87 Mercury 3.0 no spark (dist. short?)

[cbauman79]

I have an 87 mercury 3.0 that I can not get to start. It has the Delco ignition system. I've replaced the plugs, coil, wires, cap, and rotor. I'm getting spark from the coil just not from the distributor. I removed the cap after trying several time to start it and burned my finger on part of the distributor. the copper colored piece in the picture was very hot. As you can see in the pic it is discolored from the heat. Can anyone give me a clue as to what's going on.

 

[achris]

Re: 87 Mercury 3.0 no spark (dist. short?)

If you are getting spark (I assume it's a nice healthy spark) from the coil but not from the distributor, pull the cap and check that the rotor is turning when you crank....

That would be my first check...

Those points look pretty normal to me... The tip will look like it's been hot because, well, it's been hot.... If you had that must voltage and current running through you, you'd get hot too...

Chris........

 

[Bondo]

Re: 87 Mercury 3.0 no spark (dist. short?)

the copper colored piece in the picture was very hot. As you can see in the pic it is discolored from the heat.

Ayuh,... They ain't supposed to be that color,...
Them's the Points,...You need a New set,.. Badly...

 

[JustJason]

Re: 87 Mercury 3.0 no spark (dist. short?)

Ayuh,... They ain't supposed to be that color,...
Them's the Points,...You need a New set,.. Badly...

Yep... those are buuuuuuurrrned up. Don't forget to replace the condensor while your in there.

 

[backyard mechanic]

Re: 87 Mercury 3.0 no spark (dist. short?)

You burned up the points because there is a direct 12 volt current going to them. There needs to be a ballast resistor in the circuit OR a resistor wire. Sometimes the resistor is in the coil. It may even be that your points are shorted to ground. Be sure that you are wired right by checking with a volt/ ohm meter... you shouldn't have 12 volts at the points. The wire to the distributor should not come from the positive side of the coil but the negative side. That's a good way to burn up your coil wires and possibly the boat too.

Good luck but yes... change out those burned up points and condenser.

 

[cbauman79]

Re: 87 Mercury 3.0 no spark (dist. short?)

The wire is coming from the - side of the coil. Also my ignition set up uses an external resistor and it is where it's supose to be. I checked the wiring with the wiring diagram first to make sure eveerything was right. I'm picking up new points and condensor and I'll post the results.

 

[cbauman79]

Re: 87 Mercury 3.0 no spark (dist. short?)

Replaced the points and condensor and it fired right up. But I was wondering what voltage should I be getting from the - side of the coil with the key i the on position? I'm getting 12v. If it dosn't start right away and I have to crank it a couple times the + battery cable going to the starter gets hot. The cable andf coil are new. I get 12v on the - side with both the new and old coil. Is this normal. I get 0v with the key off.

 

[T-Bone Coug]

Re: 87 Mercury 3.0 no spark (dist. short?)

You need to check your ballast resistor. Should only get 12v when cranking, less (~8-9v)when in "on" position. And the starter cable will get hot if you crank it for more than a couple seconds. That's alot of amps when you're turning it over.

 

[achris]

Re: 87 Mercury 3.0 no spark (dist. short?)

You need to check your ballast resistor. Should only get 12v when cranking, less (~8-9v)when in "on" position. ....

Only right under one condition...

The drawing below is a Kettering ignition system.

Consider the system with the points open (as shown). Once the condenser is charge, which only takes a few milliseconds, the voltage on wire 2, and the + and - side of the coil will be the same, +12v, regardless of the value of the ballast resistor. When the points are closed, the voltage on wire 2 will be +12v, on the - side of the coil will be 0v, and the + side of the coil will be 7-9 volts, depending on the value of the ballast resistor and the coil.

Chris.......