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Now no spark! Coil tests bad

E

edheiser

New member
Well, I had spark when I bought this 2002 R1150rpt, but after fixing the timing issue (another thread), the coil is now not making spark. I think I fried the secondary winding by cranking it a lot with the spark plugs not grounded:banghead. I have 12+volts at the coil connection. The coil is suppose to ohm at 7.5K between 4a and 4b, the HT posts, nothing. The 1-15 posts ohm at .5, and the wires themselves ohm at 5K. So I found another on Ebay including the regular wires. Since this was a police bike, it has the special connectors and metal caged coil that costs a fortune. I believe I can substitute a non police spec coil and wires with no problem. Anyone have experience with this?
 
Have you confirmed that there is a "break" in the coils? Analog voltmeter on the ground side of the coils should bounce when cranking.
 
Good idea

dieselyoda said:
Have you confirmed that there is a "break" in the coils? Analog voltmeter on the ground side of the coils should bounce when cranking.
Click to expand...
No I haven't done that, but I was wondering how to test if it was getting a signal, break in ground contact, right?. I'm a points and condenser era guy. I'd like to try that, but, if the coils don't ohm correctly on the secondary side, it's shorted due to my poor procedure, correct. Would a shorted coil still bounce an analog meter?
I've already purchased a used set up I'll have Friday. I guess the old one will make a nice paper weight.:)
Edit:
About halfway through my shower I realized you were saying to check it at the connector, not hooked up to the coil, never mind...... Hey, could I just use a 12 volt test light?
 
Last edited:
Answered my own question

Apparently, a test light won't work. Even though there's 12 volts, it's not enough amps to light the bulb.
Edit: I measured the amps, my meter reads as low as 1,000,000th volt, and it's 348Ua, no wonder the turn signal lamp I tried wouldn't light!
I think I'll just wait for the coil and HT cables to show up before I fry anything else.
 
Last edited:
Traditional coil up by the steering head, just below the tank?

If so, they are readily available used on eBay. Do a search for the part number and you should find a few available for under $50 or so. Part number 12131341978 - IGNITION COIL.
 
An analog voltmeter will react fast enough to see the ground break at the ignition coil. If you are cranking the bike, it should blip pretty fast.

I do check coils for resistance and I pay attention to the values but more often than not, if I suspect the coils, I just replace them.

0.5 ohms primary sounds very low but some are that low. Between either post to spark plug posts should be infinite. But there is another measurement you can't do with these coils and check pos/neg posts to ground.

Rule of thumb for plug wires is 1K ohm per foot but that's only a rule of thumb.
 
edheiser said:
Well, I had spark when I bought this 2002 R1150rpt, but after fixing the timing issue (another thread), the coil is now not making spark. I think I fried the secondary winding by cranking it a lot with the spark plugs not grounded:banghead. I have 12+volts at the coil connection. The coil is suppose to ohm at 7.5K between 4a and 4b, the HT posts, nothing. The 1-15 posts ohm at .5, and the wires themselves ohm at 5K. So I found another on Ebay including the regular wires. Since this was a police bike, it has the special connectors and metal caged coil that costs a fortune. I believe I can substitute a non police spec coil and wires with no problem. Anyone have experience with this?
Click to expand...

If the secondary shows open (infinite ohms), it's dead.

Coils are basically transformers. You need resistance on the primary (.5 ohms) and secondary (around 7k).
 
wasted spark coil

I was looking for a place in the Haynes or BMW service manual that said the mentioned 4a and 4 b terminals were the HT output posts, and I couldn't find that designation anywhere. Since these were the only places left to test for 7.5K ohms, I tested there, and got no reading, the same reading I get from testing a block of wood, so I assumed they had to be 4a and 4b, but it was nagging me. I hate to ass u me.
So I read up on wasted spark coils, and now I feel more confident in my assumption. Turns out, the spark isn't really wasted, a connection is necessary to complete the circuit. So measuring between the two HT posts SHOULD give a resistance reading. Our coils either have a connection between 2 primary windings, or 2 secondary windings, making it a wasted spark coil. Bottom line, by turning over the engine with the battery and either or both spark plugs not grounded, gives no place for the current to go and turns the coil into an electric frying pan made up of thin wires with thin insulation, which doesn't last long.
 
edheiser said:
I was looking for a place in the Haynes or BMW service manual that said the mentioned 4a and 4 b terminals were the HT output posts, and I couldn't find that designation anywhere. Since these were the only places left to test for 7.5K ohms, I tested there, and got no reading, the same reading I get from testing a block of wood, so I assumed they had to be 4a and 4b, but it was nagging me. I hate to ass u me.
So I read up on wasted spark coils, and now I feel more confident in my assumption. Turns out, the spark isn't really wasted, a connection is necessary to complete the circuit. So measuring between the two HT posts SHOULD give a resistance reading. Our coils either have a connection between 2 primary windings, or 2 secondary windings, making it a wasted spark coil. Bottom line, by turning over the engine with the battery and either or both spark plugs not grounded, gives no place for the current to go and turns the coil into an electric frying pan made up of thin wires with thin insulation, which doesn't last long.
Click to expand...

The unloaded coil will generate excessively high voltages which breaks down the insulation between turns. The secondary shorts and eventually burns out.
 
New coil also tests bad, but fires engine, what the!

My new used coil arrived today, and being extra cautious, I ohm tested it first. It gets the same reading at the 2 ht (yes in the K range) posts as my old one, nothing. So I'm all upset, and my wife says, just try it on the bike. (I've been married for a long time, perhaps some of you know what I mean), so I did, and it fired right up! I'm happy but confused. The more I found out about these coils, the less I knew apparently. Anybody have a coil they want to ohm and tell me what it read?
 
Where are you measuring 7.2 K ohms?

GSAddict said:
7.2 K ohms for the standard coil

Is yours the shielded police coil?
Click to expand...

I have both now, a police and civilian coil, neither measure any value between the high tension posts, yet the civilian coil fires the bike. I have 2 multi meters, one auto range, one set to 20K ohms range. I have tested many single ht post ones, but never one like this. Does it take special equipment?
 
edheiser said:
My new used coil arrived today, and being extra cautious, I ohm tested it first. It gets the same reading at the 2 ht (yes in the K range) posts as my old one, nothing. So I'm all upset, and my wife says, just try it on the bike. (I've been married for a long time, perhaps some of you know what I mean), so I did, and it fired right up! I'm happy but confused. The more I found out about these coils, the less I knew apparently. Anybody have a coil they want to ohm and tell me what it read?
Click to expand...

Interesting result and maybe good news for me. When I read about your coil predicament I recalled I had a Cop Coil in my spare parts. I thought I would offer it to you since my bike is using a regular one. I decided to test it first and it was 8 ohms across the primary so close enough to 5. The secondary HT posts however measered zero, nada, zip, open or like a piece of wood as you mentioned. :scratch

I plan to desolder the RF can anyway since I've wanted to see what other mods this one has compared to the regular coil other than coil in a can with a braided ground wire to absorb RF and thus not interfere with the radio.
 
Zero vs open

kioolt said:
Zero and open are opposite things. How can it be both?
Click to expand...
I'm not an expert, so perhaps my terms aren't correct, that's why I mentioned the reading from a block of wood, my kitchen table to be exact. Some meters give a "ding" when there is a connection if you set it at the bell or buzzer location in ohms. Complete silence is what, open or zero? Connecting the two multimeter leads gives a small reading, .1 ohms or a "ding" if set on the buzzer on mine after it settles down a bit. These 4a and 4b terminals don't register anything on the meter, like you didn't even touch them to the posts, or a "ding", is that zero or open?
Either way, one coil fires the engine, one doesn't.
As far as the metal cage, it's not connected to the coil with anything conductive, so it's just for static control.
 
I can't comment on what sounds your meter makes because I've never seen it. But basically when you set your meter to the ohms range and don't have the leads touching anything then that is infinite resistance or open. When you touch the meter leads together that should read zero. It may at this point read slightly above zero because of the leads themselves.
 
Thanks

kioolt said:
I can't comment on what sounds your meter makes because I've never seen it. But basically when you set your meter to the ohms range and don't have the leads touching anything then that is infinite resistance or open. When you touch the meter leads together that should read zero. It may at this point read slightly above zero because of the leads themselves.
Click to expand...
Ok, thanks for the clarification. I was never sure what "infinite" meant in ohms. Usually infinite means a huge number to me. I guess that sounds stupid!:scratch, but I'm not afraid to sound stupid to learn something. That's why I'm so CAT smart.:)
 
FYI. The OL that your meter displays when set to ohms means "Over Limit". You will have to look in your meter manual to see what the range limit is for your meter. I believe my Fluke 79III has a ohms range limit of 2 Meg Ohms which means anything over 2 meg ohms will display OL. Anything over 2 meg ohms for all practical purposes that I can think of on a motorcycle is an open circuit or infinite resistance.
 
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