Start/Run question

[hunter1]

So, I am trying to start my new engine just mounted in the frame with the original wiring harness just laying loose but hooked up. Do not have the body on the frame, just engine and the rest of the running gear. It has duraspark ignition. I have the positive battery cable hooked to the starter solenoid and the negative cable hooked to a bell housing bolt. Cranks over fine with the key switch, have 9 volts to the plus side of the coil and have 12 plus volts going into the module but no spark at the plugs. I'm sure I'm missing having something grounded but not sure what? What needs to be grounded in the ignition that isn't grounded through the distributor?

Thanks

 

[gnpenning]

A picture of the wiring to the coil would help. How many volts to the coil?
Have you done a ohm reading across the positive and negative terminals on the coil?
Have you taken the distributor cap off and cranked the motor over watching to see if the rotor is turning?
Have you checked for spark at the coil high voltage wire or just plug wires?
Just worked on a tractor this past weekend that didn't have spark to the plug wire I checked. Turns out half the plug wires were bad. Lesson, check more than one plug for spark. You can do it with a timing light the fastest.

 

[DirtDonk]

Yes, pictures, pictures, pictures please.
Do you have the Brown wire connected to the "I" small terminal of the starter relay/solenoid?
No body, but do you also have a ground to the starter relay? Sounds like you must, since the starter is cranking. Just wanted to verify.
Do you have the original horseshoe connector to the coil? Original coil? Original distributor? You may need to test more before you do more cranking. Ohm out the distributor and the coil as mentioned. Maybe take the module to a local parts store that knows how to check them. Heck, maybe there's a book method of checking the module at home.

Whenever starting a fresh engine with a flat-tappet cam (is that what you have?) I almost want to use a standard points distributor and a carburetor! That way I know stuff is going to work the first time and we can break in the cam without delay.

Speaking of which... Are you running assembly lube on the lobes, and running the correct high-zinc/ZDDP oil for a flat-tappet cam? I know that's not what you were asking about, so may have all that dialed in. But we have to mention it in every discussion of a new engine, because so many people still get it wrong even after all these years.

Good luck.,

Paul

 

[hunter1]

Thanks for the replies. Found the problem yesterday. 12 volt to the coil during cranking was not there, only when going from start to run did it spark. Couldn’t see this at first, but bought a cheap HB spark plug tester and caught it lighting up when releasing the key from the crank position.

 

[DirtDonk]

That means that the starter relay is faulty, or the Brown “I” wire is not getting power to the coil.
The old Bronco ignition switches are well known for having a dead spot, even when new. If you turn it to START a little too far, it goes dead for the ignition and charging system.
You would never notice it, though, if your starter relay is connecting to the brown wire and it’s connected to the coil.
You can try turning the key, just barely to the START position and see if that fixes things. If it doesn’t, then your switch is defective.

 

[hunter1]

I'll try that. Brand new key switch and new solenoid. Had power to the coil in run position, just not while cranking. I'll definitely check it out tomorrow.

 

[DirtDonk]

Hope it works. New ones are actually worse than the old ones. Sometimes you can have an old tired one that’s 30 years old, that works better than a brand new one.
The switches aren’t as bad as some of the other parts, but they’re getting there.

If you have a multimeter, you should be able to find out if the brown wire is connected to the ignition.
Pull the small wire off of the I post of the starter relay/solenoid, turn the key to ON, and check for 6 to 12 V.
If there’s nothing there, then there’s a break somewhere between the starter relay and the ignition coil. Possibly at the red connector at the back of the engine.

 

[hunter1]

That may be it. I’ll check that also.
Thanks!