Slow starting when hot

[Big_John]

Cool has 9v going to it while running but less when cranking. Looks like 4v during cranking.

There's your problem. The ECU won't work at that voltage.

Now to find the cause.

Do you have a dual ballast resistor or a single?

Disconnect the neutral switch from the starter relay (wire coming up from transmission). Simple spade connector, just pull it off. That will keep the starter from turning. Check the voltage to the coil with key in start position. Assuming you have a single ballast resistor, that should be ~12 volts.

 

[BJS racing]

Check the power coming off of the brown wire (IGN2) from the ignition switch and see how much power you have there while cranking. If it shows the same thing replace the switch. That is what provides power to the coil while cranking and definately could be causing this problem.

 

[Big_John]

Check the power coming off of the brown wire (IGN2) from the ignition switch and see how much power you have there while cranking. If it shows the same thing replace the switch. That is what provides power to the coil while cranking and definately could be causing this problem.

He has said he's having some issues with the starter, or at least that's how I read some of this. I think that it might be prudent to eliminate that as a cause of excessive draw pulling the voltage down. I have experienced that myself and seen it on other cars.

After that, doing what you suggest is the very next step, although I'd check all the wiring before buying a switch.

 

[BJS racing]

He has said he's having some issues with the starter, or at least that's how I read some of this. I think that it might be prudent to eliminate that as a cause of excessive draw pulling the voltage down. I have experienced that myself and seen it on other cars.

After that, doing what you suggest is the very next step, although I'd check all the wiring before buying a switch.

I was understanding that it would turn over fine but just would not fire when hot. But hey I might have missed something as well. LOL.

 

[Big_John]

I was understanding that it would turn over fine but just would not fire when hot. But hey I might have missed something as well. LOL.

I think he's still having problems with it slowing after cranking a bit, but I could be wrong.

 

[pmschmitt]

Ok so to recap.
The car starts great when cold. Starter will crank and even when I disconnect coil to check starter cables the starter never seemed to slow down or get tired.

When the car is up to temp and I shut it off if I come back to start it it will struggle. The starter will turn at what appears the correct rpm for 1-2 second but then will slow down and become sluggish. There is never any clicking.

Tests that have been run:

Battery - would not hold charge and was < 10v when cranking. It was replaced with a new battery but the problem persisted.

Cables to starter- I did a voltage drop to starter and it was less than .5V. On positive and negative So therefore eliminated bad connection and or cables.

Coil- cranking v to coil ( when car is cool) is around 4V and 9V when car is running. I just pulled off the brown wire on starter switch and turned key to on position ( did not crank)and had 11.3V at coil.Placed brown wire back on starter switch and turned key to on and still had 11.3V at coil when not cranking.

So where do I go from here fellas. I feel like Sherlock Holmes. I attached a pic of the engine bay as I am unsure of single or dual ballast resistor.

 

[BJS racing]

View attachment 94925

Coil- cranking v to coil ( when car is cool) is around 4V and 9V when car is running. I just pulled off the brown wire on starter switch and turned key to on position ( did not crank)and had 11.3V at coil.Placed brown wire back on starter switch and turned key to on and still had 11.3V at coil when not cranking.

So where do I go from here fellas. I feel like Sherlock Holmes. I attached a pic of the engine bay as I am unsure of single or dual ballast resistor.

What you need to check is the power on the brown coming out of the switch while cranking the engine. You have way too low of voltage to the coil while cranking if you are at 4v. That is telling me that either there is an issue with the switch or the bulkhead connector.

 

[Big_John]

When the car is up to temp and I shut it off if I come back to start it it will struggle. The starter will turn at what appears the correct rpm for 1-2 second but then will slow down and become sluggish. There is never any clicking.

That sounds like a bad starter. IMHO, the bad starter is drawing too much current and the voltage drops.

I just pulled off the brown wire on starter switch and turned key to on position ( did not crank)and had 11.3V at coil.Placed brown wire back on starter switch and turned key to on and still had 11.3V at coil when not cranking.

I'm confused here... Did you check it with the key in the start position? or the run position?

 

[Big_John]

Wait... Does this car have an electronic ignition conversion or does it have points and condensor?

 

[pmschmitt]

Points & condenser

Brown wire output from starter switch when turning key produces 9.5v when cranking.

Something wasn't making sense so I went back and checked voltage to coil when cranking and it was 9V. I must not have had a good ground when I did the same test earlier and got 4V. So does this now point to replacing the starter?

There is one I can get here in town if need be

Could someone explain to me why the starter goes to crap when the motor is warmed up? I still haven't wrapped my head around that? Heat is the enemy of conducting the current?

 

[Big_John]

Could someone explain to me why the starter goes to crap when the motor is warmed up? I still haven't wrapped my head around that? Heat is the enemy of conducting the current?

There are a few things that can cause or contribute to the problem, both electrical and mechanical in nature, but simply stated, yes, the starter can fail when it gets hot.

 

[pmschmitt]

Ok I'll swap it out and report back! As always huge thanks to all contributors in this forum!

 

[Gerald Morris]

ok. Did voltage drop last night and never read more than 0.4 on both positive and ground. I unhooked the foul during this and the starter never got sluggish during cranking like it does when hot. Based on the voltage drop I can rule out the cables it sounds like and I have a new battery so we are left with starter?

As for the operating temp/ cooling system I have a 26 in radiator with a shroud on a 7 blade fan with a fan clutch. Increased temp happening on highway not in traffic. Fan clutch replacement ?

OK, you got plenty fan and its heating up on the highway. Do you have a thermal fan clutch or one which is just speed activated? Normally, if you have a weak fan, the motor would cool off when rolling into some air at speed. I wonder if the water pump is going south on you.

 

[pmschmitt]

Old fan clutch

New fan clutch that is thermal. Can't tell if the original is though I see no spring

 

[pmschmitt]

UPDATE
Car running cool on the highway with new fan clutch, but still having an issue with hard starts after heat soak. I believe the gas is boiling creating a vapor lock.

So I have heard about carb spacers, heat shields, and return lines. Thoughts?

I have the factory dual snorkel air cleaner so not a whole lot of room for a carb spacer, I'm currently running the 1/4 inch gasket that came with the rebuild kit. i maybe have another 1/4 inch of clearance it looks like.

 

[Big_John]

Is the car still turning over slow or does it just not want to start?

 

[70_NPORT]

UPDATE
Car running cool on the highway with new fan clutch, but still having an issue with hard starts after heat soak. I believe the gas is boiling creating a vapor lock.

So I have heard about carb spacers, heat shields, and return lines. Thoughts?

I have the factory dual snorkel air cleaner so not a whole lot of room for a carb spacer, I'm currently running the 1/4 inch gasket that came with the rebuild kit. i maybe have another 1/4 inch of clearance it looks like.

I have a carb spacer under the edlebrock carb on my 383 (needed it because of heat) and that is on top of a performer air gap alum intake..adds a bit taller). I dunno about the 440, but I used a hot dog bun to test it out...for clearance.

 

[commando1]

I used a hot dog bun to test it out...for clearance

Lmao

 

[Ripinator]

I have a carb spacer under the edlebrock carb on my 383 (needed it because of heat) and that is on top of a performer air gap alum intake..adds a bit taller). I dunno about the 440, but I used a hot dog bun to test it out...for clearance.

Was there a hot dog in the bun ?!?

 

[pmschmitt]

would crank normally never slowed down with new starter.