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dirtybass
Samba Member
Joined: October 16, 2012
Posts: 12
Location: ATL
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 Posted: Sat Apr 16, 2016 11:21 am Post subject: Bad coil? No spark. |
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Trying to start up a rebuilt 1600 that's been sitting in a 78 vert since rebuild.
Car was crushed by a tree. All ignition system looks new and checks out.
I have power to the coil but get no spark with a wire pulled with a spare plug in it. Or the four in the heads.
When testing for power, I noticed I had power on the positive AND negative posts.
Thinking this was unusual, I swapped out the coil with the one in my 65 I know is good, and same thing.
I hooked up the hot post, and get power in the neg post as well, but no spark to the plugs.
Flummoxed. |
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carpespasm
Samba Member
Joined: April 03, 2016
Posts: 37
Location: Jacksonville, FL
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| Posted: Sat Apr 16, 2016 11:40 am Post subject: Re: Bad coil? No spark. |
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you shouldn't worry about power showing on - and + ends of the coil, there's only a few ohms of wire wound in that part, so continuity is normal.
Check to make sure your points are clean and spaced right and do a static timing job if that's suspect. I chased my tail thinking I had a coil issue a few weeks ago and it was the distributor not setup right at fault. Good luck! |
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wrackman
Samba Member
Joined: December 29, 2015
Posts: 8
Location: whangarei NZ
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| Posted: Sat Apr 16, 2016 1:38 pm Post subject: Re: Bad coil? No spark. |
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The coil has ignition feed to one side of the coil (+) and the other goes to the points (-).When the points are open there is power on both sides of the coil.when the points close the (-) goes to ground (power goes away).If you fit a new set of points there should be a air gap of about 016" when the points sit on the cam.
Hope this helps |
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Cusser
Samba Member
Joined: October 02, 2006
Posts: 31360
Location: Hot Arizona
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Volks Wagen
Samba Member
Joined: February 13, 2013
Posts: 2926
Location: Germany
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| Posted: Sat Apr 16, 2016 2:26 pm Post subject: Re: Bad coil? No spark. |
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| dirtybass wrote: |
Trying to start up a rebuilt 1600 that's been sitting in a 78 vert since rebuild.
Car was crushed by a tree. All ignition system looks new and checks out.
I have power to the coil but get no spark with a wire pulled with a spare plug in it. Or the four in the heads.
When testing for power, I noticed I had power on the positive AND negative posts.
Thinking this was unusual, I swapped out the coil with the one in my 65 I know is good, and same thing.
I hooked up the hot post, and get power in the neg post as well, but no spark to the plugs.
Flummoxed. |
Check the points. I assume you are grounding the spark plug to the engine or vehicle body somehow and not just dangling the plug in the air when checking for spark?
_________________
1973 1303 with AB-motor - sporadic
reconstruction as time permits, 1986 ex-Bundeswehr Doka - on the road again.
I'm definitely, probably, the worlds greatest lover.
Aithníonn ciaróg ciaróg eile. |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Sat Apr 16, 2016 10:45 pm Post subject: Re: Bad coil? No spark. |
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| wrackman wrote: |
| The coil has ignition feed to one side of the coil (+) and the other goes to the points (-).When the points are open there is power on both sides of the coil.when the points close the (-) goes to ground (power goes away). |
This is not exactly accurate.
This has to do with voltage and current flow. At the #15 (+) terminal of the ignition coil you have an incoming wire from the ignition switched circuit. It brings 12v+ to the terminal.
Inside the primary coil circuit (between the + and - terminals) there is a long coil of wire and (in most cases) an internal ballast resistor rated at 3-4ohms. This resistor will reduce the current that will flow into the ignition coil. What ever current flows into the coil must flow out from the #1 (-) terminal to ground.
Voltage change thru the ignition coil is small. This is why you can still measure 12v at both the + and - sides of the coil.
In the normal configuration, there is only the green wire running from the #1 (-) terminal of the ignition coil to the points. The points themselves are grounded to the distributor body so once they CLOSE this green wire is connected directly to ground w/o any resistance. When the points CLOSE the create a field circuit in the ignition coil. When the points are OPEN the current flow is disrupted and the field circuit collapses. This collapse sends a surge of induced extremely high voltage (15Kv) through the secondary circuit of the coil which is grounded thru the spark plugs.
Since the path thru the points is the only output path from the primary circuit, 100% of the current flows thru the points to ground.
This is where things get interesting....
If you place a good voltmeter between ground and the (-) terminal of the ignition coil while the ignition is ON you should always read 12v... whether the points are OPEN or CLOSED. WHY you may ask? Voltage is the ability to do work, not a measure of how much current is flowing. Since the points are the switch there is always voltage upstream of the points.
If you use a 12v test lamp you might get the impression that when the points are CLOSED there is no voltage at the coil (-) terminal because the test lamp will turn OFF when the points are CLOSED. The reason for this is "current flow" not voltage. There is voltage at the (-) terminal. With the test lamp connected there are now TWO paths for current to flow from the terminal to ground. Which path the current will flow down is determined by the amounts of resistance down each path. For example, a 2W test lamp will have 72ohms of internal resistance. The points, when CLOSED, have nearly zero resistance. When they are open they have infinite resistance. This means when the points are CLOSED only 1/72th of the current available will flow thru the test lamp, the rest flows thru the points. Not enough current flows to light up the bub. When the points are OPEN there is only ONE path so ALL the current flows thru the test lamp. This explains why the test lamp turn ON and OFF, but what about voltage? As explained, even when the test lamp is OFF there is current flowing thru it. Since current is flowing there must be voltage.
_________________
AshMan40
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'67 Beetle #1 {project car that never made it to the road  }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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dfranzen
Samba Member
Joined: February 28, 2016
Posts: 30
Location: Simi Valley CA
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| Posted: Sat Apr 16, 2016 11:54 pm Post subject: Re: Bad coil? No spark. |
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condenser sounds bad
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1971 Super Beige |
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David_nc_72std
Samba Member
Joined: August 22, 2015
Posts: 841
Location: Winston-Salem, NC
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| Posted: Sun Apr 17, 2016 8:33 am Post subject: Re: Bad coil? No spark. |
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| ashman40 wrote: |
This is where things get interesting....
If you place a good voltmeter between ground and the (-) terminal of the ignition coil while the ignition is ON you should always read 12v... whether the points are OPEN or CLOSED. WHY you may ask? Voltage is the ability to do work, not a measure of how much current is flowing. Since the points are the switch there is always voltage upstream of the points.
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You will most certainly NOT measure 12v at the (-) terminal when the points are closed. Note that the measurement is made while the engine is NOT running, something that most of us just assume everyone knows. If the engine is running while you make the measurement, you will measure the average DC voltage, which will be a few volts (depends on dwell angel), but with the engine running a test light may just glow dimly all the time.
Back to the original poster, look inside the distributor and make sure the ground wire to the points plate is not broken. It is the braided wire on the right of this photo, going over the arm from the vacuum canister.
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Tue Apr 19, 2016 4:15 pm Post subject: Re: Bad coil? No spark. |
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| David_nc_72std wrote: |
| You will most certainly NOT measure 12v at the (-) terminal when the points are closed. Note that the measurement is made while the engine is NOT running, something that most of us just assume everyone knows. |
Without measuring anything let me pose this thought experiment....
While the ignition switch is ON, do you agree there will be 12v+ on the wire leading to the ignition coil (+) terminal? I think we will agree yes. And while this is connected to the (+) terminal the coil will also have 12v in the primary winding.
Now the primary winding of the ignition coil is a coil of wire with a 3ohm resistor, but it is a straight circuit so the voltage will reach the (-) terminal. With nothing connected to the coil (-) there will always be 12v at this point in the circuit while the coil (+) is powered.
Remove the points from the distributor and connect the green wire of the points to the coil (-). Hold the points away from ground. Measure the voltage anywhere along the green wire. You will read 12v. If the points are close you will read 12v everywhere on the points.
Open the points and stick something non-conductive between the contacts. The body of the points will no longer have 12v but the half connected to the green wire will. So we still have 12v in the circuit up to one of the point contacts even when the points are open.
Enough with the thought experiment.
If the points are the "switch" in this circuit, there should always be 12v+ available in the circuit all the way up to the switch (point contacts). When the points close the voltage is available along the entire length of the circuit all the way to ground (body of the points ground to the body of the distributor). When the points are open, there is no voltage on the ground side of the point contact, but there is always voltage on the coil side. You can test this with your voltmeter. This is with the engine OFF.
Remember, your voltmeter tests for the presence of voltage not current flow. When you test your disconnected battery you still read 12v even though none of it is being used to do any work like power a light (except for the small amount of current flowing thru your voltmeter), but there IS voltage there at the positive post of the battery.
Switch to the test lamp. When you connect your test lamp between the two terminals of the battery you are testing that current is flowing THROUGH the test lamp. For current to flow, there must be voltage. But if the current flow is too small through the test lamp it will not light. Usually this means there is no voltage or the voltage is so low that insufficient current is flowing to light up the lamp. But there is another explanation... there is sufficient voltage but current has chosen to flow down a different path rather than through the test lamp. This other path would need to have VERY low resistance.
When you hook your test lamp between the coil (-) terminal and a ground, you expect the current will flow through the lamp while there is voltage there and if the lamp goes out there is no voltage, but in fact that is NOT what you are testing when you connect your test lamp to the coil...
While the points are OPEN, the current flowing out of the coil (-) terminal has only ONE path.. thru the test lamp. So it lights up brightly.
Now when the points are closed there are two paths for the current to flow out from the coil (-) terminal... one is thru your test lamp (high resistance due to the bulb) and the other is thru the points (VERY low resistance). Current will always choose the path of least resistance. So much current flows thru the points that very little flows thru the test lamp. Regardless of the voltage at the coil (-) the current flow is small, so the test lamp is not lit. You might mistake this for no voltage, but really there IS voltage just no current flow thru the test lamp.
My calculation above where I say 1/72 of the current flows thru the test lamp is wrong. The resistance thru the points is not 1ohm, it is near zero. Let's just say there is 0.001ohms of resistance thru the points. The ratio between 0.001 and 72ohms is... 0.001 / 72 = 1:72,000. So only 1/72,000 of the current flowing thru the coil is flowing thru the test lamp while the rest is flowing thru the points. If I estimate 4A flows thru the coil then only 0.00005A flows thru the test lamp while the points are closed; not enough for it to light up.
| David_nc_72std wrote: |
| If the engine is running while you make the measurement, you will measure the average DC voltage, which will be a few volts (depends on dwell angel), but with the engine running a test light may just glow dimly all the time. |
Just a point (pun) on testing voltage at the coil (-) while the engine is running.... the coil works when the points open and the primary circuit collapses. This induces a spark in the secondary. Anything connected to the coil (-) providing a second path to ground for current to flow affects the coil function. If current is flowing thru the coil primary then the primary circuit doesn't collapse. That means no spark (or a weak spark).
I know if you accidentally connect your reverse lights to the coil (-) instead of the (+) the engine will die when you shift into reverse. Shouldn't the same thing happen when you test voltage from the coil (-)... you prevent the coil primary circuit from collapsing.
_________________
AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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sankaido
Samba Member
Joined: April 30, 2013
Posts: 3
Location: AUSTRALIA
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| Posted: Mon May 23, 2016 5:24 am Post subject: Re: Bad coil? No spark. |
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I think this is my 1st post after occasionally referring to this fabulous site over the last decade - and it is a question related to the coil issue for which I haven't yet come across the answer. A severe rain drenching has brought my daughters '73 (?) 1600 superbug to a stop, and as it has now dried out I am giving it a valve, points, distributor, condensor, coil check to hopefully bring it back to life. Having reached the stage of setting the spark timing which I have done 4-5 times over the years, I'm surprised to find that this time the earthing contact light is lit while the distributor points are closed, and goes out when they start to open - exactly the opposite to what I expected and to all the times I did this previously. I have not been driving the car in recent years, but am not aware of any work having been done on it other than by me. A new coil and condenser has been fitted and the wiring is all correct. I have not tried to start the car, and would be most grateful if anyone can advise either what I need to do to get the light to come on when the points are opening rather than closing, and what have I done wrong to cause it to happen.
I would also like to record my gratitude to the people who run the Samba and all the posters, whose contributions make such a huge contribution to keeping these vehicles on roads all over the world.
sankaido |
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kreemoweet
Samba Member
Joined: March 13, 2008
Posts: 3897
Location: Seattle, WA
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| Posted: Mon May 23, 2016 7:33 am Post subject: Re: Bad coil? No spark. |
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| ashman40 wrote: |
| . . . Current will always choose the path of least resistance . . . |
This is not correct. Current will flow through EVERY available path, in inverse proportion to each path's resistance.
Your posts above about electrical behavior are complete hogwash. You really need to educate yourself about basic electricity. Especially you need to grasp
the concepts involved in using Ohm's Law, and the very important subject of "Voltage Drop" when current flows through a resistance.
| sankaido wrote: |
| . . . exactly the opposite of what I expected . . . |
It sounds like you have your test light connected between the coil - and + terminals. If so, you are getting the expected results. If, on the other hand, you connect the test
light between the coil - terminal and ground, you will get the opposite behavior.
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'68 bug: seized by the authorities
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Stop dead photo links! Post your photos to The Samba Gallery! |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Mon May 23, 2016 10:49 am Post subject: Re: Bad coil? No spark. |
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| kreemoweet wrote: |
| ashman40 wrote: |
| . . . Current will always choose the path of least resistance. So much current flows thru the points that very little flows thru the test lamp. . . . |
This is not correct. Current will flow through EVERY available path, in inverse proportion to each path's resistance. |
I did mention a small amount will flow so clearly I didn't mean current ONLY flows over the path with least resistance.
I was intentionally trying to avoid the phrase "inversely proportional" because it would muddy my simplified explanation. More current will flow over the low resistance paths. If the difference in path resistance is extreme (like this example) then it could appear that no current is flowing or there is no voltage present even when there is.
| kreemoweet wrote: |
| Your posts above about electrical behavior are complete hogwash. You really need to educate yourself about basic electricity. Especially you need to grasp the concepts involved in using Ohm's Law, and the very important subject of "Voltage Drop" when current flows through a resistance. |
I would welcome a review of the amount of current that would flow thru the test lamp connected between the #1 (-) terminal and ground when the points are OPEN and when CLOSED. I did take some liberties in the estimated current and resistance since I don't have a coil and points to actually measure. I would appreciate your explanation on the voltage and current that should be expected at different points in this circuit. Rather than just stating my explanation is hogwash, please correct it in detail.
_________________
AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Mon May 23, 2016 10:58 am Post subject: Re: Bad coil? No spark. |
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| sankaido wrote: |
| ... I'm surprised to find that this time the earthing contact light is lit while the distributor points are closed, and goes out when they start to open - exactly the opposite to what I expected and to all the times I did this previously. |
Please detail what you are using as a test tool? Simple 12v test lamp? Multipurpose diagnostic probe? Continuity tester?
How have you connected your tester? The typical arrangement for static timing the ignition is to connect one end of your test lamp to the #1 (-) terminal along with the green points/condenser wire. The other end of the test lamp is grounded.
In this configuration the test lamp will turn ON when the points are OPEN.
If you instead connected your test lamp in-line with the green wire to the points (green points wire connected to one end of the test lamp and the other end of the test lamp connected to the (-) terminal) then the test lamp will turn ON when the points CLOSE and OFF when the points OPEN.
In this configuration you are testing that the points ground the green wire when CLOSED and leave an open circuit when OPEN.
_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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sankaido
Samba Member
Joined: April 30, 2013
Posts: 3
Location: AUSTRALIA
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| Posted: Mon May 23, 2016 9:35 pm Post subject: Re: Bad coil? No spark. |
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Ashman thanks for responding. I am using a standard 6/12V test lamp clamped onto the - coil terminal to which the green wire to the distributor is also connected, and grounding it onto the engine body. The black wire from the front is connected to the + coil terminal. I was pretty careful to try and ensure both my test light wire and the green wire are fastened to the - coil terminal, but as the clamp on the test light wire is (comparatively) bigger than the green wire connector and the space is restricted, it seems possible to me that it may, in-effect, have become an in-line connection without being obvious (I hope that makes sense).
The car is at my daughters place about 10 miles from my home - I will go over there again tomorrow to recheck and let you know. I also have access to a multimeter, but prefer the test light for the timing adjustment as it is easier to see. |
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catahoula lou
Samba Member
Joined: August 30, 2008
Posts: 594
Location: south of Silver Springs, NV
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| Posted: Tue May 24, 2016 7:22 am Post subject: Re: Bad coil? No spark. |
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If you have an electric choke, make sure it's connected to the same side of coil as the points/condenser. If you have it connected to the ignition side of the coil, it will steal too much electricity to make a spark.
I know this, as I accidentally did this recently, causing me to not be able to drive my lowlight for a few weeks, until I took another look (DOH!) and connected it to the correct side. Common mistake if rushed or not paying attention...
Best,
Thom
_________________
1 great wife
2 Catahoula Leopard Dogs (Mahogany Star and Spartan) - RIP Lucy, Braveheart, & Dusty!
1 1959 mango green Ragtop Bug (the "Mango")
1 1958 pantina red Lowlight Ghia (the "Chili Pepper")
Still looking for:
(1) My Dad's 1955 356 (he raced it amateur-class at Riverside and other courses during 1950s),
(2) My parent's black 1955 hardtop bug (CA license plate FWC 201 or FWG 201), and
(3) My parent's agave green 1957 ragtop bug (CA license plate LFK 734). |
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Cusser
Samba Member
Joined: October 02, 2006
Posts: 31360
Location: Hot Arizona
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| Posted: Tue May 24, 2016 9:23 am Post subject: Re: Bad coil? No spark. |
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| catahoula lou wrote: |
| If you have an electric choke, make sure it's connected to the same side of coil as the points/condenser. Thom |
If you have an electric choke, make sure it's NOT connected to the same side of coil as the points/condenser.
Electric choke, electro-jet, back-up lights ALL go on the positive terminal of coil (#15) which also has the positive feed from the ignition switch.
On other side of the coil (the negative terminal #1) goes just the wire from the distributor (and a tach - if you have that - but leave that wire off as you troubleshoot).
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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catahoula lou
Samba Member
Joined: August 30, 2008
Posts: 594
Location: south of Silver Springs, NV
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| Posted: Tue May 24, 2016 3:56 pm Post subject: Re: Bad coil? No spark. |
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My mistake. Meant to say to connect to ignition side of coil. Did not have car/wiring diagram nearby. If you do connect to points/condenser side, won't fry anything, will just steal electricity needed for sufficient spark.
Come to think of it, I posted my "advice" about 20 minutes before my blood sugar crashed to 41. A couple of Dr. Peppers brought me out of it about 30 minutes later. Confusion likely due to hypoglycemia...
Best,
Thom
_________________
1 great wife
2 Catahoula Leopard Dogs (Mahogany Star and Spartan) - RIP Lucy, Braveheart, & Dusty!
1 1959 mango green Ragtop Bug (the "Mango")
1 1958 pantina red Lowlight Ghia (the "Chili Pepper")
Still looking for:
(1) My Dad's 1955 356 (he raced it amateur-class at Riverside and other courses during 1950s),
(2) My parent's black 1955 hardtop bug (CA license plate FWC 201 or FWG 201), and
(3) My parent's agave green 1957 ragtop bug (CA license plate LFK 734). |
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sankaido
Samba Member
Joined: April 30, 2013
Posts: 3
Location: AUSTRALIA
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| Posted: Wed May 25, 2016 6:34 am Post subject: Re: Bad coil? No spark. |
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| Ashman - further to yesterday, I attached a double connector to the negative coil terminal to enable me to connect the green wire to the distributor and the test light connector on separate connections. It made no difference - the light still goes out when the points start to open at TDC, and lights up again when they separate - this is repeated 4 times in one full revolution. The only other wire connected is from the positive terminal to the carburettor. |
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Ursalon
Samba Member
Joined: February 24, 2016
Posts: 51
Location: Orange County
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| Posted: Wed May 25, 2016 11:01 am Post subject: Re: Bad coil? No spark. |
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| condenser should be on (-,1), battery and everything else on (+,15). Easiest way to check the coil is to pull the wire from the top of the distributor cap and hold it a few millimeters away from some grounding part of the engine. with the ignition on, crank the engine using the generator/alternator and watch for a spark. If you KNOW that the coil is good from your other car, that's a problem with either the condenser or the points. By checking for spark at the plug you add so many more components into the equation - coil, condenser, distributor, rotor, points, timing, wires, and plugs. If your problem is with the coil follow the above. If it's something else check to make sure your timing is right, the points are gapped properly, and there's no corrosion and then go from there. |
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David_nc_72std
Samba Member
Joined: August 22, 2015
Posts: 841
Location: Winston-Salem, NC
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| Posted: Wed May 25, 2016 6:46 pm Post subject: Re: Bad coil? No spark. |
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From your previous posts, it sounds as if the test light is ON when the points are closed, goes OFF briefly at the point where the points begin to open, and then goes ON again when the points are fully open. If this is correct, then it sounds like you are not getting a good contact to ground when the points are closed.
Try the following test:
Rotate the engine until the points are CLOSED and your test light is ON.
Remove the test light wire from the ignition coil terminal, and briefly touch it to the following points, and report whether the test light is ON or OFF:
1 - the connector that comes off the points and connects onto the condenser
2 - the moving arm of the points
3 - the stationary arm of the points
4 - the plate that the points are mounted onto
5 - the body of the distributor |
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