Coil Burning

[BradleyPLKD]

Hi iboat Community,

I have a Volvo Penta gas 5.7 PLKD (1996) motor with BID ignition. My last two trips, brand new coils have died on me...so I know I have a problem. In troubleshooting, when I crank, I get 9 Volts to the + side of the coil. Once the motor is running, I get 12 Volts to the + side of the coil. I'm pretty sure I SHOULD be getting 12 volts at crank.

So far I've checked the spark plugs, wires, cap, rotor, air gap...all are in good working order. I checked all ground connections and that looks good. Does anyone have other ideas on what might cause lower voltage when cranking? Or what may cause my coil to burn up? I'm thinking the two problem are related...

Thanks!

 

[gnathv]

Re: Coil Burning

Check your voltage at battery when cranking, if it is 9 volts that is all you will get at the coil. If it is higher, continue checking and cleaning connections.

 

[twiggy2cents]

Re: Coil Burning

You need to check your voltage at around 3k-3500 rpms to see if you are overcharging.

 

[BradleyPLKD]

Re: Coil Burning

Gnathv... good idea. Will do. Thx!
twiggy2cents...we rarely push that fast...normally a steady 2100rpm all day. Thanks for the reply!

 

[Don S]

Re: Coil Burning

Gnathv... good idea. Will do. Thx!
twiggy2cents...we rarely push that fast...normally a steady 2100rpm all day. Thanks for the reply!

Then check it where you normally run. That is the rpm that really matters.

 

[BradleyPLKD]

Re: Coil Burning

Gnathv...I get 11.2 volts at the battery while cranking. So that sounds normal.
twiggy2cents and Don...it looks like I will have to replace the coil before testing voltage at higher rpm. Tried to run it today and it just sputters above 1000 rpm.

 

[BradleyPLKD]

Re: Coil Burning

Okay I checked the voltage to the coil at my normal running speed (2200rpm) and get 13.5 volts. I still get only 8.5 to 9 volts when cranking. With the key in the complete off position, I get 5 volts. I assume I should get 0 volts to the coil when key is in full off position. Or is this normal?

I also removed the gray wire coming from the tach thinking maybe there was backfeed but the coil still read the same 5 volts. Any thoughts on what I should check next? Thanks guys!