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1987 OMC 4.3L starting and ignition system issue

RicardoMarine

RicardoMarine

Gold Medal Contributor
I started this thread for new member Garit instead of using the PM system.
PMs are great for private communication, but do not serve as well for questions like his.

Garit said:
We have an 1987 omc 4.3 that is refusing to start. At first we replaced the points with an eletronic ignition and a new coil the boat would run fine with it newly installed. But until recently the engine would start up then immediately die a few seconds later. I thought I wasn’t getting enough gas but the filters were clean and it was getting plenty of gas(fuel pump is brand new with rebuilt carburetor. After stumped on that problem we tried the next day and the thing wouldn’t start(didn’t touch anything) but yet had gas and spark. But I noticed the spark wasn’t blue anymore I thought it was in the coil because of the yellow spark it had. It seems only if you give it 12 volts on the positive side of the coil with a wire connected to the battery it will start(with a nice blue spark). But after the engine stalls like before. The engine won’t start without that wire and switching back to points didn’t work either same problem. Any clue on how to fix this problem any ideas help.​
Click to expand...


First..... a good hot proper voltage spark will be whitish/blue at the spark plug gap. Yellowish indicates a weak spark! ​
Secondly.....I don't care for the Pertronix conversion kits (if that is what you installed).

Have you tested the voltage at the coil while operating the starter motor and while NOT operating the starter motor?

I am not familiar as to how the OMC gives the ignition coil resisted voltage.
Hopefully the OMC guys will chime in.​





 
Sorry about not posting it public but thanks for doing it for me. I have noticed that there is a weak yellowing spark so I jumped a wire from the (+) of the coil to the (+) of the battery and now it gets great blue spark and starts up(but will still stall out). We have also tested the voltage at the coil with and without the starter motor operating and the voltage stays the same either way. I did have the pertronix kit in but have went back to points and this pertronix kit may be the reason it is stalling because I heard they can burn out the ESA.
 
Garit, you will need to determine if your ignition circuit offers resisted or non-resisted voltage, and then use an appropriate ignition coil.
If resisted via a ballast resistor, see what the voltage is without any starter motor engagement.
If no voltage is present, it may indicate that the ballast resistor is faulty or has become disconnected.

Perhaps look and see if your system includes a "start-bi-pass" circuit. This circuit bi-passes the ballast resistor and provides full coil voltage during starter motor operation.

ignition start-bi-pass.jpg

Since you re-installed the contact points (kettering system), be sure to adjust them using a dwell angle meter...... not by gap alone.
Points also require a good healthy capacitor.


The ESA (electronic shift assist) is there to stumble the ignition system during a Dog Clutch shift "from" gear back "into" neutral.
If you are testing while in neutral, the ESA should be passive (non-active)!
None-the-less, you may want to disconnect it during your testing.

DO NOT water test the boat without the ESA connected and working!


.
 
It currently has a purple resistor wire that goes from the coil to a splice then all the way to the alternator without a ballast resistor. It has always been that way with the points installed and it still ran fine. Even when we went to the pertronix kit it stayed the same because it requires a new coil that is is internally resisted.
When I went back to points we put in the old coil and set the dwell perfect on the points and the capacitor on it is brand new.
Next was to test to see voltage is present at the coil, there is but it is not very strong.
So maybe the problem could maybe be a problem in the ignition switch which would also cause the stalling issue.
Will test the purple resistor wire, ignition switch, and try it without esa plugged in hopefully one of these is the problem thanks for the help!
 
One quick thing as well I don’t know if there is actually a resistor within the splice that looks like fusable link or something I wouldn’t know how to check.
 
I have a 1987 how old is the cobra 4.3 you can hit the starter and it’ll start up long as you’re holding the starter switch.
 
Ayuh,.... Sounds like a bad key switch,.......

The ignition circuit is powered by the start circuit, while starting, ..then switches to the ignition circuit, in the "Run" position,....
 
It’s pretty easy to pull out the ignition switch on most boats. You should have battery voltage on the B+ terminal (red wire), and when the key is turned to the 1st notch (ignition on) you should have battery voltage at the I terminal (purple wire), when you turn the key to start you should have battery voltage at the S terminal (yellow/red wire).
Now down at the starter you should have battery voltage at the big terminal connected to the starter solenoid (battery cable or battery switch connection). When you turn the key to start you should also see battery voltage at the yellow/red terminal on the solenoid. OMC used an assist solenoid that is bolted to the shift bellcrank bracket along with the trim relays. On an 87 these are like the old style large starter relays; there are 3 identical ones 2 for tilt n trim one for the starter circuit.
One year I had a no crank no start issue although the tilt n trim still worked. All it was turned out to be an oxidized fuse/fuse box terminals. On some of these older boats it can be time to upgrade those old fuse boxes. One of my next projects.
 
I have a 1988 stingray extremely clean low hrs. 4 3 V6 w/omc set up seems to start when you let off the key I installed new points, & condenser when I check the voltage at the positive side of the coil it's 4.75 volts when I disconnect the negative side going to the distributor the voltage goes up I was considering changing the coil and ign switch any info be great thk
 
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