Something else I've noticed about those fuel primer bulbs is that when the line is lying on a deck or horizontal surface, you want the arrow oriented so that you can see it (face up so to speak) rather than have it facing down against the deck. There is a little "door" in there (for lack of a better analogy) that is "hinged", if you will, on the arrow side of the bulb. If you position the hinge on the deck, then gravity tends to try and keep the "door" open. The same applies as to why Mike says to hold it vertically while priming. The "door" just works better like that.
It can take a little "finnagleing" to get one to lie in the correct orientation but it is worth the trouble to do so.
They have a very WEAK and TINY spring holding them closed and if the spring suffers even a small amount of degradation, it just makes it all that much more likely they won't "check" the backflow of fuel.
The weak spring is necessary to keep the pump from having to work too hard to pull fuel through the "door".
We developed a policy on our rental fleet to just chuck 'em and replace them after a couple of seasons because ours were constantly exposed to the sun and, well, boat renters.We found that they caused us a lot of stranded/no start service calls and tow ins.
The other problem with them is that there are quite a few really BAD QUALITY ones for sale on the aftermarket. We found a reliable source for quality and, since the hoses seem to last for years and years, we would just clamp in a new bulb.
That bulb and the fuel tank vent are always the first places I look in a no start/hard start/won't stay running complaint.
However, the Racor and fuel fittings coming loose are good suggestions too as well as I have had quite a bit of trouble with the Honda fuel connector latches at the engine. If you don't get a good connection there it can starve the engine for fuel as well.
Good luck.
