Truck has no spark?

OLDDODGETRUCK

MEMBER
1975 DODGE TRUCK
5.2L
V8
4WD
AUTOMATIC
133,000 MILES

My dad was driving the truck and it all of a sudden starting running rough. He stopped to look at it and it wouldn't start again. So far I've replaced the resistor, coil, points, and cleaned and gapped all the plugs. I checked to see if their is power going in the coil and it's about 7 volts. The rotor spins, but when I put the timing light on there is no spark in the plug wires. I have no idea why the spark is disappearing. The rotor, cap, plugs, and wires are all pretty new. The cap and rotor don't have any scorch, marks on them. What is going on?

8 Replies

HMAC300

MECHANIC
48,601 POSTS

I fyou have spark at the coil wire where it goes to the dist cap thenit's either the rotor is cracked or the dist cap. If it 's not firing on pug wires. Check gap o fpickup coil should be >008-.010" use a non magenetic feeler gauge with vacuum advanced. Check positive side of coil if at 6-7volts and negative side very low or zero volts then control unit is probably bad.

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Thursday, September 4th, 2014 AT 4:12 PM

OLDDODGETRUCK

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66 POSTS

No pickup coil

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Thursday, September 4th, 2014 AT 7:02 PM

HMAC300

MECHANIC
48,601 POSTS

If this truck has points it 's the wrong system so if that is what you have then it's the wrong system in it and replace points and condenser also check coil for resistance. Go to our site under tune up if you don't know how. Also the pickup coil is in dist.

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Friday, September 5th, 2014 AT 6:23 AM

OLDDODGETRUCK

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66 POSTS

The engine is a '69 industrial from a case 1020 combine, the guy who did the engine swap used parts from the original engine and the combine engine. I just replaced the points, ignition coil, condensor, cap, plug wires, and plugs. There is 11 volts going to the resistor and 7 volts to and from the ignition coil is this enough voltage?

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Friday, September 5th, 2014 AT 8:18 AM

HMAC300

MECHANIC
48,601 POSTS

Should be 12 to resistor and about 9 after. See if spark comes from the coil if it doesnt' it's a wiring or points/condenser issue if spark comes from coil but not to spark plugs then it's a rotor or dist cap issue.