# 2 cycle fuel system problem



## galla4 (May 10, 2011)

I have a two year old Bolens string trimmer with a 31 cc 2 cycle motor. It ran two weeks ago (first time this season) after putting in fresh fuel, a new spark plug and piece of fuel line.

Second time trying to get to work - no go. I have emptied the fuel, and blew all lines (in and return) out with compressed air. The problem is when I press the bulb I don't get a fuel in the bulb. The bulb "collapses" after 3 squeezes, when I pull the return line off the engine, it pops back into shape.

The issue must be in the engine since the lines are clear. Any help would be appreciate.

tim


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## paulr44 (Oct 14, 2008)

How about the fuel filter? If the primer bulb extends (un-collapses?) when you pull the main fuel line off the primer (or carb. if the primer is on the carb.), the filter is NG. Usually when the bulb collapses, it can't draw in fuel due to a restriction. The primer body/plate could be NG also.
If it's an external primer, as they usually are on those types of trimmers, you can get a new primer CHEAP. Walbro part number 188-512-1.
Paul


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## galla4 (May 10, 2011)

OK, I have to show my ignorance. On the end of the fuel line there is a round cylinder with a small metal disc on the bottom. I assume this is a fuel screen/filter you refer to. I did take the compressed air and cleared the line back from the engine to the "filter" with it still attached to the line. I got air coming out of the filter. Would it be smart (given I have fresh fuel) to remove the filter, fill the tank and try and start the trimmer. If the primer fills with fuel, then the issue is with the filter. If it doesn't, I need a plan B.

Also I took a small plate held on to the engine with 4 screws that had a rubber diaphram and a small metal disc with a center pin that fit into a small arm in the engine. Not sure what that is, thought it might be some small fuel pump but doesn't seem to be the case.

Also more info. When I used the trimmer the second time, the engine fired for about 5 seconds and nothing since then.

Thanks.

tim


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## galla4 (May 10, 2011)

Ran out in garage, pulled off filter-thingy. The primer bulb issue still exists, not the filer. It has to be something inside the engine. What?

tim


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## galla4 (May 10, 2011)

Update: replaced the primer bulb, all fuel lines. No fuel is flowing from the carb to the bulb, which still collapses. Any blockage is in the engine, maddening!

tim


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## paulr44 (Oct 14, 2008)

Then it may be the inlet needle valve in the carb. is stuck closed. Take a dull probe, such as a bobby pin, and in the center of one side of the carb. is a hole in a square, or kinda square plate. Depress the primer, it's okay if it stays collapsed. Depress the carb. where I indicated, but with only a little pressure. This should open the inlet needle valve.
If the primer then expands, the carb. is the problem. Pump the primer again without touching the carb. this time. If it expands on it's own, try running the unit.
If it doesn't expand, the carb. inlet screen may be plugged. Of course, the carb. could be full of corrosion, but you said it ran 2 weeks ago so that's rather unlikely.
Paul


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