1979 johnson 100 hp

[mot007us]

It's not keeping its prime, I have to manually prime it, can anyone help me with this?

 

[RCO]

Is this while running or sitting?

 

[mot007us]

while running

 

[RCO]

Check all hoses, clamps and connectors for a leak. If they all check out ok you have a bad fuel pump .

 

[mot007us]

I just put a new fuel pump in last year and replaced all of the hoses and I used some seafoam spray, also

 

[jbuote]

I just put a new fuel pump in last year and replaced all of the hoses and I used some seafoam spray, also

That may be true, but (while I'm no pro here) RCO is right..
The primer bulb in the fuel line between the gas tank and the engine is nothing more than a manual fuel pump.

IF:
1) All the lines and connections check out and there are no leaks and no air getting in,
2) Fuel tank is vented properly
3) Any fuel filters/water separators are clear with no blockage
4) Fuel pickup screens in tank aren't blocked
etc....

If all that checks out and yet in order to keep the engine running, you have to use the primer bulb (manual fuel pump) then it's likely a bad fuel pump...

Can you disconnect the fuel hose where it goes into the carb from the pump? (Edit: Put open end in jar or suitable container to catch fuel...)
Then crank the engine.. Does fuel spit out?

Again...
NOT a pro here.. RCO and others can/will guide better.
Just adding some thoughts...

Hope it helps!

 

[racerone]

The fuel pump is operated by + pressure pulses and slight negative pulses in the crankcase.----There may be issues with that.----A cylinder compression test MAY help with diagnoses.

 

[jimmbo]

It's not keeping its prime, I have to manually prime it, can anyone help me with this?

Do you mean the bulb is no longer firm after you have run the engine? Or, do you mean the engine starts, runs then quits, and to get it to run again you have to squeeze the primer bulb, and then it starts, runs and dies again?

 

[mot007us]

engine was running good, then engine went blaaa, engine started dying so I had to prime it.

Thank You guys for all your input.:joyous:

 

[jimmbo]

Sounds like the fuel pump, hoses, tank all need some inspection

 

[mot007us]

Thanks again, Will do

 

[DRCrowe]

I just battled the pump on my 87 225. I carefully took it apart, rebuilt it with the OMC kit and full of confidence reinstalled it! It looked great, but didn't work! Had to pump the ball to keep it running. Took it apart and found the return spring was incorrectly seated (I swore I got it right). Put it back together correctly and it works great now. My point is, you never know. If you follow the advise above you will most likely find your answer. Good luck!