primer bulb sucking flat

[luv2hunt]

I have a 1985 40 hp Johnson that keeps sucking the primer bulb flat and I cannot figure out why! It will run fine for 5 minutes or so then the primer bulb goes flat and bogs the engine down. The time varies on when this will occur. <br />When I first purchased a good fuel line and got away from the walmart junk the motor did fine, but started doing it again the 3rd time out after switching lines. The motor runs great when it is getting fuel.<br />What I have tried.<br />-replaced the fuel line and bulb with a good line from an OMC marina.<br />-tried 4 different gas tanks (metal and plastic)<br />-went away from the quick connects and just put a barbed nipple on the gas tank.<br />-inspected all the filters/screens in the fuel tank.<br /><br />I would think that the motor is doing its job since it is sucking the bulb flat and it has to be in the fuel line before the primer bulb?<br /><br />I am at a loss, Any suggestions would be greatly appreciated!<br /><br />Thanks,<br />Jason

 

[Barnacle_Bill]

Re: primer bulb sucking flat

Are you opening the vents on the tanks? They have to be vented or that is exactly what will happen.

 

[LubeDude]

Re: primer bulb sucking flat

Well, there are only a few reasons this can happen. Vent not open on the tank, I asume you are doing that and with four different tanks, we can toss out the bad tank vent posibility. And the fuel bulb itself. With that new, I cant see how you are having this problem. Its just a restriction between the tank and the fuel pump some where.

 

[DJ]

Re: primer bulb sucking flat

Do you have the fuel primer bulb faced in the right direction?<br /><br />There is an arrow on it that denotes direction of fuel flow.

 

[luv2hunt]

Re: primer bulb sucking flat

I double checked the vents on all the gas tanks and the primer bulb is facing the right directions. I am taking it out tonight and going to try and run it with the cap off the gas tank to see if that helps. This just has me stumped. I am not a mechanic by any means but this should be a simple fix and it is not.<br />could there be something wrong with the motor by any chance?<br /><br />Thanks for the quick responses!

 

[herters]

Re: primer bulb sucking flat

New is not always ok. Check bulb.

 

[Silvertip]

Re: primer bulb sucking flat

The problem has to be at the primer bulb back to the tank pickup. Kinked/plugged hose, bad bulb, or fittings squeezed shut/plugged.

 

[luv2hunt]

Re: primer bulb sucking flat

I took the boat out tonight with 2 tanks and 2 fuel lines. I started heading up river and the bulb went flat so I hooked up the other tank with the different fuel line and it went flat. I tried taking the lid off too and running it. I took the fuel line off the tank connector and put it directly into the gas tank. I ran over 20 miles without a problem. I checked the line that is part of the tank and blew through it and there wasn't any restriction. How can this be that every gas tank I use will not let me get enough fuel? The line that is part of the tank is bigger in diameter than the inside of the fuel line to the motor. I have never had this problem with any other boat I have owned.<br />My 9.9 runs fine off of the same tanks and lines.<br /><br /><br />Thanks,<br />jason

 

[jason389]

Re: primer bulb sucking flat

It may sound farfetched, but could you have a fuel leaK? If the gas is pumping out somewhere it would require a lot more fuel. Chek all the lines in the motor housing, and look for leaks. How long is your fuel line? Is the tank close to the motor? I've had this bulb sucking problem too. Stupefying. There has to be an explanation.

 

[papa_Lazerous]

Re: primer bulb sucking flat

i your bulb capable of supplying enough fuel to your engine?<br /><br />does this happen at WOT or tick over? It really does sound like a restriction. it is a stumper that you have had the lid off the tank and it does it.

 

[Silvertip]

Re: primer bulb sucking flat

Are you sure you don't have debris in those tanks that's clogging the pickup. I've seen that happen, especially with plastic tanks. Debris from the drilling operations was left in the tank and it clogged the pickup. When the engine quits, the stuff falls off and away you go again only to be repeated. Not likely in two tanks but if you got fuel from the same place, who knows whats in there. Its got to be tank related since it runs with the hose simply hung into the tank.

 

[Docdoc]

Re: primer bulb sucking flat

Not all that familiar with Johnson, but don't some of them use a dual line system from tank to fuel pump?

 

[luv2hunt]

Re: primer bulb sucking flat

This happens after I reach full throttle. I will slow way down and work with the bulb to open it up again.<br />I am picking up an OMC tank tomorrow and running it Thursday or Friday to see what happens.<br /><br />I have looked in the tanks and I did not see any debris and it is not the same fuel.<br /><br />Thanks

 

[Rabbitdawghunter]

Re: primer bulb sucking flat

You could just get a vacuum guage and start teeing into the hose in front of the bulb, behind the bulb etc to see what kind of vacuum readings you get, might point you in the right direction.

 

[luv2hunt]

Re: primer bulb sucking flat

What readings/numbers should I be looking for with a vacuum guage?

 

[seahorse5]

Re: primer bulb sucking flat

4" of mercury is the highest reading you should ever see. Actually with portable tanks and a good hose and primer ball, you should not see above 2" or so. With a built in tank and an anti-siphon valve and a spin-on fuel filter, 3.5" is about average.<br /><br />Don't overlook a bad check ball in side your primer ball making it go flat. A bad fitting on the tank end of the hose can do the same thing.

 

[danny k]

Re: primer bulb sucking flat

Seems like you've either checked or replaced all the obvious. Years ago the same thing happened to me. I ended up raising my tank ABOVE the height of the engine, kind of a gravity thing. I know it sounds crazy, but it worked. Just a thought.

 

[luv2hunt]

Re: primer bulb sucking flat

I found out what the problem was. It was the gas line/filter inside the gas tank. The atwood gas tanks that you get at walmart have such a fine filter with a small opening that it was not letting enough gas get through. I tried an OMC gas tank and it worked great all day.<br /><br />Thanks for all of your suggestions.<br /><br />Jason