1979 115hp bottom cylinder cuts out

[Sherman]

I have intermittent problem with #2 cylinder not working. The bottom cylinder plug is completly black and the other three look really good. I have been fighting an ignition problem but now I have good spark 7/16 jump test on all cylinders. The compression is 120,120,118, 118. I put on a different timer base and replaced one of the power packs during the period of ignition problems. I have cleaned the carbs twice soaked, kits, compressed air used to blow out all passages. I'm thinking bottom main seal but I don't know how to check to see if it is leaking. Any help is desparatly needed. Thanks

 

[WillyBWright]

Re: 1979 115hp bottom cylinder cuts out

Self edited. Was thinking Merc, but still thinking fuel pump. What DHP says...

 

[DHPMARINE]

Re: 1979 115hp bottom cylinder cuts out

Not sure about the location of your fuel pump,but if it gets impulse from #2 cylinder,and has a bad diaphram that's leaking into that cylinder,it could be your problem.Question is whether #2 or #4 powers the pump.So much easier when it's right in front of you.<br /><br />DHP

 

[DHPMARINE]

Re: 1979 115hp bottom cylinder cuts out

WillyBWright,<br /><br />you snuck right in.But don't the V4's only have one fuel pump?<br /><br />DHP

 

[OBJ]

Re: 1979 115hp bottom cylinder cuts out

Think it's #4 DHP. Sets somewhat low on the side of the block. Not sure if Sherm knows what cylinder it is.<br /><br />Sherm...looking at the back of the block....on the port side, left, #2 is top and 4 is low. Starboard side (right), #1 is top and 3 is bottom.

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

I'm not sure of anything anymore. The cyl I'm having problems with is on the bottom of the port side and I just put on a new fuel pump.

 

[DHPMARINE]

Re: 1979 115hp bottom cylinder cuts out

Sherman, How does it run with the new pump?? <br /><br />DHP

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

Just like it did with the old one poorly. The old one was leaking gas out the little hole at the top rear. I put in a new pump assembly

 

[o/b tech]

Re: 1979 115hp bottom cylinder cuts out

Just out of curiosity, have you changed the spark plug and are you using fresh gas. Hope the info helps.

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

Ya. All new QL77JC4 plugs set at .040 new gas and oil. New fuel filter.

 

[Walker]

Re: 1979 115hp bottom cylinder cuts out

If that motor has a recirculation system check all 4 recirculation valves.

 

[o/b tech]

Re: 1979 115hp bottom cylinder cuts out

There is a small hose attached to the airbox cover. This is to allow for puddled fuel that settles in the airbox to help lubricate the bottom bearing and use up this extra fuel/oil. If it is plugged the next available source is the number four cylinder.

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

No recirulation system on this motor. I will check the little hose when I get home from work.<br />Thanks

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

I checked the hose and both end fittings all are ok. Now what?

 

[DJ]

Re: 1979 115hp bottom cylinder cuts out

I would not discount ignition.<br /><br />Do you have an inductive timing light?<br /><br />If so, put the inductive lead on the suspect cylinder plug wire and see if you have consistant spark while running, preferably under load.

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

I'll get an inductive light from my neighbor then go fishing. Thanks for the advice. On my last thread on this motor Joe Reese had an idea that it could be the stator. The dealer owes me a new power pack I hope. I returned it because I could not get any spark on the two cylinder that it supplied power for. Maybe I should get a new stator when I pick up the new power pack. The black plug looks very much like a rich fuel mixture but I don't see how that could be such a destinct droping and coming back on of a cylinder.

 

[Sherman]

Re: 1979 115hp bottom cylinder cuts out

Thanks All OBTech was right on. The small hose running to the air box was not plugged as such but was pinched closed by the carb and the bottom plate. When I checked the hose yesterday I didn't notice the pinch marks. I'm still going to check the ignition with a timing light<br />Thanks again.