Walbro Carb Rebuid - No Fuel Delivery

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Old 07-26-11, 07:48 AM
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Walbro Carb Rebuid - No Fuel Delivery

Walbro WT Carb for 32cc Craftsman weedeater does not have fuel delivery. When plunger is pumped, fuel does not get sucked into carb. Rebuilt carb with Walbro kit, cleaned carb accept for welsh plug. Carb metal fuel filter screen was replaced, needle valve, gaskets, diaphram. Carb looks very clean and holes clear.

Plunger and fuel filter seem to work fine. I attached file lines and filter directly to plunger - bypassing carb - and the plunger bowl fills up quickly and gas fuel filter allows fuel to flow to plunger.

Please help. Have tore into the carb several times now. It does not make sense why plunger will not draw fuel into carb...
 
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Old 07-26-11, 08:27 AM
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It seems you have isolated and tested the priming bulb and fuel filter and they are passing fuel so you can cross them off the list. That leave the carburetor. Is absolutely no fuel going into the carb? Here is a link to the assembly diagram for the carb. to insure you have it assembled correctly. The document also has good diagrams showing the fuel's path through the carb. which might help troubleshoot.
 
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Old 07-26-11, 08:40 AM
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Thanks. Yes, saw that link, diagram before. Have watched a couple youtube vids also. The carb gets very little fuel, mostly air, drawn into given what I see going through the fuel lines. Even the air flow seems minimal - as if their is something blocking the flow. This is the same symptom prior the rebuild and what motivated the rebuild.

Just out of sheer desperation, I removed the needle valve and reassembled carb. Still no fuel delivery. The carb passages seem clear and clean. This little carb is kikin my butt
 
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Old 07-26-11, 09:46 AM
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Have you looked into the engine itself? Maybe the carb is OK and the engine is not drawing properly. I assume there's nothing really bad in the engine but maybe the reed?
 
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Old 07-26-11, 10:01 AM
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If the primer still can't pull fuel through the carb, check the little flaps/check valves on the fuel pump diaphragm. Make sure they aren't sticking to the carb body. Also make sure they are in the exact same places as the old ones and match up to the proper holes in the carb body. Also, with the needle out and the screen out, try blowing carb cleaner through the fuel inlet hole under the screen and see if it comes out the other side where the needle goes.
 
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Old 07-26-11, 12:25 PM
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Originally Posted by cheese View Post
If the primer still can't pull fuel through the carb, check the little flaps/check valves on the fuel pump diaphragm. Make sure they aren't sticking to the carb body. Also make sure they are in the exact same places as the old ones and match up to the proper holes in the carb body. Also, with the needle out and the screen out, try blowing carb cleaner through the fuel inlet hole under the screen and see if it comes out the other side where the needle goes.
Thanks for the suggestions. Checked the diaphragm and flaps several times. The new diaphragm matches the old one and aligns with the holes. It should not be sticking - everything looks very clean.

Blew cleaner through the fuel inlet hole with screen filter removed. Checked it several times after new screen filter was installed and could see through the hole and filter.

Question - can the fuel be primed, pumped into the carb when the carb is not installed, mounted onto the engine? Their is a hole on the side of the carb that matches a hole on the engine and gasket. Not sure if the carb draws air, or heat, or ? from the engine.

Will recheck diaphragm and flaps again.
 
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Old 07-26-11, 09:33 PM
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Does the primer bulb stay pushed in, or does it just push in and pop back out without pumping fuel? It may be that the check valve that vents through the throat of the carb is bad. It is under the tab that holds the needle in place, under the part that comes into contact with the metering valve button. (on carbs equipped with this valve).
 
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Old 07-27-11, 06:17 AM
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Originally Posted by cheese View Post
Does the primer bulb stay pushed in, or does it just push in and pop back out without pumping fuel? It may be that the check valve that vents through the throat of the carb is bad. It is under the tab that holds the needle in place, under the part that comes into contact with the metering valve button. (on carbs equipped with this valve).
Primer bulb pushes in, then comes out, drawing mostly air with very little fuel into the carb.

Do not know which check valve you are referring too. Can you please look at this diagram and give me the part number? Are they parts 21, 21A, 22 - under the welch plug #23?

http://wem.walbro.com/distributors/s...s/WTseries.pdf
 
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Old 07-27-11, 09:36 PM
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22 does appear to be the one. Also if the primer bulb is not seating into the primer base, it can pull in air there, of if it is cracked, or if the check valves in the primer base aren't working properly, it could pull air in and push it out both through the return... could be a lot of things. The carbs are cheap enough usually that if I can't fix one in a reasonable amount of time, I just replace it.
 
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Old 06-03-13, 03:58 PM
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No Fuel to jets

What I found was there is a check valve that was malfunctioning that supply's the jets. I started out with a small drill bit and drilled the entire brass plug with the black center out that is on the metering side of the carb (diaphragm and needle valve). After drilling I flushed from where the needles are backwards to flush out any chips left. Then flushed the other way and flushed jets with carb cleaner to verify they were clear of debris. This worked great. I get a little air back when I use the primer bulb sucking through the jets, but it fires up every time and the fuel delivery if flawless. I have done this on my chainsaw and weed eater. Both are the Walbro carb.
 
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Old 06-03-13, 07:19 PM
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I don't recommend this, you will have gas leaking through the throat of the carb while the unit is not being used.
 
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