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Stalls at Wide open throttle. 1976 Johnson 70hp

A

AlGore

Member
I ran for about 20 seconds and the engine stalled. carbs empty. primer ball located at tank is soft and couldnt get it to pump back up. I suspect restricion in fuel line or bad primer ball. Here is what I am planning. 1st relocate a new primer ball at engine end of the fuel line. 2nd replace entire fuel line. 3rd rebuild the engine fuel pump. Any advice if I am on the correct path would be great appreciated.

thanks
 
It is an older tank but it is clean. I am concerned about rmoving the pickup tube and rendering the tank usless. It is an Attwood 6 gallon portable tank.
 
Some of these cheap plastic tanks are just that ---CHEAP-----Have seen issues with leaks inside these tanks.------------------I think the original metal factory tanks are the best by far !!!
 
ok finally got back on the water yesterday afternoon. It got up on plane and ran for about 20 seconds and then rpms started going up and down and then it stalled again. started it up again and it continued to do the same thing over and over. im at my wits end.
 
ive replaced the fuel pump, Ive replaced the plugs, ive cleaned the carbs including the high speed jets, vented the gas tank, checked the compression (105 psi), confirmed oil/fuel mix is correct. replaced the fuel line ends. replaced the CDI unit. it has new thermostat, and impeller. It is on a 15 1/2 ft fish and ski.
 
he said it would not pump back hard...if he has no fuel from the bulb to the motor and the carb floats are doing their job then i suspect a problem from the bulb back to and including the tanks...

regardless of where the problem is the bulb should pump back hard...
 
ok back on the water sunday after making more adjustments. found the throttle cable only opening the throttles about 2/3's of the way. fixed it. installed clear fuel line between all 3 carbs. this time it jumped on plane went better but still is running out of fuel. and the primer ball is sucking shut. I took the fuel tank back out. removed the pick up tube and found the plastic piece which would normally be on the cap laying in the bottom of the tank. removed it, curious if it could restrict the flow just enough to cause the bulb suckin shut. Is it possible for the check bals in the bulb to get positioned to plug the line as well???? maybe with the bulb pointing down?? I am going to try to make sure the bulb is up and try it again. anyone have a thought.
 
Run this motor with a known to be good portable tank and hose.------Borrow one from a buddy.---------If primer ball is going flat there is a restriction between the bulb and the gas in the tank !!!!!!
 
I just bought a new Atwood primer bulb. even with the new one it is doing the exact same as with the old one. the only things between the bulb and the actual fuel is about 6" of new line, the connector, and then the pick up. I have pulled the pick up out and it is in good shape. No soft spots and the screen at the bottom is clear. I used an air powered vacuum pump and tried to replicate the issue on the bench but it doesnt suck the bulb shut. It is puling 5 inches of vacuum.
 
The 5" of vacuum is what the pump I have can generate. I not only am able to blow through the tube without any restriction I can see the entire tube since I figured out how to remove it finally. I have not replaced the line between the bulb and the engine since it only flattens the bulb which is only about 6" from the tank. I am thinking the restriction is prior to the bulb since it flattens. I will try to acually plug the line and see if it will suck the bulb shut. I have really scratched my head since there is nothing appearing obvious to cause a restriction. I think I am going around in circles. I am still not certain the tank is venting properly but i have been runing it with the cap only about a turn screwed on. I am going to pressurize it next to see if it will vent from the cap.
thanks for everyones help. It is appreciated more than you realize.
 
yes i rebuilt the pump. I have taken the line off at the bulb side of the pump and it flows quite a bit of fuel quickly. He is my logic, If the restriction is between the bulb and the motor it should not collapse the bulb. would you agree? since the bulb will collapse wouldnt the restriction be prior to the bulb. In your opinion would the plastic piece I found in the tank plug enough of the inlet to cause the restiction?
 
I havent been back on the water. I hope to this week. the plastic covered about 3/4 of the opening. not sure how much actual vacuum the fuel pump can pull.
 
AlGore said:
I havent been back on the water. I hope to this week. the plastic covered about 3/4 of the opening. not sure how much actual vacuum the fuel pump can pull.
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This might be a silly question but have you checked the tank vent? When you said it sucked the bulb flat, did you notice if the tank is sucked down too? I had one of those plastic tanks with a vent in the filler cap that the seal was stuck and didn't work right. I could run a couple minutes and the motor would die like it was out of fuel. When I would finally get the back open to see the tank it looked OK, finally I left the back open and watched as the tank just sucked down and finally the motor couldn't pull fuel. Seem like you've done all the regular stuff, might be time to look a weird stuff...:) ma
 
Yes I have run it with the cap only about a turn on. I am really thinking the plastic piece I found in the tank is causeing the problem. I have not found any other problems. I have pulled from the motor side with a vacuum pump and pushed from the tank side with pressure. fuel always flows fine.
 
OK same issue Sunday on the water, still sucking the primer bulb shut. took the tank out again and found the pick up tube was wedged against a bulge in the bottom of the tank. Even after I have pulled the pick up out about 5 times. I never pulled the tube off the elbow therefore it was always going back in the same place. I have shortened the pickup tube and will try it again this week. cross fingers everyone.
 
We found another issue, the pick up in the tank was stuck against the side of the tank. We fixed that and went back on the water. When we got to the ramp, the bulb would not pump up. Took about 10 minutes. after we got fuel to the carbs, we ran it on the water. It still is sucking the bulb shut. We left and removed the quick connect at the tank, replace the entire fuel line assembly in an atempt to eliminate anything else, even though it is wide open, now when I pumped the bulb it took about 6 pumps and the bulb became firm and had good fuel at the carbs. We are going to try it again tonight or tomorrow night. thanks again for the help.
 
Got on the water last night. We have solved the problem. my last fix of replaceing the quick connect at the tank and replacing it with a barbed fitting made the diference.
thanks a tone for all the help. I cannot express my appreciation in words.
 
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