Conflicting Info on Coil

BradleyPLKD

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Jan 16, 2012
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Hi Everyone,

Have spent many hours reading all the great advice on this board and have solved many problems just by visiting. My problem now...

I have a Volvo Penta 5.7L GL PLKD model (1996) with Prestolite BID ignition. My boat was struck by lightning so blew out all electrical. Have fixed 99% of it...new alternator, new distributor assembly, new coil, new gauges... and now doing sea trials to make sure all is good. Boat fires right up and runs like a champ, but after 2 or 3 hours of running at trolling speed it sputters and dies. It usually restarts after a few tries, but after that I have to putter back to the harbor as the boat misfires and barely runs. An hour later, it runs like everything is fine again. From what I've read here, it sounds like it is the coil overheating.

I ordered a new coil from volvo, part number 3852217. Printed on the outside of the coil it says "use with external resistor." The old coil says this as well. However, according to the Volvo Ignition Manual, it says "The ignition coil used with this system has a low resistance primary winding. A low resistance primary winding achieves high output for starting. A resistor wire is not used as primary current is regulated in the electronics."

Shall I disregard the words on the coil and go with what the manual says? Thanks!
 

Maclin

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May 27, 2007
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6,761
Re: Conflicting Info on Coil

This is not specific to your boat, but the symtpoms you mention show up also when an externally ballasted coil is wired backwards. It will start and run, but spark power fades fast until you have to let it sit and cool for a spell.

I think an externally ballasted coil is less likely to overheat when the ballast is actually there and has not been bypassed somehow. I would double check all wiring and components to be sure the system is intact and wired correctly (including corrrect gauge of wires involved) as per the wiring diagram for that model.

That descripition from the manual you are reading usually pertains to a coil that is wired into an electronic control module of some kind. If your coil + is wired directly to ignition (thru a ballast of some kind) then it is not controlled by the electronics except for when to fire, not how much voltage to hit the coil with.
 

Don S

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Re: Conflicting Info on Coil

Your BID ignition never had a resistor wire or a ballast resistor in the system, nor is one needed. That particular coil can also be used with a points ignition system, in which case would need a resistor wire or ballast resistor to keep the points from burning up.
You have a problem, but it's not from being the wrong coil or needing a resistor of some kind.
 

jeffnick

Senior Chief Petty Officer
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May 24, 2004
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Re: Conflicting Info on Coil

If the key is in the running position and you have 12 volts to a coil that says "use a ballast resistor" you need a ballast resistor to keep the coil from pulling too many amps. My boat has a wire from the starter that goes directly to the coil while cranking, bypassing the resistor so the coil is fed max voltage while cranking. When I replaced the points with a breakerless module I also installed a new coil (Flamethrower) that specified removal of the ballast resistor. I no longer use the wire from the starter to the coil.
 

Don S

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Re: Conflicting Info on Coil

If the key is in the running position and you have 12 volts to a coil that says "use a ballast resistor" you need a ballast resistor to keep the coil from pulling too many amps.

Bull Hockey, read my post just above yours.

That wire from the starter to the coil feeds full voltage to the coil all right, because as those long runs of wiring on boats tends to corrode, there is less and less voltage for the coil. That wire is just to make sure it has the best possible voltage for starting.
 

RogersJetboat454

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2,964
Re: Conflicting Info on Coil

If the key is in the running position and you have 12 volts to a coil that says "use a ballast resistor" you need a ballast resistor to keep the coil from pulling too many amps. My boat has a wire from the starter that goes directly to the coil while cranking, bypassing the resistor so the coil is fed max voltage while cranking. When I replaced the points with a breakerless module I also installed a new coil (Flamethrower) that specified removal of the ballast resistor. I no longer use the wire from the starter to the coil.

His ignition system never had points and does not require a ballast resistor since it is electronically controlled.
 

BradleyPLKD

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Jan 16, 2012
Messages
27
Re: Conflicting Info on Coil

Thank you everyone for your replies. Looks like I have the right coil and the right setup, so my problem is somewhere else. Is there anything else that would be on your checklist to cause the following:

? Starts right up and runs strong for 2-3 hours before sputtering, after that it sputters all the way into the harbor
?Left to sit for a little while it, will start right up again
?Thought it was rubbish in the float needle valve or bad float but checked and all clear
? Fuel system is solid with good lines, fresh fuel, fresh fuel/water separator filter

I'm thinking there is a short somewhere in the ignition system that comes and goes? Anything else I should check?

Thanks!
 

Don S

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Re: Conflicting Info on Coil

I'm not saying that you don't have a bad coil, but you do have the correct one installed. Even though new, It could even be a bad module in the distributor, or even a bad connection somewhere in the system. After being struck by lighting, I would suspect everything made out of metal. Which includes all wiring, switches, etc. Your engine does have an electric fuel pump, and diodes in the engine harness that controls the fuel pump relay.
 

bruceb58

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Re: Conflicting Info on Coil

If the key is in the running position and you have 12 volts to a coil that says "use a ballast resistor" you need a ballast resistor to keep the coil from pulling too many amps.
I now the OP doesn't have a points ignition but this needs to be cleared up. Even if he had a points system this would only be true if the points were closed. With the points open, you would measure 12V no matter if a ballast resistor was in there or not.
 

BradleyPLKD

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Jan 16, 2012
Messages
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Re: Conflicting Info on Coil

Thanks Don, fuel pump is old style mechanical. I'll check all the wiring again for a bad connection somewhere.

Bruceb58...what does "OP" stand for in your post?

Thanks!
 

Don S

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Re: Conflicting Info on Coil

OP stands for "Original Poster" in this case, you.

fuel pump is old style mechanical.

Yeah, the GS had the electric fuel pump, the GL was mechanical. I should have looked it up first. A couple years later the GL was also electric.

Might want to check your fuel system before the pump while you are checking. Like this http://forums.iboats.com/showthread.php?t=283269
 

BradleyPLKD

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Jan 16, 2012
Messages
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Re: Conflicting Info on Coil

Just to update everyone...I think I may have found the problem. I was checking everything connected to the coil and looks like my tach has an occasional short. This makes sense since after the lightning strike, I had to replace some of the other gauges...but up to now tach and fuel gauge were working normally. I found another post about shorted tachs killing engines by grounding the coil so that got me looking in this direction. I have a new tach on order...hopefully that will do it and I can trust my boat on the water again. Nothing worse than going fishing and wondering if your boat will bring you home!
 

Maclin

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May 27, 2007
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Re: Conflicting Info on Coil

You can certainly run it without the tach hooked up just for a shakedown cruise. Good luck, I hope that is it.
 
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