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Engine will only run when pumping primer bulb

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ctoneman Fri, 21/08/2020

I am having trouble keeping a Hedge Trimmer running. Its a  Performance Power PRO24CCHTA belonging to a local community hall (with no money) I apologise that it is not a lawnmower but I am sure someone can give me some ideas on possible problems.

Basically, it has remained "not working" for several years in a shed and so I have cleaned it up and there is nothing seized at all. I have replaced the fuel pick up line and filter from the fuel tank to carburettor, and have replaced the return petrol line from carburettor to primer, and I have replaced the excess petrol line from primer bulb to fuel tank. Sorry if they are not the correct terminology but I cant find a workshop manual for it. 

I have cleaned the carburettor and reassembled. I have cleaned the spark plug and set the gap to 0.65mm and checked for a spark. I have cleaned the fuel tank. I have sprayed it with carburettor cleaner while running.

It will start after a few tugs but will only keep running if I pump the primer bulb continuously and as soon as I just let it run, then it dies no matter what throttle setting I have. I do see the fuel coming from the carburettor but it does seem to have a lot of air bubbles present ! 

Can anyone give me some tips on what to look for next please ?

Chris 

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villiers98 Fri, 21/08/2020

The primer bulb is only there to prime the carburettor. It will have a vacuum operated fuel pump built in and this may be the problem esp if it has not been used .

You can remove and strip the carburettor, and you may be able to obtain a new diaphragm or unstick the little flap valves even , but the internal passages in these carbs are tiny and if it was left with old fuel in the carb it may be beyond repair . You may be lucky but Performance Power are cheap Chinese things and getting the right parts is a nightmare . At least you know the electronic ignition still works and  trying to make one working one out of 2 or 3 may be cheapest . They drive me round the bend so I will no longer repair them

 

Will it run longer with some choke applied?  Also check the 'choke off '  symbol on the air cleaner actually corresponds with the metal flap being clear of the venturi - a few Chinese air cleaners have the ' run ' and 'choke'  positions the wrong way round

wristpin Fri, 21/08/2020

Basically you are “ force feeding”  it with fuel that it should be finding for itself. As per the last post , despite your work it is still not finding enough fuel to run on. A new diaphragm on the pump side of the carburettor may help and if you know of any one with an ultrasonic cleaning tank a long hot session may dislodge some long resident stale fuel gum but it is what it is and the passage of time won’t have helped.

ctoneman Fri, 21/08/2020

Villiers98

Thank you for your reply. Yes, the choke is the correct way round. I will try it with a little choke the next time and see if that helps. Yes, they are a cheap and nasty thing and I am looking on Freecycle/Gumtree for a local one for spares. 

I was surprised how clean the inside of the carb was and everything "seemed" to be in place with no holes in the diaphragm but it may be weak. The flap valve looked ok too. I cleaned all of it and reassembled but nothing doing. I hate getting beaten by this sort of thing.

 

Thanks again for the advice.  Chris  

ctoneman Fri, 21/08/2020

Wristpin

Many thanks for the reply. Yes, I think I am on a hiding for nothing but it has been challenging to strip down like I had it all in bits in the garden and a huge downpour and wind scattered it all around. 

I will see if I can get a similar machine and carb and strip it down again.

Thank you again

Chris