primer buld sucking flat

[greasemonkeyjmj]

hello again folks, it's been awhile. I have a 95 merc 2.5 liter EFI. it runs good at high rpm for 15 minutes or so, then it starts starving for fuel. when it does this, the primer bulb is sucked flat. i drained my built in tank and found a foil seal, like off of a bottle of fuel treatment, I thought removing this would solve my problems,i figured it was sucking up against the end of my pickup tube. but it is still doing the same thing.. the outside of the fuel lines look good, but i havent had a chance to remove them to look at the insides. does anyone have a suggestion on where i do need to look for my problem ?

thanks

 

[sxmerc]

Re: primer buld sucking flat

If this tank has a anti siphon valve, remove it and throw it out. Check to make sure that the fuel tank VENT is clear and unresticted. A plugged or restricted vent, is going to make your engine try to pull fuel through a vacuum. I'm assuming your fuel sep. filter is clean and free of restrictions? Start here. You are on the right track. Also of concern... if you can, take the pickup tube out of the tank, and make sure there isn't something plugging the pickup on the end, or perhaps further up the tube.

 

[crazymac-680]

Re: primer buld sucking flat

I dont mean to point to the obvious but it sounds like you have no air entering through the breather in your tank.
Does your engine continue to run with the cap off your tank?
What is your system?
Tank-pipe-bulb-filter-pipe-engine?
Tank-water seperator-bulb-engine?
Has the boat always done this? Is it a new system to you.
Good luck, I'm sure it will be an easy fix

 

[greasemonkeyjmj]

Re: primer buld sucking flat

thanks for the reply, ok first there is no anti siphon valve, so that narrows it down. the tanks vents through the center of my cap which runs through the hull, it has a screen in it that i checked saturday and it is clean. i have not saw a water seperator of filter on this setup. i checked the pickup tube and it as well as the screen in it are open. while i had it out i cut some small notches around the bottom of the tube, so if something got against the bottom of it, fuel could still flow into the notches.

 

[greasemonkeyjmj]

Re: primer buld sucking flat

sometimes its the obvious that we overlook. since my tank vent through the center of the filler cap, and i can see through it, i havent tried to run it with the cap open. my setup is a section of fuel line approx 5 foot coming from my pickup tube. it connects to a barb fitting that goes through the hull from my bilge to the right front splashwell area. then a 1 foot fuel line that connects to my primer bulb. the 2 more feet of line to my engine. the boat has done this the last 3 times that i have ran it. i bought it last year, and have only used it i think 6 times. has anyone ever heard of the primer bulb being too soft of rubber and colapsing from the suction of the electric fuel pump ?

 

[j_martin]

Re: primer buld sucking flat

sometimes its the obvious that we overlook. since my tank vent through the center of the filler cap, and i can see through it, i havent tried to run it with the cap open. my setup is a section of fuel line approx 5 foot coming from my pickup tube. it connects to a barb fitting that goes through the hull from my bilge to the right front splashwell area. then a 1 foot fuel line that connects to my primer bulb. the 2 more feet of line to my engine. the boat has done this the last 3 times that i have ran it. i bought it last year, and have only used it i think 6 times. has anyone ever heard of the primer bulb being too soft of rubber and colapsing from the suction of the electric fuel pump ?

I've heard of the inner tube of a fuel hose collapsing and plugging the hose.

 

[444]

Re: primer buld sucking flat

If you disconnect the fuel hose from the motor and pump the bulb and have plenty of fuel flow, I would take a look at the tank. Either the fuel pickup in the tank is clogged or your vent is clogged. Easiest way is to start it up with the fuel cap off.

 

[greasemonkeyjmj]

Re: primer buld sucking flat

o.k i may be on to something. i had asked if anyone had seen a primer bulb collapse before from being too soft.i pulled one of the end caps from my bulb and looked in it, i thought i could see a dark line inside the bulb, so i removed both ends and cut the bulb down one side and turned it wrong side out. on what would be the inside there is somewhere around 20 or so splits on the inside surface of the bulb, running long way from end to end.some of them looks as if they are almost completly throught to the outside of the bulb. so i am now thinking maybe the extra soft bulb is my cause