JB Help Johnson 90 or anyone!!!

[StratosRob]

I have a 1988 Johnson 90 Vro V4.I have fire on all 4 cylinders but when I pull number 4 plug wire off I have no change in RPM but alittle nothing like when I pull the plug wire off any other cylinder.When I pull the wire off any other cylinder(1,2,3) the motor drops RPM and just about dies.I cleaned the carbs. no change.The compression is 120 on all cylinders. The #4 plug looks real wet(fuel) compared to the other ones. Running 87 Octane quicksilver synthic. Blend. The vro is disconnected 50:1 pre mix coils omhs ok,wires ok,new plugs,sensor coils oms out ok could this be a power pack going bad. Thanks for any help.

 

[JB]

Re: JB Help Johnson 90 or anyone!!!

Sure sounds like #4 is not making power, Rob.

What happens if you squirt a bit of premix fuel into the carb throat for #4?

You might have an unsuccessful cleaning of an orifice in that carb, a gasket leak, a leaky reed or some other disruption of the scavenging cycle.

Let us know what you find, and good luck.

 

[AlanR]

Re: JB Help Johnson 90 or anyone!!!

sounds like pluged pilot in the carb or leeky reeds

 

[AlanR]

Re: JB Help Johnson 90 or anyone!!!

Also after running the motor for a while feel each plug and see if the spark plug on cyclider number 4 is cooler than the others.

 

[emdsapmgr]

Re: JB Help Johnson 90 or anyone!!!

Great compression. Sounds like the cylinder is getting gas if it is wet. You can do a simple electrical test to confirm your spark problem. Run the engine. Put a timing light on each plug wire. Compare the flashes from # 1,2,3 with those on # 4. If think you still have no fire, switch the two coils on that side. Recheck with the timing light. See if the problem moves. Does it make a difference if the cowling is on or off? Post your results.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Sure sounds like #4 is not making power, Rob.

What happens if you squirt a bit of premix fuel into the carb throat for #4?

You might have an unsuccessful cleaning of an orifice in that carb, a gasket leak, a leaky reed or some other disruption of the scavenging cycle.

Let us know what you find, and good luck.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

JB when I spray pre mix in the carb for that cylinder it just about kills the motor as if I were choking it. I will check the gaskets and the carb, again to make sure everything is ok. When they say leaky reed just what is a leaky reed and how do I check it. I have a repair manual by Clymer but its kinda short about the reeds. Sorry about the double post as you can see i'm new here.

 

[R.Johnson]

Re: JB Help Johnson 90 or anyone!!!

With the engine throttled back to full idle, loosen the adjusting link on both carb's so they snap fully closed, see if this make's a difference. If the idle change's, you have probably found your problem.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Well its not the carbs. changed the bottom one to the top got the same thing on #4 wet plug. Did notice that oil is running down the lower unit looks like it is coming from the lower crankshaft seal could this be the problem for that one cylinder.(might be a bottle cap full after running about 10 min.)Checked the timming it checked out ok also did the timming light test no diffrence in the fire on any of the plug wires. Reeds appeared to be fine.No diffrence if you cange the coils around.

 

[Dhadley]

Re: JB Help Johnson 90 or anyone!!!

The fuel pump runs off #4. If the diaphram is leaking it can put extra fuel into #4. If #4 looks and acts like it's being flooded and you've switched the carbs, it might be something to consider.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

The fuel pump runs off #4. If the diaphram is leaking it can put extra fuel into #4. If #4 looks and acts like it's being flooded and you've switched the carbs, it might be something to consider.

How do I check this ? Could the lower cranksaft seal have any thing to do with it?Thanks for all the help. Trust me It is greatly needed.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Dhadley

I think you have found the problem.Removed the diaphram found there was fuel on the pulse side of the diaphram maybe a cap full. There should be no fuel on the pulse side? Just for the vacume right ? Sure hope this is it .

 

[Dhadley]

Re: JB Help Johnson 90 or anyone!!!

Correct, there should be no fuel on the pulse side.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Do they sale the kit for the rebuild? If so where do you think I cand find it? I saw this online

Quote: They dont sell the kits anymore so purchase PN# 435921 diaphram for air motor and 436095 fuel pump kit.

Does this sound right remember I am pre mixing oiler is pluged.

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Well I found the parts for the build. Did'nt sell the rebuild kits so me and the dealer put some part numbers together.they are on order will post the outcome and part # for other members in abou 3 days thanks.

 

[clint]

JB Help Johnson 90 or anyone!!!

How is the plug wire and boot? Maybe wire old and porous and grounding out to engine or with cowel cover on. Check for shorting out to a common ground. Also check all your ground connections and coil ground. Good Luck!
Clint 8)

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

All plug wires are new. It has the miss with the cowl on or off. All wires and Electrical are ok. Just flooding #4 cylinder.

 

[jtwags]

Re: JB Help Johnson 90 or anyone!!!

I am having a similar problem, check my thread below. I found that cylinder #4 has the least noticible change in rpm when plug wire is removed.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1169857

 

[StratosRob]

Re: JB Help Johnson 90 or anyone!!!

Jtwags,

Sent post to you on yor subject.