1057 tbird stock 312 y block intermittent issues

[bobioknight]

Ok, problem fixed for now. Turns out, with the pertronix ignition it needs more power, when you divide voltage by resistance of the coil you get total voltage, right. Right! So my tbird had the coil and resister which lowered the total voltage to about half of what is required for the electronic ignition. Keep in mind the resistance wire had also been replaced years ago with standard Wire so there was no additional resistance to add into the equation. Total voltage is now approx 6.8, whereas with the coil and resistor it was down to approx 3.8.

I called pertronix to verify voltage and they confirmed it was much too low. And now I am running within spec.

Thanks for all the comments, it really helped norrow things down.

[bobss396]

Fixed is good. Odd that it was such an intermittent problem.

[bobioknight]

Originally Posted by bobss396

It still sounds like a fuel issue to me. A pint of denatured alcohol will take care of water in the gas. I'd change the gas filter as a start, maybe take the top off the carburetor for a look.

I agree with you, so much so that I have been through the entire fuel system. I pulled the fuel sending unit off the top of the tank to see inside expecting rust and dirt, but it looks brand new in there. There were some small bottom floaters which I filtered out. The glass fuel bowl inches away from the carb is also perfectly clean and continuously full with approx 4lbs of pressure. I went as far as drop a brand new Holley carb on as well.

[bobss396]

Originally Posted by bobioknight

I agree with you, so much so that I have been through the entire fuel system. I pulled the fuel sending unit off the top of the tank to see inside expecting rust and dirt, but it looks brand new in there. There were some small bottom floaters which I filtered out. The glass fuel bowl inches away from the carb is also perfectly clean and continuously full with approx 4lbs of pressure. I went as far as drop a brand new Holley carb on as well.

What's the saying... 90% of carburetor problems are electrical issues.

[bobioknight]

Originally Posted by bobss396

What's the saying... 90% of carburetor problems are electrical issues.

I don't know, but I bet 90% of carburetor problems are from lack of experience. At least that is the case with me. I don't have the experience to pinpoint and troubleshoot so I rely on forums like this one to help give me some direction. I can only tell you what I have tried and what has worked or not worked. In this case changing out the coil and removing the resister fixed my immediate problems, BUT they have been intermittent so maybe tomorrow they could show up again. I hope not. One thing I did change when I got home tonight is, I added the ballast resistor back into the mix (coil was getting too hot I feel), reset my timing and idle to factory specs which is 6* at 500rpm. Ran around town and freeway no issues, very pleasant drive. When I was testing the total resistance of the old coil and resistor, I noticed the coil was throwing off all kinds of numbers and would not lock on to any final amount, the ballast resister was intermittently failing. So, I must conclude with the old parts failing and the new ones running great, that the issues have been resolved electronically. In this case.

[bobss396]

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A bad coil can do weird things. On old cars, I tend to replace them as well as toss a whole tune up into it. I hope it continues to run well.

[bobioknight]

Originally Posted by bobss396

A bad coil can do weird things. On old cars, I tend to replace them as well as toss a whole tune up into it. I hope it continues to run well.

I really did not expect it to be a darn coil, I figured they either work or not. I have been going through these issues for 8 months and I have ran fuel lines, 2 different style bowl filters, filtered fuel tank, new carb. Changed the timing and adjusted carb more times that I can count. Took it to multiple shops and smog repair centers to adjust and tune the engine. Leave running great, 10 minutes after leaving, sputtering and dying. Just like a fuel issue, but there was nothing left to check or change.

I was ready to pull the electronic ignition and toss it away, but started with the coil and resistor. Reading that the electronic ignition needed more power than the current coil was putting out, so I figured that was it, and one installed, it started like normal just like every other time, but after driving a half hour where it would normally start giving me some issues, it did not. It was running great, but the coil just seemed hot so I added the resistor back into the system, it cooled the coil off and still ran perfectly.

Deciding to reset the timing and idle mixture, I decided to just double check the resistance of the new coil and resister to make sure I was sending enough voltage, it is a bit lower than the ignition calls for but it works fine, it is higher than what was there with the old coil and resistor, and when I checked the coil numbers were fluctuating all over the place and as I jiggled the connection on the resistor, the connection would randomly fail.

I am confident but cautious, I will still carry extra parts and tools with me on my short trips just in case problems come back.

Hope this help someone else running into intermittent engine problems, the solution may not be what you might expect.

Thanks for your help bobss396, as a nube, I'll take all the help I can get.

[50fordcoupeman]

Check my post of 9/16. A lot of coils won't break down until they hot. Don't understand why but have run into this more than once. Mine was a perfect example of this. Hope this cures your problem as good as it did mine!!

[bobioknight]

Originally Posted by 50fordcoupeman

Check my post of 9/16. A lot of coils won't break down until they hot. Don't understand why but have run into this more than once. Mine was a perfect example of this. Hope this cures your problem as good as it did mine!!

Hey 50fordcoupeman, thanks I went back and read the posts. Yep, good stuff.


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[bobioknight]

Had the car dyno tuned today. It was off the charts lien. New Holley carb 4160 640cfm was setup with size #57 jets (way too small). We replaced with #65 jets and brought the A/F to 12.1, also opened up the idle mixture which was too lien as well. Also adjusted the accelerator pump. Runs smooth today, let's see how it continue to runs.