The Stovebolt Site Forums The Shop Area The Electrical Bay 1941 1 1/2 ton primary ignition wiring

Hey guys,

I have an electrical question for those more adept in circuits than myself. I have a 1941 Chevy that has had a ca.1980 SBC implanted. I plan to remove this engine replacing with a 1954 235 and go back to 6 volt positive ground. I want to wire the current engine so that I can get it running so I can determine its condition for future sale. The truck sat in the desert for about a decade, and rats ate all of the rubber and wires under the engine compartment. The rest of the original wiring harness is not too altered, but is frayed to the point of unsafe.

Here is what I would like to accomplish: wire the current engine to test run only with new wires bypassing the old harness. I guess you could say that I wish to "hotwire" the truck. Can any of you gurus map out a simplistic schematic for a temporary primary wiring circuit? As I said, the engine is 1978-80, but has a Delco points distributer and Delco starter with solenoid. Do I need to use an ignition switch? If so, which one can I use for both a start/run system (current), and the stock run (stomp start) system that will be installed in the future.

I am great at some portions of restoration, but the concept of electrons speeding through the pores in copper to find ground is always confusing to me. Consider this a remedial instruction course.

Thanks in advance.

Paul

Hy Paul_WNC, I was waiting for someone who knows how to post a drawing to answer your question, but I can describe it for you if you can follow that? Battery connections, positive to large post on starter solenoid, negative to a bellhousing mounting bolt. Ignition wires, either from the positive battery terminal or the large post on the starter solenoid, run a wire to one side of a simple on/off switch. From the other terminal on the switch run a wire to one terminal on a ballast resistor. From the other terminal on the ballast resistor run a wire to the coil + positive terminal. The negative terminal on the ignition coil should be connected to the distributor. From the inner terminal (the one closest to the engine block) of the starter solenoid run a wire out close to the battery, this wire will cause the engine to crank when you touch it to the positive terminal of the battery. From the outer solenoid terminal, run a wire up to either the ballast resistor terminal that is connected to the ignition coil, or to the ignition coil + positive terminal. Now when everything is wired, if you turn your switch to the on position, and touch your loose solenoid wire to the battery positive terminal, the engine should crank and start, that is providing that your ignition system is in good shape, and that you have a supply of fuel getting to the engine, hope that helps.

3B,

Your written description seems clear to me. Is the ballast resister's function to reduce the voltage to the coil? Will the full voltage fry the coil in a short period of time? I think I can cobble all of the parts to make this work. As I stated, this is only to test run the engine. I will give it a shot this weekend, thanks a lot!

Paul

Hy Paul_WNC, yes the ballast resistor is to reduce the voltage to the coil, but the reduced voltage is actually more to prolong the life of the points. If you're only going to run the engine for a short time you could wire twelve volts directly to the coil. You can also eliminate the wire from the outer solenoid terminal on the starter to the coil/ballast resistor, hope that helps.

Well yesterday, I worked a little on getting the engine to fire. It cranks well, the coil shoots a good strong spark, and the engine tried to start once or twice but never actually ran. I have the fuel pump drafting from a one gallon gas can with fresh gas, and I was spraying carburator cleaner in the carb at each crank attempt. I did not have a spare ballast resister, so I just switched the positive coil feed off between battery rechargings. The weather began to get bad and I abandoned the mission.

So what do you all think? Are my points faulty (or did I burn them up) or is it something else? I did not remove any of the sparkplugs after squirting/cranking to see if they were fouled, but I did look at them before when I was rewiring and they all looked good. The battery I am using is sulphated and loses power quickly but cranks the engine at normal revolutions for two or three attempts. I rewired the plug wires from scratch (it had none) using the points type distributer firing order sequence going clockwise starting from the dwell adjustment door.

At least I cranked the engine enough to start the oil flowing again.

Suggestions?

Hy Paul_ WNC, did you verify the position of number one cylinder TDC on compression, and check the distributor rotor position once you had verified that? Sometimes old spark plugs just don't want to fire, if you verify that you have your spark plug wires in the correct position, then I would put in a new set of plugs. Did you check that the carb is getting fuel, work the carb linkage and check for fuel squirting into the throttle bores, hope that helps.

Paul,

A point not mentioned so far is that the original Chevrolet 6-volt electrical system was negative ground. GMC and some others had positive ground, but Chevrolet has been negative-ground for as long as I can remember.

Harvester

Harvester,

The engine is a ca.1978-80 with a early 70's points distributor, so it is 12 volt negative. You are correct though, the truck from the factory should be 6 volt positive (for which it once again will be when I am done).

I haven't had the opportuntiy to progess further as we are experiencing snow/wind from Sandy. I will investigate further this weekend when the weather is more hospitable.

Paul

Hello all,

Well, I had some time to look at the truck on Saturday and it turned out to be a wasted couple of hours and a heavy dose of frustration! Now the engine gets NO spark at all. It seems as though I am moving backwards.

Here is what I have done:

1) wired pos batt to a toggle switch to a ballast resister to the positive coil (in that order).

2) wired the negative coil to the points.

3) wired from positive batt to the inside terminal on the starter solinoid (touching wires to crank).

It seems so simple. It cranks well. I have checked voltage at: ballast resister (before and after), coil on both pos and neg side. In all of those locations the voltage reads the same as the battery. When cranking, the voltage at the ballast resister downstream reads approximately 10 volts. I replaced the points (new store bought, but I noticed that the contact points had some oxidation so someone used them and returned)and even ran a bypass wire from the points to the coil as the old one had mouse damage and the connector at the points would get warm to the touch (possible open circuit going to ground?). Visually the points are opening and closing, but gap not set as I typically set the dwell while cranking. I have even swapped out another used coil (although it was an Autolite from a 70's vintage Scout 11)to see if that is the culprit.

I hit the point of frustration and quit.

So above is what I know, and below are things I need to know.

1)My dwell meter formerly registered while cranking, and now the needle does not move at all. Connecting red terminal to neg coil, and black terminal to ground. I have no way to check function of meter as none of my other vehicles have coils.

2)Correct method to check resistance on a coil. All of my old manuals state that for a crank with no start failure to check coil, yet none have the acceptible ohm ranges or test procedures.

3)Correct method to check the resistance on a unipoint condenser, and the acceptible ohm ranges.

4)Any other suggestions to get this engine to run!

Thanks in advance, and I hope you all can help me out.

Paul

Hy Paul WNC, are you sure the points are closing? If you crank the engine until the points are closed, and you turn the ignition on and manually open and close the points, you should get a spark out of the coil every time you open and close the points, that is if the points are actually closing and have a good path to ground, hope that helps.

3B,

That's a great question, so if the points actually are never contacting to complete the circuit then that is why it is not creating a spark? If the points move but don't contact one another one would get no dwell measurement? I will test as soon as I can. Points are hard to get a good gap measurement, brings me back to the old days of highschool. I will be ashamed if it is that easy.

Thanks.

Paul