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Discussion
Carb not pumping
Hi,
the carb on my DLE 55 is not pumping. In the picture, should there be a connection between A and B, i.e. allowing the air to be drawn/pushed to and from the pump from the crankcase? As you can see from the picture, it is blocked. Thanks Ron |
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Des Moines, Iowa USA
Joined Nov 2007
7,494 Posts
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You show a carb from a side exhaust DLE55. That carb uses an external pulse line that connects to the fitting on the pump cover plate shown in your photo. The other end of the line connects to a fitting on the reed housing. When an external line is used, the internal pulse port is not open .... not drilled. What you show is normal!
If you have the line in place and the carb is not pumping, you have other issues. |
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Des Moines, Iowa USA
Joined Nov 2007
7,494 Posts
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A bit of gas inside the pump diaphragm never hurts anything. You can also remove the metering diaphragm and make sure the metering needle isn’t stuck in place. What kind of problems are you having?
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Des Moines, Iowa USA
Joined Nov 2007
7,494 Posts
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OK, you say not pumping. Does the carb pull fuel when it is fully choked with the throttle open? The pump doesn't have to work for the carb to pull fuel when choked. The engine will pull fuel right through the pump and metering needle when choked. If the metering needle is stuck in place, no fuel will flow. You've had the pump side of the carb apart so we know the pump valve petals are not stuck in place. Did you check the screen to see that fuel can pass through it? Sometimes if an engine sets, a sort of clear film can form on the screen and this film will completely block fuel flow. I'd concentrate on whether the carb can actually flow fuel through the various passages rather on the pump starting with the screen and metering needle. All you have to do on the metering side is remove the cover plate and press on the metering fork. If the needle is free to move, you're good to go there. Are both of your diaphragms flexible and soft or does your carb need a rebuild kit?
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Thanks for all the info. My test was to see if fuel was being drawn up the fuel line with the choke closed and throttle open. Yes, I'm happy with the pump side, all the diaphragms are good and petals seem to be ok. I have a rebuild kit and the next thing I'll do is to replace the screen. The metering needle seems to be ok, i.e. not stuck.
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Des Moines, Iowa USA
Joined Nov 2007
7,494 Posts
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Is the engine in good condition and especially the reed valves? If you remove the spark plug and turn the engine over, do you hear a good bypass sound as the engine goes through the bottom of the piston stroke?
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One little tip I learned from a guy is to loosen the big center screw on the carb to let fuel come in and prime the carb. This will bypass the check valves (little diaphragm flappers) and get them wet/loosen any dry surface tension. Just a thought?
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I tried this but no sucess! Thanks anyway for the suggestion
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I found this excellent video on how Walbro carbs work.
I have now replaced everything and it still won't pump. I have a short length of fuel line going from a jar of fuel straight into the carb, to avoid any possibility of leaks in the tank. When I rock the engine, I can see the fuel rise a tiny bit along the line (which measns that the "pull" from the engine is causing the diaphragm to rise an pull pull the fuel up the line) but it drops back immediately. It's as if the flapper on the membrane isn't sealing on the "push" cycle from the engine. I've ordered a new carb which should solve the problem but I'm getting annoyed that this isn't working as it should. It must be something very simple |
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