No spark
Senior User
Joined: Jan 2010
Posts: 279
Likes: 4
From: Morton, WA
larryb346 is giving you the best advice. Use a probe with a test light to see if you are getting juice to the coil and then to the points. If the truck has been in storage for a long time, you may not have good connections with all the wires. Take the screws or nuts holding the wires in place and shift the wire on the coil posts to 'rough up' the connection for a good contact. You may also need to rough up the connection of the main lead that goes into the coil and to the center of the distributor cap. Do other electricals work (lights, starter, etc.)? Is the ground cable from the battery making a good contact? - Just be thankful that you are dealing with an American auto electrical system. You have a reasonable chance of sorting it out. LUCAS electrics on british cars are a constant hassle. Most of the time it is due to poor grounding connections. Keep us posted on your progress.
Post Fiend
Joined: May 2008
Posts: 7,641
Likes: 21
From: Poway, Ca.
YAY, finally she fired up. The problem was when i tightened the wires up comming from the coil had been touching the body of the distributor so it was grounding out. tomorrow i will replace the fuel pump with a new one and see if she will suck gas out of a gas can so it will run longer that the 3 seconds from the shot of either....
larryb346 is giving you the best advice. Use a probe with a test light to see if you are getting juice to the coil and then to the points. If the truck has been in storage for a long time, you may not have good connections with all the wires. Take the screws or nuts holding the wires in place and shift the wire on the coil posts to 'rough up' the connection for a good contact. You may also need to rough up the connection of the main lead that goes into the coil and to the center of the distributor cap. Do other electricals work (lights, starter, etc.)? Is the ground cable from the battery making a good contact? - Just be thankful that you are dealing with an American auto electrical system. You have a reasonable chance of sorting it out. LUCAS electrics on british cars are a constant hassle. Most of the time it is due to poor grounding connections. Keep us posted on your progress.
Tuned
Joined: Aug 2002
Posts: 473
Likes: 1
From: Greatest state on earth
Electricity doesnt work that way. Both wires come from the same source give only 12 volts to the ballast resistor. It would be the same as using a larger gauge of wire. Then thru the resistor and only 6 volts out.
Again electricity doesnt work that way. It will always take the path of least resistance. Running 12 volts thru the ballast resistor is increasing the resistance to travel. So when you drop voltage in half, it will double the amperage it takes to travel thru to complete the circuit.
At 12 volts it only requires half the amperage to flow compared with 6 volts.
Post Fiend
Joined: May 2008
Posts: 7,641
Likes: 21
From: Poway, Ca.
Electricity doesnt work that way. Both wires come from the same source give only 12 volts to the ballast resistor. It would be the same as using a larger gauge of wire. Then thru the resistor and only 6 volts out.
I think I'm familiar with electricity. And it is true. We are talking about amperage here, not voltage. And you needed to consider the comment I included about the reducer dropping both amperage and voltage. The output straight out of the ballast resistor is dropped both in amperage and voltage. The voltage coming from the solenoid is a straight 12 volts AND the higher amperage associated with the unresisted 12 volt system. Voltage reducing resisters play by a different set of reles - almost backwards.
Perhaps it would have been more appropriate to say that the amperage being provided by the solenoid gives the boost because the ballast resistor has taken half the amperage with the 50% voltage reduction. It's a little difficult to verbalize on a web site and frankly isn't necessary to go into that level of detail - point is that extra power comes from the solenoid and the way the diagram is depicted while it may not be the ONLY method, will work as depicted.
Again electricity doesnt work that way. It will always take the path of least resistance. Running 12 volts thru the ballast resistor is increasing the resistance to travel. So when you drop voltage in half, it will double the amperage it takes to travel thru to complete the circuit.
I disagree - and maybe its semantics. The circuit is complete as long as the wires are intact.
I think what you mean is: When you drop the voltage in half, twice the amperage is required to satisfy the wattage needed for the appliance to perform the same amount of work.
The work demand (wattage) is what dictates the amperage needed at a constant voltage. And again with voltage reducing resistors, both voltage and amperage are reduced, thus it takes 4 times the amperage in a reduced circuit to satisfy the same wattage requirement as an unresisted circuit.
In this case it works the way I described because the electricity doesn't choose a path to follow, it is supplied through both souces, and (albeit at a reduced level on the resisted circuit) irregardless of the resistance at the ballast resistor, it still flows through it and provides amperage to the coil. It doesn't just stop and back up only to flow out through the solenoid.
At 12 volts it only requires half the amperage to flow compared with 6 volts - to satisfy a constant wattage requirement. Seems I've heard that somewhere before.
I think I'm familiar with electricity. And it is true. We are talking about amperage here, not voltage. And you needed to consider the comment I included about the reducer dropping both amperage and voltage. The output straight out of the ballast resistor is dropped both in amperage and voltage. The voltage coming from the solenoid is a straight 12 volts AND the higher amperage associated with the unresisted 12 volt system. Voltage reducing resisters play by a different set of reles - almost backwards.
Perhaps it would have been more appropriate to say that the amperage being provided by the solenoid gives the boost because the ballast resistor has taken half the amperage with the 50% voltage reduction. It's a little difficult to verbalize on a web site and frankly isn't necessary to go into that level of detail - point is that extra power comes from the solenoid and the way the diagram is depicted while it may not be the ONLY method, will work as depicted.
Again electricity doesnt work that way. It will always take the path of least resistance. Running 12 volts thru the ballast resistor is increasing the resistance to travel. So when you drop voltage in half, it will double the amperage it takes to travel thru to complete the circuit.
I disagree - and maybe its semantics. The circuit is complete as long as the wires are intact.
I think what you mean is: When you drop the voltage in half, twice the amperage is required to satisfy the wattage needed for the appliance to perform the same amount of work.
The work demand (wattage) is what dictates the amperage needed at a constant voltage. And again with voltage reducing resistors, both voltage and amperage are reduced, thus it takes 4 times the amperage in a reduced circuit to satisfy the same wattage requirement as an unresisted circuit.
In this case it works the way I described because the electricity doesn't choose a path to follow, it is supplied through both souces, and (albeit at a reduced level on the resisted circuit) irregardless of the resistance at the ballast resistor, it still flows through it and provides amperage to the coil. It doesn't just stop and back up only to flow out through the solenoid.
At 12 volts it only requires half the amperage to flow compared with 6 volts - to satisfy a constant wattage requirement. Seems I've heard that somewhere before.
Cargo Master
Joined: Feb 2008
Posts: 2,789
Likes: 123
From: Windermere Valley,B.C. Ca
[QUOTE]Would that be Joseph Lucas, also know as the PRINCE OF DARKNESS? 
Last edited by Old F1; Mar 9, 2010 at 09:28 AM. Reason: add quote block
Tuned
Joined: Aug 2002
Posts: 473
Likes: 1
From: Greatest state on earth
I dont understand how running two wires from the same 12 volt source to feed power to ballast resistor is anything but redundent.
IIRC there was even an article in Popular Science with Gus and the Model Garage explaining this to his trainee back in the 50's.
Freshman User
Joined: Jun 2012
Posts: 49
Likes: 0
Hi guys i red the whole thing about no spark problem. I have 56 f100 with 272 just rebuilt engine. It ran fine before i got this rebuilt but now it wont start my problem is I have no spark coming out from center hole of ignition coil. I have power from I terminal of soleniode with ignition switch on, this goes to positive post on coil and there is another wire coming from ignition switch that goes to one side of coil resistor then from the other side of coil resistor another wire that goes to posive post of coil. From negative post of coil there is a brand new wire to the distributor. I checked the points and noticed that with ignition on there is no spark when i open an close them i will try new points and condenser but after i red the thread i dont know if my wires in distributor are grounded how can i check this everything was just fine im using same distributor and the [pionts were good so dont know any help will be apreciated thanks
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