Logo
FULL SITE MENU

1971 Evinrude 18hp - fuel pump

S

SaltyScot

Regular Contributor
I'm wondering how this fuel pump functions. I removed it from my motor and there is just a threaded hole there. How does this thing work?

My motor won't start unless I put gas in the cylinders manually. I rebuilt the carb as I do with pretty much every motor that I acquire, but it still won't start properly. I removed the fuel line from the bottom of the carb and pulled it to see if it spits gas when I pull the cord. It does not. Maybe a drop or two. Am I on the right track here? I don't want to replace it until I have a better understanding of how this fuel pump works.

Stephen
 
Crankcase PRESSURE pulse drives the pump.-----The diaphragm is available if motor has the small square pump.---Easy to replace in my opinion.
 
Last edited:
racerone said:
Crankcase PRESSURE pulse drives the pump.-----The diaphragm is available if motor has the small square pump.---Easy to replace in my opinion.
Click to expand...

Thanks for the tip racer. It does indeed have the small square pump. I wasn't sure if there was something missing in that hole or not. ;)
 
These pumps are elegantly simple and factory repair kit comes with instructions.----About the only thing that can fail is the diaphragm.-----This pump was used from 1968 to 2005 on many different models.---Parts may not be listed for a 71 model 18 HP.----But listed on much newer motors.---All the same parts !!----The manual fuel pump fills the carburetor and motor should start on that fuel !
 
racerone said:
These pumps are elegantly simple and factory repair kit comes with instructions.----About the only thing that can fail is the diaphragm.-----This pump was used from 1968 to 2005 on many different models.---Parts may not be listed for a 71 model 18 HP.----But listed on much newer motors.---All the same parts !!----The manual fuel pump fills the carburetor and motor should start on that fuel !
Click to expand...

The pump actually looks like it was just replaced. Manual pump feels normal. Seems like gas is going into the carb when I pump the bulb. So if it's not getting into the cylinder, where would I look next? Have to pull the intake manifold?
 
Clean the carburetor.----Find the orifice plug inside the float bowl.------When you pull the choke on does it stay on ?----Perhaps a broken detent?
 
Last edited:
I did disassemble and soak the carb in acetone overnight. Followed by carb cleaner and compressed air through all of the orifices. That was before starting this thread.

I just tried bypassing the quick release fuel line fitting and got much better results. It will start and run, but only at nearly full throttle. If I lower it to the midpoint on the tiller, it will stay running for several seconds and then cut out. Seems like the pump isn't spitting out much fuel, but more than before.
racerone said:
Clean the carburetor.----Find the orifice plug inside the float bowl.------When you pull the choke on does it stay on ?----Perhaps a broken detent?
Click to expand...
 
When you answer questions you might get + results.----Does spark jump a gap of 1/4" or more?----Post results of a compression test.
 
Spark jump is non-existent. It won't jump anything. It won't even light my $6 Harbor Freight spark tester light. But it does start, with a lot of pulling.
 
Pull the flywheel.-----You will likely find 2 cracked coils or 2 new ones already.-----Post picture after you pull flywheel using the 3 threaded holes 1/4-20NC thread.
 
I am unable to upload a pic from my iphone or pc. I can choose the file, but it will not upload.

Upon removal of the flywheel, I noticed that one of the points was completely closed and the other one was at .013. Only problem is I damaged both the coils trying to get the flywheel off like a brake disc before I pulled my head out of my ***** and bought a puller. I don't know what the hell I was thinking. So I set the points to .020 and put it back together and it won't even try to fire. I guess it's better to screw up on a motor that I have no real use for than a more important one. I Imagine I will need new coils if I want this motor to fire again. I appreciate all the help.
 
Is there a way to bench test the coils with a multimeter or something else? Or should I just assume they're bad by the screw impressions in the stacked plate part of the coils?
 
Somehow, the coils ohm out right where they should. But the points on that one side closed up again by the time I took the flywheel off. Can't open it at all.
 
Back
Top