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1990 120hp V4 Evinrude weak spark

M

MrRodeoCC

Member
Hello, I just found this site and hopefully someone can help shed some light on my problem. I have weak spark on the right side of the engine, The model number is VE120TLESB. I've swapped wires around and coils, the problem doesnt change or move to a different cylinder. I just recieved the shop manual and will be going through the troubleshooting of the system. The motor has ran good and recently, you would be running up the river and all of a sudden, it just loses power, it started doing this intermittantly and now its all the time. It cranks nicely though, I think that when you throttle up, the added fuel overwelms the ability of the spark plug to ignite the fuel and therefore a loss of power. From what I've read, it sounds like either a stator or a power pack. Am I on the right track?

Thanks
Jody
 
Check the readings of the stator located under the flywheel for the proper specification as per your service manual.

Also, regardless of the readings, if any portion of that stator is leaking a sticky looking substance down on the powerhead area, replace it. The stator is the beginning of both the charging and ignition system... when it starts to melt down, a voltage drop takes place (stator to p/pack) which results in errratic, weak, and eventually no ignition.

A spark test should be made with all spark plugs removed. The spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Anything less is N/G! Note that the 7/16" gap is important!

(Spark Tester - Home Made)
(J. Reeves)
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
 
Okay, according to the manual, the coils check good and the stator checks good, the book says to change the power pack. I used a fluke multimeter and some other test stuff, an ignition tester, you plug into the wire and ground it out, you can adjust the gap and watch for the spark, I only got good spark on #1 cylinder. The easy remote switch is a switch with 2 test leads attached to the terminals, one to the hot feed to the starter, and the other to the selinoid. I saw no leakage from under the flywheel, but I have not been able to get the flywheel off, its soaking under tension with penetrating oil. Any other ideas?
Spark Tester.jpgStarter switch.jpgManual.jpg
 
Update time, I installed the new power pack and new plug wires, the flywheel finally came off and there is no signs of leakage or melting from the stator or sensor. It fired right up after the usual 5 tries when cold, once the engine warms up it will fire with just a touch of the key. I'm going to hit it with the timing light to check it out since there has been so many new parts added and it was tuned up with that old power pack that came off a 140 (that I cant validate as always being a good component). It sounds much better but does seem a tad off but thats probably timing. I will be checking the spark gap again to ensure I'm getting the 7/16's jump. I'll do that as I mark the flywheel for TDC of each cylinder. I do think I will order a new stator later on to have as a spare. I will also be adding an inline water seperator for the fuel. The VRO on this motor was disabled a long time ago and it gets a 50:1 fuel /oil mix in the tank. I did use ethanol gas a couple times, but it did run sluggish, but now the question is, was it due to the fuel, or the power pack failing, this all started around the same time. Has anyone else seen adverse affects from running ethanol fuel? The final question is with the tilt/trim system. I trim up to power out of the hole, but I've noticed that the motor will over power the trim to the down position. I can trim back up once I'm on plane, but should it bypass or should it hold steady where ever it is put?

Thanks
 
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The PTT differs between trim and tilt. From the full down position, you have 15 degrees of trim up, after that, it's all tilt. The PTT unit should hold steady anywhere within that 15 degree area BUT the tilt area cannot withstand the brute thrust force that the engine emits and will drop to the highest point of the trim range.

If however, you are indeed in that 15 degree trim range and the engine forces it down.... a problem exists.
 
I take it the difference in trim and tilt also correlates to the change in sound and speed of movement of the motor. I will mark the point of the change in speed and check it the next time I take it out. I do believe I have a problem, but narrowing the culprit problem will be the challange.
 
Well I took it out today, it cranked right up, I idled out past the no wake bouy to let it warm up, then just sat and idled a bit, all seemed well so I throttled up slowly and it came to life, up on plane and running well. Then as we throttled back and settled into our fishing hole, it coughed and choked and died. It would not crank just coughed and sputtered with the occasional backfire. There was the usual water flowing out of the motor and the temp indicator was normal. Any ideas? It was a long troll back to the ramp on the trolling motor, but I'm thankful I keep my batteries well charged.
 
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MrRodeoCC said:
Then as we throttled back and settled into our fishing hole, it coughed and choked and died. It would not crank just coughed and sputtered with the occasional backfire.
Click to expand...

At this point, start with the basic trouble shooting.

1 - Drain some fuel from the carburetors to see if water may be present.
2 - Check compression (All Plugs Removed). What are the readings?
3 - Check spark (All Plugs Removed). Spark should jump a 7/16" gap w/strong blue spark.
 
gonna jump in here and back out with a little tip for the guy Joe....if you get water in that particular fuel system and you are stranded try trimming the motor up til just enough of it is in the water to cool the engine....if its water mixed with fuel it will probably get you in....slow but better than trolling motor...outa here..
 
okay, here is what I've got so far, good strong spark on all 4 cylinders jumping 7/16's gap. Cylinder compression is
136psi 167psi
145psi 142psi

I havent gotten the flywheel off again to check the keyway for shearing/slippage. Still wont crank, just the occasional pop.
 
The term " crank " obviously means a different thing in some areas.------To most folks cranking is what the starter motor does to the engine.----------To some folks the term " cranks " means the engine starts good.-------You have to be specific in your explanations / questions !
 
If that compression statemnent is acturate (double check it), you have 31 psi difference betwen the lowest and highest reading cylinder and the other two are lower than the highest by 25 psi & 22 psi... not good at all.

If those readings are correct, it's time to remove the cylinder heads to inspect the pistons, cylinder walls, sealing surfaces, gasket, etc.
 
GRRRR typos, sorry I was in a hurry, the correct compression readings are
136psi 137psi
145psi 142psi

and it still wont start running, just spins.
 
MrRodeoCC said:
GRRRR typos, sorry I was in a hurry, the correct compression readings are
136psi 137psi
145psi 142psi......... and it still wont start running, just spins.
Click to expand...

Okay, and I assume that you've checked for water in the fuel.

If you have a good fuel mixture, compression, and spark, the engine has to run. Since it doesn't, it would be a good idea to remove the flywheel to see if the flywheel to crankshaft key has sheared. If so, that would throw the engine out of time.

Check your service manual for the proper flywheel nut torque (I believe it's 145 foot pounds). Anything less and the key will absolutely shear! If sheared, clean up the crankshaft and flywheel tapers before installing a new 304780 key. DO NOT use a key from some hardware store... it must be the key especially designed for that engine!

Also, if replacing the key.... the outer straight edge of the key must be vertical with the engine, not aligned with the taper of the crankshaft.
 
There are some sensitive components under the flywheel.--Be ultra careful with heat.-------Usually a good bump with a hefty hammer unlocks the taper fit.
 
I had to tap the nut with a brass hammer as I tightened it. Make sure your bolts are fastened all the way into the flywheel
so they dont just rip out. tighten hit, tighten hit, and eventually it wil pop off.
 
DO NOT apply heat unless you're planning on purchasing a new flywheel!

Tighten the center spindle of the three hole puller as tight as you can get it. Using a large screwdriver or whatever, pry the flywheel up slightly to remove the play that normally exists, then belt that center spindle hard with a big hammer.
 
Well after many attempts of tightening the puller and keeping penetrant on it and tapping with a hammer, I've given up on it coming off in one piece. I've gotten a new flywheel and in the process of cutting the old one off. I so want my boat back. Wish me luck!
 
The flywheel is finally off, the keyway was sheared, I wish I had tried this trick before I bought another flywheel and already cut the old flywheel partially in half. I will post pics of the tooling I used to get the flywheel off, hopefully it will help someone else.
 
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Start out by closely examining the tapers of both the crankshaft and the flywheel.... clean and refinish as needed.

Install the proper key (307480), not some key you've picked up in a hardware store. It's a special key and no other will do.

The outer straight edge of the key must be aligned with the vertical position of the engine, straight up and down... NOT aligned with the taper of the crankshaft!

The flywheel nut must be torqued to 105 foot pounds. Anything less will result in shearing the key.
 
The new flywheel was in great shape, no damage to the crankshaft that I could see, the old flywheel took the damage when the keyway sheared, you could visibly see that the flywheel had spun 3/4 of the way around, and the old keyway pieces had rounded edges. I did get a new key from the marine dealer, I guess they get their parts in bulk as it was not in a package. I got it all cleaned up and put back together. I torqued the flywheel nut to 75 foot lbs as that is as high as my torwque wrench goes, I'm checking into a higher rating torque wrench. I was happy when the motor fired right up. I have been reading a lot of posts here and now I'm going to check out the intermittant tach issue, Joe has a lot of good info. I do have a question for him though, if I touch the grey wire to the yellow and the tach starts working, can I leave it attached or do I need to remove it to keep the charging system working properly. can it stay attached long enough to set the rpm's and spark advance? Another question is, since I dont have a test prop and the marine place has a 4 week backlog on repairs, how far off would it be to use the regular prop to et the timing? I figure I'll have to strap the boat to the trailer real good to run that rpm and keep the boat under control. I know this is a lot, but I'm tired of sitting at home and all the imput from you folks is helping me get back on the water. Thanks again for all your help.
 
Well its running again, pics of my puller setup is posted in another post titled "Pulling a stuck flywheel" hopefully it will help someone else and prevent wasted time doing what I did.
 
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