Here's the next issue. I swapped out my coil, cause I figured it was bad, and noticed that I only have spark when I turn the key off. I left wire connected to coil and pulled from dizzy. Set the dizzy side next to metal surface, turned key over and no spark. turned key off and there is one spark. Turn key on, no spark. crank, no spark, turn off again, one spark. Strong spark, but I don't believe my truck will run with only 1 spark.

Any suggestions. What sucks, is I gotta head back home in about an hour. No more play time til next Friday.

I thought I was gonna have fired up today.

Mike

 

Never mind the key on/off unless you're going to measure the primary voltage. Pull the fat wire from the dizzy and hold it close to a metal part of the engine. With the engine cranking there should be a spark also.

 

This is the classic symptom of a bad ballast resistor. You can crank your brains out with no response, but as soon as you let off the key it tries to fire. Been there, done that.

-Scouder

 

actually it's a sign of a bad crank bypass circuit, assuming you are not running an electronic ignition put a jumper wire from the postive battery to positive side of coil bet it starts right up and removing the wire will keep running. If you are running electronic ignition it can be internal in the box.

 

It's electronic conversion set-up. I never had the problem before I swapped motors. I used dizzy from new motor I bought and used harness/and everything else from old setup. I just plugged it all in. Maybe I should try swapping dizzy back to original? Shouldn't make a difference thou, you'd think? Bad ballist resistor??????? What's that?

Thank for your guys' input. I was hopping to get the damn thing out of my dad's shop this weekend, since they were outta town. Heck, maybe when he gets home tomorrow and he sees it there, maybe he'll tinker with it. He's the one that bought the damn thing 25+ years ago.

Mike

 

Sorry, but I don't get what you're saying???

 

try swapping back to the old dizzy, your new one might have a bad pickup, and the spark you are seeing is when the voltage is cut to the coil it will spark once, but with a bad pickup in the dizzy that is the only time it will spark.

 

OK, I'll try that. Funny thou, cause I heard the motor run before i bought it and the dizzy was fine in the truck we yanked it outta?


Mike

 

You will only see (hopefully) repeated sparking while the crank-cam-dizzy are turning.

Think of the dizzy as a glorified switch, it will switch the primary side of the coil 4 times per crank revolution. Voltage is impressed on the secondary side when the primary side changes. For every two crank revolutions you should have 8 switching events on the primary side of the coil. Turning the key off is one event.

I think Rob has the right idea with thwe jumper, and yes, Durasparks also have a by-pass to supply the coil from the key's start position. Just like the old breaker point system, it's fed from the starter side of the solenoid.

 

Question
Is the dizzy the same year as the previous motor? If memorey serves me there where differances between years, some had three wires from dizzy some had two. I thought they had differant plugs but I could be wrong..

Jon

 

Both dizzys are 3 wire. If memory serves right, orange, purple and black. All the plugs were the same and I just plugged 'em in. As far as same years.....I'm not sure about that.

Mike

 

Mike-Disconnect the two harness connectors at the module. All checks are made at the harness end, NOT the module end, of the connectors.
1) Locate the white wire plug at the harness(not module) end, check voltage while the engine is cranking. It should be 8-12 volts.
2) Turn switch on, check voltage at the red wire of harness end, it should be within.1 volts of battery voltage.
3) With switch on, check voltage at the green wire terminal of the harness end of the 4 wire connector, voltage should be within .1 volts of battery volts.

It sounds to me like the starting bypass circuit is not hooked up or has an open in it. Do you have both wires hooked to the starter relay on the inner fender?

 

Puut, I'll check all your suggestions. Won't be til friday thou. I would thing that both wires are hooked up the starting relay on inner fender, but will double check. I didn't mess with any of that when i swapped motors. I did notice that a red wire was hanging there that went to something on the inner fender. I followed the wire and noticed it went along the frame rail all the way back to the rear bumber and went into othe rear wiring harness, that goes to both plugs (5 and 6 prong) that my dad had installed for pulling trailers. I was going to hook it up, but figured I would mess with it after I got the truck running. I wouldn't think that would be a part of the ignition system. Would it?

I'll check all voltage reading, as you explained.

Thanks guys,
Mike

 

that red wire you see is probably a power wire for the trailer (like modern trailers have a constant pwr supply for things like ABS, and interior lights)

 

I agree with Scott, it is likely a power wire for trailer interior lights. Good luck next weekend, keep us posted.