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Hard hot starting

Started by shelbydoug, September 23, 2020, 10:56:04 AM

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Kent

#15
If he cant rev over 1200 rpm I would say the power valve in the carb is blown.

ok I read that its not a carb issue, hmmmm there is not so much in the ignition system, so it should be a voltage problem, maybe your battery shows 12 V but the cells are broken so it dont has the capacity anymore that your car will need. Change the battery before you change anything. Redtop should work 100%
SAAC Member from Germany and Owner of a unrestored 1967 Shelby GT500, 1968 1/2 Cobra Jet´s and some nice Mustang Fastback´s 67/68

Bob Gaines

Quote from: Kent on September 24, 2020, 02:42:54 PM
If he cant rev over 1200 rpm I would say the power valve in the carb is blown.

ok I read that its not a carb issue, hmmmm there is not so much in the ignition system, so it should be a voltage problem, maybe your battery shows 12 V but the cells are broken so it dont has the capacity anymore that your car will need. Change the battery before you change anything. Redtop should work 100%
Nothing has been said about a dragging starter symptom. If the battery has enough voltage to crank the engine then it should be more than enough to supply the ignition system. The ignition system does not draw much.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

shelbydoug

Quote from: Kent on September 24, 2020, 02:42:54 PM
If he cant rev over 1200 rpm I would say the power valve in the carb is blown.

ok I read that its not a carb issue, hmmmm there is not so much in the ignition system, so it should be a voltage problem, maybe your battery shows 12 V but the cells are broken so it dont has the capacity anymore that your car will need. Change the battery before you change anything. Redtop should work 100%

The TACH won't indicate over 1200rpm. The engine at cold start up is 1700rpm. Second new battery.

No one wants to wager hey? :o
68 GT350 Lives Matter!

kjspeed

My bet is the starter. Maybe you should sacrifice some fire water for the Mohegans?
1968 Shelby GT350
1968 Mustang GT S-code
2009 Mustang Bullitt

shelbydoug

#19
Quote from: kjspeed on September 24, 2020, 07:10:49 PM
My bet is the starter. Maybe you should sacrifice some fire water for the Mohegans?

I'm willing but where do I leave it and are there chicken bones involved?

I have experience with alcohol and howling at the moon in Native American type surroundings but that did nothing but get the local police involved. It's definitely not the way to go.
68 GT350 Lives Matter!

s2ms

Maybe I missed it...have you tried a new solenoid? In my experience they can do freaky things like coils. Had a weird thing a few years ago where my 66 just kept running when the key was turned off. At first I was convinced it was the ignition switch. Nope, it was the solenoid.
Dave - 6S1757

shelbydoug

Quote from: s2ms on September 24, 2020, 10:19:33 PM
Maybe I missed it...have you tried a new solenoid? In my experience they can do freaky things like coils. Had a weird thing a few years ago where my 66 just kept running when the key was turned off. At first I was convinced it was the ignition switch. Nope, it was the solenoid.

No. I'm going to try the larger gauge cables first, then  the only thing left is the starter solinoid.

Parameters. One thing at a time. You shouldn't "multi-task" with mechanical devices.
68 GT350 Lives Matter!

Bob Gaines

With all of this talk about starters and solenoids could you clarify on how the the engine acts when you are trying  to start . Does the engine spin but does not fire when it is hot ? Does the starter drag when it is hot or does the engine spin but will not fire? Clarification will help with diagnosis. With the first few posts talking about coils ,points and tachs it read like a engine firing issue and not a engine spinning issue. Typically two separate unrelated issues. The starter , cables ,and solenoid typically have to do with the engine dragging when hot or not spinning at all. Those things are typically unrelated to a engine not firing situation.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

shelbydoug

Quote from: Bob Gaines on September 25, 2020, 10:27:26 AM
With all of this talk about starters and solenoids could you clarify on how the the engine acts when you are trying  to start . Does the engine spin but does not fire when it is hot ? Does the starter drag when it is hot or does the engine spin but will not fire? Clarification will help with diagnosis. With the first few posts talking about coils ,points and tachs it read like a engine firing issue and not a engine spinning issue. Typically two separate unrelated issues. The starter , cables ,and solenoid typically have to do with the engine dragging when hot or not spinning at all. Those things are typically unrelated to a engine not firing situation.

Sure. It spins the same as when cold, I would describe as normally.

The timing light shows the #1 firing "rapidly" when cold, but much less, when engine is warm. Maybe in the 25% to 33% of when cold.

Consequentially, you can here it fire like it wants to start, but it needs to really be cranked to a point where the solenoid on the firewall gets so hot, it will start to smoke.


The starter is not laboring at all. The tach shows it spinning the engine at about 750 to 800 rpm at that point.


68 GT350 Lives Matter!

Bob Gaines

Quote from: shelbydoug on September 25, 2020, 11:50:39 AM
Quote from: Bob Gaines on September 25, 2020, 10:27:26 AM
With all of this talk about starters and solenoids could you clarify on how the the engine acts when you are trying  to start . Does the engine spin but does not fire when it is hot ? Does the starter drag when it is hot or does the engine spin but will not fire? Clarification will help with diagnosis. With the first few posts talking about coils ,points and tachs it read like a engine firing issue and not a engine spinning issue. Typically two separate unrelated issues. The starter , cables ,and solenoid typically have to do with the engine dragging when hot or not spinning at all. Those things are typically unrelated to a engine not firing situation.

Sure. It spins the same as when cold, I would describe as normally.

The timing light shows the #1 firing "rapidly" when cold, but much less, when engine is warm. Maybe in the 25% to 33% of when cold.

Consequentially, you can here it fire like it wants to start, but it needs to really be cranked to a point where the solenoid on the firewall gets so hot, it will start to smoke.


The starter is not laboring at all. The tach shows it spinning the engine at about 750 to 800 rpm at that point.
Your clarification indicates to me that there is apparently no relation between the starter,cables or solenoid to the engine not firing regardless of if hot or cold. I would be interested in hearing how those starter related items have any relation to engine ignition and firing before going down that rabbit hole further.
Bob Gaines,Shelby Enthusiast, Shelby Collector , Shelby Concours judge SAAC,MCA,Mid America Shelby

Tom Honegger

I agree with Bob. Doesn't sound like a starter/battery/solenoid issue.
I would guess heat related issue with fuel and combustion.  Maybe
isolating/insulation fuel lines, carb mount insulator would help.

pbf777

Quote from: shelbydoug on September 24, 2020, 02:35:54 PM
I will say the wires do get HOT and the solenoid can wind up smoking.  :o


     Regardless of whether it solves the starting issue, apparently something needs to done as the circuit is being overloaded, ..................and that's how fires get started!               :o

     Often, if familiar, one can detect as the starter motor is cranking the engine, of the sound, as if it were creating a high draw to the point of a significant voltage drop, that being on an otherwise well charge and sound electrical system as this can be of some rather great amperage sums.   

     Check the amperage draw upon starter engagement and cranking as cooking the leads (of reasonable capacity and duration) is a subject that should be investigated, as just bigger wires, is somewhat like "fixing" the recurring blown fuse in the home with the installation of one of greater amperage rating.                  ::)

     Scott.

shelbydoug

Quote from: Tom Honegger on September 25, 2020, 01:05:00 PM
I agree with Bob. Doesn't sound like a starter/battery/solenoid issue.
I would guess heat related issue with fuel and combustion.  Maybe
isolating/insulation fuel lines, carb mount insulator would help.

When engine is hot, carbs are cool to the touch as is fuel line which is phenolicly isolated as are carbs.

As I said, coil not firing hot. Fuel not percolating and starting fluid does nothing.

In addition, the COIL is phenolicly isolated as well.

Ignition all the way...but why? That's the question.
68 GT350 Lives Matter!

KR Convertible

Is this the same car you replaced the resistor wire on?  I would check the coil voltage when cranking hot vs cold, and running hot vs cold.  Did you use good quality points and condensor?   Lots of Chinese junk out there.  I try to stay with Motorcraft or Echlin.  A faulty condensor can act up when hot.

shelbydoug

#29
Quote from: KR Convertible on September 25, 2020, 02:52:53 PM
Is this the same car you replaced the resistor wire on?  I would check the coil voltage when cranking hot vs cold, and running hot vs cold.  Did you use good quality points and condensor?   Lots of Chinese junk out there.  I try to stay with Motorcraft or Echlin.  A faulty condensor can act up when hot.
Resistor wire...yes.

Echlin points and condenser.

Was doing same thing with Petronix with 12v non-resistor wire.

Checking the coil voltage cranking...yes would confirm the issue, but no, not yet. That doesn't eliminate the solenoid either. Waiting on my 00's.

Will check that all when they get installed.


68 GT350 Lives Matter!