150BT carb issue

[wildduk]

I have a 150BT backpack blower. the last month or so it’s been really hard to start. Maybe like 25 pulls. Normally 3-4. The primer bulb makes noise like it is working, but I don’t think it is. If I remove spark plug and dump a small but of gas directly in, it starts instantly.
I thought that the primer and the fuel followed the same route through the carb. So how could it run, but the primer not push fuel through the same orifices. BTW I removed fuel line from one side and primed and it is shooting out Fuel.
Any ideas?

 

[StarTech]

I have a 150BT backpack blower. the last month or so it’s been really hard to start. Maybe like 25 pulls. Normally 3-4. The primer bulb makes noise like it is working, but I don’t think it is. If I remove spark plug and dump a small but of gas directly in, it starts instantly.
I thought that the primer and the fuel followed the same route through the carb. So how could it run, but the primer not push fuel through the same orifices. BTW I removed fuel line from one side and primed and it is shooting out Fuel.
Any ideas?

Primer doesn't push instead pull fuel through the carburetor to remove air. Primer bases do fail and no longer pump in one direction only. Otherwords as fuel is pushed out it sucked right back in.

 

[wildduk]

Primer doesn't push instead pull fuel through the carburetor to remove air. Primer bases do fail and no longer pump in one direction only. Otherwords as fuel is pushed out it sucked right back in.

Ok.
So does this make sense that it would run manually priming it thru spark plug but that the actuak primer does not work to start it....Trying to figure out what to replace...

 

[Hammermechanicman]

Could be cracked fuel line. Could be metering diaphragm. Could be clogged fuel passage in carb. Probably needs carb cleaned and rebuilt.

 

[wildduk]

I pulled carb apart and although didn’t use cleaner I hit all orifices with the air compressor.
I still find it crazy that it runs-but the primer doesn’t work. I thought the fuel traveled thru the same channels wether priming or just running normally

 

[bertsmobile1]

All that the PRIMER bulb does is PURGE the carburettor fuel system of air
It is the equivalent of filling up the float bowl on a normal carb.
It does not make the mixture richer or squirt fuel directly into the engine .
So some where between the metering chamber ( Float bowl equivalent ) and the carb venturii there is a blockage preventing fuel being sucked into the engine .
Pull the carb off but leave the fuel lines attached.
Turn it sideways and blow low pressure high volume air through the carb.
You should see the fuel coming out the engine side.
If not then there is a blockage in the carb fuel passages .
Some times a good boil in the ultrasound will free them up and some times it won't .

If you get a good flow of fuel then your problem lies in the engine itself
Can be anything from a badly clogged exhaust , to a hole in the piston, badly scored bore, broken ring or popped crankcase oil seal.

 

[wildduk]

Ok. I get all that. But the engine still runs fine once it’s started.

 

[Hammermechanicman]

When you start it cold is the choke closed properly? Even with a purge bulb a cold engine needs choked.

 

[wildduk]

Yes. been starting with choke since day 1.

 

[wildduk]

New Carb, primer, and fuel lines. Still doesn't start unless I prime via dumping fuel in spark plug hole. Runs fine after that......