1992 OMC Cobra with no spark

[MikDee]

Re: 1992 OMC Cobra with no spark

Button it up for now, crank it over, and check to see if you have spark from all the plug wires, ground them & look. Apparently you have spark from the coil, now you hafta see if you have spark at the plugs? We need to know whats going on? If so, and it doesn't attempt to fire, then the spark is not getting to the right cylinders, at the right time. This means your distributor is out of time.

If not, then your distributor cap, or coil is bad.

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

Button it up for now, crank it over, and check to see if you have spark from all the plug wires, ground them & look.

How is he supposed to see a spark if you ground the spark plug wires?

 

[MikDee]

Re: 1992 OMC Cobra with no spark

How is he supposed to see a spark if you ground the spark plug wires?

What is he supposed to hold them! :lol: Put a spark plug on them then,,, How would you check for spark at all the cylinders then?

We know hes got spark at the coil, but why is it not getting to the cylinders? Maybe just the coil to distributor wire is defective? But, if this were the case I would think the spark would be arcing to something, maybe not?

Or, maybe he has no spark only at #1 on TDC because his Dist. is out of time?

 

[MikDee]

Re: 1992 OMC Cobra with no spark

could very easily be the cap, the center electrode might be worn down enough to where is is not touching the rotor.

Ditto!

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

What is he supposed to hold them!

Putting a spark plug on them and grounding the frame of the plug is not the same as grounding the wire which is what you stated.

 

[MikDee]

Re: 1992 OMC Cobra with no spark

Is your distributor wire attached to the neg post on the coil, that is for a negative ground system, which Chevy's usually are.

 

[MohaveChuck]

Re: 1992 OMC Cobra with no spark

Yes, two wires connected to the negative post. A wire from the ignition module and one I assume is a ground wire as it goes into a wire harness and cannot see where it is grounded. I have also put a separate ground wire to it straight from the battery.

Bruce, thanks for the input on the coil. That makes sense.

Pretty sure the center post in the distributor is making contact because when I bend the contact on the rotor it is pushed back down when I remove the cap.

When I check the plugs for spark I do insert a spark plug (tried at least two different to make sure its not a bad plug) and ground the plug threads to the motor as I crank it.

Even if the distributor was put in 180 degree off, since I don't know the history wouldn't i still get a spark to the plugs?. Just not at the right time.

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

I have also put a separate ground wire to it straight from the battery.

Definitely won't work if you do that.

 

[MikDee]

Re: 1992 OMC Cobra with no spark

Yes, two wires connected to the negative post. A wire from the ignition module and one I assume is a ground wire as it goes into a wire harness and cannot see where it is grounded. I have also put a separate ground wire to it straight from the battery.

Bruce, thanks for the input on the coil. That makes sense.

Pretty sure the center post in the distributor is making contact because when I bend the contact on the rotor it is pushed back down when I remove the cap.

When I check the plugs for spark I do insert a spark plug (tried at least two different to make sure its not a bad plug) and ground the plug threads to the motor as I crank it.

Even if the distributor was put in 180 degree off, since I don't know the history wouldn't i still get a spark to the plugs?. Just not at the right time.

Okay, here's your problem, in a Negative ground system, there should be only one wire coming from the Distributor to the Neg - on the coil! That is the power wire for the Distributor! Whatever the other wire there is don't matter, its probably the Tach wire? Take it off for now, and do not ground anything to that terminal! On the other side of the coil Positive + should be your key switch (ignition) wire only.

This way, you have power to the coil, which then sends it to your points/electronic ignition. It won't have spark any other way!

 

[MikDee]

Re: 1992 OMC Cobra with no spark

Here is a diagram of basic coil wiring:

http://ts1.mm.bing.net/th?id=HN.607992396521013700&w=80&h=80&c=8&pid=3.1&qlt=90&rm=2

Right now how you have it wired, you are grounding out your ignition!

One more diagram, so you get the idea, I'm sure an OMC manual would have a diagram in it like this:

http://www.bracketracer.com/howto/ignitionWiringHEI.jpg

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

Mojave, there will likely be 3 wires on the negative post including the ESA.

 

[MikDee]

Re: 1992 OMC Cobra with no spark

You should have spark now Mojave?

 

[MohaveChuck]

Re: 1992 OMC Cobra with no spark

I'll have to take a photo and post but what I have is four wires to the coil. Two on each side. This is the way I got the boat.

A black ignition wire sending 12+ volts and a black wire from the ignition module in the distributor to the positive side.
A wire, that I assume is the ground and a purple wire from the ignition module connected to the negative post. The assumed ground wire is also black and goes into a wire harness with a bunch of wires.

I found a basic test of a ignition module in which you pull the distributor out of the block and ground it, leave everything connected except for the coil and plug wires. Leave the coil wire connected to the coil and put a spark plug testing light on the end of the wire. Turn the key on to get 12 volts to the coil then spin the distributor by hand and see if the ignition module is telling the coil to spark.
It was but the flashes were so faint you could barely see it in the daylight but it was lighting.

I then took the spark plug light and tested both of my coils the original one and the look alike one I just picked up at Checker Auto. I just hooked the positive to the battery and touched the negative with the test wire to the battery ground and it lit up the light exactly the same, very faint. I did not use the coil wire the spark plug test light fit right into the coil and was getting a good connection.

So I think my ignition module is OK and maybe getting a current to the spark plugs just not enough to see or spark.

So I could try taking off that black "negative" from the negative post and just leave the purple wire from the module. See what that does.

But why don't the coils light up that spark plug light? I don't really have another engine to test it on to see how bright it is supposed to be but surely its supposed to be brighter.
Could both the old coil and the new coil be bad? Doesn't seem reasonable. I am trying to get another multitester to test the resistance since I don't trust my cheap one.

Thanks again in advance

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

Did you ever disconnect your ESA?

 

[MohaveChuck]

Re: 1992 OMC Cobra with no spark

Yes I did and you know what I did the module test with the ESA disconnected, I should try it connected also.
Do you think that black wire on the negative coil post goes to the ESA?
But still doesn't make sense that both coils are putting out the same weak voltage.

 

[bruceb58]

Re: 1992 OMC Cobra with no spark

You need to track it down yourself. Unless you have a 1992 wiring diagram, you won't know for sure if the ESA goes to the distributor negative or to the module directly.

Just so you understand how the module works, it is basically an electronic version of points. It does not supply the current/voltage to the spark plugs directly. Its purpose in life is to allow current to flow through the coil to build up a magnetic field and then stop that current flow. When that current flow stops, the magnetic field in the coil collapses and high voltage is released out the secondary of the coil.

You are basically doing the same thing when you connect a wire from the negative side of the coil to ground and then remove it. Its the removing of the wire that makes the spark occur. When you run this test, you need to take all the wires off the negative side of the coil except for your test lead.

 

[Idlespeedonly]

Re: 1992 OMC Cobra with no spark

You say you have out of the coil. How big is the gap that the spark is jumping. Also if you havent already, check the voltage on the + terminal of the coil while cranking. Make sure it doesnt drop.

The other coil you tried, where did you get it from?

The next thing you need to do is get some pictures on here. Pictures of the coil wiring, distributor, distributor cap and rotor.

We are missing something simple here. The ignition system is probably the simplest thing on a boat.

 

[MohaveChuck]

Re: 1992 OMC Cobra with no spark

I know its got to be something simple.

I'll get some pics up as soon as I can.

While cranking the voltage just drops maybe one or two volts at the most.

The other coil is just a basic coil we got from Checker Auto that just looks like the stock coil.

Bruce,
When I test the coil itself I have it removed and the only wire to it is a jumper from the battery and just touch the ground jumper to it to get it to go off.
I'll cut open that wiring wrap and trace that other negative side wire and see if it goes back to the shift assist module. It must, how else would the shift assist module control the engine to allow the shift at a lower rpm? Remember ignition module is in the distributor and only has two wires coming out a black one to the positive and a purple to the negative. So the shift module could not be directly connected to it.


Shift assist module has 4 wires going into from parts diagram pic. Know what they are?

 

[MohaveChuck]

Re: 1992 OMC Cobra with no spark

Here is the diagram of my ignition system from a ********** part search.

 

[Bondo]

Re: 1992 OMC Cobra with no spark

I know its got to be something simple.

I'll get some pics up as soon as I can.

While cranking the voltage just drops maybe one or two volts at the most.

The other coil is just a basic coil we got from Checker Auto that just looks like the stock coil.

Bruce,
When I test the coil itself I have it removed and the only wire to it is a jumper from the battery and just touch the ground jumper to it to get it to go off.
I'll cut open that wiring wrap and trace that other negative side wire and see if it goes back to the shift assist module. It must, how else would the shift assist module control the engine to allow the shift at a lower rpm? Remember ignition module is in the distributor and only has two wires coming out a black one to the positive and a purple to the negative. So the shift module could not be directly connected to it.
View attachment 225992

Shift assist module has 4 wires going into from parts diagram pic. Know what they are?

Ayuh,.... That's Backwards,...

Black is Ground,...

Purple is Ignition, keyed power,...