no spark on top two cylinders

[sprouticus]

hello all.

I have a 1992 90 hp evinrude. It's been a pretty good motor to me. I had an issue with one of the spark plug boots coming off about a month ago.must have gotten the wire snagged on the cowl, and I never even noticed because I was just trolling that trip. next trip out, no power. so i lifted the cowl, fixed the problem, using a little electrical tape for good measure......good to go. yesterday, a month later, I was out tubing with my GF. everything is going fine for about an hour, then we lose power. seems to be familar power to last time, so I check under the cowl for disconnected wire. its still good. we limp back to the marina/parts store and I buy a new boot as they don't have the proper wiring kit in stock. it's not even the right boot, but I figure I can get the day outta it. it works great for about 10 mins, then it's acting like its running off 3 cylinders again. then it got even worse......like it was running off of 2 cylinders. I called it a day.

just came in from outside...........did a compression check. 105, 110, 100, 95. the top 2 cylinders are the 105, 110. I also changed the plugs, and replaced the wire for the one giving me problems.but still with the same boot, as thats all I have for now. can't do a spark test, as i'm all alone right now...gotta buddy coming over soon but we're heading out fishing (with the kicker motor) I did however pull the plug wires off as she was running. no difference on the top 2 cylinders.

can a motor even run on one good firing cylinder???? I think it was when I pulled off one of the bottom wires and noticed a huge difference. did not change like that when I pulled off the top wires.

anyway. is this a coil problem??? or something more serious do you think???

appreciate the help

thanx

dale

 

[wilde1j]

Re: no spark on top two cylinders

Does your motor have two power packs? If so, swap them and see if the problem moves.

 

[JB]

Re: no spark on top two cylinders

The top two do not use the same powerpak, they use the same carburetor. That is where your trouble is.

Yes, it will idle on one cylinder when there is no load.

Try squirting fuel mix into the top carb while at idle. Let us know what you find.

 

[sprouticus]

Re: no spark on top two cylinders

I just got back from fishing. we used the kicker to get out, and when we ran outta light, I started the big motor. It was running off of 3 cylinders again i'm guessing..cause it got to a top speed of about 30 mph. occasionally it seemed like it wanted to fire on all 4......it kinda hesitated, like it was gonna go, for about 1 sec, and then it would settle back down.

before we went, i had my buddy turn the key while I checked for spark on the cylinder that I suspected. it had spark, which surprised me.

I suspected the carbs after that, cause to me, if you have compression, and spark.and it still aint working right.....you don't have gas, but when I changed the plugs today, they were all kinda wet and dark.

I'll do what you suggest tommorrow., thanx for the tip.

 

[Joe Reeves]

Re: no spark on top two cylinders

As JB states, a problem exists with the top carburetor.

If those compression readings are accurate, you have a 15 psi difference between the highest and lowest reading cylinders which is excessive. Trouble is brewing.

 

[sprouticus]

Re: no spark on top two cylinders

I was worried about the compression being a problem. I'll recheck the readings. the thing that surprised me is the two cylinders that are not firing, are the ones with the highest compression.

 

[sprouticus]

Re: no spark on top two cylinders

ok, I redid the compresion test, and got :

TL=105
TR=110
BL=103
BR=101


pretty much the same numbers as last time, except the 95 now reads 103...I guess I didn't crank that side long enough or something last time.


so compression looks good.

also, I do seem to have spark on all now.....so spark isn't my problem


I went out and bought a bottle of carb cleaner..cause I've never taken apart a carb before, and i'm a little nervous. I sprayed it in while the engine was running until half was gone. then I took off the plugs one at a time, looking for a difference. now it's the top L (105 compression) thats giving me a problem (I suspected the top right before) every other cylinder seems fine.

I emptied the rest of the can into TL, but still didn't work.

I was hoping I wouldn't have to strip down the carbs.......but I'm guessing this is looking likely. I guess I should consider myseld lucky that my compression is still good as no gas=no oil and no lube going to moving parts.

I have the girlfriend emptying out a windex bottle right now so I can put some gas in it and see how she does.

thanx for reading!!

 

[mikesea]

Re: no spark on top two cylinders

the only way to clean carbs is total disassembly and soaking all metal parts in carb cleaner,you can buy omc engine tuner and spray that in every passage that sometimes is as good as soaking,soak overnite,then dunk in hot soapy water,rinse with a hose through all passages ,if you have access to compressed air ,blast them get a can of carb cleaner aerosol,shoot it in every passage let dry and assemble,the dirt that causes trouble, you cant see

 

[sprouticus]

Re: no spark on top two cylinders

how do you guys feel about that carb cleaner stuff that you just add to your gas???

I don't feel comfortable doing the carb work myself, I've never taken apart a carb before and I'm a little intimidated. I'll ask my friends how they feel about it.

 

[tashasdaddy]

Re: no spark on top two cylinders

seafoam keeps a clean carb clean, to clean a carb, it has to be dismantled.

 

[sprouticus]

Re: no spark on top two cylinders

so 2 aerosol cans of carb cleaner, plus a bottle of the stuff you add to your gas tank later, and...........still having problems.

spark is good on all cylinders.

compression is good on all cylinders.

3 out of 4 cylinders are showing a massive decline in engine performance when I pull the plug wire.

the top left cylinder shows no such decline, however, when I spray gas in it, it improves performance.

can I assume that the left side of my top carb (left when looking at it from behind the boat) has a plugged oriface of some kind??? the right side of the top carb seems to have no such problem.

It can't be anything else can it??? I pretty much have to rip the carb apart??

any tips on this

 

[JB]

Re: no spark on top two cylinders

Sprouticus, why should we waste our time advising you if you ignore our advice?

What happened when you squirted fuel mix into the top carb?

 

[sprouticus]

Re: no spark on top two cylinders

when I squirted fuel in, the revs picked up. probably just as you suspected it would. when I squirted gas into the other cylinders, rev's slowed down (due to flooding i'm guessing??)

I plan on following your advice jp, I am just intimidated on doing this myself and was wondering if there was any other easier solutions.

I guess not.

I'm going to be looking into getting a friend to help me with it.

once again, I have never taken a carb apart before, so it will be a while before I can con someone into helping me and letting you know how it went.

 

[wilde1j]

Re: no spark on top two cylinders

If you're not confidant, take to someone who does it for a living.

 

[JB]

Re: no spark on top two cylinders

And get a factory manual. Carb overhaul is not brain surgery if you simply follow the instructions in the book. . .no shortcuts.

 

[sprouticus]

Re: no spark on top two cylinders

ok guys..........thanx for the info.

I'll post back after I get a chance to either find someone else to help me, find myself a book at the library, or take it to the marina.

and once again jb, I was just hoping it could have been something else, even though I knew it wasn't.

do you guys remember your first time taking a carb apart????

 

[JB]

Re: no spark on top two cylinders

Fair point, sprouticus.

Actually, the first time I dismantled a carb I knew it all. . . manual? Manual? I didn't need no stinking manual!

Expensive learning event.:redface:

 

[Joe Reeves]

Re: no spark on top two cylinders

My first carburetor?? Piece of cake..... set the float to .020, spark improved tremendously, and the engine ran cooler than ever!

 

[sprouticus]

Re: not firing on one cylinder

Re: not firing on one cylinder

ok, it took me a while to respond because there was an issue at the marrina getting the carb kit in. originally they ordered the wrong year, and they only get deliveries on thursdays. I'm also a single dad half the week and I only have cartain days to work on things. Anyway, unfortunatly for me, the summer is almost half over, and i'm not on the water.

Here is the situation.

I brought the carb and carb kit to work, hoping to get some help there. I did not find a manual, and there was no-one at work that was familar with outboard engines, so I decided to basically just dismantle and clean the carb, but leave all settings on the float etc alone. basically the only things I replaced out of the carb kit were the gaskets.

I used air and made sure all jets were clear, and they were, then I put it all back togeather.

I came home, reassembled everything, and crossed my fingers.

didn't work. spark still seems fantastic, compression is good, but pulling the plug on that cylinder has no effect. spraying gas in that one cylinder seems to improve the rpm's.

i'm, pretty confused now, i'm thinking about putting it in the shop, but I really can't afford much for repairs. I don't need to bore you with the issues of my life.

so assuming that the jets were clear, and i'm sure the were, does anyone have any ideas????

 

[Joe Reeves]

Re: not firing on one cylinder

Re: not firing on one cylinder

Fuel must flow thru the high speed jets before it will flow thru any other fuel passageway. These jets are located in the center bottom portion of the float chamber, in back of those screw plugs on each side of the float chambers. If you're not sure that they are perfectly clean or you haven't manually cleaned them with a piece of single strand wire, do so as solvent really doesn't do a thorough cleaning job in that area.