Weak spark at points

[wore out]

I was thinking bad distributer cap, after all the parts that were changed, but not the cap (unless I missed that).Mark

The O.P. stated he is getting intermittent spark even when checking at the coil wire, that (for the most part) takes the cap and rotor out of the picture.

 

[JMOR]

He has said, "all tested good" about many, many items/things, but no one knows how he tested and what results he saw or how he interpreted the results. So that leaves us readers unsure of anything. Everyone can keep on guessing, though.

 

[Janicholson]

These ideas may find use:
The cranking voltage at the coil may be so low that the spark fails. A hot battery (no 6v battery should show more than 6.4 volts when not being charged, so your meter may be suspect) If voltage falls below 4.5 volts that might be reason for no start. Battery cables need to be 1-O gauge.
The reduces sparking is correct at the points with the condenser in place. The spark is much less, and different than the high voltage spark at the plugs.
The distributor shaft should be checked for bushing wear. Side to side, and up and down, not in and out, axially with the shaft.
Manually opening the points may cause them to move sideways at the moment of opening causing poor actual spark.
Jim

 

[13fx]

Do you have a test light? Transmission in neutral. Ground the lead to the block. Put the probe on the coil terminal with the wire that goes to the distributor. Ignition on. Crank the engine over with the starter. Does the test light blink on and off as the engine turns over?

Yes, and that's exactly what I have been doing. I will get the light to flash once every 2-3 full crank rotations. When I open the points manually I get a spark at the points every time but it looks really weak.

 

[Brownie450]

Not to sidetrack here, but have you got an idea of the
value of a typical cap in an ignition system, Jim?
We checked one the other day, & it had 180 ufd.
Sound about right?
Jim

 

[JMOR]

Not to sidetrack here, but have you got an idea of the
value of a typical cap in an ignition system, Jim?
We checked one the other day, & it had 180 ufd.
Sound about right?
Jim

Farrrrrrrr too big! 0.3 microfarad is common

 

[zuhnc]

All of the above discussions/comments are good reasons for electronic ignition.

 

[wore out]

So this is a Ford 134 with a side mounted distributor. I have tried a different rotor, a different cap, a different condenser, a different coil and non of that has changed. The points are not new, but I had them put and cleaned them up. The points are not pitted, the contact points on the arm is nice and shiny, the contact points on the base is a dull grey metal that won't shine up. I'm definitely not ruling out the possibility it could be bad points still, but every time I open them manually they throw spark. I have cleaned up almost every metal contract area that I can think of.

"contact points on the base is a dull grey metal that won't shine up"

And you think that's "normal"/OK? You've seeing the source of the problem and denying it to yourself!

 

[wore out]

"the ALL Important points-file"

The ONLY use for a points file is to scrape up a set of points is to get an engine to start and run long enough to get it to the garage to replace the points.

Once you have roughed up a set of points with a file the likelihood that they will fail to make contact soon and "need" to be filed again and again is almost guaranteed.

 

[Janicholson]

Farrrrrrrr too big! 0.3 microfarad is common

Agree: between .2 and .35 Microfarad. any within that range will make spark with most coils. and they need near 500 volt dielectric to withstand the ringing of the coil discharge. Jim

 

[Janicholson]

"the ALL Important points-file"

The ONLY use for a points file is to scrape up a set of points is to get an engine to start and run long enough to get it to the garage to replace the points.

Once you have roughed up a set of points with a file the likelihood that they will fail to make contact soon and "need" to be filed again and again is almost guaranteed.

Very fine paper to polish a contact, then post abrasive cleaning. Flat hitting flat points will conduct 4 amps as a switch (for a while) Jim

 

[Jim.ME]

Yes, and that's exactly what I have been doing. I will get the light to flash once every 2-3 full crank rotations. When I open the points manually I get a spark at the points every time but it looks really weak.

You originally posted you were using a timing light to test for spark. That is testing on the high side of the coil, to do that you need to connect it to the coil wire or a plug wire. I suggested using a test light on the primary side of the coil, the small terminal the wire that goes into the distributor body, then the points, hooks to. No where until you posted this did you say you were testing as I described. They are two different methods, which did you actually do?

What is the voltage at the battery terminal of the starter solenoid at rest? What is the voltage at the battery terminal of the starter solenoid When the starter is cranking the engine over? Too much voltage drop during cranking can affect the ignition function.

 

[JMOR]

You originally posted you were using a timing light to test for spark. That is testing on the high side of the coil, to do that you need to connect it to the coil wire or a plug wire. I suggested using a test light on the primary side of the coil, the small terminal the wire that goes into the distributor body, then the points, hooks to. No where until you posted this did you say you were testing as I described. They are two different methods, which did you actually do?

What is the voltage at the battery terminal of the starter solenoid at rest? What is the voltage at the battery terminal of the starter solenoid When the starter is cranking the engine over? Too much voltage drop during cranking can affect the ignition function.

His 180 microFarads ought to quench the H... out of points arc!

 

[miner09]

I have problem and it was ground not making good ground. Took grinder and cleaned under cable. Started right up.

 

[Jim.ME]

What do you have the point gap set at?

After filing and gapping the points did you rub the contacts with a piece of brown paper bag, uncoated card stock, even a folded-up dollar bill to clean any residue from them?

 

[Ericp351]

We are well down the Rabit Hole. Since we are at "PLAN F" level- check the/any dist cap center Carbon Button. Can jam up, or become Glazed over. When in doubt- bend up the rotor tab up with your thumb-nail. Did you wiggle rotor/ shaft side to side to check for grossly trashed bushings? These are forgiving, but a bit of brass each 1/2 century needs to get swapped sometimes. Lastly, old machines can sometimes wind up with rotors and caps that do not quite match up, even if they look OK. Decades for "LOOKS Good enough" / "what the parts store has.." types of fixes. Hope you get her running.

 

[13fx]

The is a lot of wisdom there from Tom. Although the tests you have performed have some value testing the ignition circuits to see what their voltages are during the cranking mode tells you much more.

If the points are basically new this is probably an acceptable test. If the points have been ran a while I prefer to test their ability to provide a ground to the primary circuit against the load of the coil. When they close it should drop to a .5 volts and .2 or less is better. What is the engine and what is it in? Yes answers about Kettering ignitions (points) should be universal but certain system have nuances that need taken into consideration. It seems engines that are 200CID or less give far less problems for a 6 volt cranking system than bigger engines with longer strokes and increased compression ratios from stock such as a Farmall M with Fire Crater pistons. What is the battery voltage you see when cranking? Checking it both at the battery and at the starter can also provide additional insight into proper amperage transfer.


Checking “spark” at the points is one of the most misconceived diagnosis for points. You are actually checking for an “arc” Should you see an arc there when the points are opened? Sure, but judging the effectiveness of your ignition to provide a good spark by that is a guess at best, in fact points that are working the most effectively will show a lesser “arc.” Seeing any kind of spark there only somewhat reliably tells you the primary circuit is seeing some voltage.

Your timing light is likely powered by the battery, is it a 6/12 volt unit? Operating on 6 volt probably is on the low end of its circuits range to function properly. Back to what is the battery voltage dropping to while cranking? If it drops quite a bit expecting the timing lights induction clamp to pickup every spark is asking a lot. An adjustable gap spark tester is the best tool for checking spark, see link. Example Adjustable spark tester Powering the timing light from a separate battery would help it to be more reliable in this case.

So I've set the light on a 12v battery. Went back over all the connections, re cleaned the points again and turned the engine over by hand. I get the same results. What I was able to determine by turning it over by hand is that cylinder #2 is the only one firing and it fires every time it's supposed to. So I changed the plug wire and spark plug on #1. No change. Cap and rotor replaced with one I know work, no change. Checked the distributor shaft for play side to side and up/down and side to side is almost non existent and there is no up/down play. Took the dust cover off of the distributor and watched it as I cranked over the engine. The points fire every time they open on all four of the rounded corners. Ran a hot wire from the battery to the coil to rule out anything behind the coil. No change. I'm going into town to get a new set of points, but have very little faith in that just because I get consistent spark on #2.

 

[used red MN]

His 180 microFarads ought to quench the H... out of points arc!

Wrong guy with the 180 ufd, not the OP 13fx

We checked one the other day, & it had 180 ufd.

 

[used red MN]

So I've set the light on a 12v battery. Went back over all the connections, re cleaned the points again and turned the engine over by hand. I get the same results. What I was able to determine by turning it over by hand is that cylinder #2 is the only one firing and it fires every time it's supposed to. So I changed the plug wire and spark plug on #1. No change. Cap and rotor replaced with one I know work, no change. Checked the distributor shaft for play side to side and up/down and side to side is almost non existent and there is no up/down play. Took the dust cover off of the distributor and watched it as I cranked over the engine. The points fire every time they open on all four of the rounded corners. Ran a hot wire from the battery to the coil to rule out anything behind the coil. No change. I'm going into town to get a new set of points, but have very little faith in that just because I get consistent spark on #2.

Consistently fires only number 2 cylinder?? You bought a replacement engine, did this distributor come with it? Maybe there is something oddball about that distributor. Not sure what that would be that would allow it to fire at one distributor cap terminal and not the others. Does this use the rotor clip I hear repeatedly mentioned in Ford circles?
Bottom line is have you seen this distributor run an engine?

 

[Ray,IN]

Intermittent spark is caused, probably over 95% of the time, by breaker points that don't consistently/reliably make "good" contact each and every time they close.

I agree, I once bought a new set of points, they didn't work. Where they fit over the mounting peg had no insulation, so they were constantly grounded.
Perhaps 13x has that situation, poor insulation.