Hard hot starting

[shelbydoug]

I've been chasing a hot start problem that I just can't find.

The engine starts fine cold. Runs fine.

In trying to restart it warmed up, it's being difficult.

I've isolated this down to the coil firing at something like 25% of what it should or what it fires at cold.



Also the tach won't rev over 1,200 rpm.


What's been done so far, cleaned all grounds and checked for resistence. New ignition switch. New ignition coil (the third one). Switched to yellow top with new resistance wire to ignition. Took out Petronix and went back to ignition points.

Coil phenolicly isolated from engine heat.


Again, this is the ignition not firing hot. Carbs are not involved in this. This won't even fire hot with starting fluid.

...and yes Coralsnake, pump gas with ethanol (corn juice) in it. 


In 50 years of running these cars, I can't say as I've ever encountered anything exactly like this and stated plainly, I'm stumped.

I'm open to CONSTRUCTIVE ideas. Nothing like, well push it off a cliff or gt a Corvette please?

[67350#1242]

Does the tach read properly when cold?  Could try bypassing it to see if it fixes the hot start problem.

[shelbydoug]

Does the tach read properly when cold?  Could try bypassing it to see if it fixes the hot start problem.

No it doesn't.

Something out of the ordinary is going on here. I was wondering what the tach might have on this and also the starter solinoid. Both are in the ignition circuit.

[kingchief]

I had the same issue recently. Once heated up the car would not start. Changed coil and all good for the moment! Have not really tried a long cruise then tried restarting but on a short one she starts right up after shutting off. That was the problem before the issue so I went with an older coil that I knew was in good shape.

Steve

[shelbydoug]

I had the same issue recently. Once heated up the car would not start. Changed coil and all good for the moment! Have not really tried a long cruise then tried restarting but on a short one she starts right up after shutting off. That was the problem before the issue so I went with an older coil that I knew was in good shape.

Steve

I agree, that if someone asked me what I thought the issue most likely could be, I'd say that it sounds like an intermittent coil.

I followed my own advice. I had a Petronix "flame thrower" in the car. Replaced it with a new one. Same issue.

Then I replaced it with a reproduction "yellow top". Same issue. Fires right up cold. Not so much hot.

Now to me, all the three coils test "good" and what are the odds that all three are no good? Very, very low?


To answer  67350#1242's question, it makes no difference. I just tried the switch to verify this and nada.

The only thing left in the system is the starter solenoid. I'mwondering if somehow the internal contacts are carbonized? It takes more power to start a hot engine then a cold one. I suppose that is worthy of a try as well?


I know that I am right on an ancient Mohegan hunting trail. That's documented. I'm wondering if I've pissed off the ghost of the medicine man and I need to make some sort of offering to make things right? I often have bizarre electronic haywire malfunctions.

Anyone know anything about that? John Barnes was always swearing about that. Where he was from, you couldn't stick a shovel in the ground and not find bones from a "French and Indian War" gravesight?

Maybe this is like the "south seas anomaly"?

[Royce Peterson]

More likely the starter is junk. Or a bad battery. Either of those are under a much more severe load when hot and the voltage drop in that circuit directly affects coil voltage while starting.

I would start by having the battery load tested. Free at any auto part store.

If that's not it then make sure all the cables are good. If they are then have the starter load tested. Free at any auto part store.

[BryanT]

shelbydoug,
Does the car turn over if it does no problem with the solenoid?  Are you getting 12 volts to the coil at start up? Should have 12 and then 6 when running. I had the same problem that kingchief talked about 15 years ago and replaced an aftermarket coil with my original ford yellow top coil no problems since.  Weird that your tach does not work. I have been running a Petronix set up for 25 years no problem. Good luck
Bryan

[shelbydoug]

shelbydoug,
Does the car turn over if it does no problem with the solenoid?  Are you getting 12 volts to the coil at start up? Should have 12 and then 6 when running. I had the same problem that kingchief talked about 15 years ago and replaced an aftermarket coil with my original ford yellow top coil no problems since.  Weird that your tach does not work. I have been running a Petronix set up for 25 years no problem. Good luck
Bryan

My son is always criticizing me for too many parameters going at the same time.

I think that Royce MAY have hit on the significant factor?

One of those, "too many parameters"...I replaced the cable to the starter with a "correct" 4 gauge and the same to the battery negative.



I probably don't need 00 (some call it 2/0) gauge but tomorrow I am changing them out. This is a recent issue and so is changing out those cables.

I've "smoked" the solinoid a couple of times trying to start this thing hot. Where there's smoke, there's fire.

I'll bet Royce drinks Jim Beam? If this works, I'll need an address for that shipment.



The tach is a separate issue. I think I'm gonna' need another one? It didn't like the Petronix I guess?

[68krrrr]

My KR would go through starters like crazy i swear every couple of years i would have to replace it , i think the heat soak from a big block would just cook them.

[shelbydoug]

My KR would go through starters like crazy i swear every couple of years i would have to replace it , i think the heat soak from a big block would just cook them.

I would agree with this if you are speaking of the Ford starter.

I went with a Tilton race starter. They are MUCH heartier.

[69 GT350 Vert]

I bought a Tuff Stuff starter for my shelby through NPD several years ago.  Works great.  100% new, Made in USA in Ohio. 

Link below:
https://www.tuffstuffperformance.com/i-24485973-oem-style-starter-full-size-2-bolt-mounting-black-3124b.html?ref=category:1267354

[KR Convertible]

I thought this was a spark issue, not a cranking issue?

[Bob Gaines]

I thought this was a spark issue, not a cranking issue?

+1. I don't believe a starters draw would drag down spark performance.

[pbf777]

....................... severe load when hot and the voltage drop in that circuit directly affects coil voltage while starting (cranking).

      This IS a real possibility, as we have witnessed this in particularly rear mounted battery relocation installations repeatedly over the decades.         

     Scott.

[shelbydoug]

....................... severe load when hot and the voltage drop in that circuit directly affects coil voltage while starting (cranking).

      This IS a real possibility, as we have witnessed this in particularly rear mounted battery relocation installations repeatedly over the decades.         

     Scott.

We're going to find out by changing the battery cable size. If nothing else, this is educational but as stated by me, two wires were changed out by me (to 4 gauge). I doubt that it is coincidental?

2/0 (00) cable takes a day or two to get here. Nothing local. So nothing happening today with that.


Should we have a para-mutual event here? Who wants to lay a wager and who wants to give odds? Anyone?

I think that I can change this to a survey? Bet it's the cables/bet it's something else?


To add interest to the wager thing, I will say the wires do get HOT and the solenoid can wind up smoking.