Small Engines (Lawn Mowers, etc.): Stuck primer bulb, needle nose pliers, vapor bubbles

Question
Hi. I have a Poulan Pro gas trimmer (model PPB250) that has a stuck primer bulb. Not only does the primer bulb stay pushed in, I took needle-nose pliers and had to lightly tug on it to come out. What could be wrong?

Thank You

Answer
KC
There is clog in the fuel lines or the bulb pump is bad.Generally, when an inlet line to the diaphragm pump is plugged and fuel will not flow, the primer bulb will not return back to normal size because a vacuum holds it compressed. A restricted fuel line may cause fuel bubbles in the primer bulb that clear up when the primer bulb returns to its normal shape. These are not air bubbles, but negative fuel vapor bubbles caused by the vacuum created by the bulb as it reforms to its normal shape. Additionally, when lines get plugged, the vacuum created by the pump may cause air to leak in through connections. Quite often, these connections are just tight enough to prevent liquid from leaking out, but not tight enough to prevent air from being drawn in. (This is a major problem in hydraulic systems known as cavitation and aeration.)

Is there an air leak? If fuel is not visible or flowing through the primer bulb when the primer bulb is repeatedly pushed, then there may be an air leak somewhere in the inlet line to the primer pump. Gaskets may be leaking or lines could be cracked, swollen or loose and not attached tightly. Screws should be tightened and lines should be checked before any other tests are made.
You may have to replace the primer and the fuel lines.