Stumped! No Spark!?

[country_bumpkin]

Mercruiser 488

Replaced and then bypassed shift interput and still no spark.

at the coil it reads: pos (5.9V), neg (-.1V) and I noticed that the wires on the pos side are getttin HOT!

where do I go from here for a diagnosis? Thinking it's something simple that I can repair and not take it to the marina.

Thanks!

 

[Laddies]

Re: Stumped! No Spark!?

Remove the - side wires at the coil, you should have about 9+ volts at the + side at this point if the 5.9 don't increase you have a bad coil it it does then you have a short at the dist or wire leading to it

 

[country_bumpkin]

Re: Stumped! No Spark!?

Remove the - side wires at the coil, you should have about 9+ volts at the + side at this point if the 5.9 don't increase you have a bad coil it it does then you have a short at the dist or wire leading to it

Thanks, I'll try that right now!

 

[country_bumpkin]

Re: Stumped! No Spark!?

11.5 V with the side wire off, put it back on and dropped to 5.9V again.

So, I have a short somewhere, right?


Thanks.

 

[Reel Poor]

Re: Stumped! No Spark!?

Does that engine have points?

 

[country_bumpkin]

Re: Stumped! No Spark!?

Does that engine have points?

Yes it does.

Does it matter if they are open or closed when doing this test?

 

[Reel Poor]

Re: Stumped! No Spark!?

If they are closed when testing for voltage that is like a dead short. Remove the distributer cap then turn the motor untill the points are open the voltage should be back to the same voltage that you got with the -neg wire disconnected. When checking for spark remove the coil wire from the coil and check the coil for spark. This eliminates the possibility of a bad coil wire.

 

[country_bumpkin]

Re: Stumped! No Spark!?

Still stuck.

When I turn on the ignition the wires on the plus side get HOT! and read 5.9v. If I remove the wires they then read 12v. This is whether the points are open or closed. So somethings shorting out, right? Or is the coil bad?

There are 2 wires form the neg side of the coil. One goes to the dist, the other goes behind the engine and I can't trace it.

I appreciate all the help so far, but dang...now I'm frustrated any other hints or suggestions would be great.

 

[freddyray21]

Re: Stumped! No Spark!?

the two wires on the neg side. One goes to the points the other goes to the tach. Read the previous posts from people trying to help.

They said

"Remove the - side wires at the coil, you should have about 9+ volts at the + side at this point if the 5.9 don't increase you have a bad coil it it does then you have a short at the dist or wire leading to it"

Sounds like you have a bad coil, but unless you unhooked the neg side wires it's hard to tell. Get a new coil even an automotive one from Auto Zone just to check it. I would replace it with a marine one though before running it.

 

[Reel Poor]

Re: Stumped! No Spark!?

With wires connected to the coil, check voltage to +(pos) side of coil while removing -(neg) side wires one at a time. Disconnecting which wire allows voltage to return to normal? One of the -(neg) side wires goes to the point set and the other goes to the tach.

Check the wire connection on the point set, sometimes they get twisted and will ground out on the dist housing.

If the wiring is OK between -(neg) side of coil and the points connection, and the points are open voltage should read normal value at the +(pos) side of coil.

 

[country_bumpkin]

Re: Stumped! No Spark!?

With wires connected to the coil, check voltage to +(pos) side of coil while removing -(neg) side wires one at a time. Disconnecting which wire allows voltage to return to normal? One of the -(neg) side wires goes to the point set and the other goes to the tach.

Check the wire connection on the point set, sometimes they get twisted and will ground out on the dist housing.

If the wiring is OK between -(neg) side of coil and the points connection, and the points are open voltage should read normal value at the +(pos) side of coil.

Thanks RP,

Feeling much better now!

Removing the wire that you say goes to the tach lets everything go back to normal. The tach has never worked since I bought the boat.

and everthing looks good when the points are open

Should I try and fire it up now?

The tach is an problem I'll tackle after getting the engine up and running again.

 

[Reel Poor]

Re: Stumped! No Spark!?

Sure give it a try. Tachs failing are a common problem causing ignition system shut down.

 

[country_bumpkin]

Re: Stumped! No Spark!?

Sure give it a try. Tachs failing are a common problem causing ignition system shut down.

Okay RP! It worked!

Fired her up, then touched the tach wire back to the coil and she stalled, so that is were the probleme is.

Next question though: Do you think fixing the tach issue is as easy as replacing the gauge? I have no experience with this at all, but would love to get it going again, at a reasonable price.

One more question: I snapped a little plastic (sensor? monitor?) off, that was mounted just below the transom on the right side of the outdrive, last summer that controled the speedometer. Where can I get a replacement?

Thanks so much

CB

 

[country_bumpkin]

Re: Stumped! No Spark!?

Okay, a few minutes research on Google and I found I can probably get a universal "pitot" replacement.

How about the tach question?

Many thanks

 

[freddyray21]

Re: Stumped! No Spark!?

tach's are not hard to replace. Most new ones come with instructions for setting them up to work for your motor. It could also be the wiring going to the tach shorting out. At the back of the tach disconnect the wire that was coming from the coil. With a continuity meter with that wire disconnected at both ends see if it shorts to ground.

 

[country_bumpkin]

Re: Stumped! No Spark!?

tach's are not hard to replace. Most new ones come with instructions for setting them up to work for your motor. It could also be the wiring going to the tach shorting out. At the back of the tach disconnect the wire that was coming from the coil. With a continuity meter with that wire disconnected at both ends see if it shorts to ground.

Thanks, that sounds easy enough. I can absolutely do that.

CB

 

[Reel Poor]

Re: Stumped! No Spark!?

Good to hear you got her goin.

I'd recommend a Teleflex tach. It's probably a direct replacement. Be sure to read the instruction as the tach has to be set for the number of cylinders on your engine.