Logo
FULL SITE MENU

Fuel line not holding suction...70 hp

C

Cdory

Member
1984 70 hp Johnson, Original owner.

I have had all sorts of issues with this motor holding vacuum on the fuel lines. I find myself replacing the fuel adapters every year because the o-rings crack every season. Now, on to the problem...it holds suction while running but once the engine stops it loses pressure and I have to pump it back up to get gas in the line. I have installed new clamps, new fuel lines and a new primer bulb. I Tightened the fuel clamps on all the connections till my fingers bleed. Also, I made sure the carb assembly connections were tight.

Is there something I am missing here?
 
make sure the little connector at the motor snaps into place..there is a groove that the lever that you push to remove the gas line has a tip on it that must fit into that slot..you have had the motor 20 years but i am going to ask anyway...is the choke working?..the normal operation of the bulb is to get hard when you pump it but it wont be hard when you are running and it wont be hard when the motor is stopped..the only time it gets hard is when you pump it...this normal..but if you pump it up hard and just let the motor sit without starting it the bulb should remain hard..do you have excess gas line that has a sag in it or is laying in the bottom of the boat...this is a no-no...you could also try running with a different tank just in case the problem lies there..
there is a possibility that you are working on a fuel problem when you actually have a fire or compression problem...so check the compression and make sure the fire will jump 7/16 inch with a tester..the tester is cheap and your local auto store has them..these two things should actually be done before you do anything else...
 
There should be a "Anti Siphon" valve right where the rubber fuel line connects to the built in tank. If the valve is stuck open, OR the inners have been discarded, OR if the valve doesn't exist at all..... the fuel can siphon backwards into the tank when the engine is shut down.
 
Back
Top