View Full Version : No Spark
04-11-2017, 05:40 AM
I haven't used the TBird for a few weeks so went to fire it up today & go cruising but it was a "no go".
Motor turns as usual but no spark.
I had a local mobile auto electrician call in & check for faults.
His diagnosis was that the coil was the problem, power to it but nothing out.
On his advice, I purchased & fitted a new coil but still no spark.
Put a plug lead on an old spark plug & the body to ground while turning the engine over....nothing.
Points are opening & closing & correct setting.
Is my next step to replace the condenser???
Could it be a problem with the coil resistor???
Also, where is the coil resistor located????
Not being at all an electrical person, any advice will be greatly appreciated.
04-11-2017, 07:23 AM
Sounds like a bugger. If the coil has power then I suggest taking you dizzy cap off and getting someone to crank the engine over, make sure the points are opening and closing.
If you're handy with a test light, connect the clamp to battery positive and put the test light on coil negative. The light should flash on and off with the engine cranking.
If it doesn't come on at all could be your points are not closing to earth out the coil, if it stays on all the time, your points are never opening. If it comes on goes dim, bright, dim, bright but never actually goes out, I'd say your condensor.
If you don't have power at the coil your ballast resister is a good cause, located on the firewall near where the brake lever is ( if it's a 60 just to the right of the booster - towards cars centre)
If you want to bypass the resister put a cable from battery positive to coil positive and crank her over if it fires your issue is definitely on the power side. Don't leave it connected to battery positive 2 long as it is an 8 volt system. Though a little while won't hurt.
If could be that the ballast resister bypass isn't working any more and it simply doesn't get a strong enough spark while cranking, if that is the case you will need a new start solenoid as that sends a signal to the coil on crank giving it full system voltage bypassing the ballast resister.
Edit: that bit is a touch confusing so I added a pic I borrow from Google, not off this car but same principle, as you can see one wire from start solenoid goes to coil positive so on crank it gets full system voltage not ballast resister voltage this bypass allows a strong voltage at the coil to help with starting
04-11-2017, 09:09 AM
...His diagnosis was that the coil was the problem, power to it but nothing out...Lex, I'm going to give simple instructions that are NOT found in your Shop Manual. This will prove your coil and condenser. If you get spark, they are good, so let's start:
This is high voltage so do not touch high-tension wires while the key is on. Let's start with the key off.
Take the cap off your distributor and 'bump' the engine so the points are OPEN.
Unplug the high-tension coil wire from the coil. Find an old spark plug wire and attach a spark plug to the end. If you don't have a spare, use one of the spark plug wires from your engine.
Lay the connected spark plug on metal, and temporarily, simply stick that wire into the coil tower.
Get a small-ish wire (#16 or so about a meter long) and connect it to a solid ground or to the battery neg. This is a 'test wire'.
Turn the key switch on but don't crank. Just leave it on.
Touch the grounded 'test wire' to your coil's neg post. When you let off the coil's post, the spark plug should 'snap' and you should see a pretty blue spark.
If what your mechanic says is true, that the coil has power with the key on, you should get a spark. If you don't see a spark, turn the key off, inspect the short distributor-to-coil wire's insulation (so that it doesn't short to ground). If the wire is good, change the condenser. After changing condenser, try the procedure again.
Looking down at the point's mounting plate, you should see a small ground strap that connects from the sliding points plate to the distributor case. Make sure it isn't broken or loose.
Ok, so what did we just do? We simulated your points. Normally the rotating engine opens and closes your points. Points simply ground the coil, just like the 'test wire'. - Dave
04-11-2017, 10:56 AM
Everyone should print that out and save it!!
04-11-2017, 03:51 PM
Great information...Thanks Dave!!!
04-11-2017, 09:41 PM
Ignition coils put out thousands of dangerous volts that the average meter cannot handle. So, 'trial and error' is the only alternative but testing must be done safely.
The procedure I described shows a few things:
If you get a spark...
Notice we eliminated the distributor cap, rotor and all the wires? If the coil produces a spark, use this test to find cap and rotor shorts, (usually from a crack or carbon trace to ground).
Is the spark pretty blue or orange? An orange color indicates a weak spark, possibly from a bad coil, bad ballast resistor or bad condenser.
The spark should produce an audible, 'snap' or 'tick' as it fires.
If you don't get a spark...
No power is feeding the coil
The coil is bad
The condenser is bad
The neg post of the coil is shorted to ground.
Check the ground strap on your points plate.
We are only using three essential components to prove their functions (power from the ballast resistor, the ignition coil and the condenser). This test intentionally does not get power from the starter solenoid so we can prove the ballast resistor.
As a teenager with no money, I learned to use a matchbook cover to set my points (in a pinch). The paper is .016" and matches were never far because I smoked cigarettes. I also used that same matchbook cover to keep the points open during testing. - Dave
04-11-2017, 10:12 PM
All fixed & running beautifully.
It was the small ground strap that connects from the sliding points plate to the distributor case had come loose.
While I was at it, cleaned & reset the points.
Such a relief to discover it was something very minor & easily fixed.
I totally agree with Joe that we should all print out the information supplied by both Dave & Wyldie.
I find electrical work a lot like rocket science so to have information supplied in easily understood language is very much appreciated.
Have a great Easter & happy cruisin'.
04-11-2017, 10:39 PM
All fixed & running beautifully...That's why we are here.
Most Squarebirders are really tired of reading my rants about grounds. That 'leg' is more important than the power side because we take it for granted. I'm glad that one-inch wire didn't cause a tow back home. Good job and Happy Easter, Lex. - Dave
04-12-2017, 06:28 AM
Happy cruising 😎
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