1997 120Hp Force one cylinder not working?

[onthechip]

It sure seems like I have a cylinder that isn't firing, maybe some of you can help? PLEASE!
At slow speeds I get a little to much vibration. At top speed it seems ok, but maybe not as fast (hard to tell with the conditions I was in). Coming back to the dock after about an hour on the lake I had a hard time keeping it running. It would only continue to run if I kept up the RPM's.

Back at home on the muffs: It would stay running at idle, but it is a bit rough. Ok, here's why I think one cylinder isn't working...As it is idling I pull off the top spark plug wire, the motor runs extremely rough and stalls. I do the same thing to the second plug wire, same result. I do the same thing to the fourth plug wire, same result. I do the same thing to the third plug wire, no change....the motor continues to run as it did before I pulled the wire.

The third cylinder (assuming they are numbered 1-4 from top to bottom): When I pull the plug wire off, there is spark. I swapped the CDM module with the fourth cylinder just to be sure. Compression from 1-4 went 160,150,160,160 (before de-carbing).

So if I have spark and compression,...is it gas? Is it possible that the carburetor works for the fourth cylinder, but not the third???

Any input is greatly appreciated!

Thanks to all of you for your help!
I found one of the Reed petals broken. A new set of Boyesen Reeds and the motor runs great, no more dead cylinder, no more water...

 

[pnwboat]

Re: 1997 120Hp Force one cylinder not working?

How does #3 spark plug look compared to the others?

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

How does #3 spark plug look compared to the others?

Sorry, I probably should have included that in the original post.
All of the plugs are new. And I swapped the #3 plug with a known good plug just to make sure I didn't purchase a bad one.

 

[bentle]

Re: 1997 120Hp Force one cylinder not working?

You swapped with a known good plug, ok. But how did it look when you took it out.
Was it blackish oily or spotless but fuel soaked. Any chance your getting water in that cylinder and if so then the plug may appear steam cleaned or maybe a milky color.

 

[jerryjerry05]

Re: 1997 120Hp Force one cylinder not working?

#3 runs the fuel pump.
Check the diaphram for holes or streched out.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

You swapped with a known good plug, ok. But how did it look when you took it out.
Was it blackish oily or spotless but fuel soaked. Any chance your getting water in that cylinder and if so then the plug may appear steam cleaned or maybe a milky color.

I didn't notice anything unusual but I didn't pay that much attention either. Right now they are soaking in seafoam. After I run it today I will check that.
That sounds like a good possibility unfortunatly...

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

#3 runs the fuel pump.
Check the diaphram for holes or streched out.

Will this cause only the #3 to not fire?
I replaced the fuel pump last season, but I'll try anything.

 

[bentle]

Re: 1997 120Hp Force one cylinder not working?

After running it awhile, pull number 3 plug and inspect. Post what you find.
Another possibility is to check the fuel recirculation system for any hoses that may have come unhooked, or clogged check valves and screens.
Bad fuel pump diaphragm would affect all 4 cylinders, but worth a look anyways.
Have you checked number 3 for good spark with an in-line spark tester, possible your getting weak spark or erratic spark on that cylinder.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

I do not have an in-line spark tester. I'm assuming I can get one at the auto parts store? Are they pretty obvious to understand?

The picture on the left are the plugs I ran last year and just ran for 1/2 hour while de-carbing.

The picture on the right are the new plugs that I just ran for 1/2 hour after de-carbing.

The plugs are 1-4, from left to right.

What do you think? I'm going to check out the fuel system...

Thanks for all your help!

 

[pnwboat]

Re: 1997 120Hp Force one cylinder not working?

Seems like there's a tad more fuel/oil residue on the plugs than there should be. Kind of hard to tell. Do like Jerry mentioned, check the fuel pump diaphragm. Also make sure the "fuel enrichment" solenoid is not stuck open or leaking. This takes the place of the mechanical choke on older motors and dumps extra fuel into the intake right at the base of the carburetors when you push in on the ignition key when starting. You can eliminate a the fuel enrichment solenoid (stuck open or leaking) by pinching off the 1/4" supply hose that comes off of the fuel bowl of the top carb. You could also disconnect the two 1/4" lines that run from the solenoid to the base of the carbs. Either way it will stop the flow of gas to or from the solenoid and into the engine. You get the general idea.

Took a picture of my plugs after running it out on the lake today for about an hour.

Cylinder 1 - 4 left to right. Seems like they have less liquid fuel/oil residue on them that yours.

 

[bentle]

Re: 1997 120Hp Force one cylinder not working?

Agreed. Does seem a bit on the rich side.
You can get in line spark testers at your local auto parts.
A timing light will help to at least tell if your getting spark on number three as well.

 

[jerryjerry05]

Re: 1997 120Hp Force one cylinder not working?

(Bad fuel pump diaphragm would affect all 4 cylinders, but worth a look anyways.)

Not necessarily so!
A hole would allow fuel back into the #3 cylinder and not affect the others.
It would choke or flood out that cylinder.
Make sure the valves (in pump) are flat no bends or lumps.
A leaking head gasket can cause a miss.Even with good compression it can be bad.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

Seems like there's a tad more fuel/oil residue on the plugs than there should be. Kind of hard to tell. Do like Jerry mentioned, check the fuel pump diaphragm. Also make sure the "fuel enrichment" solenoid is not stuck open or leaking. This takes the place of the mechanical choke on older motors and dumps extra fuel into the intake right at the base of the carburetors when you push in on the ignition key when starting. You can eliminate a the fuel enrichment solenoid (stuck open or leaking) by pinching off the 1/4" supply hose that comes off of the fuel bowl of the top carb. You could also disconnect the two 1/4" lines that run from the solenoid to the base of the carbs. Either way it will stop the flow of gas to or from the solenoid and into the engine. You get the general idea.

Took a picture of my plugs after running it out on the lake today for about an hour.

Cylinder 1 - 4 left to right. Seems like they have less liquid fuel/oil residue on them that yours.

View attachment 142381

I don't think my plugs have ever looked that clean.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

After running it awhile, pull number 3 plug and inspect. Post what you find.
Another possibility is to check the fuel recirculation system for any hoses that may have come unhooked, or clogged check valves and screens.
Bad fuel pump diaphragm would affect all 4 cylinders, but worth a look anyways.
Have you checked number 3 for good spark with an in-line spark tester, possible your getting weak spark or erratic spark on that cylinder.

Fuel recirculation appears to be ok. One of the check valves leaked slightly until I sprayed it out. As far as I can see, the fuel pump looks ok.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

(Bad fuel pump diaphragm would affect all 4 cylinders, but worth a look anyways.)

Not necessarily so!
A hole would allow fuel back into the #3 cylinder and not affect the others.
It would choke or flood out that cylinder.
Make sure the valves (in pump) are flat no bends or lumps.
A leaking head gasket can cause a miss.Even with good compression it can be bad.

I think you answered what my next question was going to be.
If I was getting water in the cylinder (head gasket) wouldn't I see that in the compression test?

I didn't look that deep into the pump. I'll look tonight.

Thanks!

 

[pnwboat]

Re: 1997 120Hp Force one cylinder not working?

If you're getting water into the cylinder, usually you will either see very fine water droplets on the plug, or white milky residue on the plugs. Looking at your pictures, your plugs look free of any water or moisture.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

After inspecting the fuel pump a bit closer it looks like the diaphram is good, the valves look good, but I did find what looks like water on the inside of the fuel pump (outside of the diaphram). Refer to picture...


The milky white liquid is on the diaphram side and in the case opposite the diaphram (not sure if you can see it in the pic). There was a bit more that leaked out before I could snap the picture.

Should there be water there?

Also,...The fuel enrichment solenoid checked out ok. I also disabled the solenoid with no change in performance. I double checked the spark with an inline tester and there is definitly spark present. The spark doesn't seem to be erratic and seems just as strong (compared to the other cylinders).
I pulled the #3 plug again and it looks the same, no water, a little fuel.

I'm still at the same symptoms: The motor fires right up. It idles rough. When I pull the #3 plug wire the motor runs the exact same (at idle). I did notice that when the moter is running around 2000-2500 rpm's and I pull the #3 wire, I notice a slight difference.

 

[bentle]

Re: 1997 120Hp Force one cylinder not working?

Water in the fuel tank would be where I would start.
You may need yo drain the fuel that's in the tank and start fresh 50:1 ratio.
well if you have a portable tank then hook it up and see if it clears up, ift then rule out water in the fuel.
Shouldn't be any water in the fuel pump though.

 

[pnwboat]

Re: 1997 120Hp Force one cylinder not working?

+1 with what bentle said. Looks like you have water (or something) in your gas.

 

[onthechip]

Re: 1997 120Hp Force one cylinder not working?

The part of the fuel pump that is in my hand, on the inside(between the two diaphrams), is the only place that there should be gas, correct?

The milky substance is on the outside of the diaphram. There shouldn't be any gas or water on that side, correct?

The gas should be good....The tank was emptied at the end of last season. 12.5 gallons of gas and 1 quart of oil was put in last week. I would see a problem with all 4 cylinders if it was the gas?

Thanks again to all of you for your help!