For sure being able to check for spark is a positive as far as diagnostics go. When it wont start and it for sure has no spark you will then know it was not fuel. Then again if it does have spark its on to plan B. One last item to try when it is acting up is the jumper from the battery to the coil positive. That 9 volts is at the minimum . You could also make up a jumper for that modified ballast just in case it is goofy. Your voltmeter will tell you the story. I have seen modules fail unpredictably.

So my question is, for that jumper cable from the battery to + terminal of the coil, so that is just a wire from and to those points, then when I turn the igition key what happens? I'm guessing it will turn over the starter and since it already has a direct 12v wire your'e not hurting anything, is that right?

Yes that's right. Attach the jumper and crank right away. You should see a higher voltage reading as you are not going through the cars wiring hence no voltage drop. It is just an easy test to see if it makes the igniter happy.

Ok thanks, I'll try that this weekend

I'm not familiar with the pertronix setup, but if it has it, can you check the gap between the reluctor wheel and pickup? That's the first thing I think of when people have this problem. My dad's car had that problem and we found the reluctor gap (on a MP distributor that came with the electronic ignition conversion kit back in the day) was too wide, so the heat widened it and no start when hot. We tightened it to .007ish and that resolved it.

Had a chance today to work on this, same as before cold start no problem, after a cruise shut it down and it started ok after 5 and 10 min, but after an hour no start. I did the jumper from the + battery to + on the coil and it didn't help. After two hours it started no problem. Noticed again when it didn't start the fuel was like a vapour (lighter than air) at the carb when I manually pumped it.

All the prior electrical test were done with the same results, nothing obviously wrong.

Question, battery is 7 yrs old, tested ok like I said , but could it be affected by heat, I can test the voltage but the CCA i can't. How about the starter, could heat affect its cranking power?
Also looked at the Petronix inginitor in the distributor, gap was .018 between the hall cell and the distributor. There is no mention of gap in the installation instructions, and they also say its unaffected by heat.

Any other suggestions?

With the jumper wire to the coil from the battery what was the voltage while cranking on the volt meter? What is the history on this car and the present problem?

The voltage was 12.7 before cranking, didn't get it while cranking. The car has been hard to start all the time, but it started. It has gotten worst. I talked to an engine builder around here and he says he's seeing lots of crap in the carbs because of today's fuel. I'm taking the car to him next week for him to try and figure out what is going on. But I don't know if a dirty carb would be worst when its hot.

Noticed again when it didn't start the fuel was like a vapour (lighter than air) at the carb when I manually pumped it.

The car has been hard to start all the time, but it started.







Trying to figure that statement out because it’s like the third time you mentioned it - Vapor at the carb

Go back to my July 2 posts

Do you know how an accelerator pump circuit works ?

I am having this exact same problem with my stock '71 340. Starts easy after 10-15 minutes but after 1/2 hour, will not start. Next day, started ok when cold but same problem when hot. I thought it was initially it was ignition. I swapped out the point distributor for electronic - no help. So either the fuel is vaporizing as the OP is suggesting or the opposite is happening, a slow leak of fuel past the seat causing a delayed flooding condition. To restart my car after 1/2 hour, I need to hold the pedal to the floor while cranking maximizing air into the carb. When it finally starts, it lopes to life like a flooded condition. I am convinced now, especially after reading this post that I am having a slow flooding condition causing the no start after 1/2 hour. Makes sense since the problem just started happening one day with no mods or changes.

Knowing what the battery voltage will tell you a lot as to the battery's voltage under load. A 7 year old battery is definitely a candidate for replacement. I also recommend a mini starter. I can not tell you how many hard starters that the mini has made a whole lot quicker to start. I can see fuel doing certain things to make it difficult however operator technique to each situation can usually overcome the situation. If starved a simple shot of fuel from a squirt bottle should make it fire. If flooded you definitely do not want to pump. I found out if the car was indeed flooding holding the pedal 1/3 of the way down would overcome the problem. Never let up or pump until it starts even if you quit cranking hold the pedal 1/3 open until you crank again.

I'm thinking it is the ethanol gas. I would plumb a gas can of non ethanol fuel (hard to find these days) to the pump inlet & see what transpires. If you do find a pump with non ethanol, know that an amount of ethanol will still be in the hose cuz of how the pump is plumbed when it switches from tank to tank. when I do this I pump several gallons or so into the car to clear it out then some undiluted non ethanol in a gas can. Holler how the problem is resolved. it's been an interesting topic

As Robert mentioned, if you have ethanol based fuel it will definitely cause the problem due to it's lower boiling point. Even if it's not ethanol based it could still be the cause of your issues.

One thing you can try is to open the hood and remove the air cleaner to allow the trapped heat to escape and then repeat your testing. Once confirmed there are different ways of trying to correct the issue. Keep us posted

Check your fire wall wiring connections i have owned a A12 for 40 years and yes they loose contact But I think It just flooded I have to hold the gas pedal down every time the car sits for a hour

Interesting, well as far as the fuel I'm unsing Shell V power 91 octane, supposed to be ethonol free, I see your point on the common parts of the pump. I'm going the take it for a ride today again but this time after an hour I'm going to try my best to get it start instead of waiting another hour for it to cool down. I'll try it assuming its flooded idea, then I'll spray some easy start fluid, I'll have the volt meter attached also and record the readings.I've tought about the battery, I know it tested ok at the store under load, but I wonder if heat is affecting its performance, it is a Turbo Start Retro battery and seven yrs old, and I've read lots of people having issues with these, I guess I've been lucky so far for it to last that long.

This morning I had some time, so took it out for a drive, came back and parked it. Like prior test after an hour I tried to start it, this time assuming its flooded so I depressed the pedal 1/2 way, no pumping and it started. Tried again, now 1.5 hours since the ride and it started again using the same procedure. I will try again later once the rain goes by and road are dry. So maybe I was making it worst in all my prior tests by pumping and adding fuel.
Thanks all will post when I try agian

I use ethanol free fuel and even thou it's better than regular pump gas with my shaker holding in so much heat it can still have some problems. It changes based how long it sets and how hot it is. Short time just hit key no gas fires right up. If after sitting a while and it doesn't start right up without giving it any gas the trick is to hold pedal to floor as flooded. After long time cooling off just push pedal down once like regular cold star and fires right up.

So best guess is it will sometimes boil fuel out and vapor lock and other times boil fuel through carbs and flood intake or combo of both. If car sits for more than around 3 days the bowls will go dry and need new prime. Start it every other day just hit key. An electric pump would cure the cold start problem but I haven't gotten to it yet.

You might be on to a better understanding as to what the car is doing and what you need to do to correct it. Through the years I can not tell you how many people I have observed trying to start a car and making it worse. You can be under the hood telling them to try starting and observe them pumping the gas. You tell them to quit pumping and they claim I am not. Must be a reflex that some people have. So back to your issue no doubt if you had a slightly flooded engine you could of been making it worse. Just develop a new technique to starting it and your wallet will get heavier. Again if this is your problem as I previously stated a mini starter will make an unbelievable difference.

Sometimes the obvious isn't so obvious. My carb was professionally rebuilt 3 years ago and I put about 500 miles on car since. I believe my flooding condition was caused by the ethanol degrading the rubber bowl seal. I wish I had somewhere in NJ to buy ethanol free gas.

pure-gas.org

Try here.