3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

J

jvpartin2

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Hi and thanks before hand

I have a 1988 3.7lx mercruiser twin drive and the port engine will not start.

I have no spark checking the voltage at the coil + and ground to block gives no voltage.

The purple resistance wire from the coil to the choke is getting very hot.

Does this wire need to be replace periodically? If so can it cause the no spark condition/no voltage?

Can i just disconnect the wire at the choke?

The starboard engine reads about 10 V DC with the key on
 
Reel Poor

Reel Poor

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

Disconnect the purple wire from the choke and test it again.
 
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stonyloam

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

jvpartin2 said:
Hi and thanks before hand

I have a 1988 3.7lx mercruiser twin drive and the port engine will not start.

I have no spark checking the voltage at the coil + and ground to block gives no voltage.

The purple resistance wire from the coil to the choke is getting very hot.

Does this wire need to be replace periodically? If so can it cause the no spark condition/no voltage?

Can i just disconnect the wire at the choke?

The starboard engine reads about 10 V DC with the key on
Click to expand...

With the key on you should have voltage at the coil +
If the resistance wire is getting hot, that indicates a high current draw to ground.
The wire should never need to be replaced. Only if it is not making contact.
No, then you will never get a spark, because the coil gets its voltage from that wire.
Try removing the gray wire (tach) from coil +, leave the purple, and the purple/yellow wires.
 
cr2k

cr2k

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

OK the purple wire going to the choke is NOT a resistance wire. It is key switch power to the choke. If it is getting very hot there must be a short in your choke heater coil grounding all the power from the coil. IF you have a resistance wire is is probably a brown one going to the coil. If you have a purple wire (other then to the choke) to the coil you should have an internal resister coil. I would check your wiring because I don't remember the choke wire coming from the coil.
 
Eric 3.7LX Alpha 1

Eric 3.7LX Alpha 1

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

the coil receives power from two locations.
The prpl/yel from the starter solenoid when starter is cranking the engine, and when the key is released, and is in the "run" position.

and from the Prpl resistance wire which is run to the electric choke.

The elect choke has another prpl wire attached which is switched 12v from the key.
 

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stonyloam

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

There should be two purple wires going to the connector on the choke. One comes from the ignition, the other is the resistance wire and goes to the coil +. The purple/yellow wire should go down to one of the small terminals on the starter slave solenoid bolted to the side of the engine.
 
Reel Poor

Reel Poor

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

The reason I said disconnect the choke and test it again is because I believe the choke is shorted to ground. All you have to do is unplug the purple wire from the choke and try it.
 
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stonyloam

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

Reel Poor said:
The reason I said disconnect the choke and test it again is because I believe the choke is shorted to ground. All you have to do is unplug the purple wire from the choke and try it.
Click to expand...

I see where you are coming from, but if the choke were shorted, there would be no current through the resistance wire except during starting, so it might be worth a try. Could try removing the tach wire from the coil +.
 
J

jvpartin2

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Re: 3.7lx mercruiser no spark no voltage at coil purple resistance wire gets very hot

cr2k said:
OK the purple wire going to the choke is NOT a resistance wire. It is key switch power to the choke. If it is getting very hot there must be a short in your choke heater coil grounding all the power from the coil. IF you have a resistance wire is is probably a brown one going to the coil. If you have a purple wire (other then to the choke) to the coil you should have an internal resister coil. I would check your wiring because I don't remember the choke wire coming from the coil.
Click to expand...


Thanks for the replies.

The purple resistance wire is indeed a resistance wire as stated in the wiring diagram in the mercuiser manuel.

I searched the forums and my question differs in that I have no voltage which I think the that wire is shorted at some point.

I will try removing the wire to the choke (it just plugs on) and see what result I get. I think it continues on (after the plug) to a ground. (don't quote me on that one).

I was thinking that if it were shorted across the plug somehow then the current would go straight to ground.

Thanks again for the replies
 
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