Primer bulbs?

[coveman]

I have an 8hp two stroke connected to a remote tank. Between the tank and the engine there is firstly the primer bulb and then an inline filter prior to the engine fitting.

I can prime the engine fine and it starts and runs ok, but if I then stop the engine for say an hour, the engine has to be re primed. Is this normal or is it likely that the spring valves in the primer bulb are weak and allowing fuel back to the tank?
The inline filter never stays full of fuel when the engine is running but this, according to an engineer I know, is normal. The fittings on the engine and tank appear to be air tight.

Just wondered what experiences others had?
Thanks

 

[AngusMcDoon]

Not normal.

 

[QBhoy]

Hi. Sure sounds like you might have the primer bulb/line going the wrong direction Perhaps. These are unidirectional things. There is an arrow usually marked on the bulb to indicate.

 

[coveman]

Hi. Sure sounds like you might have the primer bulb/line going the wrong direction Perhaps. These are unidirectional things. There is an arrow usually marked on the bulb to indicate.

I have the arrow going in the correct direction. When I prime the engine I hold the bulb with the arrow pointing vertically which is apparently the correct way of doing it so that gravity helps open the ball valve in the bulb, though I think it should work in any orientation.

 

[VicS]

I have an 8hp two stroke connected to a remote tank. Between the tank and the engine there is firstly the primer bulb and then an inline filter prior to the engine fitting.
I can prime the engine fine and it starts and runs ok, but if I then stop the engine for say an hour, the engine has to be re primed. Is this normal or is it likely that the spring valves in the primer bulb are weak and allowing fuel back to the tank?
The inline filter never stays full of fuel when the engine is running but this, according to an engineer I know, is normal. The fittings on the engine and tank appear to be air tight.
Just wondered what experiences others had?
Thanks

If the filter is not remaining full there is probably air leaking into the system between it and the tank. It may be slight and causing no problem at the moment but if it gets worse it could result in complete fuel starvation.
Id say it was normal to re-prime the carb after standing for an hour. If the engine is hot the fuel will to some extent evaporate. The valves in the primer bulb are unlikely to be 100% and will allow at least some of the fuel in the line to drain back to the tank.

I have the arrow going in the correct direction. When I prime the engine I hold the bulb with the arrow pointing vertically which is apparently the correct way of doing it so that gravity helps open the ball valve in the bulb, though I think it should work in any orientation.

It is usually recommended that the bulb should point skywards when priming .

If you had it fitted the wrong way round it would never prime the carb.
.

 

[Clunk]

I had a 10hp same set up, if the primer bulb sat horizontal it needed priming after an hour or so of turning it off. If I pulled some hose back through and it sat vertical it stayed primed all weekend. It was always a bit disconcerting to see so little fuel in the filter but would run all day like that after initial priming.

 

[Refueler]

?????

I have a number of O/bds and none of them need re-priming if stopped for hour or two. Choke yes ... but definitely no need to prime. I go fishing often on the river with a Mariner 20 ... remote tank etc. We can be all afternoon with engine off .... still starts fine with only choke to assist. The Evinrude Fast Twin ... same. Johnson - same ....

If OP is finding fuel starvation after a relatively short stop - then the bulb valves are faulty. Good enough to pump - but not good enough to prevent back flow when stopped.

I would be testing the bulb valves .... by holding vertical arrow UP with a filled pipe above ... see if it runs out bottom of bulb .....

 

[thinwater]

I have an 8hp two stroke connected to a remote tank. Between the tank and the engine there is firstly the primer bulb and then an inline filter prior to the engine fitting.

I can prime the engine fine and it starts and runs ok, but if I then stop the engine for say an hour, the engine has to be re primed. Is this normal or is it likely that the spring valves in the primer bulb are weak and allowing fuel back to the tank?
The inline filter never stays full of fuel when the engine is running but this, according to an engineer I know, is normal. The fittings on the engine and tank appear to be air tight.

Just wondered what experiences others had?
Thanks

Normal on some engines if the engine has been tipped and sailing.

In any event, the needle valve in the carb will prevent flow-back, so it can't be the primer. (primers do go bad, but this is not a symptom)

 

[Graham376]

A few years ago, our primer bulb went faulty as described so just replaced it for a few quid.

 

[Arcady]

Fairly normal in my own experience.

 

[Refueler]

Normal on some engines if the engine has been tipped and sailing.

In any event, the needle valve in the carb will prevent flow-back, so it can't be the primer. (primers do go bad, but this is not a symptom)

Sorry have to disagree ... having had precisely primer bulb fail in the past. The bulb and valve material went hard and action was affected.

It also may be of interest that not all have needle valves - if the engine has a Walbro or Diaphragm type carb ....

 

[coveman]

Thanks for the replies guys - I think I'll try a new primer bulb and see what happens then!

 

[thinwater]

Sorry have to disagree ... having had precisely primer bulb fail in the past. The bulb and valve material went hard and action was affected.

It also may be of interest that not all have needle valves - if the engine has a Walbro or Diaphragm type carb ....

What outboard, large enough to have a remote tank, has a diaphram carb? Chain saw or line trimmer, sure.

 

[DownWest]

Not had this prob, but I usually give the bulb a quick squeeze before starting. If the bulb does have faulty valves (both?) then air will get in from the carb needle valve, on the assumption that the carb loses a bit of fuel due to evaporation and opens the valve.

 

[Refueler]

What outboard, large enough to have a remote tank, has a diaphram carb? Chain saw or line trimmer, sure.

It may surprise you to know that there are small O/bds with remote tanks ... not many - but it used to be an option.

Also I only mentioned Diaphragm type as example ..... there are various other forms of carbs as well ..... but don't let that spoil a thread !!

 

[thinwater]

It may surprise you to know that there are small O/bds with remote tanks ... not many - but it used to be an option.

Also I only mentioned Diaphragm type as example ..... there are various other forms of carbs as well ..... but don't let that spoil a thread !!

Not surprised.

Not ruining thread. Is there an outboard that does not have a needle valve and float? Serious question, I want to learn about failure modes and I doubt I'm the only one. It would not be Evinrude, Yamaha, Nissan, Tahatsu, or Merc.

Yes, it's never wrong to replace the primer and hose; the fittings also wear and it is cheap. Done it many times.