What can be causing coil to fail?

[rwaterbury]

I've got a Chaparral with a Volvo Penta 5.7GS. In the last two months I've replaced the coil cause I get no spark out of the coil. Each time the engine immediately starts and works for about a month ( 2-4 trips for a total of ~6 hours of use). When the first coil failed I just assumed I got a bad coil (not that I've ever heard of that) however this second failure tells me something else is causing them to fail.

The symptons are that I get no spark out of the coil (as determined by holding the wire real close to engine ground and looking for a spark) and there is 12V at the coil. Both bad coils seem to measure OK (no shorts between terminals and case). What can cause a coil to fail?

THanks in advance

Rob

 

[Wet Wonder]

Re: What can be causing coil to fail?

I was advised by a boat mechanic this season that a coil placed on the motor can fail from the engine heat. Based on his advice, I moved my coil to the bulkhead. If you're coil is mounted on the motor you should try moving it.

 

[JustJason]

Re: What can be causing coil to fail?

Bad or old cap rotor plugs and plug wires will kill a coil quickly. Plugs that are grossley over gapped will do the same thing.

 

[jtybt]

Re: What can be causing coil to fail?

...or you may have the wrong coil for the application.

 

[gadget73]

Re: What can be causing coil to fail?

If you have an ohm meter, see which side of the coil is dead. Do you get a few ohms resistance terminal to terminal? What about - to coil tower? If its open on the primary side (terminal to terminal) I'd guess wrong coil. If its open on the secondary side (tower to -), then you're probably over-working the coil, maybe from bad wires, bad plugs, etc.

For what its worth, I've got original coils on both my 1993 engines, and they are both mounted to the back of the heads. I'm somehow doubting the mounting location is to blame for such short life, unless you have just a horribly hot engine compartment, but thats another issue in and of itself.

 

[proxyx]

Re: What can be causing coil to fail?

bad wires running close to engine block may overwork the coil, you may have a coil over-voltage issue (battery voltage applied directly to the coil) or poor grounding, do you have a original resistor wire in place (not familiar with Volvo) if so equipped? were replacement coils OEM or substitutes? check coil temp after a short trip, is it overheating? how quickly? check voltage supply wire hookup... compare to schematics

 

[bruceb58]

Re: What can be causing coil to fail?

As JustJason said, its going to be bad wires or overgapped plugs or something that does not allow the charge from the coil to reach ground. Replace the cap, rotor, spark plug wires and plugs.

 

[musella]

Re: What can be causing coil to fail?

I went through a few coils before I found the cause.. in my case, it turned out to be a small water leak through the engine box. Too small to cause problems usually - except after bad storms, then enough rain water got directly onto the coil and wires to cause problems.
So check the engine - is there any moisture? I actually had standing water on top of the engine at times.
I fixed the hole and the engine has been bone dry even after a few recent storms.

 

[proxyx]

Re: What can be causing coil to fail?

so... your coils were partially or fully grounded/shorted, hopefully your wires are still in decent shape, "leaking" (after being wet) wires close to the block... and you may be back to square one, anyway good it was a cheap fix

 

[bruceb58]

Re: What can be causing coil to fail?

so... your coils were partially or fully grounded/shorted, hopefully your wires are still in decent shape, "leaking" (after being wet) wires close to the block... and you may be back to square one, anyway good it was a cheap fix

Musella is not the original poster.

 

[proxyx]

Re: What can be causing coil to fail?

easy to get confused here... think I'm getting older by the day

 

[bruceb58]

Re: What can be causing coil to fail?

easy to get confused here... think I'm getting older by the day

he made it sound like he was the OP.

 

[proxyx]

Re: What can be causing coil to fail?

he made it sound like he was the OP.

No doubt he did. Maybe a brother... ? haha.