No spark '31

[1939mars]

I am trying to solve a no spark problem with no luck so far. I am new to A's but have some V8 era experience.

It was running (not terribly well - little power on hills). When I went to pull it back into the garage it would not start. I am getting absolutely no spark.

I find 6V to both sides of the coil. I had an extra coil so tried that. Nothing. The 2 I have show about 1.5 ohms primary and 8.5 kohms secondary.

I checked the key switch by jumpering it.

I tried 2 new condensers I had on hand.

I have done a lot of reading & video watching and found that if everything is set up properly, one should get a spark at the points just by cycling them. I get nothing. I checked voltage at the points with paper in between them and I do not get a full 6 V. I don't think that is too surprising with the condenser in the circuit, but I would expect it to come up to 6 after a bit. What is normal? I checked that the other side of the points is grounded.

I read that the shield of the key switch cable can be screwed too far in and short. I checked for continuity between the shield and the wire and got open as expected.

With the points closed I checked current with my current meter. Zero +/- 1 milliamp. I would expect there to be current flowing so this has me puzzled.

I have made other measurements and don't find anything else unexpected but I do not know for sure what is expected! Any help would be appreciated.

[1crosscut]

With the rubbing block of the points on one of the 4 low spots on the cam so the points are closed hold the coil wire a short distance from one of the head stud nuts and snap the points open/closed to see if you have a good blue spark that jumps to the head stud nut. If you have a good spark there then your problem is somewhere in the distributor.

Make sure your point gap is between .016 and .020 and the points are smooth and clean. A few passes with some 220 sandpaper between the points is a good thing to do also.

For the armored cable that screws into the distributor I turn the distributor three full turns once the threads catch and stop there. Never have had a problem with it getting too far in and shorting out.

[1939mars]

Originally Posted by 1crosscut

With the rubbing block of the points on one of the 4 low spots on the cam so the points are closed hold the coil wire a short distance from one of the head stud nuts and snap the points open/closed to see if you have a good blue spark that jumps to the head stud nut. If you have a good spark there then your problem is somewhere in the distributor.

No spark that way either.

[Gary WA]

Ignition off: 6v at battery connection on starter,6v both terminal wing nuts,6v both coil terminals, paper between points to keep open, turn on ignition switch 6v at open point arm? this test has checked all wiring from battery to points; failed test broken or disconnected wire in circuit! worn point arm.? Loose Ammeter connection?

[nkaminar]

With the point open, short across the points with a screwdriver. You should get a spark. If you do than the points need dressing (sanding with 400 grit paper or a points file) or install new points. If you do not get a spark by shorting across the points then there is a problem inside the distributor. Trace the wiring with an ohm meter to check for conductivity and shorts. There are plenty of places inside the distributor where things can go awry.

[wwirz]

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[vern hodgson]

Originally Posted by Gary WA

Ignition off: 6v at battery connection on starter,6v both terminal wing nuts,6v both coil terminals, paper between points to keep open, turn on ignition switch 6v at open point arm? this test has checked all wiring from battery to points; failed test broken or disconnected wire in circuit! worn point arm.? Loose Ammeter connection?

Little black wire?

[Chuck Sea/Tac]

Here’s a simplified ignition diagram.

[Big hammer]

An original ignition system? Less than 6 volts at the movable points side ? You should have the same voltage there as a the coil, terminal post, starter switch, battery. The condenser won’t slowly build voltage. Little black wire as Vern hinted to, maybe.

[Mike Peters]

nkaminar
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Default Re: No spark '31
With the point open, short across the points with a screwdriver. You should get a spark. If you do than the points need dressing (sanding with 400 grit paper or a points file) or install new points. If you do not get a spark by shorting across the points then there is a problem inside the distributor. Trace the wiring with an ohm meter to check for conductivity and shorts. There are plenty of places inside the distributor where things can go awry.
_________________

This is what I do as well. Old points on Model A's don't seem to age well. If I have 6V to the points, then the best fix for me is always replacing the points and problem solved. Dressing or filing them doesn't usually work for me. OP does not say if he replaced the points.

[burner31]

Back the ignition cable out of the distributor, make it just finger tight.
If you played with it it may be grounding out...worth a try

[1939mars]

The simplified diagram did it for me - thanks! I had tried everything I could think of until I saw the ammeter in series with the ignition system. A bad ammeter could fit what I saw - low voltage points open and no current points closed. Sure enough, I jumpered across the ammeter and got spark at the points!!
Thanks for all of the suggestions. Now my question is whether or not ammeters originally had a ford script on the face or not - I see with and without in the catalogs.

[Gary WA]

No Ford script! 20; thanks for the follow up!

[Patrick L.]

Need an ammeter ? I'd recommend trying to find an original rather than repro.

[1939mars]

I've got a repro on order while I look for an original one. Is there a good way to tell original from repros? Did ford stamp a part number in the case or anything like that? I know originals were +/-20A and did not have the ford script on the face.

[rotorwrench]

The ammeters Ford used were just as simple as the late reproductions but they were a lot better quality in the needle pivot function plus they have an iron or steel C ring in there that the repros don't have. I believe this to be the magnet that keeps the needle centered but I don't have one to check. They used special nuts to secure the terminals to the case. This link is a good illustration of their construction. I think only the early ones had the Ford script.
http://www.fordgarage.com/pages/ammetertool.htm

If your ignition system functions by bypassing the ammeter then the shunt in there must be burned out like a fuse and is no longer passing current flow through. Either that or one of the terminals is cooked or loose.

Does your car have a pop out switch as OEM or has it been modified to a regular key switch? Pop outs can have problems over time that won't allow a good ground path from the coil to the breaker points when the switch is ON. Another thing is whether you have the original points and condenser set up or a late type. This makes a difference on the grounding circuit inside the distributor which can also experience problems with the connection between the lower plate and the movable upper points plate.