Engine dies when shooting premix into the bottom cylinder...

Z28_Pilot

Recruit
Joined
Sep 8, 2006
Messages
2
Hello,
I have a 1976 Johnson 70, I have rebuilt the carbs changed plugs, etc. The problem I'm having is that it just doesn't want to start, then after starting and dying out a hundred times (while playing with the choke and throttle) it will finally idle if I keep it at a fast idle. It ran pretty good after the carb rebuild,,,had a little hesitation at about 3/4 throttle. It started not idling very well (especially when warm) then would start but just bog down when you tried to rev it up. I took the carbs apart again and everything looked clean, put them back together and messed around with it for awhile and it started running ok again. Then I went to use it again after a couple weeks and it is doing this crap.....It has good spark on all 3 cylinders, havent checked the compression in awhile. If I shoot a little starting fluid (I know, it dries the cylinders but I do it very little and while the engine is running) into each cylinder, the top one seems to have no effect, the middle one makes it rev up and the bottom one kills the motor. The primer bulb is staying hard and fuel comes out of all the hoses going to each carb.
Just looking for any ideas for what to chack...other than compression!

Thanks in advance!!!
 

wildmaninal

Lieutenant Commander
Joined
Jul 14, 2007
Messages
1,897
Re: Engine dies when shooting premix into the bottom cylinder...

If you haven't done a comrpession check in a while I would start with that.

Have you checked the fuel pump its self? Have you done a link and sync on the carbs? Is the vent cap open or is the tank able to breath?

Welcome to Iboats by the way.
 

Z28_Pilot

Recruit
Joined
Sep 8, 2006
Messages
2
Re: Engine dies when shooting premix into the bottom cylinder...

I need to get around to a compression check....the engine has done this before and somehow started running decent again....so I'm not sure whats going on. The plugs all look the same when I take them out, so I don't know why each cylinder would react differently when I spray a little fuel in the carbs? The fuel pump is pretty new, the screen is clean on it and it sprays fuel out with the line off....pumping the primer ball has no effect at all.

P.S. Thank you for welcoming me to the board!
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Engine dies when shooting premix into the bottom cylinder...

Start with the absolute basics

Check compression

Check spark quality with a 7/16 gap testor

If it passes both those tests then move on to the carbs (again) as something is not quite right yet.
 
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