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Rick
Rick, Factory Authorized Trainer
Category: Small Engine
Satisfied Customers: 8057
Experience:  Outdoor Power Equipment technical trainer since 1990, covering eight states.
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I have an Old Poulan Super 250A chain saw with a Tillotson

Resolved Question:

I have an Old Poulan Super 250A chain saw with a Tillotson carburetor.
I've clean the carburator thorughly and installed a rebuild kit in the carburetor. The carburetor will not pump fuel into engine. You can prime it with fuel or starting fuel and it will run for a few seconds and die. I've used air pressure on the fuel tank to force fuel to the carburetor and started engine that way, but will not continue to run.
Any suggestions.

Thanks,
George Barnett
Submitted: 6 years ago.
Category: Small Engine
Expert:  Rick replied 6 years ago.
Is the in-tank fuel filter in good shape?
Customer: replied 6 years ago.
I replaced it with one from a working tool. Blow breath back through the fuel line indicates it is open.
Expert:  Rick replied 6 years ago.
Did you do a complete cleaning on the carburetor, all the small passages, when you put in the kit? What is the compression reading on the cylinder?
Customer: replied 6 years ago.

I cleaned all the passages with WD 40 and blew out with compressed air. Detected air flow through passages. I have not checked cylinder compression.

 

I engine sounds good when it running.

Expert:  Rick replied 6 years ago.
Does this saw have a pulse passage in the block that may be plugged?
Customer: replied 6 years ago.

No, there is a single fuel line to the carburetor only.

 

What should the cylinder compression be if I can get my a gauge into the plug hole?

Expert:  Rick replied 6 years ago.

Then it has a pulse passage that may be blocked. Be sure and check. Look for a small hole underneath the carburetor that supplies a pulse to operate the fuel pump.

 

A two-cycle should have at least 120 psi.

Customer: replied 6 years ago.
Yes, I've checked to be sure the gasket was not blocking the passage, what additional test can I do to assure it's open to the cylinder?
Expert:  Rick replied 6 years ago.
Can you blow air through it?
Customer: replied 6 years ago.
Yes, it's open.
Expert:  Rick replied 6 years ago.
If you are sure of the lines, the filter, the carburetor rebuild, and the pulse passage, then the compression would be a key thing to check.
Customer: replied 6 years ago.
I couldn't get a real good test, but what I did, indicates very low compression.
Expert:  Rick replied 6 years ago.
That would prevent the fuel pump from operating and make the engine very hard to start. I'd try to get as accurate a reading as possible, but if it's low, you're looking at a piston and rings, plus possibly a cylinder, unfortunately.
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