Intermittent spark to coil

"Have had several problems try

"Have had several problems trying to find the problem with our 4.3l mercruiser stern drive. Wouldn’t fire - changed the distributor cap, ignition sensor, rotor & plugs & coil. Now only gets intermittent spark to coil. Did fire but died shortly, and then no spark again???"

"Debbi;
I am not sure you hav

"Debbi;
I am not sure you have the interrupt switch issue satisfied yet. I did not see where you had tried to isolate it.

A simple test is to disconnect the interrupt switch at any convenient connector in either wire going to it. Then try to start the engine.

If it runs, the switch or its wiring is your problem.
If not, then its something else.

Rod"

"We disconnected the green wir

"We disconnected the green wire that goes to the interupter switch and no spark at the coil, still.

I am all ears! "

"1) At the coil you will s

"1) At the coil you will see a harness going to the module and a harness going to the engine wiring.On the engine wiring one, disconnect the Grey wire from the coil(this is for the tach)
Try to start
2) hot wire from the + battery to the + side of the coil(purple wire)
Let us know the results"

"Thanks BT Doctur, I am going

"Thanks BT Doctur, I am going out to do that right now, will be back in a few minutes with the results"

"ok, removed grey wire from en

"ok, removed grey wire from engine side of harness, still no spark from coil. Put jumper on from battery to pos. side and it an alarm off and still have no spark from coil."

"Thank you so much, I can'

"Thank you so much, I can't express enough how much we appreciate your help.

My husband is on his way home to help me try again, but he asked me to ask you one question before we start working again.. Could it be a loose wire in the shift control box - where you actually shift the throttle? Reason why is, the boat was working fine all last summer and into the fall. Then I complained because the throttle was gettting hard to shift. I asked him to replace the cables or whatever needed to be replaced. He removed the shift or throttle assembly from the side of the boat and greased them, and also greased the cables at the motor, and said it was corrected. Could he have done something or bumped something that would cause this to happen?"

"Debbi;

If is is equipped w

"Debbi;

If is is equipped with a kill switch at the throttle quadrant; that would be a prime suspect. The kill switch is in series in the ignition circuit, and if the wiring or switch is open circuit, there will be no spark.

Rod"

"Also, on the other end of the

"Also, on the other end of the throttle cable is the shift interupt switch. That could be grossly misaligned, loose or corroded wires, shorting out the ignition system."

Troy;
They have tried disconn

Troy;
They have tried disconnecting the interrupt switch; no joy.

Rod

Debbi
Can you further explain

Debbi
Can you further explain intermittent spark to the coil. And no spark at the coil please. What type of testing are you doing to arrive at these conclusions.
Thanks
Bert

"*****&#42

"******** FINAL REPORT *******

MANY THANKS FOR ALL THE ADVICE FROM EVERYONE!!!!
As it turns out, it was a long lesson, but relatively inexpensive one to learn. Although many of you may get a chuckle out of the simplicity of it, only one of you came up this advise. The winner and who now has my loyal following is Ed @ sterndrives.com . His advise was as follows:
“A word of caution. Damage, injury or death can result if extreme caution is not taken. Always stay clear of any potentially moving parts. Gas fumes can ignite and cause a fire and/or explosion so make sure you have no gasoline fumes in the boat. Exhaust can kill you. Make sure you have adequate ventilation. Safety comes first.
Here is another trick we use to rule out the possibility of a bad dash harness or tach or lanyard... we simply unplug the main harness from the engine. Then we hook up a jumper lead from the battery positive to the positive pole on the coil (purple wires). This gives you a sure positive source to the ignition.
This next step will cause the engine to crank and possibly start so stay clear of the belts and pulleys.THE COIL JUMPER LEAD will HAve to be removed to turn off the engine if it starts.
Make sure you have water hooked up to a flushett to the drive in case it starts.
We use a jumper wire to jump a positive to the starter solenoid terminal (small yellow with red stripe) to get the engine cranking.
Hopefully one of these items will reveal the problem.
It's almost never the module itself.”"

"[b]"He removed the shift

""He removed the shift or throttle assembly from the side of the boat and greased them, and also greased the cables at the motor, and said it was corrected. Could he have done something or bumped something that would cause this to happen?"

Ayuh,......

I'm Bettin' your Problems Aren't over just Yet.......

The Cables Aren't Greaseable, nor really serviceable in any way,......
Except,....
Replacing them........

I'd say Most of your problems stem from a Bad Lower Shift Cable........"