear to the diaphragm.
Is it possible some little bit of crud is stuck somewhere inside? No vacuum to pull in gas? If so, what would cause that?
Bad kit? God knows now days whether or not these things are made right.

Other than that the rebuild went great, lol

 

[DWilkison]

Have you installed a new check valve?
I have an old Mac 10-10 that I got for free. Didn’t run. Super dirty. Cleaned up/reset the points, cleaned carburetor installed new kit and it fired up. But stopped getting fuel eventually. Went through the carb a few more times until I remembered the check valve. The little disc of diaphragm was in pretty bad shape. Ordered and installed the new check valve and I’ve been using it ever since.

 

[singinwoodwackr]

Have you installed a new check valve?
I have an old Mac 10-10 that I got for free. Didn’t run. Super dirty. Cleaned up/reset the points, cleaned carburetor installed new kit and it fired up. But stopped getting fuel eventually. Went through the carb a few more times until I remembered the check valve. The little disc of diaphragm was in pretty bad shape. Ordered and installed the new check valve and I’ve been using it ever since.

Kit came with new needle valve.
Haven't vac tested it yet...next step.

 

[Automender]

On a different saw I had an issue with the carb internal check valve that works with the primer bulb. I could not get any gas into the carb or any into the primer bulb. Is the primer bulb filling and getting hard?

 

[singinwoodwackr]

On a different saw I had an issue with the carb internal check valve that works with the primer bulb. I could not get any gas into the carb or any into the primer bulb. Is the primer bulb filling and getting hard?

No primer bulb on this saw

 

[nckcalifornia]

If you’re sure the path from the tank to the carb is solid (pres/vac test?), maybe the impulse line not working the pump side of the carb?

 

[singinwoodwackr]

If you’re sure the path from the tank to the carb is solid (pres/vac test?), maybe the impulse line not working the pump side of the carb?

Would a pressure and or vac test show that?

I’ll run the fuel line again but I’ve got plenty of gas coming out the fuel line when I pull the carb out …fuel line disconnects.
both top and bottom of the carb are dry regardless of #of pulls attempting to start.

 

[nckcalifornia]

If you can hook up your pump/vac up to the fuel line you can test the line for leaks but sounds like you’ve worked the fuel side of the carb so I would test everything on the cylinder side (focus on the impulse) for air leaks. I’m not familiar with m tronic stuff so I could be off base.

 

[singinwoodwackr]

If you can hook up your pump/vac up to the fuel line you can test the line for leaks but sounds like you’ve worked the fuel side of the carb so I would test everything on the cylinder side (focus on the impulse) for air leaks. I’m not familiar with m tronic stuff so I could be off base.

Saw is not moronic
I’ll try that as well…pressure test the tank via the fuel line.
but, this won’t explain why the carb is dry as I get plenty of gas at the fuel line going into the carb.
lol, spell check…didn’t like mtronic

 

[Vintage Engine Repairs]

Feet up, tea in hand and watch this video.

 

[Brufab]

Feet up, tea in hand and watch this video.

Great video. Not sure if my 1960s remingtons have an impulse line. Or do all carbs have that? I'm pretty new to this stuff.

 

[Woodslasher]

Great video. Not sure if my 1960s remingtons have an impulse line. Or do all carbs have that? I'm pretty new to this stuff.

I believe all carbs have impulse passages of some sort, some are external lines that run to the crankcase and others are mini holes/passages that are integral to the carb body. You’ll be able to see a tiny open hole on the face of the carb body where the carb seats against whatever mounting system your saw uses.

 

[Brufab]

I believe all carbs have impulse passages of some sort, some are external lines that run to the crankcase and others are mini holes/passages that are integral to the carb body. You’ll be able to see a tiny open hole on the face of the carb body where the carb seats against whatever mounting system your saw uses.

Thanks @Woodslasher. I think I know what your talking about after your explanation. Appreciate the information, I learned something new. Is this impulse? It corresponds with a hole on a Carter carb on a remington.

 

[Okie]

What carb do you have?
You indicate when you look inside the carb it's completely dry of gas?
You need to check the Impulse side of the engine and the carb. On the carb this is the side that has the two little reed flapper valves. They PUMP the gas in towards the metering diaphragm side of the carb (opposite side from the pump flappers) If you take the cover off the needle diaphragm side and its dry the problem is the impulse pump side. The pump side has to work first to pump/suck fuel to the carb then into the metering side. The crankcase impulses operate the carb reeds.
The little internal check valve in the idle circuit will not cause your no gas issue.

You can go here and pick a carb type to see how the impulse pump section operates.
https://www.walbro.com/service-manuals/?cclcl=en_USNote it indicates that the flapper reed valves have to be flexible and the carb body under the flappers clean with no scratches. It also helps to have the proper flapper pump material from a kit. Most are the black rubber type, but sometimes the nylon brown works better, some now days use the blue plastic mylar. You have to also make sure the associated outer gasket is installed properly. (not on wrong side of the impulse flappers)

 

[Old2stroke]

Are you sure the choke butterfly is closing completely? That is the usual cause of not getting fuel into the carb. Another issue is the inlet valve control lever may be set too low for the diaphragm to activate it, or the diaphragm is too stiff, or on the wrong side of the gasket, or the diaphragm is upside down and the nub that operates the control lever is on the wrong side. As mentioned a nozzle check valve (not the inlet valve) could be stuck open and not allowing vacuum to build up enough to pull the diaphragm down. To get the carb to fill with gas for starting it's all about the choke closing properly and allowing intake vacuum to pull the diaphragm down and pull fuel up the line and into the carb and not about the fuel pump as the pump doesn't deliver much fuel at cranking speed. Even without an impulse to operate the fuel pump, if the choke is operating right, the carb will fill with gas and the saw will start and run for about 2 minutes after the choke is turned off.

 

[Okie]

As oldstroke mentioned
also make sure that the fuel line is not cracked above the level of the tank fuel and the fuel hose fits onto the carb barb snug. You can vacuum test the fuel line.
You can also apply about 5 lbs pressure to the carb and submerse it under water and see if the gasket covers are sealing. (air leaks will upset the fuel suction)

 

[Woodslasher]

Thanks @Woodslasher. I think I know what your talking about after your explanation. Appreciate the information, I learned something new. Is this impulse? It corresponds with a hole on a Carter carb on a remington.

Looks like it!

 

[Okie]

As woodslasher mentions about impulse
if someone turned the carb base gasket wrong the impulse hole from block to carb can become blocked.

 

[Brufab]

As woodslasher mentions about impulse
if someone turned the carb base gasket wrong the impulse hole from block to carb can become blocked.

Thanks guys, I think I am guilty of that atleast once so far . Took carb apart twice before I noticed the gasket mistake

 

[singinwoodwackr]

Pressure test is good. Impulse seems to be clear both in the carb and the manifold
just thought of something really stupid…not quite enough gas in the tank for pickup? I usually just add a little gas initially, like 1/4 tank.
will try filling the sucker up

nope

choke closes as normal
hi and low screws set at 1 1/2 and 1 turns…as per the manual.
I tried opening both up like on most zama carbs I’ve had but no joy