89 90hp Rude missing on one cylynder

[Dennisanoka]

When running on the muffs all cylinders fire, no matter how long I let it run. I have had the cowling off when running on the muffs, if that could make any difference. In the water however, after warm up one cylinder, still has spark but does not fire at idle. I can tell because when I pull the plug wire no change occurs to the rpm. If I bring up the rpm's to around 4000 then it begins to fire. If I then slow down to around 3000 I can tell it stops firing because I can feel the vibration begin. If I speed back up it goes away again. It is always the same cylinder. I have rebuilt the carbs completely. I have done a compression check, they are on the low side but all are 85-90 psi. I have tried new plugs, 3x. I have done the link and sync but re-did it again today just to be sure. One last thing the cylinder that stops firing is getting gas/oil because it does get all fouled up once it stops igniting at idle and the lower rpm range.
I hope the experts out there have some ideas for me to check out before I break down and take it in for service.

Thank you in advance

 

[Barnacle_Bill]

Re: 89 90hp Rude missing on one cylynder

The coil for that cylinder could be braking down. Try swapping it with another cyl and see if the problem follows it.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

I'm sorry, I should have listed that as things that I have tried, But it had no effect. I have also conducted the sensor coil resistance test and the charge coil resistance test and no faults were found. I do not have the ability to test the power pack however. It's the #4 cylinder giving me the problem. I have not actually tested the spark strength but it appears the same color and brightness as the others. I am hoping someone could shed some light on this because it has become a mystery to me.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Well I am hoping at some point here I will post some clue that one of the seasoned members will recognize the problem. Last night we re-did the link and sync and the timing. Everything seemed to work like a fine tuned clock. We thought we had it fixed even though no real big changes were made. The problem had gone away. Then today the same problem returned but I seem to have found a way to make it happen. If I am running at 3000 rpm and I give it a quick hard right turn then straight again, that seems to bring it on. If I continue straight it will smooth out again. On the otherhand a quick turn to the left does not cause the issue. Seems strange to me I hope this is a clue to someone.

 

[Cricket Too]

Re: 89 90hp Rude missing on one cylynder

OK, so you mentioned that one cylinder still has spark, but does not fire at idle. Does this mean that you found that cylinder to be getting spark at idle and just not firing, or did you mean that it is still getting spark at higher RPM, but getting NO sparkk at idle?

You also mentioned that you moved ignition coils around, what happened when you did that? I assume the problem stayed on the #4 cylinder, or else you would have found your problem, correct?

Have you tested to make sure there is no spark at idle, with a timing light?

I don't know about the turning to the right thing.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Crickit Too,

It is still getting spark and fuel at idle, but it is not firing. If I then put the plug back in and bring it up to around 4000 it then begins to fire. I can tell because the engine smooths out and the vibration is gone. But as soon as I bring in down under 4000 it stops firing. I have verified it is only that cylinder by pulling the plugs immediately and the other three are dry and brown but that one is black sooty and fouled. As I mentioned before though it is somewhat intermitent. I have checked every wire and harness for something loose to no avail. I did read on a post about the magnets in the flywheel causing issues but not sure if they would be intermitent. I 'll pull it off if someone thinks it would be worth it.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

I just read on this site that power packs can be damaged by turning the engine over without the spark plug grounded. I know I have been guilty of this when doing compression checks and general troubleshooting. So what is the likelyhood of damage occuring and do my problems resemble those of a partially failed power pack?

 

[Cricket Too]

Re: 89 90hp Rude missing on one cylynder

Well I'm a little confused. Why would you suspect anything electrical is wrong, if you are saying that it is getting spark at idle, but just not firing.

If it's getting spark and fuel at idle, then how is it not firing? Also how do you know it's getting spark at idle, if you say you took the plug wire off and saw no difference, wouldn't that mean that there isn't spark at idle?

I think what you really need to do is put a timing light on each wire and see if you are getting output from each coil and current through the wire, see if you can get it to drop out and stop flashing the light. Then get a spark tester and see what kind of spark you are getting at idle, weak or strong 7/16" snap.

If you have been pulling the wires off while it's running and not grounding out the wire, you could be hurting your power pack.

I'm actually trying to hunt down a similar situation on my '97 115 Johnny. Went out and had no power at all, found one of the wires pulled out of the boot, so obviously it wasn't grounded, and was run for about 10 minutes like that and higher RPM. Fixed the wire and engine runs fine, up to 5500 WOT. But in neutral or idle in gear, it has a misfire and jumps around a bit until you bring the throttle up just off idle to about 1200 RPM, then it starts firing. Hope my power pack didn't get fried.

Very frustrating, I know. But this forum can help a lot. Keep posting.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Sorry if I caused confusion. I often tell my wife she needs to know what I mean not what I say. When I said I saw no difference I meant I saw no difference in spark intensity between a cylinder that is firing and the one that is not. What I have begun to wonder and I am just taking a shot in the dark is that for some reason the bad cylinder is getting spark BUT not at the right time. I mean only that cylinder gets out of time because of??? maybe the timing base or the power pack heats up under load and begins to fail. Mine is similar to yours in that the #4 cylinder will begin to fire but not until 4000 rpm's. BTW this thing has some intermitentcy to it. As I mentioned yesterday I had it out and for the first 2-3 miles it ran like a top then it began to act up more and more and after 3-4 more miles it was no longer intermitent at under 4000 whereas when I first went out it was. Again, I am just guessing but I have ordered a new power pack, because if turning the engine over without the output leads grounded can cause failure I certainly have done that many times. The only other suspect part is the timing base but since it costs alot more I'll start with the power pack. I should have it by Monday or Tuesday.

If someone knows for certain that my therory is simply impossible please let me know or post another possible solution.

Thanks

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

I have decided that I need to do more indepth analysis while the bad condition is occuring. 1) I plan to make a spark tester for testing just that one cylinder. 2) Take the compression tester out on the water with me. I'll take it out this weekend and once the problem begins I'll run some more tests. If anyone has ideas of additional tests I could run, please let me know. You may have thought me nuts to suggest a quick turn of the boat would bring on the problem but it did, and my reasoning is that the load change on the engine is what changed. Why turning right caused it and not left ? My theory is, because there is greater load on the engine when turning right, because of the prop rotation.

Open to suggestions....

 

[cat5cable]

Re: 89 90hp Rude missing on one cylynder

Hi i have a jonhson90 1986 and had a misfire on one cylinder when out at sea and sometimes it would start misfiring when we hit a wave or made a sharp turn, but it never misfired with the cover off.
What we found was when the cover was put back on the securing catches moved the plug lead enough to come loose it was very intermitent but in the end very simple to fix, new plug lead and cap.
Anyway hope you sort your problem out soon.
regards
tim

 

[tashasdaddy]

Re: 89 90hp Rude missing on one cylynder

Cat 5 is correct, there have been incidents where the spark was jumping to the cover latches, either misrouted, or cracked wires.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

First off thank you for the tip. I have replaced the plug wires and since it still does it with the cover off that may not be it, but what I will do is run it at night, get it to fail again and look for arcing somewhere else. I'd love to find that it was something like that. Not sure why it only does it at RPM's under about 4000 though, but I'm sure that when I do find the culprit it will all make sense.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Oh and just in case I will swap spark plug wires and see if the problem moves.

 

[reeldutch]

Re: 89 90hp Rude missing on one cylynder

the cylinder closest to the flywheel is nr1 the lowest is nr 4.

is nr 4 causing you problems?

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

Reeldutch are you going to make my day? Yes it is #4 (bottom left as you stand behind the engine).)

 

[reeldutch]

Re: 89 90hp Rude missing on one cylynder

thats the cylinder that is making your fuelpump (vro) pulsate.

if your fuelpump(vro) has a fuel leak treu the pulse hose than it will create a very ritch condition and fauling your nr 4 plug only at idle and might clean up at full trottle.

the 3 remaining cylinders with enough fuel pressure just keep doing there job.

that might be your problem.

fauling and ritch at idle, or so ritch it is flooding just your bottum crankcase.

when you start it up cold it will use all that gas to fire up.
does it smoke when you coldstart it?
badly?

good luck

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

You my man may be my hero. That makes sooooooooooo much sense. When I re-built the engine last year to the tune of about $1000 in parts, I decided to start mixing my oil rather than take any chances. This problem started after I disconnected the VRO, though I still use the fuel pump built in. Based on what I just told you could this still be the problem. I guess I need to make sure I have disabled the VRO correctly as well as look for an air leak. I'll have to check but going from memory all I did was plug the oil input tube to the VRO. I can do a search again for the procedure but if you know for sure, please post it again or a reliable link to it. BTW way still can hear the VRO pulsate but I thought it was normal, I thought it was the fuel pump inside. Please keep me going in the right direction here.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

This is the procedure I followed to disable the VRO:
Remove the oil inlet hose connection nearest the vro pump and plug it off with a suitable plug and clamp.I used a I believe it was a 3/8" sized stainless steel bolt with a smoothe shank and cut the threads off leaving just the smoothe shank and bolt head and inserted into hose and secured it with a stainless steel hose clamp.Next ..trace the three wires leading from the vro pump to a rubber amphenol connector in the engine compartment and disconnect it and secure both ends so they aren't flopping around loose.This will disable the vro alarm.Then.. trace the two wires from the vro oil reservoir to their connectors in the engine compartment and disconnect and secure them.This will disable the low level oil reservoir alarm.

 

[Dennisanoka]

Re: 89 90hp Rude missing on one cylynder

So I will look for an air leak in the crankcase pulse hose, either at the VRO fitting or at the engine or in the hose itself. I will report back. This would be great if this proves out.