Mercruiser no spark - UPDATE 8/28/09 SOLVED

[Wet Wonder]

1977 Merc 351 windsor 233hp, pertronix elec ignitor II ign, flamethrower coil, 2bbl

No spark at distributor, motor just cranks. I'm following Don S.'s flowchart on ignitions, but am stuck on step 3.

1) connected voltmeter from positive coil post to ground with inition key turned on and got 12 volts.

2) with Bubba's help, tested coil by jumping positive and negative and sparking lead against engine block upon pulling the ground, so coil works.

3) I don't understand next instction in the flowchart, to check for 1-12 volts at white/red terminal at distributor. The electronic ign has a red wire which I have terminated to 12 volt source, and a black wire that is terminated at neg ground on coil. How do I do this test with the white/red?

4) If that test does fail, it says to address the bullet connector on the distributor. What is that?

Thanks, Dave

 

[Don S]

Re: Mercruiser no spark

Re: Mercruiser no spark

I'm following Don S.'s flowchart on ignitions,

Mind posting a link to that flowchart? I have no knowledge of one for that ignition system.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

Here's the chart I'm referring to - http://forums.iboats.com/showpost.php?p=2137376&postcount=2

Starting with everything hooked up, if I pull the lead of the distr center post and try to spark to the block when the motor cranks, I get no spark.

I'm getting 12 volts the coil. An independent test of the coil showed that it does spark. That's where I am now.

From reading other posts, it seems like there is a problem with the coil being perpetually grounded, but I don't know where.

 

[Bt Doctur]

Re: Mercruiser no spark

Re: Mercruiser no spark

Your system has no bearing for that chart, you had points that you replaced with an electronic version. The 2 wires from the unit in the dist go to the coil ,red to + ,green to - (I think,just checked the link and it shows red and black) . +12V supplied to the coil + lead.
Check the air gap on the magnetic trigger

 

[Don S]

Re: Mercruiser no spark

Re: Mercruiser no spark

That flowchart is for a Mercruiser Thunderbolt IV ignition system, has absolutely nothing to do with your Pertronix system. Not even close.

 

[180shabah]

Re: Mercruiser no spark

Re: Mercruiser no spark

That flowchart is for a Mercruiser Thunderbolt IV ignition system, has absolutely nothing to do with your Pertronix system. Not even close.

...but no worse than a seloc...

Dave - Check the pertronix website for your ignition system.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

I don't think the no spark problem has to do with the Pertronix ign. I can't get a spark from the coil lead to the engine block ground when I crank it. If I'm understanding right from reading other threads, that means the problem is somewhere from the coil backwards, rather than in front of the coil and at the distributor.

If this is correct thinking, can someone give me some tips on what to test and rule out from this point?

 

[Provo5]

Re: Mercruiser no spark

Re: Mercruiser no spark

Check for 12v at the ignition switch during cranking. I had been beating my head against the wall for days because all checks on the flow chart were good. Put the switch in the on position and coil had 12v.Crank the engine and I would get no spark. Changed out the ignition switch and engine fired right up. Ignition terminal on switch was going dead during cranking. I am sure this is a rare failure but an easy check to rule out for you.

 

[Showtime22]

Re: Mercruiser no spark

Re: Mercruiser no spark

1- Has this system ever worked or did you install the Pertronix?
2- Did you use a light tester to check voltage to the positve side of the coil or was the independent test from an different power source?

On my pertronix install I ran a wire from the back of the key to the postitve side of the coil. My positive terminal has the wire from the key and the red wire out to the pertronix module. My negative terminal has the black wire to the pertronix module and a grey wire to the tach.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

1- Has this system ever worked or did you install the Pertronix?
2- Did you use a light tester to check voltage to the positve side of the coil or was the independent test from an different power source?

On my pertronix install I ran a wire from the back of the key to the postitve side of the coil. My positive terminal has the wire from the key and the red wire out to the pertronix module. My negative terminal has the black wire to the pertronix module and a grey wire to the tach.

I installed the Pertronix in the beginning of the season and it's been running well. The spark problem just happened this week.

The instructions said that the positive from the ignitor II could be connected to any 12v source. I have it essentially connected to a source to the battery and it had worked that way fine.

I don't know what the light test is yet, though I did see reference to it in some threads. What I did was a few tests on the coil.

First, key on and voltmeter to the positive post and grounded read 12volts.
Second, key on and voltmeter to the negative coil post and grounded read 12 volts.
Third, same voltmeter to negative coil post and I cranked the motor - the voltmeter kept at 12 volts and didn't flicker, which may be a problem?
Fourth, independent coil test, I disconnected postive and neg wires and jumped it to the pos on the battery and brushed a neg jump to engine block ground and got a spark from the lead to engine block, so I believe the coil is OK.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

Check for 12v at the ignition switch during cranking. I had been beating my head against the wall for days because all checks on the flow chart were good. Put the switch in the on position and coil had 12v.Crank the engine and I would get no spark. Changed out the ignition switch and engine fired right up. Ignition terminal on switch was going dead during cranking. I am sure this is a rare failure but an easy check to rule out for you.

Provo, tell me if what I did was correct. I put a voltmeter, positive to coil and negative to ground, which read 12 volts with key on - and then I cranked the motor, and still read about 12 volts or so while cranking. Is that doing it right?

 

[bruceb58]

Re: Mercruiser no spark

Re: Mercruiser no spark

What your measuring is fine. Sure sound like the pertronix unit is not working correctly though.

If you had a points ignition, you would rotate the engine until the points would close and then you would measure 0v at the negative terminal of the coil. Not sure If you can do the equivalent test with the pertronix. Is the pertronix unit securely fastened to the breaker plate? Not sure if there is one on your distributor but is there a ground wire from the breaker plate to the distributor housing? Is the air gap correct on the pertronix unit?

I suggest calling their tech support line.

This is why I don't like the pertronix sytems and prefer to keep points but that is a different story.

 

[jtybt]

Re: Mercruiser no spark

Re: Mercruiser no spark

Could be the shift interrupt switch is stuck 'out of the U'

 

[bruceb58]

Re: Mercruiser no spark

Re: Mercruiser no spark

Could be the shift interrupt switch is stuck 'out of the U'

Doesn't that switch ground out the negative side of the coil? He is measuring 12V there I believe.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

I'm calling Pertronix right now.

 

[jtybt]

Re: Mercruiser no spark

Re: Mercruiser no spark

Bruce,
You're right. He has early switch (1977).

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

Could be the shift interrupt switch is stuck 'out of the U'

When I pt the voltmeter on the negative post of the coil with the key on, I get 12 volts. And then when I crank it the voltmeter stays at 12 volts. Should the voltmeter bounce between 0 and 12 when I'm cranking?

Where is the shift interrupt switch? There's a wire going into the transmission. When it's connected, the motor cranks. When I disconnect it, the motor won't crank. Is that related to the switch?

 

[180shabah]

Re: Mercruiser no spark

Re: Mercruiser no spark

There's a wire going into the transmission.

Transmission or shifter???

If it is the shifter, it for the neutral start switch, it kills the starter circuit, not the ignition.

 

[Wet Wonder]

Re: Mercruiser no spark

Re: Mercruiser no spark

Transmission or shifter???

If it is the shifter, it for the neutral start switch, it kills the starter circuit, not the ignition.

The wire I mentioned is going into the housing of the transmission.

When you say shifter, does that mean the actual paddle shifters at the helm? Or where the shift cable connects to the transmission and mechanically actuates it?

 

[Bondo]

Re: Mercruiser no spark

Re: Mercruiser no spark

Ayuh,... Is a Shift Interupt Switch even used on an Inboard,..??
What transmission Is it,..??

I don't think the no spark problem has to do with the Pertronix ign. I can't get a spark from the coil lead to the engine block ground when I crank it.

That comment is bothering me,....
The Pertronix is What is supposed to be firing the Coil....
Everything you've stated leads Me to believe it's Not working....

Only when the coil Grounds out does it Fire.....
Per your statements,... It's continuously Open,+ reading 12V....

The questions about the Switches don't apply to your motor,.... Forget about 'em...
And if that switch Was stuck, you'd have Ground on the (-) terminal, not 12V....