how to test coil/condenser

[retro rider]

i think i have lost spark on my 30 model a. what do i need to test coil/condenser. is there a way to diagnose where the failure is?

[Mike V. Florida]

I posted this a couple of days ago;

Some possibilities are:
1.Blown or defective fuse (use of a fuse is an aftermarket item)
2.Bad connections at ammeter, or ammeter itself (ti find out put a jumper wire from one post of the terminal box to the other to take the ammeter out of the circuit temporarily)
3.Bad ignition switch and/or cable, or loose cable connection at switch.
4.Loose or broken wires at bottom of coil
5.Loose or broken wires inside terminal box
6.Loose, bare or broken pigtail wire under distributor plate, or wire grounding to plate or distributor body
7.Points not opening, or point arm grounding to cam due to worn rubbing block
8.Worn electrode in underside of distributor cap
9.Loose or broken high tension wire from coil to cap
10.Condenser burned out or grounding (some condensers are too long and can touch the distributor body inside)
11.Weak coil
12.Rotor not turning due to loose cam screw or bad timing gear.


Ok now break out a volt meter (a light bulb can give false readings).
Start at the fuse block, you should have voltage on both sides of the fuse. If you only have voltage on one side, replace the fuse of fuse block.

Now with voltage on both sides of the fuse, move up to the junction box. There should be voltage at both terminals. If voltage is present only on one side the problem is at the ampmeter and you should Jumper the ampmeter for now.
You should have voltage on both sides of the coil. If not,
remove the red wire on the coil and check again. If you now have voltage on both sides, you have a problem further on. If the voltage is still only in one side you have a bad coil.

Open the points with a piece of paper and remove the condenser. Turn the key on and you should have voltage at the points.
Replace the condenser and you should still have voltage.

If voltage is missing, remove the top plate and check for voltage on the bottom plate.

Check is the connector from the ignition switch screwed in to far? Do you have voltage on the wire to the upper plate?

Is this wire shorting to ground or broken?

Are the point closing.
Let us know what you find.

[Tom Wesenberg]

The easiest way to check the coil is to use a volt meter or test light. With the key OFF you should always have voltage on both coil primary terminals. With the key ON and the points closed, you should have voltage on the feed side of the coil primary terminal, but you should have ground (no voltage) on the other primary terminal, which leads to the points.

If you still have voltage on both coil primary terminals, with the points closed and key ON, then touch the test light to each of the points contacts. If the movable contact shows voltage, but the ground contact doesn't, then the points are dirty, or not fully closed.

If you don't have a test light or voltmeter handy, then just stop the engine with the points open and key ON. Short across the points contacts with a screwdriver and see if you now have a hot blue spark out of the coil wire.

[retro rider]

seems i have spark as far as points. i set gap because they were barely opening. would i be able to see my little test light fire on the plug wires as i turn it over. also at first i thought maybe it was a fuel issue because plugs are dry. wouldn't they be wet after cranking it if i had no spark? i put my test light on the plug wires and cranked it but don't see any light.

[Milton]

Don't use the test light on the plug wires, use an air gap. If the spark can't get across a slight gap it will surely not get across a plug gap.

With the points closed wipe between the points with clean paper, turn on the ignition, open the points with your finger and you should get a spark from the coil wire. If not, crank the engine to open the points and connect a jumper wire to the points lead. Ground the jumper and open it, when the jumper is removed from ground a spark should occur across the gap in the coil lead.

In my youth I did that for about a week before I figured out my points were bad.

[BILL WILLIAMSON]

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Originally Posted by Milton

Don't use the test light on the plug wires, use an air gap. If the spark can't get across a slight gap it will surely not get across a plug gap.

With the points closed wipe between the points with clean paper, turn on the ignition, open the points with your finger and you should get a spark from the coil wire. If not, crank the engine to open the points and connect a jumper wire to the points lead. Ground the jumper and open it, when the jumper is removed from ground a spark should occur across the gap in the coil lead.

In my youth I did that for about a week before I figured out my points were bad.

I've found that crummy, burned points are the most overlooked problem, when one contact has a pointy build up and the other contact has a deep blackish hole. A way to test, is with plugs out, key on give a long constant crank and observe the spark between the point contact. You should see a barely discernable, bluish white spark constantly. If tou see a yellowish spark flare out at times, the points are bad! Filing doesn't do much good. The old Snap On flex strips could remove the pointy build up and could get you going temporarily. The Modern upper plate with modern Ford points and condensor eliminates this pointy build up because one point contact has a hole, letting it contact in an ever changing circle and not causing any pointy build up. I ran late points for 9 years with only a couple of gap adjustments and those late condensors are almost failure proof. Also use an approved distributor cam lubricant, not vaseline!!

[Tom Wesenberg]

The points with the hole in the center are known as "ventilated points" or "vented points" and run a bit cooler because the air can circulate through the hole.

When points have a pointed mound on the + contact, it's a result of under capacity of the condenser. If the points have a mound on the - contact, it's a result of over capacity of the condenser.

My original points have worked fine for many years, and I find them the easiest to adjust. A small tube of cam lube will last a lifetime. I'm still using the same tube of cam lube that I bought in the 70's.

[retro rider]

after going through the steps above, thanks mike v, i have voltage to the points and they open and close. still no fire, not even a pop or a puff. i've cleaned the carb and i believe it is working properly. would bad points or condenser fool me. even if i have voltage and they look like they are working.

[Tom Wesenberg]

By "STILL NO FIRE" do you mean you still have no spark?

Or, do you mean you have no fire from combustion in the cylinder?

[Milton]

Originally Posted by retro rider

after going through the steps above, thanks mike v, i have voltage to the points and they open and close. still no fire, not even a pop or a puff. i've cleaned the carb and i believe it is working properly. would bad points or condenser fool me. even if i have voltage and they look like they are working.

Turn the engine to close the points and tell me if the voltage drops to zero. If it does then the points seem right, if it does not then there is a bad ground on the adjustable point side.

[Bruce,Upstate NY]

The distributor body needs to ground to the head.

[Mike V. Florida]

Originally Posted by retro rider

after going through the steps above, thanks mike v, i have voltage to the points and they open and close. still no fire, not even a pop or a puff. i've cleaned the carb and i believe it is working properly. would bad points or condenser fool me. even if i have voltage and they look like they are working.

Voltage when they are open and nothing when they are closed?

[retro rider]

what i mean is i have voltage when the points are open but i can't get the engine to fire. i took the plugs out and turned the garage lights off and then turned the engine over and i can see spark at all four cam breaker points but it is irregular and white and somewhat scattered. not a nice even blue spark. but shouldn't the engine at least spit or sputter or something? i have ordered new points, condenser, rotor, cap, coil, and more. parts seem inexpensive enough and i figure it can't hurt.

[Tom Wesenberg]

Stop the engine with the points OPEN and key ON. With a piece of wire, ground the movable points contact to a head nut and remove several times. While doing this hold the coil wire 1/2" from a head nut and each time the ground wire is removed from the head nut you should get a nice blue spark from the coil wire. Do you?

[Milton]

Originally Posted by retro rider

what i mean is i have voltage when the points are open but i can't get the engine to fire. i took the plugs out and turned the garage lights off and then turned the engine over and i can see spark at all four cam breaker points but it is irregular and white and somewhat scattered. not a nice even blue spark. but shouldn't the engine at least spit or sputter or something? i have ordered new points, condenser, rotor, cap, coil, and more. parts seem inexpensive enough and i figure it can't hurt.

When you say that you can see spark at all four cam points is that spark at the points or from the coil wire?

[retro rider]

i see spark where the points open and close.

[Milton]

Originally Posted by retro rider

i see spark where the points open and close.

Assemble the dist. rotor and cap. Take the coil wire out of the dist. cap and hold it about a half inch from a head nut and crank the engine. Does spark jump the gap between the coil wire and head nut?

[BILL WILLIAMSON]

Originally Posted by fordgarage

According to Ford, vaseline was the approved distributor cam lubricant!

That was a long time ago, and there was a lot of crap that Dear Henry didn't know and a lot of good products that had not been developed yet that are very helpful. I think we tend to overate ol' Henry at times.