Engine Cranks yet Won't Fire

[Captain3]

Engine cranks Won't Fire

1985 Sunbird with 3.0 Mercruiser. I replaced the coil and points, yet there is no spark. The coil has power going to it. The boat has to be in neutral to crank, yet I can't find any type of kill switch? It has to be some simple wire I am overlooking, any guesses???

 

[Scott Danforth]

welcome aboard

file and service your points, adjust the gap, set the dwell.

if the dwell meter isnt moving, you either have your points adjusted wrong or you dont have power to the purple wire on the + side of the coil

 

[Captain3]

Thanks! So I checked the coil and there is power there to the pos and neg terminals when the ignition is on. Actually, I placed a grounded spark plug in the wire coming out of the coil to the distributor and there is no spark there. So shouldn't that mean that something is not letting the coil produce high voltage. Do you know if a boat that old came with a kill switch?

 

[Scott Danforth]

Thanks! So I checked the coil and there is power there to the pos and neg terminals when the ignition is on.

your points are not set right

 

[Captain3]

I will check them again and set them to .019 or check with a dwell meter, yet I am afraid that is not it. If there is no spark coming out of the coil wire before it is connected to the distributor then that is prior to the points correct? Anyhow, I appreciate your help! Should I post this question in the engines section, just new to this forum, thanks!

 

[Scott Danforth]

the 0.19 is to get close enough to set with the dwell meter. make sure you set the 0.19 at the lobe of the dizzy cam

the points are simply a switch that opens and closes with the cam lobes in the dizzy. only when they open, does the magnetic field in the coil collapse on the primary side, generating a current on the secondary side.

 

[Captain3]

Okay, I am going to double check now. If that is not it do you think anything such as the red 50 amp circuit breaker, slave solenoid or any of that stuff could be preventing it from firing?

 

[alldodge]

Need to be sure the point gap is measured on top of the lobe of the distributor. The points also need to close when the lode is on the flat section

Yes this should have been posted in the engine section

 

[Captain3]

I have a 1985 Sunbird with a 3.0 Mercruiser. I replaced the coil and points and the coil is getting power. I checked the gap on the points several times and still no fire. It has to be in neutral to crank, yet does anyone know if a boat that old had an emergency kill switch? I can't find one, yet this seems like a simple wire I am overlooking. There is a yellow wire with a red stripe coming out of the wires that go to the slave solenoid that is not hooked to anything? And there is a push button type of switch attached to the main ignition terminal that doesn't seem to do anything? Any thoughts??? I just bought this boat and really want to use it!!!

 

[wellcraft-classic210]

Have you checked for spark by pulling a wiire and grounding an old plug to the block or a good gnd ?

If that's not happening --next test -- Do you get 12 volts on the positive side of the coil when you turn the key to run and or when its cranking over ?

 

[achris]

Here are the wiring diagrams for the engine (as new). I does sound like someone had problems in the past and has done some mods :facepalm:

 

[Captain3]

Yes I just checked for a spark with a grounded spark plug and nothing. And there is 12 volts going to the coil. The last owner kept talking about the points giving him issues, yet it ran when he last used it. I have triple checked the points. I would be willing to put electronic ignition on it, yet I don't think that is the problem???
Thanks for the wiring diagram that is awesome. I will try to trace a few wires and check some grounds!
I don't think there was ever a kill switch from the factory???
Do you know if this problem could happen if the 50 amp circuit breaker or the starter slave solenoid was bad? I'm guessing it would not crank if that was the problem?

Thanks Again!!!

 

[achris]

If you have 12v on the coil, and the points keep burning up.... Sounds like the resistance wire has failed and someone has (cleverly :facepalm bypassed it. Put a jumper wire between the coil - and ground. Check the voltage at the coil +, it should now be around 7v. If it's still 12v, you have no resistance wire in!

 

[Captain3]

Okay, well when I said I had 12 volts I meant there was power at the positive side of the coil with a test light. And when you put the test light on the neg side of the coil and crank the engine the test light blinks on and off, which I was told is correct or working. The coil says on the side "no external resistor needed".

 

[Captain3]

It wouldn't burn the points immediately if there was a problem with resistor wires, etc., I mean it would run for a few seconds wouldn't it? Would it be worth investing in electronic ignition, how much would that cost? I hate to just waste money on that and find out it is a simple wire not connected???

Thanks!

 

[Scott Danforth]

Okay, I am going to double check now. If that is not it do you think anything such as the red 50 amp circuit breaker, slave solenoid or any of that stuff could be preventing it from firing?

the 50 amp breaker controls all the power to the helm. no this isnt your problem as you have power all the way back to the coil.

go to the stickies https://forums.iboats.com/forum/eng...ion-for-diyers-an-work-safe-search-version-of

look at links 18, 19, and 20

 

[Captain3]

Thank you Scott! I am reading through the links you suggested and am going to troubleshoot step by step this afternoon. I never knew this was available, great step by step instructions, a great help. I'll let you know if I have any luck.

Thanks Again!!!

 

[wellcraft-classic210]

If you have access to a dvm you may want the added detail of the actual DC voltage measurements


Coils do not fail often -- but I am wondering if yours is OK -- and also pretty sure the marine ones are different that auto -- Hopefully hou have the correct type.

I do know older cars often used 12 volts during cranking for a faster start and dropped to 6 volts for point longevity -- so I would not expect 12 volts to damage the points quickly -- but yes it will shorten the life.

 

[Captain3]

Awesome, I read the "How to troubleshoot a points ignition" link you suggested. So I disconnected the grey wire from the neg side of the coil and wham it sparked indicating a shorted tach wire or bad tach. It starts fine now! Awesome, awesome, awesome, I owe you a case of beer!!!
So I guess I can run it forever without a tach? Although I will try to figure out if if is the tach or a bad wire???
Thanks Again!!!

 

[Captain3]

Thanks for all of your help. I read through "how to troubleshoot a points ignition" and disconnected the grey wire only from the neg side of the coil and voila it fires! Indicating a bad tach or shorted tach wire. I guess it can run forever without a tach, yet I guess I should try to figure out if it is the tach or the tach wire? Hopefully it won't be a recurring issue if I replace the tach!
Thanks Again!