The Stovebolt Site Forums The Shop Area The Electrical Bay No Spark - FIXED

My father-in-law passed away this year and we brought his 1950 3100 5-window home with us. It looked all original, but when I tried to start it I see someone converted it to 12 volts. Looks like original 216 engine. The battery is dead, purchased in 1991; the last registration is 1992. Fresh battery gives lots of power to the starter. I have 12v at the coil, but no spark. Replaced the points, plugs, condenser, rotor, and distributor cap - still no spark. Wires are not great, but are serviceable. Lights and horn work (woohoooo!) Any recommendations? Thanks in advance.

Thanks

Just follow the electricity in a logical order.

With the key on, remove the coil wire fron the center of the dis cap and hold it close to a block ground. Use a small jumper wire to connect the dist terminal of the coil to ground. When you lift the jumper off the ground you should get a spark at the coil wire. Do it a couple times to confirm. Spark = coil good, no spark = coil bad.

Remove the dist cap and look at the points. If they are open, hold the coil wire near the ground and use the blade of a screwdriver to bridge the gap in the points. When you remove it the coil should produce a spark. If they are closed, use a something plastic or wood to open the points. Should get spark each time you open them. That would generally mean the point and condenser are good. (I can think of at least 3 exceptions to that)

If you are good so far, The spark now has to get to the plugs. Cracked cap, shorted rotor, short rotor in a tall cap, can all cause the problem. Make sure the dist shaft is actually rotating when you crank the engine. Be sure to check for spark at the plugs with a fresh plug and a good ground.

Hi Jim - thanks for the guidance. Test #1 (coil check) worked out fine. Test #2 resulted in no spark. I bought a new condenser and will install it and try to track down the problem this afternoon. Everything was new in the distributor; but the "new" parts could well be 20 years old for all I know. I will also check resistance on the plug wires just to be sure it isn't that simple of a problem. One problem at a time. Thanks again for your help.

PM UPDATE - new condenser installed - no joy. I assume this means I have a short somewhere in the distributor? Seems like a pretty simple distributor, shouldn't be too many places I have to look? Any suggestions?

NIGHT UPDATE - lost now. Not getting spark when doing the gap test. I checked and have 12 volts at distributor, inside on point that pivots and to condenser. I have no voltage on the body or bottom plate of distributor. The point that does not pivot has no power if the other point is not touching it. All test on the coil tell me it is good, what now?

12V at the stud going into the dist.
Points open - 12v on the beaker arm - good
- 0v on the breaker arm - connection between the stud and arm faulty. Also try disconnecting capacitor and check arm voltage again.

12V on arm - bridge gap with screwdriver - produces spark - good - No spark = plate not grounded.

Touch a jumper wire grounded to block to the breaker arm. Spark confirms no dist plate ground. Install a ground wire from the stud on the opposite dist body to block ground. Make sure it is long enough so the dist can turn.

Found today that the connection prong from the capacitor was grounding against the distributor plate. Got that taken care of. 12V on arm, spark when gap is bridged. Touched a test light from 12v on coil to dist body and dist plate, light came on as expected. Still no spark. Not much left, or so it seems. Maybe I should buy a new coil, even though everything seems to check out ok with it? Rotor looks good, tried old distributor cap and new one. Done three capacitors, so I don't think that is the problem. Neighbor said he is pretty familiar with these old ignition systems, said he would come over and give it a look. I don't know - can a truck have a poltergeist?

By "still no spark" you mean at the end of the spark plug wires?

In the present state, if you pull the coil wire from the dist cap and hold it close to ground, do you get a spark good when you crank?
If you do the possible problems are very limited.

Center terminal of the dist cap isn't making contact with the rotor
Cap has a crack from the center terminal taking the spark to ground.
The rotor has in internal short to the shaft
The end of the rotor is too far away from the plug contacts in the cap
The spark plug wires are bad

You are correct, no spark at plugs. I will double check each of your points tomorrow when the sun is up. It does seem we've covered about everything. Thanks for your help Jim - I really appreciate it. I will get this thing to fire! I don't know if it will run, but I will get spark to the plugs.

Since you've replaced the cap and rotor be sure the cap is not too tall or the rotor too short to make contact. use ohm meter to test from cap center to end of spark plug wire while turning engine manually. Keep in mind that resistance will be high if using resistance wire. Look for open or high resistance reading. High resistance will show continuity meaning cap & rotor match. Doesn't discount bad spark plug wires though.

Thanks Ed, I will double check that today. Yesterday I found the ground from the engine to the frame was rusted over, so I took it off and cleaned it up - that did nothing for the no-spark situation though. :-(

GOT SPARK - removed all wires from battery to coil and checked resistance, cleaned ends and connections. Replaced all spark plug wires. Put old points back in, new plugs, new rotor, new condenser and new distributor cap. Hit switch and we had spark. Now I'm moving on to the fuel side of the equation. Thanks to all for your help. One step at a time. :-)