'51 Desoto Custom Distributor and Ignitition

[Tim Larson]

Good Morning!

 

I'm trying to help my neighbor get his 51 Desoto running for the season and have got myself it a pickle of sorts.

 

I know the car is getting good shots of fuel from the carb. and the engine turns over fine, but just won't fire. 

 

I had him turn the engine over with the dist. cap open so I could see if the points were sparking - at first they were, but it didn't last long. 

 

I suspected one of the tiny wire in the dist. might be grounding out on the dist. housing since it is missing the coating (see photo below)

In the process of removing the screws one of them flipped behind the breaker plate....

 

Doing some crowd sourcing on Facebook I am getting the sense that my best option is to remove the distributor (marking the rotor and vaccum advance location first)

 

Then I will try to rattle the screw out in an effort to not need to disassemble the unit further.

 

Anything else I need to consider? Was I jumping to conclusions with the small wire causing issues? 

 

 

 

 

 

[Dennis Detweiler]

Before removing the distributor, I'd try to retrieve it with a small magnet. Check with a couple of automotive parts stores and see if they have a magnet on a flexible shaft. I have a larger one that has saved me several times, but probably too large to get through the opening shown on your distributor. There may be smaller ones available.

As far as the initial problem, maybe the condenser is bad and won't hold a charge? I would replace the small wire. After looking closer at the photos, I would also get a new cap, rotor and wires. That should cover any current or near future problems.

[Tim Larson]

4 minutes ago, Dennis Detweiler said:

Before removing the distributor, I'd try to retrieve it with a small magnet. Check with a couple of automotive parts stores and see if they have a magnet on a flexible shaft. I have a larger one that has saved me several times, but probably too large to get through the opening shown on your distributor. There may be smaller ones available.

As far as the initial problem, maybe the condenser is bad and won't hold a charge? I would replace the small wire. After looking closer at the photos, I would also get a new cap, rotor and wires. That should cover any current or near future problems.

 

Thanks. Is removing the distributor that major of a project? I feel like it would be easier to replace the points/condenser/etc. with it out of the car. That way I can also make sure I get the correct points/condenser based on the number. 

 

I've never done this before, but probably a good learning experience. 

[Sniper]

That wire grounds the breaker plate to the housing, it is not your problem.

 

The distributor only going in one of two directions.  I would put the engine at TDC first, then not the location of the rotor and vacuum can as you mentioned, a picture with your phone will really help.  You can more easily change out the points and condensor as well as adjust the points on the bench.

[Tim Larson]

2 minutes ago, Sniper said:

That wire grounds the breaker plate to the housing, it is not your problem.

 

The distributor only going in one of two directions.  I would put the engine at TDC first, then not the location of the rotor and vacuum can as you mentioned, a picture with your phone will really help.  You can more easily change out the points and condensor as well as adjust the points on the bench.

 

Thanks for the input. So the wire I show out of the distributor will not cause a problem the way it is pictured? 

 

 

[Sniper]

Not a problem.  See pic of my distributor.  BTW the pic also shows the points riding on the point of the cam, this is where it needs to be to set the gap for your dwell, remember to check and adjust that when you put the new points in.

 

 

 

 

Edited May 7, 2020 by Sniper
I can't type or spell apparently

[Tim Larson]

6 minutes ago, Sniper said:

Not a problem.  See pic of my distributor.  BTW the pic also shows the points riding on the point of the cam, this is where it needs to be to set the gap for your dwell, remember to check and adjust that when you put the new points in.

 

 

 

 

 

Thanks, I should have double checked before messing around, but I'll consider this a learning experience. 

 

Would you suspect the points are the problem if I wasn't seeing a consistent spark? 

[Los_Control]

9 minutes ago, tjlarson88 said:

That wire grounds the breaker plate to the housing, it is not your problem.

Sorry that just seems wrong to me, seems sniper agrees with tj also.

I remember reading post in the past telling us to be sure and check the insulation on that wire as it will cause intermittent spark issue.

Very first thing I did while had my distributor out is replace that wire. I wonder if it makes a difference if +/- ground?

 

The distributor is slotted like a small block chevy, very easy to pull the distributor out and put it back with the rotor pointing in correct direction ... just do not rotate engine while out.

Then it is very simple to work on the distributor, very good chance the points need a good filing.

[Tim Larson]

5 minutes ago, Los_Control said:

Sorry that just seems wrong to me, seems sniper agrees with tj also.

I remember reading post in the past telling us to be sure and check the insulation on that wire as it will cause intermittent spark issue.

Very first thing I did while had my distributor out is replace that wire. I wonder if it makes a difference if +/- ground?

 

The distributor is slotted like a small block chevy, very easy to pull the distributor out and put it back with the rotor pointing in correct direction ... just do not rotate engine while out.

Then it is very simple to work on the distributor, very good chance the points need a good filing.

 

Thanks, I appreciate the input. I'm willing to learn through this process. 

[greg g]

If when the breaker plate moves, that wire contacts the dist body, it will cause the coil to ground. If it is in contact when the points should be open there will be no collapse of the field so no apart to the rotor.

[Los_Control]

1 minute ago, tjlarson88 said:

Thanks, I appreciate the input.

It was troubleshooting advice to others, complaining about a random miss while driving, they tried everything and a few spoke up and said to check that wire as it would cause this?

 

I only replaced mine because others said to, not because I had a issue.

[Loren]

One of the most basic tools in your tool kit should be a Test Light. It looks like an Ice Pick (with a clear handle and a light bulb inside) with a wire and alligator clip on the end.

Without taking anything apart you can see if the points are working and even check the timing.

Connect the alligator clip to the points side of the coil and the ice pick to the ground side of the battery.

With the ignition on roll the engine over. If by hand you will see the light go on and off. If by the starter it will flash. When the light is on the points are open. When the light is off the points are closed and the coil is being energized. When the points open the magnetic field in the coil collapses and the secondary creates the spark. So you can check the timing by observing when the timing mark comes up and the light goes on.

 

If you've removed the distributor and on replacing it you can't get it to start, it could be you are 180 degrees out. To check that take number one and number six spark plug out and use an air hose to blow air in the cylinder (at TDC). With the air cleaner off and the throttle open, if you hear air rushing out of the intake, the valves are on overlap and the other cylinder is on the power stroke. Needless to say double check your work. 

 

On distributors with vacuum advance (or in some cases retard) there are two plates to the breaker plate. These plates (one stationary, one movable) allow the vacuum chamber to change the timing independent to the centrifugal mechanical advance. That wire connects the movable plate to ground. The car may run without it but the point of contact with the stationary plate will begin to erode from the spark passing thru it. Eventually any time the vacuum chamber moves the breaker plate the eroded contact point will lose its ground connection and the engine will miss. I've seen breaker plates so eroded that even replacing the wire doesn't improve the way the engine ran. You had to replace the breaker plate as well. 

[Sam Buchanan]

There seems to be some confusion as to which wire needs to be insulated from ground...if I'm confused please correct. 

 

The wire from the power terminal on the distributor body to the points has to be insulated from ground. It is the wire with the black insulation in the photo.

 

The bare wire is merely a ground strap and it doesn't need insulation, polarity of the ignition system is not a factor. That is the wire under discussion.

 

 

 

Edited May 7, 2020 by Sam Buchanan

[Tim Larson]

39 minutes ago, Los_Control said:

It was troubleshooting advice to others, complaining about a random miss while driving, they tried everything and a few spoke up and said to check that wire as it would cause this?

 

I only replaced mine because others said to, not because I had a issue.

 

I only messed with the wire because I had read the same thing and this Desoto does not even seem to fire at the moment. The wire looked like it could have been grounding out on the side of the distributor. In my Plymouth the wire looks worn, but the car still runs and drives fine - I have spare wires just in case they do end up needing to be replaced at some point. 

 

The strange thing is that ever since last October the car does not want to start. It turns over fine, but will not fire. All I did was change the oil and filter for my neighbor in October and the car started and ran fine for me. Once parked in the garage it seems to want to stay there... 

 

I'll figure this out eventually - it's not that complicated. 

[Tim Larson]

2 minutes ago, Sam Buchanan said:

There seems to be some confusion as to which wire needs to be insulated from ground...if I'm confused please correct. 

 

The wire from the power terminal on the distributor body to the points has to be insulated from ground. It is the wire with the black insulation in the photo.

 

The bare wire is merely a ground strap and it doesn't need insulation. That is the wire under discussion.

 

 

 

 

Thanks, Sam. I appreciate the input.

 

Once I get the screw out that dropped in I'll put everything back together so I can do more testing. 

[Los_Control]

3 hours ago, tjlarson88 said:

I'm trying to help my neighbor get his 51 Desoto running for the season and have got myself it a pickle of sorts

When you say for the season, I get the impression it has not been sitting for 20 years and running last season?

 

Then I imagine that it has newer tuneup parts installed?  We are just guessing here.

 

It is very common for condensers to fail. Sometimes they are bad out of the box, sometimes they work for a short time then fail. Sometimes if they die slowly they will burn the points out.

Just saying, condensers are always suspect.

[Tim Larson]

Just now, Los_Control said:

When you say for the season, I get the impression it has not been sitting for 20 years and running last season?

 

Then I imagine that it has newer tuneup parts installed?  We are just guessing here.

 

It is very common for condensers to fail. Sometimes they are bad out of the box, sometimes they work for a short time then fail. Sometimes if they die slowly they will burn the points out.

Just saying, condensers are always suspect.

 

It was definitely running last fall. He bought and in Iowa and I drove it home 4-5 hours to MN. 

 

It didn't seem to ever have trouble starting until it did all of a sudden. 

 

Thanks for your input - I appreciate it. 

[Sniper]

Inconsistent spark can be caused by a number of things.  The points, the condensor, the coil, the coil wire, the cap, the rotor, the wiring.  Basically, anything in the ignition system.

 

Let's go over each item separately.

 

The points -  nothing but a switch, when they are closed they let the coil charge up, this is the dwell.  When the open the coil fires.  In your pic the brown looking wire is the one that goes to the coil and it should be well insulated as well as the wire that goes from the the distributor to the coil +.  If either is shorted to ground you get no spark.

 

The condensor -  it's the canister looking thing with the red wire.  The condensor is used to limit arcing on the points to increase their life.  The red wire should also not be grounded.

 

The coil - the coil takes the 6v and turns it into several thousands of volts to fire the coil.  When the points are closed the coil charges up primary side, creating a magnetic field.  When the points open that magnetic field collapses and sends the thousands of volts out the primary side via the coil wire.  I have seen other brands not run right, if at all, when the coil is hooked up backwards though mine was hooked up that way when I bought it and it ran.  I've seen coil work fine cold but when they get hot fail.

 

The coil wire - takes the voltage from the coil to the cap, this wire can be back or breaking down cause lack of spark out of the cap to the plugs.

 

Cap and rotor -  just a distribution system, but if the rotor is bad or the cap has carbon tracking it can cause issues. 

 

Wiring - inspect all of it closely.  It is very common for old wiring to have the insulation physically fail and start falling off causing issues. 

 

Assuming you are wired stock (coil- is to v, coil + is to points) the following applies.

 

You need 6v at the coil - connection with the key in run or start and you need a switched ground to the coil +.  You can run a temporary jumper from the battery - to the coil - and test for spark.  This will test the source to the coil.  if there is no difference then the source is likely not the issue.

 

For the points you can run a jumper from the coil + (remove stock wires for this test) and touch the other end of the jumper to ground.  Every time you take the jumper off ground it will cause a spark.  I pull the coil wire from the cap and put a spark plug in to test here, make sure you ground the outside of the plug.  Don't leave the jumper hooked to ground for long it will heat up the coil, a couple quick on/off tests should be enough for this test.  If this makes no difference then the points are probably not the issue.

 

If you pass those two tests closely inspect the cap and rotor for issues.  If you see none there then move on to the coil.

 

Inspect the coil so signs of leakage, they are oil filled for cooling.  If there is evidence of leakage, replace it.  Look for carbon tracking or arc marks between the tower (where the coil wire plugs in) and anywhere else, other terminals, case, mounting bracket.  If yu have an ohm meter measure the resistance from the coil - terminal to the coil + terminal and from the coil - terminal to the coil tower connection.  Tell us what they are.

 

Let us know

 

 

Edited May 7, 2020 by Sniper
more info

[Tim Larson]

3 minutes ago, Sniper said:

Inconsistent spark can be caused by a number of things.  The points, the condensor, the coil, the coil wire, the cap, the rotor, the wiring.  Basically, anything in the ignition system.

 

Let's go over each item separately.

 

The points -  nothing but a switch, when they are closed they let the coil charge up, this is the dwell.  When the open the coil fires.  In your pic the brown looking wire is the one that goes to the coil and it should be well insulated as well as the wire that goes from the the distributor to the coil +.  If either is shorted to ground you get no spark.

 

The condensor -  it's the canister looking thing with the red wire.  The condensor is used to limit arcing on the points to increase their life.  The red wire should also not be grounded.

 

The coil - the coil takes the 6v and turns it into several thousands of volts to fire the coil.  When the points are closed the coil charges up primary side, creating a magnetic field.  When the points open that magnetic field collapses and sends the thousands of volts out the primary side via the coil wire.  I have seen other brands not run right, if at all, when the coil is hooked up backwards though mine was hooked up that way when I bought it and it ran.  I've seen coil work fine cold but when they get hot fail.

 

The coil wire - takes the voltage from the coil to the cap, this wire can be back or breaking down cause lack of spark out of the cap to the plugs.

 

Cap and rotor -  just a distribution system, but if the rotor is bad or the cap has carbon tracking it can cause issues. 

 

Wiring - inspect all of it closely.  It is very common for old wiring to have the insulation physically fail and start falling off causing issues. 

 

Assuming you are wired stock (coil- is to v, coil + is to points) the following applies.

 

You need 6v at the coil - connection with the key in run or start.  You can run a temporary jumper from the battery to the coil and test for spark.  This will test the source to the coil.  if there is no difference then the source is likely not the issue.

 

For the points you can run a jumper from the coil + (remove stock wires for this test) and touch the other end of the jumper to ground.  Every time you take the jumper off ground it will cause a spark.  I pull the coil wire from the cap and put a spark plug in to test here, make sure you ground the outside of the plug.  Don't leave the jumper hooked to ground for long it will heat up the coil, a couple quick on/off tests should be enough for this test.  If this makes no difference then the points are probably not the issue.

 

If you pass those two tests closely inspect the cap and rotor for issues.  If you see none there then move on to the coil.

 

Inspect the coil so signs of leakage, they are oil filled for cooling.  If there is evidence of leakage, replace it.  Look for carbon tracking or arc marks between the tower (where the coil wire plugs in) and anywhere else, other terminals, case, mounting bracket.  If yu have an ohm meter measure the resistance from the coil - terminal to the coil + terminal and from the coil - terminal to the coil tower connection.  Tell us what they are.

 

Let us know

 

You need a switched ground to the coil +

 

I will inspect all of this.

 

Thank you

[desoto1939]

another good thing to get for your specific distributor is a NOS breaker plate.  The breaker plate contains the moving upper and lower plate that has the wires, condenser, points. Since these units are NOS it is just a matter of taking out two screws and then replacing the entire unit and then resetting the points.

 

The take your old breaker plate and rebuilt it with the same NOS parts to have as a spare.  Tellme you dizzy number IGS or IGT and the digits after that and I will tell you the proper breaker plate to look for.  Carry the rebuilt unit in your tool box in the car.

 

Rich Hartung

desoto1939@aol.com

[Tim Larson]

I was able to remove the distributor yesterday afternoon and got the screw out easily. 

 

Re-installed the tiny wire and made sure it does not touch any metal.

 

Re-installed the dizzy and it acts the same - limited spark showing when turning over - not consistent - it seems to spark when first turning the engine over and then barely anything. 

 

I'm going to get new points, condenser, cap, rotor, and coil. This will cover the main pieces and will help me be confident that all is new. 

 

I did check all the plugs and can see they are all getting fuel so it shouldn't be stuck valves. 

 

I did get the number off the dist. - can I get the pieces I mentioned at Napa or should I order from Andy Bernbaum? 

 

I will update once I get the new parts installed - it will feel good once this gets solved!

[Los_Control]

seems likely a local parts store would have them or can order them. I took my distributor to my local parts store. Charlie I believe is a retired mechanic and a good man to have at the counter.

He had the points and condenser on the shelf, when we opened the points and compared them, they were backwards from the points I have.

He doubled checked his numbers and confirmed correct ones.

He thinks that maybe someone changed the breaker plate in my distributor.

I think he has the wrong part in the box.

I just cleaned my points and never checked another store like napa. But they made these engines into the 1970's There is a good chance they would have them or can get them from there warehouse and have next day.

 

I wonder what others think of Bernbaums quality? Far as I know all these parts are made over seas and seems that is all he will have also.

Last set of points/condenser for a 1967 international I got from napa, condenser was bad out of the box, bought another and the truck ran a couple times and condenser died again. Went out to the shed and grabbed a used condenser and truck was fine then.

[Dennis Detweiler]

I'm not sure about auto condensers, but I know that NOS electronics equipment (amplifier) condensers/capacitors can deteriorate on a shelf.

Check the number on the distributor. It may not be original? I have a later model distributor in my 39 Plymouth.

[Tim Larson]

[Los_Control]

I think it is the IAT-4012 number is all you need. Myself would write all them down and bring it with you.

I would think napa has them or can get them next day, while Bernbaum I would love to recommend and have you send your money to them ... just a matter of convenience.

 

Even if they only have the condenser in stock, I would bring it home and try it first .... what you describe I think the condenser is suspect.

At least you will find out what the problem was. If you change everything at once and it works, you never really know. It could be the coil also. And napa should have that in stock.

At least if you find out what part is bad, you can throw it away, the rest you can clean up and keep for spares in the trunk for emergency roadside repair?