110 hp running on 3 cylinders

[dsujen]

I have a 1986 110 hp evinrude vro. I put a regular fuel pump on it 4 years ago and mix the gas by hand. Ran great for 4 years. Last time I went out I floored it and it stalled. Started back up floored it again, rumbled, hesitated and eventually went to W.O.T. Changed out my 3 trip old champ. plugs with last years plugs. Had no effect. Noticed that 1 of em was wetter than the other 3. Stumbled but made it to dock. Today in the yard I ran it. Reved up in neutral but was missing. Put in gear and floored it briefly and repeatedly. Started to rumble and stalled. Started back up. Reved in neutral and ran for a bit then rumbled and shut off. Checked compression. 2 were 110 one was 115 and the other was 120 psi. Ran motor and pulled spark plug wire off on suspect cylinder and motor ran the same. Assumed that coil is bad. Removed the suspect cylinder's spark plug from block left it in its wire and grounded it. Big blue spark. Now what???

 

[Daviet]

Re: 110 hp running on 3 cylinders

First, don't rev your engine over about 1500-2000 RPM on the hose.
Try swapping the coil with one that is firing properly, if the miss moves to the other cylinder, replace that coil.

 

[dsujen]

Re: 110 hp running on 3 cylinders

I'll try that tomorrow. Thanks

 

[emdsapmgr]

Re: 110 hp running on 3 cylinders

It's easy to check spark on each plugwire when it's running with an inductive timing light. It will show the quality of spark on each wire. It's a good method to check spark when the engine is under load, like idling at the dock in gear.

 

[dsujen]

Re: 110 hp running on 3 cylinders

I installed a brand new set of spark plugs and switched around the coils. I also cleaned all corroded connections. Same problem. Coil swap and new plugs had no effect. The suspect cylinder has the wet spark plug. And it still misses and rumbles and almost stalls. What do I do now?

 

[mamm7215]

Re: 110 hp running on 3 cylinders

power pack?

 

[dsujen]

Re: 110 hp running on 3 cylinders

I have a big blue spark @ the plug. When installed in the engine it misses as if it only wont fire when inside the cylinder. if the power pack is bad would I get such a nice arc @ the plug with it grounded in the air?

 

[blimp]

Re: 110 hp running on 3 cylinders

does that year have 2 power packs? if so, swap em.

 

[dsujen]

Re: 110 hp running on 3 cylinders

I think I got it licked. I pumped up the primer bulb and noticed a hiss coming from the fuel pump. I heard that if the diaphragm is ripped in the pump it will allow fuel to flood the #4 cylinder which is my problem area. I took off the crankcase hose to the pump and pumped the bulb.Sure enough gas came out of the pump. Removed the fuel pump and took apart and the diaphragm is ripped. I hope this is it

 

[mamm7215]

Re: 110 hp running on 3 cylinders

Good find.