Ignition Coil Voltage Drop

[Rhinedog]

02-02-2012 10:17 AM
Rhinedog

My 1979 GS 850 runs fine, but has an extreme voltage drop immediately upon start up (7 volt drop). Low DC back to batt. The voltage drops from 13.5 (ignition on, engine not running, new batt.) to 7ish volts at start up then continues to drop further down to 3 volts as RPM increases up to 6000 RPM. Stator delivers 72vac@3500 RPM up to 115vac@10K RPM(no load). Three different Reg/Rec (2 known good) all have same result while connected to bike wiring. I have disconnected literally EVERY system from the bike except the ignition system (additional jump wires run independent of wiring harness). Same result as with all systems connected thru bike harness. I would expect no more than 2 volts absolute max. required for ignition. Is this assumption correct? Is it at all possible that some portion of the Dyna III system with aftermarket coils can have that much of a voltage drop and still operate the ignition system correctly???

 

[koolaid_kid]

Please tell us all the current mods so we can better diagnose your problem(s).
Thanks.

 

[Steve]

Have you run through the Stator Papers?

There are a few connections that are very critical to the proper operation of your charging system, which is where I think your problem lies, not your coils. The tests you will run in the Stator Papers will help isolate the problem area.

First area is the loop that takes one stator leg up into the harness, then to the headlight switch and back down to the R/R. If the contacts are dirty in any of the connectors or the headlight switch, you will automatically lose one third of your input to the R/R. Also make sure that the connectors between the stator and R/R are clean and tight.

Second area I would check would be the red output wire from the R/R into the harness. Just after it disappears into the harness, it is crimped to the main wire from the MAIN fuse to the ignition switch. Over the years, that crimp might not be as good as it used to be. Since that is the primary connection from the charging system to the rest of the bike, it is VERY important.

Third area I would check is R/R grounding. There is usually a short ground wire from the R/R to the battery box. Problem is, the battery box is rubber-mounted, so relies on another wire to ground it. It is FAR better to extend the ground wire directly from the R/R to the battery. Almost as good would be to add a new ground wire between the current R/R 'grounding point' and the battery. Just make sure all connection areas are clean and shiny.

I was going to suggest the possibility of a replacement stator with an incorrect number of poles, but if that had happened, you would not have the AC voltages that you do.

.

 

[Rhinedog]

Ignition Coil Voltage Drop

Thanks for replies. Yes, checked "papers" thouroughly. All new and good grds. Additional grds to RR, mount plate, eng to frame, batt, ing.mod., and wiring harness. Stator wired direct to RR. RR wired direct to batt. Volt drop still there even with stator and RR disconected, ONLY ignition system connected direct to batt with jumpers, not bike harness.

 

[Steve]

What is the resistance of each coil?

Primary and secondary resistances, please.

You might try disconnecting the coil wires from the bike's electrical system and using jumper wires to another battery, like the one in your car (not running would be great). That way, you will not have the load of your ignition system on your bike and will be able to see if the charging system can actually keep up with the rest of the load.

.

 

[Rhinedog]

Ignition Coil Voltage Drop

Excellent idea about the separate source for ignition.
The primaries both have about 2.7ohms. I will check secondaries and report back.

 

[Steve]

The primaries are more important for determining their load on the system, but the secondaries will tell you whether they might work or not.

2.7 ohms is a bit low (but within spec), meaning they will pass more current. Drawing more current from a marginal supply will lower the voltage.

It will be interesting to see the results of the "separate supply for the ignition" test.

.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. Rhinedog,

You may benefit from the "coil relay mod". It's a little different for the Dyna-S ignitions. Mr. posplayr has written a guide, CLICK HERE (PDF file). Basically it puts a relay between the battery and the coils so that you get full battery voltage to the coils. Ensure the entire wiring harness is clean including the grounds, fuse box, everything. Check the electrical section of my little website for lots more tips.

Now let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

 

[posplayr]

02-02-2012 10:17 AM
Rhinedog

My 1979 GS 850 runs fine, but has an extreme voltage drop immediately upon start up (7 volt drop). Low DC back to batt. The voltage drops from 13.5 (ignition on, engine not running, new batt.) to 7ish volts at start up then continues to drop further down to 3 volts as RPM increases up to 6000 RPM. Stator delivers 72vac@3500 RPM up to 115vac@10K RPM(no load). Three different Reg/Rec (2 known good) all have same result while connected to bike wiring. I have disconnected literally EVERY system from the bike except the ignition system (additional jump wires run independent of wiring harness). Same result as with all systems connected thru bike harness. I would expect no more than 2 volts absolute max. required for ignition. Is this assumption correct? Is it at all possible that some portion of the Dyna III system with aftermarket coils can have that much of a voltage drop and still operate the ignition system correctly???

The battery sounds like it is dead, it should only drop 0.5V with head lamp and ignition from about 12.8v to 12.3V (not under 12.0)

See diagnosis on Quick Test #1

Quick Test Steps:

1.) key off................Normal 12.7 volts-12.9 volts

2.) key on (but not cranking with lights for 10 sec).....Normal 12.2-12.5 volts

3.) at idle (1500 rpm).....12.6volts - 13.2volts

4.) at 2500 rpm 13.5 -14.0 volts

5.) at 5000 rpm.....14.0 -15.0 volts

6.) key off.....slightly higher than measurements # 1 (12.8-13.0 v)

QUICK TEST Diagnosis Summary:

Basically Step #1 and #2 is making sure the battery is charged and in good health. The drop should be about 0.5 volts for normal headlamp and coil load (without cranking the starter). Anymore than 0.5V drop indicates the battery is weak even though the static voltage is OK (12.7-12.8V)

Step #3 is get a baseline starting voltage. This will vary some depending upon your idle and the particular R/R you have. It could be lower than the off voltage or as you idle up it will increase to 13.0 v

Step #4 by the time you get to 2500 RPM you should have close to the maximum output voltage even if you have bad connections. You are not pushing as much current and this shows that the stator is likely good.

Step #5 by the voltage at 5000 RPM being higher than at 2500 RPM you have a pretty good indication that your connections are good. If the voltage at 5000 drops from 2500 you have bad connections. If you already checked the grounds then it is likely in the positive legs between R/R(+) and Battery (+) check fuse box and the large bullet connector to the battery. The voltage climbs above 15.0 V it is likely the R/R not regulating and is bad bad.

Step #6 If after running for a few seconds in a charging state the voltage to the battery should have risen a bit. If it is lower than where you started then you did not charge at all, Again this will vary some what depending upon how long you let the bike run.

 

[koolaid_kid]

The primaries are more important for determining their load on the system, but the secondaries will tell you whether they might work or not.

2.7 ohms is a bit low (but within spec), meaning they will pass more current. Drawing more current from a marginal supply will lower the voltage.

It will be interesting to see the results of the "separate supply for the ignition" test.

.

Steve, I am not sure you can make this statement. What if he is running an ignition that needs the 2 Ohm coils? He seems to have stated that the ignition is not stock, but he has not stated what he has. Hence my request for more information.

 

[posplayr]

Steve, I am not sure you can make this statement. What if he is running an ignition that needs the 2 Ohm coils? He seems to have stated that the ignition is not stock, but he has not stated what he has. Hence my request for more information.

He is running a Dyna III with stock coils

 

[koolaid_kid]

He is running a Dyna III with stock coils

I could not tell, because he also states:

Is it at all possible that some portion of the Dyna III system with aftermarket coils can have that much of a voltage drop and still operate the ignition system correctly???

So which is it? IDK.

 

[posplayr]

I could not tell, because he also states:
So which is it? IDK.

His email to me.........

Finally I resorted to disconnecting individual circuits from the bike to try to track down where a 6vdc drop immediately after start up, then proceeds to drop further as RPM increases, down to 3vdc at 6000RPM is coming from. I finally have it down to only the ignition system (Dyna III with OEM coils).

 

[Rhinedog]

Ignition Coil Voltage Drop

WOW!!! Thanks to ALL of you for your input. I thought they where OEM coils b/c the hi voltage leads are "molded" into the coils, but now I'm not sure, will check closer tomorrow.You have actually inspired me to go out and work on the ole girl again, maybe I really can get her going! I am kinda lookin' forward to what new info I can find, and will report back. The welcome from Basscliff was almost overwhelming....Thank you! What a GREAT resource. Until tomorrow!

 

[Rhinedog]

Ignition Coil Voltage Drop

Not sure this is the proper way to get this to you but hope both of you get this. posplayr and koolaid kid here are the results of the further troubleshooting. My old faithful simpson meter matched almost exactly to the digital. Key off-12.8v; key on, not running-12.3v; idle-4v (yes 4volts @ 1500RPM); 2500-5v; 5000-2v; Key Off-13v. Oddly enough with the ignition only connected to the aux batt and nothing connected to the bike batt except the bike ground, the system was drawn down to those low #s on both batts. New coils did the trick. Runs great! idle-13v up to 5000 14.5v. The old coils are "Nippondenso" I assume OEM. They allowed proper ignition until it ran the dynamic voltage (engine running) down to 2v at the batt. All is well now. Thanks for your input.

 

[Rhinedog]

Ignition Coil Voltage Drop

Steve thanks to you as well. I'm not sure how all of this forum stuff works. Not being sure if Steve and koolaid and posplayr etc are 3 different people or who's who. I figure I'm doing pretty good for an old guy. Don't want to seem ungrateful to anyone. Thanks to you all.

 

[posplayr]

Not sure this is the proper way to get this to you but hope both of you get this. posplayr and koolaid kid here are the results of the further troubleshooting. My old faithful simpson meter matched almost exactly to the digital. Key off-12.8v; key on, not running-12.3v; idle-4v (yes 4volts @ 1500RPM); 2500-5v; 5000-2v; Key Off-13v. Oddly enough with the ignition only connected to the aux batt and nothing connected to the bike batt except the bike ground, the system was drawn down to those low #s on both batts. New coils did the trick. Runs great! idle-13v up to 5000 14.5v. The old coils are "Nippondenso" I assume OEM. They allowed proper ignition until it ran the dynamic voltage (engine running) down to 2v at the batt. All is well now. Thanks for your input.

It is hard to imagine pulling The battery down that far. i assume,e you are measuring directly across the battery? Glad it is working

 

[Steve]

Steve thanks to you as well. I'm not sure how all of this forum stuff works. Not being sure if Steve and koolaid and posplayr etc are 3 different people or who's who. I figure I'm doing pretty good for an old guy. Don't want to seem ungrateful to anyone. Thanks to you all.

Have not yet met Posplayr, but I have met koolaid_kid, and I can assure you that at least the two of us are not the same person.

Can't say for sure that k_k is not posplayr, but they claim to be from different areas.

.

 

[Rhinedog]

Ignition Coil Voltage Drop

I was surprised as well. That's why it was so hard to troubleshoot. Yes I was measuring right across the batt. I've been a working as a mechanic every day for over 35 yrs and have never seen a coil of anykind have that much of a draw and still operate. Very strange one to add to our collections of things that make you say "Hmmm".

 

[koolaid_kid]

Have not yet met Posplayr, but I have met koolaid_kid, and I can assure you that at least the two of us are not the same person.

Can't say for sure that k_k is not posplayr, but they claim to be from different areas.

.

I can assure you we are 3 different people. I have not met posplayer either, but we have had some interesting exchanges on the forum. So unless I have multiple personalities (not verified yet) we are different folk.