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No spark produced by new coil

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cnewton700

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Have an 84 Mercruiser 5.7L 260 sterndrive. It was running rough I pulled the distributor cap and found the contacts covered with green corosion, the rotor contact was black and rusted to the shaft. Had to cut it off. The connections on the coil were also badly coroded. So I replaced the cap, rotor and coil. It started up easier and idled better but shortly started backfiring and when shifting gears it would die. Within an hour it died while idling and would not re-start. No spark being generated by the coil. Testing shows the coil receiving correctly. A test light on the pos and neg coil terminals flashed on and off when cranking over so I assume it's receiving the order to fire but there is no spark at all leaving the coil. Could a new coil have gone bad that soon.
 
Once you get it running again.... At most, I've gotten 2+ seasons on that type of MERC Cap/Rotor. Replace while it's still running well. It can go from OK to NG in just a few mins of running.
 
sandkicker said:
Once you get it running again.... At most, I've gotten 2+ seasons on that type of MERC Cap/Rotor. Replace while it's still running well. It can go from OK to NG in just a few mins of running.
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Capt Bob, I'm curious as to how you know which cap and rotor I got and also you recommend I replace it when I get it running but you didn't say what I should replace it with.
 
1. The neg (-) of coil is NOT ground so putting the meter lead to - doesnt work. Neg lead of meter needs to go to a GROUND.

2. When doing power testing on 12 volt systems it is better to use a 12 volt test light.

3. Disconnected the GREY wire at coil which is the Tachometer lead. (if tach is bad it can short out ignition)

4. Follow the procedure i posted. This test procedure has been used since the Thunderbolt ignition has been in use (early 80's)

if you have any questions on the testing and/or results then ask.

Based on your original post, the odds are the pickup sensor that is still in the distributor could have died.

your pick up sensor is an older style. The newer ones are completely encapsulated in a epoxy and have a third wire (ground). These new ones are no longer susceptible to corrosion.
 
Question

what coil did you purchase?

there are two types

External resister
Internal resister

Thunderbolt electronic ignitions require a Internal resister coil.

The old point type ignitions used a External resister coil.
 
I believe it was internal. It was an OEM advertised as a Thunderbolt IV system compatible. But I read the primary ohm were supposed to between .6 and .8 and I got 1.4 on the one I bought. They are sending me a replacement coil. I should have it by tomorrow. I really appreciate you helping me through this mess Jack.
 
Dont get hooked on the coil as the issue.
Not that it is possible but to have a new one fail is very rare.

You can still perform the troubleshooting as I posted.
 
cnewton700 said:
Capt Bob, I'm curious as to how you know which cap and rotor I got and also you recommend I replace it when I get it running but you didn't say what I should replace it with.
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I have pretty much the same engine/ ignition ( a V).. MERC inboards/sterndrive engines pretty much have one of two different "Thunderbolt" ignition systems... the IV and the V ( 4 and 5)... For your year it should be an IV. (4)... Replace with same P/N MERC OEM replacement part... just consider it an annual or at most ( if you're lucky) every other year replacement item. IMHO, there isn't enough price difference between aftermarket ( Sierra) and MERC OEM to warrant going non MERC. If no MERC locally avail, then Sierra OK.

If you go to the marine engine .com boat parts section and plug in your engine S/N into the appropriate place you will get the needed parts. My boat is underused most seasons, so if you put more hours on your engine, it may become a once a year replacement. If the rotor was less of a PIA to remove and replace I'd replace the cap/rotor annually. It's easy to misalign the rotor which can damage it. Replacing these parts does not seem to disturb the timing, but I check it anyway.

Of course, someone could have replaced your distributor with a different one, a DELCO EST for example, and you would need different parts.
 
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Thank you Capt Bob, and I read somewhere those systems were supposed to be super reliable and problem free. I just found out what a used module goes for now that they are NLA. Thinking about alternatives now.
 
There is NO need to replace with aftermarket.

There are plenty of OEM old and in working condition parts for Thunderbolt IV and V.

Once you get this sorted out you should be good for 5-10 years.......just need to change cap and rotor and plugs about every 5 years or so.

These ignitions used in FRESH water in northern climate (where used only in the summer) can run for 15+ years before any parts replacement is needed
 
cnewton700 said:
I believe it was internal. It was an OEM advertised as a Thunderbolt IV system compatible. But I read the primary ohm were supposed to between .6 and .8 and I got 1.4 on the one I bought. They are sending me a replacement coil. I should have it by tomorrow. I really appreciate you helping me through this mess Jack.
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I will say this,

I have been working on Mercruisers for over 30 years and have NEVER measured the coil resistance for either points or Thunderbolt ignitions.

For thunderbolt you simple follow the test procedure and it will find the problem if an ignition part is the problem.

I forgot to mention one important thing to check.

Alpha drive systems use a shift interrupter switch. It is located on the shift cable bracket where the two shift cables connect typically on the exhaust elbiow.

That switch if bad and shorted to ground will kill the ignition. SO, find the switch, it has two wires. find the one that goes to ground. Disconnect that wire and retry and see if you have spark. There should be a small two wire terminal strip, again find the one that goes to a ground and disconnected at the terminal strip.
 
I disconnected the grey wire from the coil to take the tach out of the system and started going through the troubleshooting steps this morning. I was stoked when I got 12.37 volts in step 4 since a 0 took me to 'replace the module'. At that point I was thinking it's down to either the coil or the sensor. Replacing both would be better than needing another module. Step 5 produced no spark so I'm not out of the woods yet regarding the module but I'm stuck until I can replace the coil and repeat step 5. I'll have that and a new sensor tomorrow.
Re: Step 5 Some of the terminology is unfamiliar to me ('high tension lead' and 'coil tower') so this is what I did. I pulled the short, middle wire from the dist. cap leaving the other end still plugged into the coil. I plugged the spark plug tester into the opened end of the short wire I pulled from the cap. I clipped the other end of the tester to a ground on the engine. There are two grn/wht wires that connect to the same terminal on the distributor. One from the module and the other from the shift switch. I used the one from the module as instructed but I left the one from the shift switch disconnected while doing so. Was that correct.
 
I just noticed your post regarding the interrupter switch while posting a response to one of your earlier posts. If I was doing step 5 correctly I can deal with the shift switch now and test again for spark not having to wait for new coil. Thank you
 
By leaving the wire from shift interrupter to dist disonnected you have removed the interrupter from the system so that is correct.

whith white/green from interrupter disconnected, with other white/green disconnected, with white/red connected, Key in ON/RUN position, with spark checker connected to coil wire, now take White/green wire which goes to timing module and strike it to ground (any bolt head near by)
And if you have spark out of coil then the sensor in distributor is bad and needs to be replaced.
 
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Ok with red/wht reconnected, interrupter disconnected, spark checker connected to coil and grnd, key in run position, still no spark at coil from tapping grn/wht from module to grnd. Next I'm to replace the coil and repeat this last test. I bought a new sensor anyway. Should have it and a new coil today and find out if I need a new module. Saw several used ones on ebay they want 300 to 450 for some without the wiring harness. another 75 for that. Know of any good salvage yards in So. Calif.
 
The timing module controls timing.
It is very rare that it is the cause of no spark.

Typically if the timing module fails it would not allow engine when in use undsr laod in the water, not to get past ~2500 rpm...(No Advamce of timing)
 
Finished step 5 by putting in another coil and still no spark. I also put the new sensor in. So, next step is replace the module. I'll start looking around. Saw a video about converting to a delco est ignition system. May look in to that. Thanks again for the help.
 
Does the engine spin when you try the starter? I ask this silly question because you said the distributor was full of green scuzz. This makes me think that there are other corrosion-type issues that may be the cause of the problems. Have you done all the basics like undoing the wiring connections cleaning and reattaching with new fasteners and coating with grease or Mercruiser wire sealant (Permatex Liquid Electrical Tape is similar)? Be sure to do that with the engine ground (battery negative) cable. Establish that you have good flow of electrons before you start blaming components.
 
cnewton700 said:
Finished step 5 by putting in another coil and still no spark. I also put the new sensor in. So, next step is replace the module. I'll start looking around. Saw a video about converting to a delco est ignition system. May look in to that. Thanks again for the help.
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That is the only down side to the TB ignition - if you need a module they are NLA or expensive. I bought one used off eBay a few years & bought a spare would try looking there.

Other option is the delco est which the whole set up is cheaper than a new module. EST is an OEM quality ignition system used as stock on many VP and Merc units
 
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