1989 120 johnson vro primer bulb going flat.

[roypretty]

hey everyone.new to the forum. my 1989 120 johnson vro is sucking my primer bulb flat at higher power settings and shutting off the engine.i have an integral 90 litre tank and previously changed my bulb with a mercury bulb but it seems to be worst. i changed all the fuel lines from the bulb to the tank.removed the reciever in the tank and i do not have a anti syphon valve installed.theres no filter on the reciever in the tank either, just a straight hose on the end. when i blow in the gas tank vent line the air comes out of the gas filler neck so i don't think the vent is clogged. i want to try to put an aux tank in the boat just to try to see what happens if the problem stays or not. also iam suspecting that the fuel pump may be weak and is not overcoming the new check valves in the primer bulb. Can anyone add some info or thoughts to my problem.thanks

 

[Joe Reeves]

Re: 1989 120 johnson vro

Re: 1989 120 johnson vro

The fuel primer bulb being drawn flat proves that the fuel pump has perfect drawing suction.

There is a fuel restriction between the primer bulb and the fuel supply. I understand what you've said via the trouble shooting mentioned above BUT trust me......... the restriction I mention here exists.

Either you're overlooking the anti siphon valve, OR something is within that fuel tank that is being drawn into the fuel pickup tube.

Many years ago, one of the marine patrol boats encounted this type problem but everything checked out. It was an intermitent problem. I eventually went into the built in fuel tank itself with a hook device and found a plastic bag that had been left in there when it was either built or installed at the factory...... it happens.

 

[roypretty]

Re: 1989 120 johnson vro primer bulb going flat.

thanks for your info.i noticed that the fitting thats screws into the tank has a 90 degree turn and to me is the smallest restriction in the system.can this be something to look at.also is there a way i can keep the suction on the line to see if there is something stuck on the reciever when i remove it when the problem happens. when i removed the reciever previously i could not see anything in the tank but it may have fallen back into the tank.who knows.

 

[Joe Reeves]

Re: 1989 120 johnson vro primer bulb going flat.

A 90? fitting wouldn't cause a fuel restriction UNLESS something was stuck inside of it.

There are various diameter fuel hoses. If the hose from the primer bulb to the tank is the older smaller type hose (1/4"), that might cause a problem. It should be the larger size which is (I believe) either 5/16" or 3/8". I'm sure someone will jump in here with the proper size.

However, to draw that primer bulb flat, it would need to be a bad restriction.

Try another (portable) tank BUT use the hose setup you're using now. Disconnect from the built in tank and hook that present hose up to the test fuel tank. If all is well, that leaves the tank itself.

 

[roypretty]

Re: 1989 120 johnson vro primer bulb going flat.

yeah thats what i was also thinking of doing. just join a piece of hose to the reciever and throw it in an aux tank. like u said it would elimate the integral fuel tank. my fuel hose is currently 3/8 throughout the system. i think this is stand size. thanks again for your info. i will post my results

 

[ebry710]

Re: 1989 120 johnson vro primer bulb going flat.

Nice engine. It is the same as I have. My problem was a stuck check value at the tank. Replaced it, have not had a problem since.

 

[roypretty]

Re: 1989 120 johnson vro primer bulb going flat.

i checked but i don't have a check valve installed.just a straight fitting.thanks for info

 

[Jayboid]

Re: 1989 120 johnson vro primer bulb going flat.

My 1989 150 johnson also doesn't have a check valve. It just has a 90 degree fitting like yours. When my primer bulb went flat, I removed the 90 degree fiting and found a screen in the bend which had accumulated bits of junk which finally restricted the fuel supply.

Another possibility is delaminated hoses. Gas hoses have an inner layer which can delaminate and cause fuel restrictions. If you have any old hoses in your system, you could check them.

If your primer bulb is going flat, you fuel pump is sucking it flat and is working fine. Don't worry about that.

 

[roypretty]

Re: 1989 120 johnson vro primer bulb going flat.

hey guys.thanks again for all you info. yeah i think i found my problem today. while i was scooping my fuel tank for debris with a wire coat hanger i noticed that my reciever in my tank was not very deep where it accepts the straight fitting for the fuel hose. So when i screwed the fitting into the reciever it was closing off the hole and alot.the i/4 inch hole was covered by at least 3/4 of the way. iam pretty sure this is my problem but i haven`t run the boat yet. I guess the guy that owned the boat before me removed the antisyphon valve and replaced it with a straight fitting but it was too long for the reciever. And yes i have changed all my hoses with new marine hoses.i will post my runs results as well .thanks again guys for all your help.