Apha One V6, Thunderbolt IV

[grandpaking]

I have a 1994 Mercruiser Alpha One, V6, 4 Barrel, 4.3L, 262 CID, Gen II, Serial # 0F281678. I am not getting spark to the plugs. We get spark out of the coil but not out of the distributor. With the help of a local Mercruiser dealer, Southern Marine, and a local "expert tech" we have run all the tests (several times) called, "Troubleshooting Thunderbolt IV Ignition System." We have replaced the coil, distributor cap, rotor assembly, and sensor assembly (twice). All the experts say it can't be the ignition module, but no one is willing to bet the price of one to see if it might be! Can we remove the module and bench test it with a high degree of accuracy? If, yes, tell us how. If, no, tell us what else we can do to find the problem and fix it? I will appreciate any help you can give us. Mercruiser has refused to help. Bob

 

[dubs283]

Re: Apha One V6, Thunderbolt IV

if you get spark from the coil tower then the module is working

your "expert tech" should be able to figure this out rather easily

if you set your meter to dc volts and connect the positive to the negative side of the coil and the negative side to a good ground, with the ignition "on" hold the white/green wire from the module to ground for a few seconds, if the voltage drops to 7-9 volts, then returns to 12, the module is good

 

[zbnutcase]

Re: Apha One V6, Thunderbolt IV

Exactly as dubs said. If you truly are getting "spark out of the coil" it can only be a cap/rotor issue, and barely that, as it would run(or try to) on at least a couple of cylinders... That said, make sure you didn't get a V8 trigger wheel by accident if you just replaced rotor...count the windows in 'er...

 

[JustJason]

Re: Apha One V6, Thunderbolt IV

Wouldn't kill ya either to pull the cap off, crank the engine, and see if the rotor is a spinnin....

 

[zbnutcase]

Re: Apha One V6, Thunderbolt IV

Except there would be no spark out of coil if dist wasn't spinnin...

 

[JustJason]

Re: Apha One V6, Thunderbolt IV

Doh.... Your right... thought it was a no spark at all condition.... Don't have me reading glasses on.

 

[Don S]

Re: Apha One V6, Thunderbolt IV

Don't see any mention of the coil wire being replaced. The one between the coil and the distributor cap.

 

[Bondo]

Re: Apha One V6, Thunderbolt IV

Ayuh,... If it's Sparkin' at the coil, it's gotta be an issue Downstream from there,...
Coil wire,...
Cap,..
Rotor,..
Plug wires,..
Or the Plugs themselves...

 

[grandpaking]

Re: Apha One V6, Thunderbolt IV

Thanks for your input. I have the module out. How can I run the voltage test without putting it back in the boat? Is there a test I can run on the coil/distributor wire?

 

[dubs283]

Re: Apha One V6, Thunderbolt IV

How can I run the voltage test without putting it back in the boat?

you can't, the module needs to be connected in the ignition system in order to properly troubleshoot

Is there a test I can run on the coil/distributor wire?

you could ohms test it, or substitute another wire

 

[grandpaking]

Re: Apha One V6, Thunderbolt IV

I made the test. It did drop to about 7 volts and then returned to 12.5 volts. What is the next test I can do to see why I do not get spark out of the distributor to the plug wires? I made it spark through the coil-distributor wire, but when I put the other end into the distributor I get nothing out of the plug wires. The rotor is turning and I can't turn the rotor with the engine stopped so I would say the gear on the bottom of the distributor is good. What about removing the distributor cap and put a spark tester on the end of the coil-distributor wire and see if it will continuously fire when the engine turns over?

 

[dubs283]

Re: Apha One V6, Thunderbolt IV

the problem is with one or more of the following:
-the cap
-the rotor
-the plug wires
-the plugs

 

[Bt Doctur]

Re: Apha One V6, Thunderbolt IV

With the dist cap off,crank motor, check for spark from the coil lead
Replace dist cap and check for spark from a sparkplug wire, if no spark ,remove dist cap and recheck spark from the coil wire.
If spark is now present ,the rotor is shorting out to the dist shaft where is slides on the shaft.Replace rotor and test for spark.

 

[grandpaking]

Re: Apha One V6, Thunderbolt IV

I now have a new coil, coil/distributor wire, distributor cap, and rotor assembly. I have tested the module and it tests okay. I get interrupted spark out of the distributor end of the coil wire, which tells me the coil, the sensor and the module are working. But, I don't get spark out of the distributor. I am not sure the strength of the spark is correct. Could it be too weak to pass the air gap in the distributor? I can see no evidence that the spark is leaking from the rotor to the shaft. How can I test the strength of the spark?

 

[nola mike]

Re: Apha One V6, Thunderbolt IV

I now have a new coil, coil/distributor wire, distributor cap, and rotor assembly. I have tested the module and it tests okay. I get interrupted spark out of the distributor end of the coil wire, which tells me the coil, the sensor and the module are working. But, I don't get spark out of the distributor.

so nothing from any of the plug wires?

I am not sure the strength of the spark is correct. Could it be too weak to pass the air gap in the distributor?

what air gap? no.

I can see no evidence that the spark is leaking from the rotor to the shaft. How can I test the strength of the spark?

get a spark tester, or put a plug on the end of the wire and look for a blue spark. what evidence are you looking for? you could align the rotor with a post on the distro cap--you should have continuity from the center rotor post to the post that the rotor's pointing to. and no continuity to ground.

 

[JustJason]

Re: Apha One V6, Thunderbolt IV

I have tested the module and it tests okay

How exactly did you test it? There's only a few high end DMM's that will test a hall effect sensor, other than that you need a scope. I know there are voltage tests for it, but they can pass a voltage test and still not work.

 

[dubs283]

Re: Apha One V6, Thunderbolt IV

How exactly did you test it?

see post #2, 3rd paragraph - this is the test for the module

OP said the module passed the test by saying the voltage dropped to 7 volts momentarily then returned to 12 volts

There's only a few high end DMM's that will test a hall effect sensor, other than that you need a scope. I know there are voltage tests for it, but they can pass a voltage test and still not work.

the test for the sensor is outlined in the troubleshooting flow chart on the OEM manual

 

[ussoldier_1984]

Re: Apha One V6, Thunderbolt IV

I have a very similar issue with my ignition system (same as yours) its the Ignition module bad. Its heating up and causing my boat to pop back and die after 30 mins of running great

 

[Bondo]

Re: Apha One V6, Thunderbolt IV

switching to a chevy hei distributor much more reliable and a whole lot cheaper!!

Ayuh,... It's also Not igntion protected, 'n What are ya gonna do with the vacuum advance,..??

 

[ussoldier_1984]

Re: Apha One V6, Thunderbolt IV

Anyone know where I can get a ignition module for less then the 300 bucks?