OMC Cobra 3.0L starting problems

[jouniraiha]

Hi, I have OMC 3.0L 1989 and something hit to it quite suddendly. I had a successful 2-day trip and parked it normally. Next weekend I tried to go out, but the engine did not start. I started to examine the problem. First I checked the ignition. I could (and still can) get spark if I put the key to run position and open and close the points. However, when cranking, no sparks.

I looked at the forum and similar type of problem was described in post http://forums.iboats.com/showthread.php?p=1491230

I ave done all the suggested tests like detaching the tach and ESA connection, but still no luck. I measured the voltage between coil+ and ground, it was 4,8 volts. When cranking, it dropped to 0V. I guess that is the reason for not having sparks, but what could be the cause and what to fix? I tried with another coil and the behaviour is the same.

The 12V cranking feed to coil should come from the starter engine solenoid, correct? Any ideas what could be wrong in there? I tried also with direct jump wire from the battery to coil+ but still no sparks.

I am out of ideas, any help? I would appreciate a lot. Weather is getting colder and I would like to get the boat winterized fairly soon.

best regards, Jouni.

 

[Don S]

Re: OMC Cobra 3.0L starting problems

I ave done all the suggested tests like detaching the tach and ESA connection, but still no luck. I measured the voltage between coil+ and ground, it was 4,8 volts. When cranking, it dropped to 0V.

Sounds to me like you have 2 problems. since you are only getting 4.8 volts with the key on, you may have a correded connection somewhere. Check the voltage on the purple and the red purple on the alternator also, if it's ok, the splice may be bad that connects all the purple wires together (see splice next to alternator in diagram). Or maybe a bad ignition switch, kill switch, etc. Trace the voltage from the ign. (purple terminal all the way from the ignition switch to the engine and find where full power stops.
You also have a wire (purple black) that should go from the starters small outside terminal to the + side of the coil. That should give you full battery voltage to the coil while cranking only.


Wiring diagram

 

[jouniraiha]

Re: OMC Cobra 3.0L starting problems

Thanks Don, I will inspect more and do some voltage measuring. Thanks for the wiring diagram, too.

I have a new ignition switch, but the kill switch is original.

I will post here my findings later.

BR:Jouni

 

[jouniraiha]

Re: OMC Cobra 3.0L starting problems

Trace the voltage from the ign. (purple terminal all the way from the ignition switch to the engine and find where full power stops.

I checked the voltage and it was 12V at ignition switch.

Check the voltage on the purple and the red purple on the alternator also, if it's ok, the splice may be bad that connects all the purple wires together (see splice next to alternator in diagram).

The alternator end showed 11,7-11,9V.

The 4,8V was a bit misleading, since the coil+ is 12V when the points are open. When points are closed it is the 4,8V.

You also have a wire (purple black) that should go from the starters small outside terminal to the + side of the coil. That should give you full battery voltage to the coil while cranking only.

I detached the purple black from solenoid and metered the solenoid output, it was 0V while cranking.
Is my solenoid broken? The starter works otherwise ok, i.e. it is cranking when turning the key to start position.

BR:Jouni

 

[Boatin Bob]

Re: OMC Cobra 3.0L starting problems

You should have 12v on that terminal of the solenoid when it's energized but above you said you ran a wire from the battery right to the coil (this would bypass the solenoid) and it still didn't work?

 

[jouniraiha]

Re: OMC Cobra 3.0L starting problems

I will recheck tomorrow. One of my friends will come and help me. It is quite hard to jump down to machine pit and up again onto deck to turn the key.
I'll be back...

BR:Jouni

 

[Don S]

Re: OMC Cobra 3.0L starting problems

http://forums.iboats.com/showthread.php?t=183904

 

[jouniraiha]

Re: OMC Cobra 3.0L starting problems

Hi, I couldn't help myself and I went to the boat still today, too.

I started all over again, detached all the wires from coil and also purple-black from the solenoid. Then I jump wired 12V from battery to coil+ and connected black from points to coil-, cranked and got sparks.

Then I added ESA and tach to coil-, coil+ still directly from battery, cranked and got sparks.

Added purple-red (from splice) to coil+, cranked and got sparks.

Connected purple-black to solenoid, cranked and no sparks. Disconnected the purple-black from solenoid and again got sparks.

I was getting confident that the engine could even start with the jump wired coil+ and therefore put distributor cap back and connected spark plug wires. After some starting the engine promised few times and then actually started!!

I measured all the time the voltage between coil+ and battery minus, while starting it was just below 12, but when engine running near 14 (13,7 to be exact).
I disconnected the battery end from jump wire and noticed that the voltage between coil+ and battery minus dropped to 10,6V, however, the engine ran still.

I was getting high hopes, stopped engine, took all the tools and extra wires away from engine department. Then I thought why not connect the purple-black to solenoid and try "the normal" setup. Maybe all the disconnecting and connecting the wires cleared possible corrose etc.
That was a mistake. First starting resulted the starter to jam; it did not revolve the engine anymore. I disconnected the purple-black from solenoid again, but still the same.

Could it be that the starter engine along with the solenoid is broken? I had to use the starter to cranking quite a lot in these past days. On the other hand, I managed to start the engine today once, so any hints?

I will continue tomorrow, anyway.

BR:Jouni

 

[jouniraiha]

Re: OMC Cobra 3.0L starting problems

Hi all,

it is fixed!!

The fix was new starter engine. Now it really starts easily. I guess the old one was weared and somewhere inside was shortcirquit or breakage (because no 12V thru purple-black).

Anyway, now everything is OK and next weekend (if it is not snowing) I will ride the boat to winter yard.

Thank you all for valuable hints and support.

Best regards, Jouni