ESA module, how does it exactly work ?

We are talking OMC Cobra dog clutch.

I know that the ESA module causes the engine to stumble, when the shift interrupt switch is activated, but exactly how does it do that?

I'm asking, since a friend of mine has a 1988 Bayliner with 2 x 5.0 GM engines, where he has replaced the distributors with new Delco electronic ones. According to the installation instructions, the ESA module should be ditched and the interrupt switch should be connected so it kills the engine completely. It is however quite difficult to adjust the system, so the engine doesn't die now and then, when shifting. So he would like to have the ESA module installed again.

If we knew EXACTLY how it causes the engine to stumble, I believe we could make it work with the electronic distributor, somehow.

Re: ESA module, how does it exactly work ?

The interuptor probably just needs to be adjusted properly, but here is what I found on the ESA

http://forums.iboats.com/omc-i-o-in...ow-how-test-esa-switch-esa-module-479987.html
http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/omc-esa-module-51467.html
http://forums.iboats.com/mercruiser...mc-esa-roller-switch-cam-question-392594.html

Re: ESA module, how does it exactly work ?

An outfit, CDI electronics had a module that was supposed to be the cat's meow, to make ESA's work with electronic ignitions. Here is the link but it no longer works for me. Maybe they went out of business?

CDI Electronics | Outboard Motor Parts | Ignitions | Marine Engine Diagnostic System | Stators | Ignition Packs | Regulators | Coils | Wiring Harnesses

Let me know if it works for you. I get this message.

Forbidden

You don't have permission to access / on this server.

There are other vendors that deal in their products, like E-basic Power. So you could call them to find out about the CDI module and if they are still in business.

Re: ESA module, how does it exactly work ?

Apparently they have a new website:

CDI Electronics Launches New Website

Re: ESA module, how does it exactly work ?

Boomyal said:

Apparently they have a new website:

CDI Electronics Launches New Website

Click to expand...

Both links works here.

looks like CDI has an ESA module that could work with the Delco distributor, might be the easy way to install ESA again.

I was thinking about something else. From my memory, the esa module is originally connected to the negative side of the coil. This probably means that the ESA module grounds the coil now and then, so it doesn't fire as often as it normally would. Probably not at a high frequenzy. If it grounds at a high frequenzy (eg 50 hz) I believe that the engine wouldn't stumble much.

Again, as I remember, the signal from the shift interrupt switch is going directly to the distributor as it is now, with the Delco distributor.

So if we installed an ordinary relay on this wire/connection, which is controlled by the old esa module, shouldn't we have a system that works?

If the ESA module is just creating a ground, at a frequenzy not too fast for the relay to follow, I think it should be possible to make it work. Might be worth trying at least.

Re: ESA module, how does it exactly work ?

My understanding is the GM interuptor grounds out the coil for just the split second to allow shifting which unloads the gears, shift is made and the ground is released. The ESA does the same thing but at a fast pulsing frequency. Putting in a relay is only going to put another switch in line and thereby increasing complexitty. Then the question will be, does the relay installed have the ability to make rapid make/break connections at the same speed as the ESA? I would not use a regular relay if you go down this path, I would recommend using a solid state relay

Good luck

Re: ESA module, how does it exactly work ?

Contact CDI. They had a schematic on how to connect their ESA to a Delco Voyager distributor at one time.

The Delco Voyager distributor needs 12V to interrupt it...not ground.

edit: Found the schematic
http://www.marineengine.com/parts/technical_information/cdi_123-7566.pdf
I would still confirm with CDI on what they reccomend.

Re: ESA module, how does it exactly work ?

Looks promising with that CDI module, I'll pass that on to my friend.

Wednseday evening, we did a little experiment on his engines. We operated the interrups switch by hand, and found out that if the switch is activated 3 times per second, the engine stumbles almost like it would, with the old ESA module. With that knowledge it should be possible to build a home made ESA.

Depending on how much money my friend is willing to spend, I think he will take the CDI module.

Re: ESA module, how does it exactly work ?

HorizonblueDK said:

We are talking OMC Cobra dog clutch.

I know that the ESA module causes the engine to stumble, when the shift interrupt switch is activated, but exactly how does it do that?

Click to expand...

The ESA is wired in parallel with the points, both on the negative (-) terminal of the coil. The other coil terminal (+) gets +12V. Either the points or the ESA can "ground" the (-) terminal of the coil, creating an electromagnet inside the coil.

Ignoring the ESA for a moment, the coil kicks a spark when the points *open*, and that magnetic field in the coil collapses. (The cycle repeats when the points close again, setting up a new magnetic field in the coil, ready to kick another spark when the points open again.)

The ESA interferes with this by grounding the (-) coil terminal and holding it there when the points open; the coil thinks the points are still closed, so no spark.

The ESA counts spark pulses, and interferes with only some of the sparks. I don't know what pattern OMC chose, but it's probably something like "count two sparks, interfere with the third, repeat". Every third spark will be prevented, and 3 won't divide into 8 evenly, so the bad sparks work their way around the engine, and all the cylinders are treated equally. Of course, you'd want a different pattern on a six-cylinder engine...

HorizonblueDK said:

If we knew EXACTLY how it causes the engine to stumble, I believe we could make it work with the electronic distributor, somehow.

Click to expand...

You could re-create the ESA, but there's an easier way.

The incompatibility between the ESA and electronic ignition is: the ESA senses when the points close, and counts those pulses. However, electronic ignitions can't drag the (-) terminal all the way to 0 volts; semiconductors always have a voltage drop of their own, typically about 0.7 volts. When your electronic ignition "grounds" the (-) terminal of the coil, it drags the (-) terminal down to +0.7V, and the coil is O.K. with that, but the ESA isn't. (I suspect the folks that designed the ESA never anticipated customers replacing their points with electronic ignition; I'll bet the ESA could have been designed to work with points AND electronic ignitions.)

Pertronix figured all this out years ago, and developed a kludge circuit to work around the problem. The kludge circuit lets the ESA see 0V (real ground) when a Pertronix gadget really only gets to 0.7V (.7V above ground). I suspect the Pertronix circuit (it's two resistors and two diodes) would work with other electronic ignition setups. Here's a link:

http://www.hastings.org/~stuart/cobra/diodefix.jpg

Best of luck,

stuart hastings

Re: ESA module, how does it exactly work ?

gawbl said:

The ESA is wired in parallel with the points, both on the negative (-) terminal of the coil. The other coil terminal (+) gets +12V. Either the points or the ESA can "ground" the (-) terminal of the coil, creating an electromagnet inside the coil.

Ignoring the ESA for a moment, the coil kicks a spark when the points *open*, and that magnetic field in the coil collapses. (The cycle repeats when the points close again, setting up a new magnetic field in the coil, ready to kick another spark when the points open again.)

The ESA interferes with this by grounding the (-) coil terminal and holding it there when the points open; the coil thinks the points are still closed, so no spark.

The ESA counts spark pulses, and interferes with only some of the sparks. I don't know what pattern OMC chose, but it's probably something like "count two sparks, interfere with the third, repeat". Every third spark will be prevented, and 3 won't divide into 8 evenly, so the bad sparks work their way around the engine, and all the cylinders are treated equally. Of course, you'd want a different pattern on a six-cylinder engine...



You could re-create the ESA, but there's an easier way.

The incompatibility between the ESA and electronic ignition is: the ESA senses when the points close, and counts those pulses. However, electronic ignitions can't drag the (-) terminal all the way to 0 volts; semiconductors always have a voltage drop of their own, typically about 0.7 volts. When your electronic ignition "grounds" the (-) terminal of the coil, it drags the (-) terminal down to +0.7V, and the coil is O.K. with that, but the ESA isn't. (I suspect the folks that designed the ESA never anticipated customers replacing their points with electronic ignition; I'll bet the ESA could have been designed to work with points AND electronic ignitions.)

Pertronix figured all this out years ago, and developed a kludge circuit to work around the problem. The kludge circuit lets the ESA see 0V (real ground) when a Pertronix gadget really only gets to 0.7V (.7V above ground). I suspect the Pertronix circuit (it's two resistors and two diodes) would work with other electronic ignition setups. Here's a link:

http://www.hastings.org/~stuart/cobra/diodefix.jpg

Best of luck,

stuart hastings

Click to expand...

Thanks for this explanation, Stuart and welcome to the board. You have a good informative website regarding OMC Cobra.