Please explain fuel system/pump 50hp Evinrude.

[jnaarnold]

Maybe someone can just explain the fuel system on my engine, a '86 Evinrude 50HP VRo. The VRO has been taken off and a different fuel pump put on, from what I gather. How does the system work, including primer system? Does the engine pulses create pressure in the pump? Does the primer use any electric pump type function, or does it just re-route the fuel behind the carburetors. I am desperately trying to solve my problems. I will be doing a lot of tests tonight. Just ttrying to do some ground work now.Thanks.
John

 

[bgbass.1]

Re: Please explain fuel system/pump 50hp Evinrude.

the fuel pump draws from pressure when you pump up the ball. the electric primer acts like a choke puts straight gas into carb. what kind of problem are you having?

 

[tashasdaddy]

Re: Please explain fuel system/pump 50hp Evinrude.

when you go to start the motor, when you pump the bulb, this moves gas thru the lines,thru the fuel pump, to the carbs, and primer. this is the only function of the bulb. the fuel pump works off the vacuum, of the cylinder, via a diaphram in the pump, and draws gas from the tank, and pressurizes it to the carbs, and primer. there is no electric pump, the needle float valves in the carbs, allows fuel to flow into the bowls, when the bowl is full the valve stops the flow, until part of the fuel is used up, then it replenishes the supply, just like a toilet float in the tank. the primer is and electric solenoid, that allow pressurized fuel to the sprayed into the back of the carb, directly into the intake for the cylinders, it is also known as and enricher, the reason that it enriches the fuel mixture (more fuel to air) the purpose is cold engine starting. once the engine is running the carbs take care of the fuel mixture. they primer serves the same function as the choke on older motors. when the choke butterflies were closed, they was little air entering the carb, so the pistons pull in mostly gas, and enrichened mixture. there is a set of reed valves behind the carbs, if these are dirty, varnished, or distorted, they can effect the running of the engine. that the basis of the fuel system.

you can go to this site, and see the complete breakdown of you engine, parts diagrams,and list. "http://www.evinrude.com/en-US/Accessories/Literature/"


post a picture of the fuel pump the person added, it could be the wrong one, or misinstalled.

 

[tashasdaddy]

Re: Please explain fuel system/pump 50hp Evinrude.

Ok, what your model number, as none of the 86 50hp had vro, according to BRP they had this fuel pump http://www.iboats.com/18_7352_Fuel_...8118897--**********.433900912--view_id.174141

here is a picture from my 88 50hp same motor one is fuel pump the other is hose routing.

 

[Silvertip]

Re: Please explain fuel system/pump 50hp Evinrude.

1) The primer bulb in the fuel line sucks fuel from the tank and forces it upstream to the carburetors where it fills the float bowl. 2) When the float bowl is full the inlet needle closes off the fuel flow. 3) When the primer bulb is firm fuel pressure is built up in the fuel system, and is present at the primer solenoid. 4) The primer solenoid IS NOT a pump -- it is a valve. 5) Pushing the key in for cold starts activates the primer solenoid opening the valve which sends fuel to the intake behind the carbs. 6) When the engine starts, pressure/vacuum pulses from the crankcase pulse a diaphram in the fuel pump which sucks fuel from the tank and pushes it to the carbs.

The red knob on the primer solenoid has a manual position to provide a "manual priming method" should you have to rope start the engine due to a dead battery or a failed solenoid. No -- the battery is not needed to run the engine. It is only needed to start the engine. Placing the lever in the manual position and squeezing the primer bulb forces fuel into intake as it did electrically.

If you are sure the engine is loading up or flooding at idle, have you adjusted the idle mixture screws properly, have you adjusted the floats properly, and are you sure the inlet needle and seat are installed correctly.

 

[jnaarnold]

Re: Please explain fuel system/pump 50hp Evinrude.

I did not know there were mixture screws, where are they locate? I'll post some pics a lil later-after supper. thanks guys!!!!

 

[rickdb1boat]

Re: Please explain fuel system/pump 50hp Evinrude.

Don't think the 50 had low speed/idle needles..

 

[Silvertip]

Re: Please explain fuel system/pump 50hp Evinrude.

Some did some didn't. Whether or not they are present should be obvious. I though you said you had a manual for this engine? If you have idle mixture screws they are a slotted screw with a spring under it. They stick out the side of the carb. If you have no idle mixture screw on each carb and you feel its running rich, then you still have a carb problem (such as float levels set too high).

 

[jnaarnold]

Re: Please explain fuel system/pump 50hp Evinrude.

My pump is as shown.....the fuel tank goes to the filter, round part of pump. The middle part goes to the fuel manifold, the back part goes to the crankcase. Is this correct? I wonder if it is backwards. What would that do? Would I have high pressure to the tank and low pressure to the carbs if it were backwards? I will try and switch tomorrow and test. Please reply, thanks.
J

 

[jnaarnold]

Re: Please explain fuel system/pump 50hp Evinrude.

Hey tashasdaddy, something I noticed from your picture....You only have two lines on your pump, where does your crankcase pressure go to 'pump' your pump? I might also try tomorrow to apply pressure to the pump and see if this improves condition. Let me know on you pump pressure routing thanks.
J

Tashasdaddy, I sent you a PM

 

[tashasdaddy]

Re: Please explain fuel system/pump 50hp Evinrude.

that is not the fuel pump for what the evinrude site show for an 1986 50 hp, that is and earlier pump. what is the model number on your motor. is it actually and 86. the 86 pump is like my pictures.

 

[jnaarnold]

Re: Please explain fuel system/pump 50hp Evinrude.

Yes, it's an 86, it a VRO motor, but the VRO was removed. The fuel manifold was used on the VRO. Thats why I asked what you used to pressurize the system. What do you use?
J

 

[tashasdaddy]

Re: Please explain fuel system/pump 50hp Evinrude.

i have sent a pm to one of the guru's to look at this.

 

[JB]

Re: Please explain fuel system/pump 50hp Evinrude.

Sorry, I can't help you with this one. My '86 Johnny 48SPL looks just like Daddy's 50. Yours looks like a one-off conversion. Check the articles in Engine FAQs for some clues as to what you actually have there.

The pressure +/- pulses from the crankcase come to the pump from inside the block, behind the pump.

 

[rickdb1boat]

Re: Please explain fuel system/pump 50hp Evinrude.

Your pump is plumbed correctly. Incoming fuel line to the front, middle to the carbs and the rear line to the pulse fitting on the crankcase...

 

[rickdb1boat]

Re: Please explain fuel system/pump 50hp Evinrude.

Tashas fuel pump bolts directly to an engine opening for vacuum pulses. The back of that particular pump is open in the back to crankcase pressure. It is just a different configuration than yours....

 

[tashasdaddy]

Re: Please explain fuel system/pump 50hp Evinrude.

i realized that after much more research, that why i asked JB to come in. we still don't know why it is having a fuel starvation problem.

 

[rickdb1boat]

Re: Please explain fuel system/pump 50hp Evinrude.

Really need more info to help solve the problem. I don't see where he says what the problem is and what he has done so far to solve it. Only asks about the pump in this post. If you feel the pump is the problem, then try squeezing the primer bulb when trying to accelerate. Also try pushing the key switch in, which will activate the primer allowing more fuel to flow to the cylinders. If that helps, then the carbs are clogged. Don't know if this helps...

 

[rickdb1boat]

Re: Please explain fuel system/pump 50hp Evinrude.

Did you clean the carbs thouroughly? Remove the jets, spray the passages out with carb cleaner and then compressed air? From your other posts, it sounds like you still have a restriction in the carbs. I say this because you can manipulate the primer to make it run better. This makes up for the lack of fuel going through the carbs.

 

[jnaarnold]

Re: Please explain fuel system/pump 50hp Evinrude.

Ok guys, problem solved, well kind of. I at least determined why it is starving for fuel. I didn't want to think I had major problems, but I do. You see, in my very first thread here on iBoats, I had asked about a scored cylinder wall in this engine ( http://forums.iboats.com/showthread.php?t=214726 ). Well, if you read the thread, I left it at having good compression, and good compression I do have. However, I realized that I also have positive pressure at the carburetor on the cylinder with the score in it. So, instead of drawing air over the fuel rod, it is pulsing fuel back to the air box, thus starving the cylinder of fuel. This is why with the prime lever set on manual helps with top end, it is putting fuel 'manually' in behind the throttle plates. Same with pushing the key in, it adds fuel behind the throttle plates. I confirmed this tonight by getting the engine running and putting my hand over the carburetors(very difficult. The top cylinder ( the one without the score in the wall) sucked my hand right in. If I covered the air bleed up, it choked out and stalled. On the bottom carburetor ( the one WITH the score in the cylinder wall), if I put my hand over it, it pumps my hand back and forth and gets fuel all over it. Correct me if I am wrong, but this is not normal is it(only answer if you know for sure ). Maybe I am wrong. I don't know. What I do know is I am going to fix the cylinder( bore job and new pistons) and go from there. Thanks for all you help guys, I really mean that, you guys have helped me immensly!!
John