1987ish Merc 200hp no spark on one cyl.

[coonman444]

Ok folks, first off I would like to say hi to everyone here. This is my first time to this site and let me tell you there is a heap of info on here. Thanx to all in advance that reply to this and anyone elses problems.

My problem is that after finally get time to put my boat in the water for the first time this year it was only running on 4 out of 6 cylinders. Knowing it was not a fuel problem I started pulling plug wires and sure enough cyl 1 and 5 had no spark. It was not that the plug was fouled, it just had no spark at all trying to jump a screwdriver gap. Ok, no problem as I had the complete electrical off another 200 in my garage.

I get home and change out the coils on 1 and 5. Now i got spark on 1 but nothing still on cyl 5. I take the wires off of three and put them on cyl 5 and there is spark. Ok, nothing wrong with the coil, big blue spark. Then I change out the brain box ( not the corect name I know) that feeds the cyl coils 1,3, and 5. Still no spark on cyl 5. I checked the resistance of the power wire for number 5 and its good with no breaks. I checked the ground wire resistance on the coil and it to comes back good. Still no spark on number 5 cyl.

Can anyone help me out here and tell me where to look next. Could it be a stater problem even if it is only missing spark on one cyl.

 

[j_martin]

Re: 1987ish Merc 200hp no spark on one cyl.

Ok folks, first off I would like to say hi to everyone here. This is my first time to this site and let me tell you there is a heap of info on here. Thanx to all in advance that reply to this and anyone elses problems.

My problem is that after finally get time to put my boat in the water for the first time this year it was only running on 4 out of 6 cylinders. Knowing it was not a fuel problem I started pulling plug wires and sure enough cyl 1 and 5 had no spark. It was not that the plug was fouled, it just had no spark at all trying to jump a screwdriver gap. Ok, no problem as I had the complete electrical off another 200 in my garage.

I get home and change out the coils on 1 and 5. Now i got spark on 1 but nothing still on cyl 5. I take the wires off of three and put them on cyl 5 and there is spark. Ok, nothing wrong with the coil, big blue spark. Then I change out the brain box ( not the corect name I know) that feeds the cyl coils 1,3, and 5. Still no spark on cyl 5. I checked the resistance of the power wire for number 5 and its good with no breaks. I checked the ground wire resistance on the coil and it to comes back good. Still no spark on number 5 cyl.

Can anyone help me out here and tell me where to look next. Could it be a stater problem even if it is only missing spark on one cyl.

1 and 5 share the same trigger coil. Could also be a switchbox.

Parts are expensive. The fault can be found with a shop manual and a DVA or DVA adapter and a multimeter.

hope it helps
John

 

[coonman444]

Re: 1987ish Merc 200hp no spark on one cyl.

thanx John. Where would I find the trigger coil for cyl 1+5? One more question is what is a DVA and where could I buy one or the adapter for it?

 

[j_martin]

Re: 1987ish Merc 200hp no spark on one cyl.

thanx John. Where would I find the trigger coil for cyl 1+5? One more question is what is a DVA and where could I buy one or the adapter for it?

The trigger coil is under the flywheel, and also under the stator. It is the device that the throttle lever is moving under the flywheel. It has 6 wires going to the switchboxes, one for each cylinder. The way it is wound, opposite cylinders share a coil.

I just discovered an error in my post, it would be 1 and 4 that shares a coil, so my point is mute.

Cylinders are numbered by their position on the crank, thus starboard top is 1, port top is 2, etc, just to be sure we-re on the right page. starboard top and port center would share the same trigger coil.

Usually this type of problem is either a switchbox or coil or wiring.

It is possible for a particular ground fault in the trigger to act this way. Unusual, but possible. More likely would be #5 trigger wire shorted to ground by bad insulation. Check the trigger with an ohmmeter, chart's in the book, or might be found here in the FAQ's.

You could swap both the trigger and the coil wires at the switchbox to see if the bug stays with the switchbox terminal, or moves with the wiring.

Question #2. A DVA is a peak reading voltmeter. It converts AC to DC, storing the peak value in a capacitor for the meter to read. DVA stands for Direct Voltage Adapter. Using it would likely quickly isolate this problem.

The adapter amounts to a diode and a capacitor. Diode needs to be fairly high voltage, like 400 or better. common 1 amp rectifier diodes are fine for the application. The capacitor has to be 250 volt or better, about 1 mf. Less if your meter is real sensitive.

There's diagrams here and elsewhere for the adapter.

hope it helps
John

 

[coonman444]

Re: 1987ish Merc 200hp no spark on one cyl.

thanx for the info and the quick respose John. I will try and hunt for the short to ground later tonight.

 

[coonman444]

Re: 1987ish Merc 200hp no spark on one cyl.

Well, after replacing the trigger assembly with a new one I still have no spark on number 5 cyl. The old one looked fine and the wiring was in great shape. I switched the two brain boxes around with the wires as well and i still have no spark at number 5 cyl so I know it is not a problem with the box or wiring. What else could be giving me a no spark issue at number 5 cyl. I am 100% positive it is not a coil problem or brain box problem. It seems like it just aint getting any feed into the brainbox or switchbox for number 5.
Anyone out there have any input..........could it be a stator problem?

 

[j_martin]

Re: 1987ish Merc 200hp no spark on one cyl.

Well, after replacing the trigger assembly with a new one I still have no spark on number 5 cyl. The old one looked fine and the wiring was in great shape. I switched the two brain boxes around with the wires as well and i still have no spark at number 5 cyl so I know it is not a problem with the box or wiring. What else could be giving me a no spark issue at number 5 cyl. I am 100% positive it is not a coil problem or brain box problem. It seems like it just aint getting any feed into the brainbox or switchbox for number 5.
Anyone out there have any input..........could it be a stator problem?

A stator problem will affect one bank or the other, all 3 cylinders equally. If you want to check it, there are 2 independent circuits in the stator. You could swap the wires between the switchboxes in groups. (2 on each) I bet bug won't move.

Simple fact, you missed something. Replacing the trigger cleared the trigger and wires to it. Swapping coils cleared that as a possibility. That leaves wires between the switchboxes and the coils, and ground wires on the coils.

Which cylinder is the lead to the oil alert connected to? If it's 5, disconnect it. Yer oil alert will go off, but you might get spark.

hope it helps
John

 

[coonman444]

Re: 1987ish Merc 200hp no spark on one cyl.

Ok, so plot thickens........... I changed out the stator last night with a known working one. Still no fire on number 5.

Ok, now heres where it gets thick. When i go to jump the solenoid with the key in the run position i can feel a real faint spark out of number 5 coil wire. When I try to repeat the same faint spark feeling (in my hand) on any other cyl I cant feel a thing. The spark feeling just happens after I jump the sol real quick. Like a jab type thing and it only happens once right at the intial jump of the poles on the solenoid.

I again switched all wires to the switchboxes (vice versa) and the problem is still with number 5.

I am totaly stumped.

As far as the low oil circut thing.......someone before has already removed it. The motor has to be now premixed.

 

[j_martin]

Re: 1987ish Merc 200hp no spark on one cyl.

Don't go hot wiring the coils unless you completely disconnect them from the switchbox. You could blow the electronics. Even then, I don't think it's recommended.

I suggest you get a DVA, a book, and troubleshoot it from the ground up the right way.

On the low oil thing, did they remove the wire to the switchbox?

hope it helps
John

 

[coonman444]

Re: 1987ish Merc 200hp no spark on one cyl.

thanx for all the info John.

What did you mean by hotwiring the coils. When I noticed that faint spark I caught it by accident when checking for spark jumping from the coil wire end with a screwdriver in it to the block (ground). My finger just happened to be touching the metal of the screwdriver as well. There was not enough spark to arc but enough to feel it faintly. The others would not do this at all.

My last question is what color would that wire be to the switchbox for the oil sensor? I dont think there is one there. Both boxes have all the same wires basicall with no extra oddballs.

I guess after that I have pretty much used up all my resources and will maybe have to take it to a dealer with the right equipemnt.

Thanx again John for your time and knowledge !!!

 

[j_martin]

Re: 1987ish Merc 200hp no spark on one cyl.

It's green. Usually goes to the bottom coil terminal on the top switchbox (#2 cylinder).

Please let me know what solves your problem.

John