GM-GMC: chevy c-10 straight six 250 spark prob., chevy c, resistance wire

Question
My truck has no spark to the plugs, I changed everything plugs,cap,rotor,starter,coil,points everything but distributor itself and wiring. the points have spark when you take off the cap but the plugs dont spark. checked the continuity of wires and theyre good, help im stumped. could it be the timing cause even when i turn the distributor i dont get anything
   thanx for you time.

Answer
Did you change the condenser?  If not, it may be bad.

Check for voltage at the + terminal of the coil with the key in the "Run" position.  It should be about 6 Volts since a resistance wire is used to drop the voltage (or, if the vehicle is older, a separate balllast resistor is used).  When you crank the engine, a separate wire bypasses the resistance wire and provides full battery voltage (which will be 9 to 12 Volts).  Make sure that you voltage present at the + terminal of the coil with the key in "Run" and also while it is turned to "Start".  No voltage means a bad wire from the ignition switch to the coil.

If the coil voltage is okay, trace the wire from the - side of the coil to the points.  Look for rubbed off insulation that is shorting out or maybe even a break in the wire under the insulation (replace this piece of wire if you think it may be bad).

Finally, get the coil checked to make sure it is okay.  Even a new part can sometimes be bad.  The same goes for the distributor cap.

The last part of the question is not clear.  Are you removing the distributor to turn it?  If so, you need to bring the timing marks together at the front of the engine and then check to make sure that the #1 cylinder valves are closed by removing the rocker arm cover.  If both valves are closed, #1 is at TDC on the compression stroke.  If the exhaust valve is open (rocker depressed) turn the crankshaft 360 degrees and align the timing marks again.  Then put the distributor back into the engine with the rotor pointing where the #1 wire is on the distributor cap.  The firing order is 1-5-3-6-2-4 and the wires should be arranged in that order, after #1 wire, with the vacuum advance body "pointing" at the direction of distributor rotation.

If the distributor does not turn when you crank the engine, you have a distributor with a drive gear pin that has sheared off or a far more serious engine problem.