No Spark

[jabos]

What are some things to check when getting no spark? The coil is new and there is power to the distributor. The engine is a 1961 235 in a 51 truck. Thanks

[1project2many]

The answer depends on whether or not you have points or electronic ignition. With points you should make sure they are gapped properly and not grounded, and that you have a complete circuit from coil to points. An assistant can crank the engine while you watch the points open and close, checking for spark at the points.

[jabos]

I do have a white spark at the points. Not sure what to check next.

[OrrieG]

Originally Posted by 1project2many

The answer depends on whether or not you have points or electronic ignition. With points you should make sure they are gapped properly and not grounded, and that you have a complete circuit from coil to points. An assistant can crank the engine while you watch the points open and close, checking for spark at the points.

Need to set the dwell too. On the 235 distributors it is really easy to turn the wire that attaches to the points just enough so it grounds out. Always replace the condenser too. Did you replace the dist. cap and is the wire between the cap and coil good? Basically the coil stores energy and the points trigger the release. Also check wire from coil to dist. for grounding outside and inside the dist.

[dsraven]

check for blown fuse anywhere.you never know what has been done to these old workhorses over the years,
check for power at the coil with key on. disconnect the coil power wire so you get an accurate reading with a test light because the ground through the points can nullify the test light,

check if there is a ballast resistor inline that could be blown,

check the connections at the coil and distributor, like Orrie says,they can be grounded easily and you may not see it unless looking for it,

check the points for dirty by running a white business card though them, clean or replace as required and ensure the gap is at spec when completed,

check for a good engine ground cable from battery to frame and also battery to engine block,


remove the coil high tension lead from the distributor cap and use a spark checker tool to see if you have spark when the engine is cranked, if the distributor cap is off at this time then check for arcing at the points which may indicate a bad condensor,

[mr48chev]

A spark at the points shows that you indeed have power going thought the primary circuit of the coil to the points.
Thing is, a bright white spark there is a bad thing. You want the points to open and close with no sparking as they are the switch that turns the primary winding in the coil on and off so it builds up a magnetic field and then the magnetic field collapses and creates the high voltage in the secondary of the coil that is the spark that goes to the plugs.

With the rubbing block of the points on the tip of one of the distributor cams (that's that little plastic looking block on the arm of the points against one of the points on the six sided piece on the distributor shaft) you want about .016 gap between the points. Then the points can open and close and make the coil work.

Since the later engine was installed did they convert to 12 volts and is there a ballast resistor? If you have a resistor you also have to have a resistor bypass wire from the solenoid to the coil so that you get a full 12 volts at the coil when cranking.
Also if someone did a switch change there are a few ignition switches that do not put power to the coil when they are in start position relying on the bypass wire to do that. On those if everything is perfect in the universe the truck will actually start after you let off the key when you are cranking it and it goes back to the on position.

[jabos]

Thanks for all the help. I did get it running, I put new points and a new condenser and we got it running. How can I tell if it was converted to 12volt? It had a 12volt battery in it that I replaced. I think I am going to need to put on a new alternator.

[55dude]

if it has a 12 volt battery in it it probably has been converted, points and condenser don't know the difference between 6-12 volts. i always put 12 volt battery in my AD trucks and then used a ford truck step down on the gauges, replaced the heater blower motor with a 12 volt one off whatever was laying around. 12 volts seemed to start those 235's in even the cold weather really nice.