Really Strange Starting Problem, Please Help.

[jerthemost]

I have something really strange going on. I have a 68 mustang 302 with edelbrock 321/347 package and 500 cfm carb with performer intake. Recently started having start problems. Flamethrower coil was leaking and finally blew out. Changed to accel super stock coil and problem was fixed for about 2 months. Then suddenly same problem with starting came back. I rewired my ignition about 2 years ago using a 40 amp relay to make and break run wire from battery to coil +. Changed out the relay at the same time I put in new coil. Relay is made by run wire from ignition switch bypassing the resistor wire completely. My battery voltage reads 12.50. If I turn on switch I get 12.5 at + side of coil. Car still will not start or might once in a while. I even put dielectric grease on all connections at the relay and at the fuse that feeds the coil power from the battery. Two days ago I started blowing the ignition fuse when this problem started. Sometimes I can put a jumper from the battery plus to coil plus and get it started when I cannot any other way. The jumper seems to work more times than without it. but keep in mind I still have 12.5 volts to coil + without the jumper. A spark tester will show no spark when trying to start and doesn’t start. Tester will show good spark if I ever do get it running. Today I replaced the coil again. The first time I tried it it started right up but turned it off and would not start again. Finally got it started again with the jumper and drove it home from shop to see if you guys have any ideas. I am completely out of ideas.
To summarize all wiring form battery to coil is good.
Fuse is good.
Changed coil wire and is making connection or so it sounds like. I hear it click at both ends when I push it in.
Second new coil in 3 days.
Relay is new from yesterday and is making according to volt meter.
Have a pertronics ignitor. How can you troubleshoot one? It is only thing not been changed.
Any help or ideas greatly appreciated.
20a Relay n.o.
Battery +--------- fuse ----------0---| |----0----------+ ig coil
Ign switch +-------------------------rly coil----------grd

 

[PoppyMod]

Hi,
Why was a relay added to the ignition system? I, for one, have never heard of a relay in the ignition ckt. The ign. system doesn't need one. That Pertronix sparkie needs a dedicated 12Vs too.
I would remove the relay, re-check the starting and ignition circuits, insure your "sparkie" is getting it's 12Vs.
BTW, what's a 321/347? Why the small carb?
Good Luck!

 

[jerthemost]

Hi,
Why was a relay added to the ignition system? I, for one, have never heard of a relay in the ignition ckt. The ign. system doesn't need one. That Pertronix sparkie needs a dedicated 12Vs too.
I would remove the relay, re-check the starting and ignition circuits, insure your "sparkie" is getting it's 12Vs.
BTW, what's a 321/347? Why the small carb?
Good Luck!

The relay is there because the coil does need 12 volts. The run wire from the ignition switch is a resistor wire which drops the voltage down to 6 volts. As for using a relay, lots of people have done it search the forums. The relay is obviously not the problem since it ran fine with it for 2 years. And there is a full 12.4 volts to the coil and pertronix. Maybe the question should be what coil should i use with the pertronix? Maybe pertronix has to have a flamethrower coil. However it did run fine with the accel coil for about 7 weeks before this problem started. I think it may be the pertronix going bad.

 

[PoppyMod]

Hi,
While I understand the need for 12Vs, I just never considered a relay as a means to that end. I've been running one of the first Gen Pertronix ignitors for years with a Jacob's box and their coil, so, It's not a case of needing the accompaniment of the flamethrower, specifically. Throughout all of this, does the engine consistently "crank fine" but, doesn't fire? Not sure what you mean when you say "start". As these are two separate systems to some degree.
The mention of your "hot wire", is causing me to think of your solenoid and the ignition switch ckts. Cause, you've by-passed your ign. ckt on the solenoid. If I'm thinking this correctly.
I've read reports of the "sparkies" failing but were mostly in the later models. But, then, who's to say this wasn't caused by user error.

 

[bartl]

Maybe you should try a coil with an internal resistor. This will give you your 12V at the + side for your Pertronix but your resisted voltage at the - side.

 

[jerthemost]

Problem solved, missing ground strap in the distributor. I bought the car with pertronix already installed. Have had chronic starting problems from day one just not as bad as recently. Put in a ground wire and it starts perfetly everytime.