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grandpaking
10-10-2010, 03:07 PM
I have a 1994 Mercruiser Alpha One V6 4 Barrel 4.3L 262 CID Gen II Serial # 0F281678. I get spark out of the coil but not out of the distributor. I have replaced the coil, distributor cap, rotor assembly, and sendor assembly (twice). Have run the "Troubleshooting Thunderbolt IV Ignition System" test several times and it says to replace the sensor. Can I remove the module and bench test it with a high degree of accuracy? If, yes, tell me how. If no, tell me what else I can do to find the problem. I will appreciate any help you can give me.

makomark
10-11-2010, 02:09 PM
If the coil is sparking and you've changed the cap and the rotor, maybe the spark plug leads are 'broken' internally (including the coil-distributor lead).

You can check them with a good ohm meter. Should show around 5000 ohms for every foot of lead. Don't forget to flex the lead when connected.

Make sure the end of each lead is clean and fully seats in its socket. a bit of dielectric compund around the boot will help to keep them clean, too.

grandpaking
10-11-2010, 08:28 PM
I know how to check voltage but I don't know how to measure ohms. My meter is digital; it has a scale that has a symbol like a horse shoe that goes from 200 to 2000k. I use it to measure continuity. Please give me the steps I need to go through to make an accurate reading. I doubt that all the plug wires and the coil-distributor lead all failed at the same time. Today I set up a bench test with the module and coil; it fired a spark tester through the coil wire, but I don't know if it was as good a spark as it was putting the tester directly into the coil. What about putting the module and coil back on and see if it will fire continuously without connecting to the distributor cap? I will appreciate all the help you will give me!

grandpaking
10-13-2010, 07:36 AM
I know how to check voltage but I don't know how to measure ohms. My meter is digital; it has a scale that has a symbol like a horse shoe that goes from 200 to 2000k. I use it to measure continuity. Please give me the steps I need to go through to make an accurate reading. I doubt that all the plug wires and the coil-distributor lead all failed at the same time. Today I set up a bench test with the module and coil; it fired a spark tester through the coil wire, but I don't know if it was as good a spark as it was putting the tester directly into the coil. What about putting the module and coil back on and see if it will fire continuously without connecting to the distributor cap? I will appreciate all the help you will give me!

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makomark
10-13-2010, 11:08 AM
using the tester at the coil output shows the coil is working. I'd add the test to the dist. end of the coil wire as the next step.

The horseshoe is Omega and means resistance. I'd use the 20K ohm scale. if your meter has alligator clips for the ends of its leads, put them on. clip one lead to each end of the high tension lead. It should show ~ 5K-7K ohms per foot of lead. now shake the wire, like the engine would when running, and see if the value of resistance changes. it should be rock steady. if not, either the 'gator clip isn''t holding well or the wire has an internal break in its conductor.

grandpaking
10-14-2010, 10:11 AM
Even though the old coil/distributor cap wire tests okay I bought a new one. They both test nearly the same. Even though I get spark out of the coil, broken up by the sensor, is it possible the spark is not strong enough to pass through the air gap in the distributor? How can I test the strength of the spark? The coil is a new mercruiser brand, but it is possible it is defective. I will appreciate help.

makomark
10-15-2010, 08:31 AM
If the coil will fire thru a spark tester, the distributor-rotor gap shouldn't be an issue. The T-bolt setups are great when they work and usually make a strong blue 'snappy' spark. Many times, it the containment system leaks, you can hear the arc when ground is found.

grandpaking
10-18-2010, 08:10 PM
I have connected the distributor end of the coil wire to a timing light and when I turn the engine over I get an erratic display of light as though the coil is firing but not sequentially; like it would fire two or three times in a row then skip a beat and fire again! When I put everything back together I still do not get spark coming out of the distributor. I have even put the old rotor back and get the same results. Is there another ignition system I can change to that would be more reliable and less costly?

makomark
10-22-2010, 12:47 PM
running the ignition without a "load" on it isn't good - load means a gap tester, a spark plug, or grounding the coil. That HV needs a return!

The popular replacement is the DELCO Voyager system, for both V-6 and V-8 configurations. Whole system for the same $$ as a T-bolt module.

grandpaking
10-30-2010, 05:50 PM
After two months of blood, sweat, and tears the engine is back in service! Let me give you a recap: After running for 45 - 60 minutes the engine would begin to surge. I had this same problem two years before and solved it by replacing the coil. I replaced the coil and then I couldn't even start it! So, I used the diagnostics chart to find the problem. After having replaced the coil, coil wire, distributor cap, rotor, and sensor unit I still could not get spark to the plugs. Friday night I decided to start over. I took out the new coil and replaced it with the old one - WHAM! I am in business. The store that sold me the coil will not replace it. He claims I damaged it. Thanks to everyone for their help. Like someone said earlier; don't overlook the simple things!!