Steve69 wrote:

Hey Guys,

Was going to go to a car show on Saturday and my engine wouldn’t fire. It had sat for a couple of weeks prior and ran fine to parking it in the garage. Usually I disconnect the negative side of battery cable for safety reasons and forgot about doing that.

I have a hyfire ignition box that’s probably 15 years old. Had power going to it for full power and ignition power. When I checked the power output from ignition box positive side of coil nothing. So I believe maybe the box is bad. I bypassed the ignition box and connected the ready to run distributor directly to the coil. Ignition hot and distributor red to positive side of coil. Yellow on distributor on negative side of coil and black to ground. I now have 12 volts at the positive side of the coil but still no spark at the coil to fire the distributor cap. The coil is a blaster 2 which is new. The distributor is new and blueprint distributor that is a Petronix. Any other tests I can do to determine if the coil or distributor is bad? I’m stumped.

Thanks!

Steve69

I'd pop the dist cap and turn the engine over before tearing in to your wiring.
 

Sounds like the “New Pertronix Blues”.  Been hearing of lots or early fails.

With a Hyfire or other spark box you will not see 12 volts at the coil so the lack of 12 volts when the engine is not running is not a valid test of the box.  High voltage to the coil will only be delivered when the ignition fires.  You should confirm that you do have 12 volts coming from the ignition switch.

To verify your coil and spark box, conduct the basic white wire test as described in the instructions -
CHECKING FOR SPARK If triggering the ignition with the White wire:

1 Make sure the ignition switch is in the "Off" position.
2. Remove the coil wire from the distributor cap and set the terminal approximately 1/2" from ground.
3. Disconnect the White wire from the distributor's points or ignition amplifier.
4. Turn the ignition to the On position. Do not crank the engine.
5. Tap the White wire to ground several times. Each time you pull the wire from ground, a spark should jump from the coil wire to ground (the LED should also blink). If spark is present, the ignition is working properly. If there is no spark skip to step 6.

Wiring should be similar to the bottom of page 8 - https://documents.holley.com/690.pdf 
Since your system has run for years it must have been wired correctly.

Steve is probably on track with the Petronix and the white wire tap test will help prove that.
 

Ignition Coil Tests:
Coil + to -: should be about 1-2 ohms
Coil + to Center (Hi Voltage): should be about 8,000-10,000 ohms.
These values are nominal, and if close, the coil is likely good.

Another thing you can try; 
Disconnet the '+' wire and the '-' wire from the coil.
Connect an inductive timing light on the hi-voltage lead.
Apply +12v to the '+' side of the coil.
Quickly 'ground' and release the '-' side of the coil, if the timing light flashs, the coil is good.
What you're doing is the same thing that points, or electronic ignitions are dong. 
 

Thanks for all the Great Information guys!   BP engines did sent me a new distributor.  I received it yesterday.  Not bad for 2 days after I call them.   Im going to do your tests above.   like I had said I did bypass the ignition box with no fire at the coil.

Thanks Steve69

Last edited by Steve69 (8/22/2024 11:31 AM)

Ron68 wrote:

I have the MSD box and MSD distributor. I had a no fire situation. I did the troubleshooting to verify the box was good, but no fire. It turned out to be the coil in the distributor was bad. I had to pull the dist. and remove the drive gear to get the thing apart to  install the new coil. That was 10 years ago, and no issues since I did that.

Thats probably what I have going on too.   Im going to check the coil this weekend and test the box one more time. 

Thanks
Steve69
 

The 'S' terminal on the solenoid provides full 12v power to the ignition coil during cranking.  There could be a short in the starter that is being back-fed to the coil via the 'S' terminal wire that was causing your problem.  Note that once the solenoid is de-powered, the ‘S’ terminal is isolated from the starter's cable.

 

Last edited by BobE (9/05/2024 5:43 AM)

The reason an "I" terminal is on the solenoid is for supply full voltage to the coil during cranking.  Anything connected to the "S" terminal will be drawing power through the switch.  This can't be a good idea for the switch.

If you wire it with a jumper, full starter current will have to travel through 2 sets of solenoid contacts.
Unnecessary.

The foxbody setup uses the fender mounted solenoid as a “relay…pilot circuit” to energize the starter mounted solenoid that connects full load of starter on the “starter solenoid” only.

The foxbody setup places a small current through the fender mounted solenoid.
That is reason the PMGR starter can be connected directly to the battery (+) positive.

I have a PMGR starter and eliminated the solenoid on the fender wall. In my fuse/relay box I have a relay that controls the solenoid on the starter and another relay to control 12v to the coil.

50vert wrote:

RTM wrote:

Isn’t that jumper the way you’re suppose to wire up a late model starter? I think that’s what I did on my old 65 fastback.

I need to look into again because I need to wire up the T5 starter.

A Permanent Magnet motor acts like a generator while spinning, The created current is enough to keep the starter engaged.
Like Keith, I'm using a relay instead of the original solenoid. This is how the 95 is wired.

I'm also using a dedicated relay to trigger my PMGR starter.  I did it this way after having the issue of the run on starter.  As a bonus, the only load the key switch sees (and the old wiring) is the load of the relay, so very small load.
 

This is a stock ‘92 starter.
The original Ford starter mounted solenoid had a slip on connector.
Most rebuilt/new starters will have a terminal lug and perhaps an adapter for original wiring connector.

Notice the starter mounted solenoid terminal opposite of the blade terminal is connected via jumper to the starter winding.  This is why it is not a good idea to use the ignition switch only.

Late model Mustang ignition switches are designed differently compared to the first generation Mustang.