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Dellorto petrol pump - issue


gleiwitz
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Hello,

I would like to ask for your help before I order a new petrol pump. Maybe I missed something during my investigation.

The problem with my Sherco St 300 from end of 2013 is that the carburetor does not get fuel or gets too little.

I first checked the vent of the fuel tank - one-sided valve ok,  fuel hose - ok,  fuel tap - ok.  Just to be sure I started the engine with the unscrewed fuel tank to be sure the reason was not to vent the fuel tank

I disassembled the fuel pump -  cleaned - I have not seen any signs of wear or damage.

I started the engine. After a while the fuel stopped flowin. I disconnected the fuel lines and fed the fuel directly to the carburetor using a syring. From disconnected fuel supply line from the pump to carburetor fuel does not flow. During engine operation in a normal situation petrol pump should pump fuel  ?

Do you have any ideas what else should I check?

 

Edited by gleiwitz
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2 minutes ago, oni nou said:

Pump works by vacuum  created by piston downstroke  so check the vacuum pipe that goes from the carb intake rubber area to the pump itself.....if it has a cut/hole in it or is trapped/pinched somewhere then you have no vacuum and therefore no pumping will take place.

Thank you very much for the reply!

I checked the hose only visually. I did not dismantle it.  I checked its position so nowhere is trapped / pinched. I will check tomorrow whether there are any holes or cracks.

Apart from the vacuum pipe, something may be the reason for not creating a pump-induced depression? 

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3 minutes ago, oni nou said:

Yes a hole or non sealing of the diaphragm in the pump itself.

 Thank you very much for your help.

I will check it and if vacuum pipe will be ok  then I will order a new pump because I am slowly losing patience :)

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Problem solved :)

The cause of the problem was vacuum pipe. It was not visible but when  I disassembled the vacuum pipe I noticed that hose/pipe clip was badly mounted at the very end which caused the hose to deform and consequently leak / catch the air.

 I mounted a new vacuum pipe on the lef side of carburetor where I my opinion is more space and pipe will not bends

79f89d49fae56d28med.jpg

 

Thanks a lot for your help.

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