fuel system

[rpmdj1]

hi all heres the latest problem on my 1975 25 horse evinrude
the fuel system wont prime or pressureize I can squeeze the primer til I get a cramp in my hand
I can here air going in to the carb
my fuel line and connectors are new and are functioning well
that's it
and as always thanks for any help
russ

 

[ondarvr]

If air is being pumped then you aren't getting any fuel coming out of the tank, could be an air leak, hole in the pickup tube, empty tank, etc.

 

[racerone]

Check the fuel pump diaphragm.

 

[F_R]

If you are using the original factory tank, check for the possibility that it is sucking air around the pins that get pushed in when you plug the hose onto the tank. If it sucks air, it won't suck fuel. You can test the theory by removing the connector plug and stick the end of the hose directly into a container of gas.

 

[rpmdj1]

Check the fuel pump diaphragm.

I'm assuming that the fuel pump is in the carb

 

[rpmdj1]

Also the fuel line the connectors the primer bulb the gas can our gas tank all check out fine so it's got to be engine related

 

[F_R]

I'm assuming that the fuel pump is in the carb

You assume wrong. The fuel pump is a separate item. As for your statement that everything checks out fine, well I can't argue with that. But if it is fine, why is it pumping air (that's what you told us----you said you can hear air going into the carb)

 

[ondarvr]

Like I said before, if the squeeze bulb is pumping air, then this particular problem is located somewhere between the fuel in the tank, and the bulb itself, nothing from the squeeze bulb to the carb is involved. You may have other problems too, but this one is isolated to that zone.

If you have an air leak no fuel will be pulled from the tank.
If the squeeze bulb check valve has failed, then air will be moving in and out when the bulb is squeezed, which could be the sound you hear. The squeeze bulb should be held in the vertical position when squeezed or it may not work correctly and priming can be a problem.

 

[F_R]

Yeah, I was just thinking the same thought. The hose is new. So the primer bulb is empty. Hold it vertical so the check valves will fall into place by gravity. That may be the only problem.

 

[rpmdj1]

I disconnected the fuel line from the engine and it pressurize are pumped up just fine but I'll triple check it probably is something else altogether the motor itself is a 75 year that is so I wouldn't doubt all those things could be going on

 

[rpmdj1]

I can't find the fuel pump in any of my diagrams or pictures can anybody tell me where it is

 

[F_R]

Follow the hose from the motorside fuel connector. It goes to the fuel pump on the side of the block, then another hose from there to the carburetor. If you can't find it, that's interesting. It should be very obvious. Unless somebody has removed it. Interesting indeed.

 

[rpmdj1]

thank you all for the advice and suggestions I will post when I figure it out

 

[Vic.S]

thank you all for the advice and suggestions I will post when I figure it out

Well here is an exploded diagram of the pump

Hose #8 comes from the fuel line connector

#3 is the fuel filter gauze

#1 is the pump itself

#9 is the hose to the carb inlet.

The whole thing is screwed directly to the crankcase from where it gets vacuum pulses to operate it

 

[racerone]

The fuel pump operates with a positive pressure pulses and slight vacuum pulses.

 

[Tim Frank]

Make sure the arrow on the bulb points TO the engine.

 

[rpmdj1]

thanks

 

[rpmdj1]

I have learned a lot from you folks so thank you this is my first outboard and even though its an internal combustion engine there is still so much to learn
thanks again
rpm

 

[rpmdj1]

I disconected the fuel line from the engine and squeezed the primer bulb and it pressurized so do you all still think its some where between the tank and fuel line or the primer bulb

 

[ondarvr]

The air you heard was probably from the check valve in the squeeze bulb not sealing, so air was just going back and forth. With the air not being able to reverse direction it allowed the fuel to move up throught the fuel line and into the bulb, once the fuel reaches the squeeze bulb the problem normally goes away.