Ignition: Distributor Grounded ?

[Robert Crandall]

I am trying to start a 1949 2R5 truck without luck so far. There is a lot of information on the forum. Thanks to those who have taken the time to put it here. I have whittled things away until I found that I have continuity between the wire connection to the distributor and the body of the distributor, as shown in this picture:

I do not think there should be continuity between these points. Am I on the right track? If I am, then what would be a suggestion on how to fix it?

Some history: This truck was last driven in 1988. Since 1992 it has been in a garage. It started and ran for a few minutes in 2000, 2002, 4 and 6. In 2008 is would not start due to no spark. I did not try again until yesterday.

Yesterday it had spark and was attempting to start, but I was also working on getting the fuel into the pump and carburetor. Then it stopped attempting to start, and there was no more spark. My investigation has lead to this continuity question.

Thanks for any help.

[bezhawk]

No, that terminal should be isolated from ground. As well as one side of the points. The fixed side of the points is grounded, and the moving arm is isolated. The closing of the points grounds the primary side of the coil. That's what collapses the magnetic field of the coil primary circuit, inducing voltage into the secondary windings.

[Robert Crandall]

Thanks for that. It looks like I need to take the distributor apart to find out why the input lead from the coil is grounded. I have not yet looked in the repair manual to find if it tells me how to do that. Looking at my picture gives me hope that the crud on the lead terminal may be making contact to the base. I could not see that looking down from the top of a fender. I will take the distributor out maybe this afternoon to have a look.

[Dwain G.]

What you are showing in the photo is normal. The black lead is touching a source of battery voltage and the red lead is touching ground. Yes, the breaker plate should be grounded. If you use the same connection with an ohmmeter you should get ?, infinity, overload, open circuit.

[StudeRich]

What you are showing in the photo is normal. The black lead is touching a source of battery voltage and the red lead is touching ground. Yes, the breaker plate should be grounded. If you use the same connection with an ohmmeter you should get ?, infinity, overload, open circuit.

Yeah BUT, wait a minute Dwain, that solid METAL strap connecting the "Ground" (Positive) Coil lead on a (+) Ground circuit, looks to me like it is constantly GROUNDED to the Dist. Case by touching it.
So HOW can it get it's INTERMITANT Ground through the Points to charge the Condenser and Fire?

Did I miss something here?

[Dwain G.]

True, I don't like the looks of that missing rubber insulator (516188) either, but as long as the terminal doesn't touch the sides of the distributor it should work. The terminal is insulated from the breaker plate by two fiber washers.

[Robert Crandall]

Thanks for the input. I had to go out of town today, but I hope to investigate further this evening. I will look up the part 516188 to see if I ever had it. I agree the fiber washers and the reading of continuity do not match. Maybe I will get lucky enough to find something touching the case. If not, then I will remove the distributor to look further. I changed this truck to 12 volt negative ground soon after I bought it in 1980. Probably now I would leave it 6v positive, but there was not so much information back then.

[Dick Steinkamp]

I agree the fiber washers and the reading of continuity do not match.

They match to me. The fiber washers insulate the +12V connection from the dizzy body and breaker plate. The dizzy body and breaker plate are grounded. Crossing the two points as you have done in your picture should show continuity and that is normal and correct.

[bezhawk]

They match to me. The fiber washers insulate the +12V connection from the dizzy body and breaker plate. The dizzy body and breaker plate are grounded. Crossing the two points as you have done in your picture should show continuity and that is normal and correct.

The picture shows the insulated terminal that the coil wire to the points attaches. In order for it to possibly work It MUST be isolated from the advance plate and the distributor body. If it shows continuity (zero ohms) then the coil is constantly grounded and will never form any field strength. It's the points that make and break the ground circuit.

[Robert Crandall]

Thanks for your help. I took the top plate off the distributor and found no continuity across the two insulated parts, so that is OK. I put it back together and now have continuity again. It turns out to be from the coil. I disconnected the wire from the distributor to the coil, and the continuity now correctly reads none. I have continuity also across the + and the - terminals on the coil. I also now find that checking voltage with the + meter lead on the + battery terminal and touching the - meter lead on either coil lead shows 12 volts which makes me think that either lead on the coil is somehow a ground source. I think that is odd. I still have no spark at the points or at the spark plugs, so something is amiss.

Enough for now, so I have to set it aside, and probably will not be able to look at again until Sunday at the earliest. I will research more to learn more about how a coil works and redo some of the tests I tried yesterday. A new bonus is that the new points need to have their spring bent in order to have tension to hold the points to the cam. I had tension until I put the screw in. Now the points hang in mid air 1/16 inch away from the cam, so I need to bend some more. I may put the old ones back in.

[bezhawk]

You should have very little resistance between the + and - terminals of the coil....it is a single piece of wire (coil primary) between the two terminals. There should be no continuiy between either terminal, and the case, or ground. The output side is the center terminal (high voltage, and a totally seperate isolated coil) to ground thru the spark plugs. The coil is essentially a transformer to step up voltage. Since a transformer requires an alternating current, the points provide the switching of the dc current.

[Dick Steinkamp]

The picture shows the insulated terminal that the coil wire to the points attaches. In order for it to possibly work It MUST be isolated from the advance plate and the distributor body. If it shows continuity (zero ohms) then the coil is constantly grounded and will never form any field strength. It's the points that make and break the ground circuit.

Yep...you are right. I had the wrong definition of "continuity" in my head. Sorry about that.

[Milaca]

A new bonus is that the new points need to have their spring bent in order to have tension to hold the points to the cam. I had tension until I put the screw in. Now the points hang in mid air 1/16 inch away from the cam, so I need to bend some more. I may put the old ones back in.

Are you certain that you have the spring installed? What appears to be the spring may only be the flexible piece that carries the current from the wire to the tip of the points. You might have a separate, thicker spring in the package that needs to be inserted in tandem.

[gordr]

To chime in: attempting to chase down a suspected short to ground, as illustrated in your photo, can't be done effectively with a wire connected to the terminal.

Question. Does this truck have overdrive? If so, there is a kickdown switch, connected to the distributor or points side of the coil, which grounds it out when the accelerator is floored. A faulty or incorrectly-wired kickdown switch could cause an unwanted short to ground.

Incidentally, I am not a fan of throwing parts at a vehicle in an effort to get it to start. Presumably, it was running when it was parked, unless you know from its history otherwise. The ignition was working. Chances are, all it will take to make it work again is quick clean of the points with some abrasive paper, followed by a clean business card. Now, once the vehicle starts and runs, you may well want to install new points and condenser as part of a routine tune-up. But throwing new parts into a non-starting vehicle just introduces uncertainty, because sometimes new parts are defective. If you have a running engine, and you install new points, and it then fails to start, then either you have installed defective points, or you muffed the installation somehow. We've all done it. Point is, you KNOW it ran before the new points went in, now it doesn't. The answer is obvious: recheck your work. But do that on a non-starting engine, and it still fails to start, well, you have no way of knowing if you "fixed" it, or made things worse.

[Robert Crandall]

Thanks for the further advice. As for the spring, yes it was separate in the box. I had to bend it to make it cause the point lobe to contact the distributor cam. I thought I had it right, but when I put the screw through it and the condenser wire clip, it changed. I will have to undo it and bend some more.

As to the advice just above, this truck does not have overdrive. Good thing I live in suburban sprawl.

I do agree with the advice of not throwing parts at it, so I have not added anything since I lost spark. I did, however, contradict myself by changing the spark plugs, condenser, rotor, cap, and points before I attempted to start it. The truck was running well when it was put away in 1988, but it would not start due to not having spark at the points in 2008. You can see on my other posts that I lost perfectly good brakes and a fuel tank due to it setting idle for 26 years, so I am trained that things fail over time and thought I would save irritation by putting these new parts in before I attempted to start it. However, I got lucky because I initially did have spark. I lost it after maybe 5 or 6 attempts to start it.

I will now follow the advice of starting over with my checks of what may be wrong. I should have marked those posts that had the 'how to videos'.

Thanks again for all of your input.