Ignition Problems with my 70 Stang

[70grande]

Hey all,

So I've got a 351C 2V stang and we've been fighting recently. I went to a buddies house for the super bowl on Sunday and when I went to leave it just kept cranking and cranking and it wouldn't start. I figured it was the starter solenoid (I think thats what it's called, its the little cylindrical thing with 4 terminals, one from the +bat, one to the starter, and two smaller ones labeled I and S) I went to the parts store and grabbed a new one and a coil just for good measure and installed it and ended up killing the battery trying to get it to fire. Went home with my tail between my legs that night. Got the battery fully charged the next day, plugged it in and it started right up, no tinkering required. Got it home and then went to go for a victory drive an hour later and it wouldn't start again.

It would crank for days but never fire. After accidentally (stupidly) frying a harbor freight voltmeter on the battery charger I bought a nice new one and started testing around. With the key in the ON position, I get voltage to the S position on the solenoid, but not to the I. Not sure if that's how it's supposed to be. The strange thing is that I get 12V to both the + and - side of the coil.

Can anyone help me out here? It's driving me nuts, and the people at work can't be happy that I haven't come in the past 3 days.

Thanks in advance!

Tim

 

[70grande]

Found out I was measuring the voltage wrong.

With the key in ON position:

12V to I
12V to + and - of coil
nothing past that point that I can tell.

The frustrating thing is that its very inconsistent. One moment it's reading 12V and the next I've got 0.0. I may just be using my voltmeter wrong. I've got no problem admitting I'm an amateur.

 

[2+2GT]

OK. You should have no voltage to the S or I terminals with the ignition on. While the starter is engaged, you should have 12V at both the S and I. With the ignition on, you should have about 7V at the + side of the coil. With the starter engaged, you should have 12V at the + side of the coil.

 

[70grande]

Any ideas as to where the fault could be? I'm having a hard time figuring it out. I don't understand how it could be fine to drive one second and then wont fire immediately after that. Could my ignition switch be going out?

 

[72 fastback]

It could be the ignition switch. I have had that same problem in the past. It ended up being the switch located on the column up under the dash.

 

[68keyblr]

+1 for ignition switch. They tend to be intermittent like that when they start going

 

[70grande]

Is there any way I can bypass the switch to determine that it's the fault? I've already got the entire dash taken out from my troubleshooting over the weekend.

 

[BarnStang]

If you have the dash out, you should be able to see the switch on top of the steering column. Check for 12v on the switch in RUN with your volt meter. The Red with green strip wire should be wire # 16 to the coil. It "may" also be a pink wire at the switch...I have seen it both ways.

 

[70grande]

Interesting, on mine there are both a red w/green stripe and a pink wire right next to it. When in RUN, pink has 12V, red-green has 0V. I'm pretty sure red-green is the for the starter, because it gets about 12V when the key is in START, and the pink gets about 7.5V.

 

[pabear89]

look for a break in the pink wire from the switch out to the coil.
Place a jumper wire to both ends of the pink wire and try starting it.
If it runs you have isolated your problem.

 

[BarnStang]

Right. Been awhile. THe Red w green strip is the starter solinoid. Sorry for the confusion.

 

[70grande]

Alright, so I've bypassed the pink wire and I'm still getting the same situation, 12V to both + and - side of coil and all the way up until the digital replacement for the points Pertonix sells in their electronic ignition kit. What are the chances that this thing is fried? I have noticed that in the first couple miliseconds of cranking, the coil will spark every once in a while. I've tried two different coils and they both act this way. Also, the + cable from the battery get very hot during these starts. Any ideas?

 

[BarnStang]

Possible. What model is the Pertronix unit? The Igniter instructions show that you need to feed the module prior to the ballest so you will need a premenent line from the switch to the module if thats what you have.
I have seen some of the shutter wheels need minor clearencing. Make sure the shutter wheel swings through the module with no contact. And that the sleeve is pushed down all the way.

I'm not a uge fan of Pertronix, but the problems they had in the past have been corrected long ago-it is supposed to be a solid unit now. THere are other brands out there that DO allow you to feed power to the module through the resistance wire which is a billion times easier. THe Pertronix still does not.

The other problem that comes up depends on where and how you source switched 12v for the module-I have had cars that will not get the 12v from the I term on the solinoid in the START position after the conversion, but will "catch" and start if you let the key snap back to RUN while the engine is still rotating...Make sure you are getting 12v in start and in run at the coil + and that you are feeding the Pertronix red wire with switched 12v before the resistance wire.

 

[70grande]

Thanks for the help gang! Finally got it running again! It was the ignition module inside the cap. Bought a new dizzy from Craigslist that had the electronic module in it and it fired right up no problem. Only thing is that now I think I got the timing off 180 degrees because at #1 TDC, the timing mark is at about 4 degrees, but then when I fire it up and use a timing gun, the marks are nowhere to be seen.

The way I determined TDC in #1 is take the spark plug out, crank motor and wait for finger to be pushed out by compression, and then get timing mark to TDC and use that for #1 on the dist. cap.

Any input on why my timing shows up so weird? Luckily I can tune it by ear for the time being but I would like to have it dialed in. I'm thinking I just got it 180 inverted.

 

[woodsnake]

"Any input on why my timing shows up so weird?" Is your vacuum advance plugged/ capped off? If not, you will see some really high numbers..

 

[68keyblr]

it wouldn't run at all if you were 180 out. How is it running, is it backfiring at all, either through the carb or out the exhaust?

 

[70grande]

I was just being hasty and forgot that I needed to disconnect the vacuum advance to set the timing! Got it all tuned up now and shes running great! Thanks for the help everyone!

 

[88dragtop]

I've got my own starting issue so I'll just add. I'm starting to suspect my pertroinix, again. The 1st one I put in ran about 3 years then when the car warmed up it would start to miss/run rough. This 1 is 4 years old and the car has developed a hot start problem. Will just crank and crank, if I look down carb it's getting gas. The coil I replaced 4 years ago before the pertronix but it's clamped to the head like stock. No voltage on S or I when key in on, 12V from coil + to bat - but only 6V across coil + and -. Same voltages when the car is running. Is the coil - tied to ground? Car cools down, will fire right up. I wouldn't think I have had a wiring issue for it to run for years w/o issue and then become a problem. Electronics do act this way. WTF is going on with this thing?

 

[horse sence]

i have been running mallory unilite dist. in all my cars no problems yet
i have been hearing a lot of similar complaints about pertronix units

 

[bartl]

I've got my own starting issue so I'll just add. I'm starting to suspect my pertroinix, again. The 1st one I put in ran about 3 years then when the car warmed up it would start to miss/run rough. This 1 is 4 years old and the car has developed a hot start problem. Will just crank and crank, if I look down carb it's getting gas. The coil I replaced 4 years ago before the pertronix but it's clamped to the head like stock. No voltage on S or I when key in on, 12V from coil + to bat - but only 6V across coil + and -. Same voltages when the car is running. Is the coil - tied to ground? Car cools down, will fire right up. I wouldn't think I have had a wiring issue for it to run for years w/o issue and then become a problem. Electronics do act this way. WTF is going on with this thing?

When the key is in the "ON" position, you should have coil+ voltage backfeeding the solenoid "I" lead. When the key is in the "START" position, you should have same voltage at solenoid "I" terminal and coil+. Yes, the coil is tied to ground......every time it is saturating its magnetic field before the ignition module triggers a spark.

I had an '80 F250 that would crank like mad, but would only fire up when I let go of the key. Turns out the solenoid was bad - most likely there was enough arcing on the "I" contacts to not make a connection.