bad fuel pump?

[Jhnnyboz]

I have a 2002 50hp mercury 2 cycle. after I prime the bulb and start the engine it runs fine and then starts to sputter and die, unless I give it a little gas. after driving at WOT then sitting I have to prime the bulb before taking off or else the engine either will go and then die out or not even reach a high rpm. I also found that the primer bulb is slightly depressed after driving and it takes a while for the primer bulb to inflate after being squeezed.

if I keep squeezing the primer bulb it will idle

Whenever I start the engine I have to hold the throttle open

I replaced the primer bulb and fuel lines that are attached to it. is this a possible fuel pump problem or maybe air in the gas lines or a clogged anti siphon?

Once the engine gets to WOT it runs good which leads me to think its not a compression problem


Thanks

 

[sam am I]

Hmmmm, could be or tank intake restriction perhaps. Flattened bulb says good vacuum and restricted intake to me!!

Short of using a bunch of gauges and fitting to diagnose, take a spare can of mixed gas/oil, safely sit/secure it next to the engine, drop a clear (poly or tygon if ya got it) hose directly into the spare can of mix and the other end hooked up directly to the intake of the pump....fire it up!!!

Lil oil will drip from the oil pump...don't worry, put a towel over its end, but this will let ya know what direction to go.

Runs good?... tank/pickup/screen, H2O separator, hose leak etc etc issue.

Runs same?...fuel pump, fuel filter, primer bulb(you replaced) etc etc issue.

 

[enginepower]

If you keep squeezing bulb and it dies, sound like a needle valve isn't sealing off in carb and causing it to flood out. Since you say it runs pretty good at wot, willing to bet that's what it is. You should only be able to squeeze bulb a few times then it should get hard to squeeze when the carbs are full and the needle seals off.

 

[Jhnnyboz]

I have bypassed the primer bulb and tank by hooking up a gas tank to where the line connects to the engine and still will begin to sputter and die unless I give it gas.

If I prime the bulb just as it is sputtering it will rev back up to idle speed and idle fine.

This is erratic though and it sometimes runs fine.

 

[sam am I]

Well..ya least broke the problem in half, probably just low fuel pressure sounds

Have a fuel filter somewhere down stream? That'll probably be next easiest and cheapest to just shot gun in......Has it ever been replaced?

Next, fuel pump......Can you put a pressure gauge on the pump outlet somewhere? Think its like 2 PSI @ idle up to like 10 PSI or so, could just shot gun rebuild it, might need it anyway at 12 yrs old. Real easy to do, lots of good folks here to help ya if ya need.

Other than that, carb cleaning and kits time perhaps w all the tweeks/adj's that go with rebuilding, but thinking one of the above is the issue. Real easy as well.