New member with ignition issues

[LickskilletM37]

I'm a new member with a '52 m37 that I am trying to get running again and am having issues with the ignition.

It used to run, but quit getting spark. I've since replaced the forward wiring harness because the old harness had a lot issues. The following are also new: plugs, plug wires, coil, and cap/rotor. Upon getting it back together I cranked it over to check the spark at a couple of the plugs and it had a strong blue spark. I then tried to start it and after cranking for a very long time with sporadic intermittent firing it finally started and ran very poorly for about 20 seconds while missing on several cylinders. After it died it would not start again and there was no spark whatsoever. By this time the batteries were very low from all of the cranking so I charged them. I then took off the distributor cap and did the following: lightly sanded the point contacts, checked the points gap and reset to .020 (it was about .024), check the resistance across the coil (~12 ohms primary, ~11k secondary), installed a new condenser, and checked for continuity from the battery to the distributor lead. It has a full 24+ volts at the distributor lead when there is no load on the system.

After doing all of this , and with the batteries fully charged I checked for spark at a couple of the plugs and it was still dead. Does anyone have any suggestions? Could it be the distributor mounted RF filter or the voltage regulator? What else is there that could be causing this?

[w30bob]

Hi Lick,

You confirmed you have 24V at the distributor connector. Did you check to see that you have 24V at the coil? Also, check the coil's primary and secondary resistance with a meter.....I don't have the manual in front of me but I think the primary should come in around 6 ohms and the secondary around 15K ohms.

regards,
bob

[LickskilletM37]

Thanks for the suggestion on the checking the coil.

I just checked the voltage at the coil. It has 24.2 on the left connector stud and less than 1 volt on the right connector(left/right as looking over drivers side fender). The coil was 12 Ohms primary and 11,000 Ohm secondary. I found one source that says primary should be 6 Ohms, but a quick google search found that most people are seeing about 11,000 to 12,000 Ohms on the secondary. My old original Autolite coil also shows about 11,000.

[w30bob]

Hi Lick,

Looks like the next step is to check the condenser......seems they just don't make 'em like they used to and some are bad even when new. When you checked for spark at the plugs did you see ANY spark or nothing at all?

regards
bob

[LickskilletM37]

I'm not getting any spark at all.

Is there a way to check the condenser, or do I just swap it for another one and see if it works?

They are not easy to swap out with the distributor in the truck, I was barely able to get onto the screw for the wire connector. My new one definitely looks cheaper made than the old condenser, so you are probably right about the quality.

[w30bob]

Hi Lick,

I stole the following off the web..........

regards,
bob

1.) Remove the condenser from the engine (or at least disconnect the lead wire). Note the small metal connector located on the end of the condenser. This connector is the "hot" or power connection. The metal case of the condenser is the grounding point. Discharge the condenser by shorting the lead wire to the case.

2.) Switch the meter to the ohms position. Place the red lead into the "ohm" connector on the meter. Insert the black lead into the "com" or common connector on the meter. Set the resistance range to the highest available setting (if it is selectable). Connect the test leads together and zero the meter. If the meter won't zero replace the battery. (Yes, an ohm meter has a battery).

3.) Touch the red lead to the hot connector on the condenser. Place the black lead to the metal case on the condenser. The meter's needle should jump slightly to the right (toward 0-ohms), then should drop back to the left towards infinite resistance). Hold the leads in place for 15 to 20 seconds. This action places charge in the condenser. If the test shows any reading other than infinity, the condenser is leaking and needs to be replaced.

4.) Remove the leads and reverse the placement to the condenser. Move the red lead from the hot connector to the metal case, and move the black lead from the metal case to the hot connector. At the moment where both leads are touching the correct points, the meter should jump towards the right. The second time the needle may move twice as far, as this action discharges the condenser. Holding the leads in contact should again result in movement of the needle back toward infinite resistance.

5.) Movement of the meter's needle indicates the condenser is good. If no movement was indicated on the meter in any circumstance, the condenser is bad and must be replaced. Retest the condenser several times for a consistent reading.

In operation the condenser will "ring" at up to 300 volts, so the condenser needs to be rated much higher, no less than 600 volts DC. The ignition will likely work with any capacitance value between 0.05 and 0.6 microfarad. Too high or too low value may eventually transfer metal from one side of the contact points to the other side leaving a pit and a point. Capacity of spark coil capacitors ranges from 0.2 microfarad to 0.33 microfarad. Almost all automotive coils use a 0.25-0.29 microfarad capacitor.

A capacitor may absorb moisture over a long period of time, and moisture can cause failure of the condenser. So it is possible that a condenser stored for 10 years or so might be bad or might fail prematurely in service. It is a good idea to check your traveling spare condenser occasionally.

[LickskilletM37]

Thanks Bob, this makes sense, but I'll need to get an analog meter. I think I know someone that I can borrow from.

Since I am getting no spark at all, I'm starting to wonder if I have bad ground, a short to ground, or a bad connection somewhere between the coil and the points/condenser.

I'm going to poke around a little with the Ohmeter to try confirm that everything is as it should be.

[LickskilletM37]

I just checked a few things, and it looks like I've always got a ground regardless of whether or not the points are open or closed. With the points open, coil primary, points, and distributor housing are all grounded.

I'm going to look into this.

[LickskilletM37]

I pulled the distributor yesterday and reworked the connection where the screw holds the two wires and the spring to the points and now it starts easy and runs. It does have a bad miss when throttle is applied and held, but it had that when it was last running over a year ago. I still have some work to do.

Does anybody know what the timing should be once the advance kicks in, and at what RPM this should occur?

Thanks

[T. Highway]

A good starting point is 4* BTDC (with a timing light) at idle to start with and adjust to your liking after that.

Bert

[LickskilletM37]

Thanks Bert, 4 degrees sounds reasonable at idle. I still need to buy a plug wire adaptor for the timing light, so there is no telling what it is at right now.

Does anyone know what the characteristics of the mechanical advance should be (total advance and at what RPM)?

[ZGjethro]

My truck is currently at 10 degrees btdc, and when it is running it runs well. I am at 8000' though.

[jimmy_stikx]

Are all the wire connections good? May seem dumb, but mine died once because the power wire to the coil had worked itself loose from the distribution board.

[LickskilletM37]

I've finally got it back together after fixing the wiring inside the distributor and it starts now. It run pretty well at idle, but it starts missing as I apply throttle and let the rpm rise a little.

I still need to set the timing, so maybe that will help some.