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1999 90 Johnson V4 weak spark

H

humm9er

Member
Hi gang,

I have an issue with my 90 Johnson 60 degree V4 any insight greatly appreciated!!

Carbs were gone through and cleaned out along with new gaskets this winter. Tach was dead so I swapped rectifiers (had another used but good one) and tach functionality has returned. Pulled compression a month ago (do it every spring) and it was 120psi on all 4.

When I fired her up a month ago and idled her on the hose I thought all 4 holes were firing. However, this weekend when I cranked the motor it sounded a bit off. On the hose, I pulled the plug wires one-by-one. 3 of the 4 plug wires, when pulled caused a major RPM drop / near stall. 4th (top stbd) wire when pulled causes no change.

I don't have a spark tester however I did pull the plug and wire and had my son crank as I held the plug against engine ground and I'm getting some spark. That plug also shocked me through the boot (not sure if arcing??).

Tried swapping coils -- no change.
Tried swapping plug wires -- no change.
Tried swapping plugs -- no change.

Motor has only idled on the hose a few times since a month ago when I pulled compression. I can't imagine I somehow lost compression / blew the hole? But I will re-check (don't have a gauge will have to borrow). Also skeptical it's starving for fuel but I can go through that cylinder's carb again and check -- do these carbs cross-feed (ie, top stbd cylinder fed by top port carb)?

Stbd tan temp wire is somewhat close to coil wire however I can't re-route it further away without cutting/splicing it and while I don't make a habit of winding a motor up on the hose it will rev past 2500 so not thinking this is a SLOW issue. But I could be wrong?

My question is, can weak / intermittent spark cause a situation where I am getting some spark but not enough to efficiently produce power in a cylinder? Has anyone ever seen something like this? If so, is a bad pack more likely than a bad stator? I don't have a DVA.

Any other ideas? Thank you!!
 
With "all" spark plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that checking spark via using the spark plugs is a waste of time... the 7/16" gap is important.

Spark Tester - Home Made)
(J. Reeves)

You can use a medium size Philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Let us know what the results are of this proper spark test and we'll go from there.
 
Thanks Joe. I will borrow a spark tester tonight. I get that if spark jumps 7/16" I have fuel or compression problems (I doubt this).

If spark is not strong, is the pack the most likely suspect? thanks!
 
If spark is weak, yellow or red, look closely at the stator under th flywheel to see if it has overheated and is dripping a sticky looking substance down on the timer base and/or powerhead.

The stator is a two fold component... the beginning of the ignition and also the charging system. A melt down results in weak, erratic, and eventually no ignition.

The powerpack, if faulty would normally be a case of no spark (individual or all cylinders)... never had one with weak spark.

Compression of 120 on all is great.
 
Hi,

I will inspect the stator however it's well hidden on this motor. Any trick to popping the bolt holding the timing cover to the flywheel (covering the optical eye)? When I go to turn it, it just turns the crank and there is no good way to hold it still since it's plastic...

Also I just replaced most of the ignition system on my 1999 225 Johnson because the stator had overheated but I am new to this OIS -- can the optical eye cause spark problems?

Thank you!
 
On those questions (Post #5), hopefully another member will jump in here with knowledge that surpasses mine. I retired in 1991 so the design and some circuitry of your engine is foreign to me. I'd rather not do guess work as one wrong guess would be expensive.
 
IMG_3725.jpgIMG_3726.jpg

Hi, I pulled the flywheel yesterday -- what a pain getting the plastic timing wheel off. I broke mine but have a new one on the way.

I have seen plenty of bad stators in my day and this one looks like it just came off the assembly line -- no brown goo, no burnt windings. I don't have a DVA meter but I am thinking this stator is okay. Am I correct that an overheating stator almost always shows physical signs?

Also, to be safe, I pulled compression again -- 125-130lbs in all 4. I don't see any sign of water intrusion in the non-firing cylinder (#1). Piston head is coked with carbon and plug comes out wet w oil/fuel.

Unless the stator is indeed bad, this leaves the optical eye and/or the powerpack. Any other possibilities? I know I need to get a DVA meter...

Thanks for any input
 
(" Am I correct that an overheating stator almost always shows physical signs?")

Normally Yes. The two large black coils that are alongside each other are the two coils that provide AV voltage to the powerpack capacitor. If they (either one) starts to melt down, you would see a sticky looking substance dripping down on the powerhead.

The pictures aren't clear enough for me to see those coils properly so I can't make a judgement call on them.
 
IMG_3727.JPGIMG_3728.JPGIMG_3729.JPGIMG_3730.JPG

Closer photos of those coils attached. I see a small amount of brown goo on the last 2 pics ... nothing dripping onto the block the goo on the coil is all there is.
 
humm9er said:
View attachment 13353View attachment 13354View attachment 13355View attachment 13356

Closer photos of those coils attached. I see a small amount of brown goo on the last 2 pics ... nothing dripping onto the block the goo on the coil is all there is.
Click to expand...

Yes, especially #4..... that is the beginning of the meltdown at a point where the dripping hasn't got to the point yet that it drips down on the powerhead. Those 30 ampere stators run extremely hot! I can't say for sure of course if this is the cause of your problem BUT it is a problem that will affect the ignition. Unfortunately the stator needs replacing.
 
Okay this is most helpful thanks Joe! I will replace Stator and see how she behaves. Fingers crossed.

I imagine that when my voltage regulator went out it overcharged / overheated the stator. I caught that early which is likely why the brown goo isnt crazy. I will replace the stator and report back.
 
Yeah, I got my fingers crossed for you also.

In my above reply post #8, I stated a quote "AV Voltage" which should have been "AC Voltage" however I'm sure you knew what I meant. (This damn keyboard!) :cool:
 
Yes I did Joe new stator on order...weighing whether to just replace the powerpack too the season is short in Maine I don't want to monkey with this too much longer.

I will report back on my results. Thanks again
 
New stator here...but luck not being with me, I sheared 1 of the 5 flywheel bolts :(

I assume running with just 4 of the 5 bolts is a no-no? I may farm this extraction out...the bolt is sheared flush with the top of the crank so I can't get vice grips on it.

Any tips greatly appreciated!
 
That touchy... BUT... a routine problem for a machine shop. That would be my route.

However, if you're handy and can center punch that bolt accurately, you could use a drill bit that has a reverse cut that may remove that stud.

Running with just 4 bolts, although not a great weight loss, might set up a balance problem. I wouldn't do it.
 
Ok good spark on all 4 now however 1 cylinder is not getting good fuel. I have swapped the top carbs and the issue follows the carb. I am going to go through the idle jet again with a fine tooth comb but just to be sure I'm not chasing the wrong carb:

these carbs cross feed the cylinders, correct? IE, starboard top cylinder is fed by port top carb?

Thanks anyone for clarifying!
 
Sorry, I'm not sure about the carburetors cross feeding. I'm at that stage of life when memory may beginning to fade, just don't remember although it sounds familiar to me about the loop charged models.

The jets.... be sure to manually clean the high speed jet with a piece of single strand wire. That jet is located horizontally in the bottom center portion of the float chamber, way behind that drain screw plug.
 
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