No power to ignition coil - PeachParts Mercedes-Benz Forum

tr1cky · #1 03-30-2010, 02:25 PM

I'm not getting 12v to the coil. In fact I'm not getting any power to the coil.

I recently pulled the points and distributor in favor of a Hot-Spark setup.

Upon installing the Hotspark I now do not get 12v power to the positive terminal of the ignition coil.

Any suggestions on where I should look?

Any electronic part cause this?

Edit: So, for those who have been discussing the Pertronix electronic ignition kit, i researched and found a similar solution called Hot-Spark. They are sold on eBay and on their website. The reason for the swap was to hopefully eliminate the need for periodic timing adjustments due to wearing mechanical parts such as the points.

So, prior to the swap, I had a working ignition system.

Now, after installing the Hot Spark, I have no spark. Following their directions, which seemed simple enough I'm at a point where I'm about to pull hair out trying to figure out why I can't get a spark at all. The post created at around 9:40 PM ET today 3/31/10 will have more information for you rock star troubleshooters to chew on.

Thanks!

TnBob · #2 03-30-2010, 02:37 PM

Your ignition switch sure comes to mind.

A wiring diagram and a schematic are now worth their weight in gold for
chasing things down.

tr1cky · #3 03-30-2010, 02:47 PM

Quote:

Originally Posted by TnBob

Your ignition switch sure comes to mind.

A wiring diagram and a schematic are now worth their weight in gold for
chasing things down.

If this additional information helps great:

Prior to pulling the old points/condenser I did test coil voltage and resistance. All checked out. I did get power to the coil.

Regarding the ignition switch, it too was working well. What is the least arduous procedure for testing the ignition switch?

Agreed schematics are needed.

Thanks

Mike D · #4 03-30-2010, 02:57 PM

There is a ballast resistor BEFORE the coil. There are two leads going to the coil. One is the "start" circuit which by-passes this resistor. It is operated directly from the starter solenoid. It supplies 12V when the starter is engaged. The second, or "run" circuit is routed through the ballast resistor. THIS is the one you need to have connected. You may or may not need to leave the resistor "in circuit" depending on your coil.

Use a test light to determine the supply to your ballast resistor.

tr1cky · #5 03-30-2010, 03:14 PM

Quote:

Originally Posted by Mike D

There is a ballast resistor BEFORE the coil. There are two leads going to the coil. One is the "start" circuit which by-passes this resistor. It is operated directly from the starter solenoid. It supplies 12V when the starter is engaged. The second, or "run" circuit is routed through the ballast resistor. THIS is the one you need to have connected. You may or may not need to leave the resistor "in circuit" depending on your coil.

Use a test light to determine the supply to your ballast resistor.

If this is that pale ceramic-looking resistor I did test power at both sides and can't say that I saw power on either side of this resistor.

I may have missed the reconnection of a wire to the coil as the only wires going to the coil at the time are the red wire for the hot-spark and the wire to the resistor. I will check for oversight, though I don't recall another wire attached to the + terminal of the coil.

Mike D · #6 03-30-2010, 03:37 PM

Quote:

Originally Posted by tr1cky

If this is that pale ceramic-looking resistor I did test power at both sides and can't say that I saw power on either side of this resistor.

I may have missed the reconnection of a wire to the coil as the only wires going to the coil at the time are the red wire for the hot-spark and the wire to the resistor. I will check for oversight, though I don't recall another wire attached to the + terminal of the coil.

The "start" wire is usually connected to the output side of the resistor. I wasn't clear on that part. There should be only one wire running from the resistor to the coil. The "start" circuit side steps the regulated voltage provided by the resistor.

pchbreeze · #7 03-31-2010, 01:08 AM

I have a Haynes manual with a few wiring diagrams...http://www.haynes.com/products/productID/279
its not the best for my car (US version 4.5 engine) but should be ok for yours. let me know if you want some pages scanned. I'm sure your model is in there and wiring should be applicable. In the meantime, I've enclosed two pdf's that might help.

meltedpanda · #8 03-31-2010, 08:27 PM

could you be shorting to ground somewhere, happened to me and I searched for two days before finding it . The line off the condensor was shorting to the distributor body

tr1cky · #9 03-31-2010, 09:29 PM

Quote:

Originally Posted by meltedpanda

could you be shorting to ground somewhere, happened to me and I searched for two days before finding it . The line off the condensor was shorting to the distributor body

Okay, so here's the deal.

I did mention that I swapped out the points and condenser for a Hot-Spark kit.

Prior to the swap all was working, and while I wasn't getting a great spark, it did run.

Save for the removal of the points, the only change was the addition of the Hot Spak module which screws in place where the old points lived just prior.

meltedpanda · #10 03-31-2010, 09:31 PM

I saw that you swapped out the points, just thought you could still be shorting to ground, somewhere

tr1cky · #11 03-31-2010, 09:40 PM

So tonight I figured something out.

I was not getting power to the ignition coil, or so I thought. Well actually I'm not. With both the + and - cables properly attached to the battery I get no power to the ignition coil + terminal.

I pulled the negative cable from the battery and wouldn't you know. Now I have power at the coil of approximately 12.8 volts.

Now, here's a question. The Hot-Spark kit that replaced the points and condenser left me with a wire that was attached to the points and condenser. Is this wire no longer necessary? This wire runs to the factory ignition box under the battery. Now its left on its own without a place to plug into.

I'm totally baffled here.

tr1cky · #12 03-31-2010, 09:42 PM

Quote:

Originally Posted by meltedpanda

I saw that you swapped out the points, just thought you could still be shorting to ground, somewhere

Thanks for your thoughts. its a good suggestion. Check out my previous post here to see what you think.

When I remove the negative battery cable I do get voltage to the coil.

That could very well be. But I'm not sure where to look. I did remove the points and condenser, which didn't leave any exposed wires.

There is the wire that connected to the plug on the points and condenser that goes to the factory ignition control module. I wonder if this wire that now has no home has something to do with the issue?

marcedesbenz · #13 04-01-2010, 02:36 PM

No you don't need the old wire, unless you plan on using the ignition module, I replaced mine entirely. On the hot spark the negative to the coil does your firing, Positive volts should be present at coil with key on at all times. Where are you measuring voltage, you will not get a reading by probing pos and negative on coil itself. If car is not running with key on you should get 12 volts positive on both coil terminals, as you are reading through the transformer. You need to probe around at the resistors and find the wire that is 12 v. with key on. Connect that to pos on coil, connect hot spark as directed. Note if your car is like my 280 was the original ignition module uses the positve side of the coil to fire spark, which is oposite of what you will have now. Make sure you are not still using the old wire to coil+ as it will not work.

tr1cky · #14 04-01-2010, 03:09 PM

Quote:

Originally Posted by marcedesbenz

No you don't need the old wire, unless you plan on using the ignition module, I replaced mine entirely. On the hot spark the negative to the coil does your firing, Positive volts should be present at coil with key on at all times. Where are you measuring voltage, you will not get a reading by probing pos and negative on coil itself. If car is not running with key on you should get 12 volts positive on both coil terminals, as you are reading through the transformer. You need to probe around at the resistors and find the wire that is 12 v. with key on. Connect that to pos on coil, connect hot spark as directed. Note if your car is like my 280 was the original ignition module uses the positve side of the coil to fire spark, which is oposite of what you will have now. Make sure you are not still using the old wire to coil+ as it will not work.

Ah, yes, I noticed that too. Perhaps the pollen in the air has made me loopy but I am going nuts with this.

Not getting a spark at all has me baffled.

Should the factory Ignition Control Unit be unplugged and removed?

I did flip the wires as you instructed above, so I have the 12v power wire going to the (+ 15) post of the coil.

I'm psyched to get this car on the road. I rebuilt the carb and have the brake lines ready to go in. Some fresh tires and I'll be good to go.

Any other thoughts about lack of spark would also be helpful.

Thanks to all who've contributed to this thread!

marcedesbenz · #15 04-01-2010, 05:28 PM

Are you using stock coil? If so then I think you will still need the ballast resistor, I purchased a new coil that has internal resistor. Bypass the ignition module completely for simplicity, just leave it in place in case anyone later is insane enough to put points back in. The wiring of my pertronix was really easy. there are schematics floating around these forums, but 12 volt hot to coil at all times ( when key on), black from hot spark to coil negative, nothing else should be on the coil negative ( thats what fires ). Red from hotspark to any positive 12v ignition source. I put mine straight to the same positive for the coil. Its that simple. I am going by the pertronix, the hot spark may be different but should be same logic.