Cylinder not firing?

[Xelaw]

I have a 1990 Bayliner Capri with a Force 90 motor. Last time I took it out, it stalled when put into gear after I'd been using it for a few hours. It still started without much trouble, but it would stall out after idling for a bit or as soon as I put it into gear.

I was messing with it today to see what's wrong. While running the motor, I unplugged each of the three plug wires. When I unplugged the middle there was no change in how the motor ran. It stalled out when I unplugged either of the other two. I then switched the top and middle plug and had the same result, so I know it's not the spark plug. All three plugs and wire caps are new. The compression is also good.

Worth mentioning...there was black residue on the top plug when I pulled it out. Also, my tank is almost out of gas and I recently realized (thanks to this site) that I've been putting my oil in with my gas improperly, so there may be too much oil in the gas. I'm going to fill the tank with properly mixed gas tomorrow to dilute it.

Based on everything I've checked, I'm thinking gas isn't getting into the cylinder properly. How can I check for this? What else should I check?

 

[Xelaw]

Re: Cylinder not firing?

I should also mention that I confirmed (by getting shocked when sticking needle nose pliers into the wire cap) that the power pack is working.

 

[Jeremy90bay]

Re: Cylinder not firing?

The plugs should all have a residue on them. if they are clean they are not firing. I would go to your local parts store and get a spark tester and start there. I you have good clean spark in all three cyl. then go onto fuel. In mt opinion, spark issues are easier to figure out over fuel.

Jeremy

 

[Xelaw]

Re: Cylinder not firing?

I used an ignition tester and confirmed there is a spark. How do I check to see if the cylinder is getting gas?

The gas may have too much oil, I'm going to put new gas in tomorrow. Is it possible for bad gas to cause only one cylinder not to fire (same one every time)?

 

[jerryjerry05]

Re: Cylinder not firing?

Do a compression test,then the check the diaphram as the second cylinder draws for the pump.J

 

[Xelaw]

Re: Cylinder not firing?

I don't have a compression test kit. It was tested about 3 weeks ago and was good. How do I check the diaphragm? Not sure what you mean.

Also worth mentioning, I sprayed Seafoam into the carbs two weekends ago. Maybe that screwed something up?

 

[notsunkyet]

Re: Cylinder not firing?

seafoam isnt going to hurt anything itll help more than it will hurt...did you say you put pliers in the spark plug ends and got shocked to ensure that they were working?

ok so i biught fuel pump diaphrams today they were like 5 bucks (without valves) at the boat store.... not a big deal to replace.....

 

[Xelaw]

Re: Cylinder not firing?

Mentioned the seafoam in case anybodys seen it kick up crud that caused problems. I actually stuck the pliers in the coil because I was going to ground it on the plug base to see if it made a spark. Instead the current went through me. Anyway I checked with a real tester too.

I know the diaphragms are cheap, but I want to know how to check to see if that's what I need to replace.

 

[jerryjerry05]

Re: Cylinder not firing?

Take the pump apart,thats how to check the diaphram.It needs to be flat no holes not streched.J

 

[Xelaw]

Re: Cylinder not firing?

The diaphragm is in good shape, looks pretty new. I took the float chamber off of the carburetor and confirmed that gas gets in there when I squeeze the bulb. Anything else to try?

 

[CharlieB]

Re: Cylinder not firing?

If the spark plug fired the OTHER cyl when you switched them then you know the plug is OK and not fouled.

If the plug was DRY when you pulled it then chances are the idle jet is clogged and not passing enough fuel for the cyl to fire.

Test by squirting pre-mixed fuel into that carb throat while the engine is at an idle, if you hear the idle speed/quality pick up then you know you need to clean and adjust that carb. Alternately, you can place two fingers across the carb opening to simulate a choke partially on to richen the mixture, which also indicates a dirty carb passage.

Don't do just the one, clean them all.

Install a water separating fuel filter to prevent future occurrences of either water or crud getting into your carbs.

If idle speed/quality does NOT improve while spraying fuel into the carb, then you really do need to recheck compression AND timing on each cyl.

 

[Xelaw]

Re: Cylinder not firing?

Took it to the lake to see if I could burn off any crud at the bottom of the tank or in the lines. It ran great at high idle, but kept stalling at normal idle.

Plug is ok, and yes it was dry. I sprayed seafoam into the carb but it didn't seem to pick up at all. I'll put in a fuel filter in the next few days, I don't have anything right now other than a screen on the pump. When I loosened one of the float chambers to look in it, there was a small amount of sediment, so I'm probably dealing with some crud.

I'll take the carbs off tomorrow and clean them up and see if that helps. Never done it before, but my service manual comes in the mail tomorrow so that should help me some. Didn't seem too complicated when I looked at it.

Thanks everyone for the input. I'll let you know how it goes.

 

[CharlieB]

Re: Cylinder not firing?

You REALLY need to check compression also.

If that carb was lean there is a greater possibility of piston damage and compression loss.

Remove the spark plugs, crank the engine over by hand, use a small mirror to reflect sunlight into the plug hole and describe how the piston looks.

Smooth to slightly grainy black, wet or dry is O.K.

Grey or aluminum colored, pebbly, cratered, molten, is a serious problem.

Anywhere in between the two and there is still a possibility of ring damage and compression loss, enough for the cyl NOT to fire at an idle, yet seem to run at higher throttle.

Clean all carbs, if it hasn't damaged the cyl by now it soon would have.

Test compression so that you KNOW that cyl's condition.

 

[borns@live.com]

Re: Cylinder not firing?

Good morning everyone. I just came across this forum and I think it the greatest thing in the world.... or a close second to drinking beer out on the boat on a hot, sunny, summer day....

I have almost the same problem with my 1989 Force 125HP engine.
The # 2 cylinder (of the 4 cylinders) is not firing. I have good compression, and good spark.
My guess is I'm having gas problems.

One person thought that I have a vacuum problem in the crank case. I sprayed starter fluid all around the casing seal checking for "pick-up". nothing.
I was wondering if the reads in the carb might have something to do with the cylinder not firing?

What other problems could cause the cylinder to not work?
AND....
If the problem is gas related, is their some kind of device I could rent to check the amount of fuel making it into the cylinder?

Thanks for your help.
Bill

 

[Xelaw]

Re: Cylinder not firing?

Bill,

Would you mind moving that message and starting a thread of your own? I hope you get your problem solved and I'll let you know what happens with my issue. The problem with posting your own question on a thread I started is that everybody will be responding back and forth to two people instead of one and it will get confusing. We'll both get more attention if we keep them in separate threads.

 

[borns@live.com]

Re: Cylinder not firing?

Right-On!
I'm guessing the problems your having are related to same problems I'm having. "Something to do with the fuel that is not alowing the cilinder to fire".

Have you been able to check the vaccum in yout crank case? I have been told that has something to do with drawing the fuel into the cylinder head.

Bill

 

[Xelaw]

Re: Cylinder not firing?

Got a compression tester today. 110 PSI in the top and bottom cylinders, 60 in the middle. I haven't taken a look inside yet to see what's up. I'm not sure what happened, the compression was fine a couple of weeks ago. CharieB might be right.l

 

[Xelaw]

Re: Cylinder not firing?

Took the cylinder head off. They cylinders and pistons are in great shape. The head gasket is blown between the middle and bottom cylinder, so that's the issue. I have 3 sheared bolts to remove, then I'll put in a new gasket. Unfortunately, one of the bolts is at the bottom of the block and I have little room between the outboard case and the bolt so I'm going to have to get creative.

 

[Bill is ok]

Re: Cylinder not firing?

Hi Xelaw.
Can you post a picture of your head gasket.

Thanks
Bill

 

[Xelaw]

Re: Cylinder not firing?

Here you go.