Primer bulb - should it stay hard?

[exp2000]

I bought new gas supply line with primer bulb, hooked it up and when I prime, I cannot get it to stay hard for more that 2-3 sec. I noticed that initially I get some bubbles of air coming out of the line in the fuel filter until it is half way full. Should primer bulb stay hard and for how long.

 

[my1stboat1]

Re: Primer bulb - should it stay hard?

i never really understood the whole hard thing on the bulb, My has never gotten Hard once primed on mined its firm and squishy at 1st but I dont have any problems... hope this helps

 

[steveclv]

Re: Primer bulb - should it stay hard?

Well yes, it should get hard and stay hard unless there are leaks. It's a pressurizing system that sucks up fuel on one side (low pressure) and forces it into the carbs on the other side (high pressure). As the pressure increases, the bulb get's harder. Unless there is a leak somewhere in the high pressure side then it should stay hard indefinitely.
In the real world, it should stay hard/firm for at least an hour.
The most frequent problem is that the fuel pressure overcomes the needle valve seal and the fuel leaks into the carb bowls and will eventually leak out of the carbs - depending upon the angle of the engine, this may mean it leaks into the engine or out of the carb mouth. Also the valve in the primer bulb can fail over time.
A leaking fuel pump diaphragm will also leak fuel into the engine.

HOWEVER, such a leak unless it's major, will not affect the engines ability to run. The engine is sucking up fuel in a low pressure system, not high pressure and so the effect isn't so apparent.

Just remember that if your primer bulb does not get hard, don't keep pumping it to try and make it hard - you will flood the engine. 2 or 3 pumps are fine if you can hear/feel fuel being pumped.

 

[exp2000]

Re: Primer bulb - should it stay hard?

Thanks for such a detailed answer. Since gas supply line and bulb were bought as a kit, I don't think there is a leak there. My old bulb would stay hard as rock. I've rebuilt the pump, changed the filter and rebuilt carburetors. So maybe one of the lines is leaking somewhere. But as you say it should not affect the operation. I will however change all other fuel tubes. Fuel does not leak out when I prime it, but it does when I choke the engine.

 

[jerryjerry05]

Re: Primer bulb - should it stay hard?

No it shouldn't necessarily stay hard..Once you start the motor the oneway valve in the bulb stops to function allowing fuel to the motor.The only way it would stay hard is if you had a pump pushing fuel to the bulb.The bulb is to bring fuel to the carb/pump.Because the pump on the motor doesn't have enough suction to draw from the tank.
The gas you see when you choke is the excess fuel pulled through the carb by shutting the choke plates.Mine do it all the time.J

 

[exp2000]

Re: Primer bulb - should it stay hard?

Thanks again, my question was about before I start the engine. Like it should not be squeezable after 2 sec. for example.

 

[mark806]

Re: Primer bulb - should it stay hard?

I have a Mercury 150, I would prime it every time to start but then a few minutes or hours later it would be completely drained and I would have to pump it all over again till it got hard, turns out I had a cracked fuel line to the enricher valve, replaced it and 24 hours later the bulb is still full of fuel/hard, before I changed the fuel line it would be completely drained 24 after hours.