Hot Starting Problems

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Thomas Sottile
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Re: Hot Starting Problems

#16 Post by Thomas Sottile »

Has any one thought of a way to grease the starter bushing or maybe install one with ball bearings?
Last edited by Thomas Sottile on Thu Feb 22, 2018 3:20 pm, edited 1 time in total.

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Doug McDonnell
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Re: Hot Starting Problems

#17 Post by Doug McDonnell »

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Re: Hot Starting Problems

#18 Post by Fred Winterburn »

When bump starting is successful over using the starter motor it is usually an indicator of a bad coil. In your case, the fact that it starts cold (but not really cold in Perth, not cold like a Canadian winter) and not hot, is a further indication that you probably have a bad coil. I'd swap coils before trying anything else. Fred
Edit, As an aside, you should never run a starter more than about 15 seconds maximum at a time without a cooling off period. Running longer will cook the windings especially in hot weather.
marcsherriff wrote:Firstly, I apologise if this topic has been discussed time and time again. I have searched the forum to no avail.

I live in a warm climate. Too hot to drive my BT5 coupe in the summer.
Fresh motor, 9:1, big bore kit, 912 heads, Weber carbs, 123Ignition dizzy.

Whenever my car has been sitting for a while, or started "Cold". It starts like a champ. Starter motor, which is only a year old, turns slower than I'd like, but fires the car up immediately. Almost like it was made for cold weather.... I have cleaned all earth points, have a replacement 6v Optima battery, which maintains voltage.

If the car gets to operating temperature, about a needle width or two short of centre of the temp gauge, then turned off. It will not fire up again. The starter spins appropriately, if a little slow, and will do so until battery will no longer turn it, if I let it. 45 seconds to a minute of continuous cranking, I have discovered.

The car will bump start straight away, just not key start.

Timing and valve clearances are correct.

I originally suspected that possibly fuel was evaporating, but when trying to start it hot, after a couple of pumps on the pedal, fuel can be smelt, which leads me to believe, there is plenty of it going somewhere.

Concerned that maybe the engine was not getting the spark it needed, through dropping voltage, I run a hard wire to the Coil from battery, and still no joy. Due to my lack of owning a hoist, nor an earlier career of being a contortionist, I have not tried a hard wire to Starter solenoid, from the battery.

If anyone has a magic wand, I wouldn't mind borrowing it....

Any/All advice welcome.
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Al Zim
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Re: Hot Starting Problems

#19 Post by Al Zim »

Try this! When you have the car hot, before you shut off the ignition shut the fuel off. Let the engine run for another minute to a minute and a half. this will give the boiling fuel a place to expand to without flooding the engine. Do not turn the gas on till the engine starts. You may also want to try a tank of leaded aviation fuel or a tank of leaded racing gas. Have a friend crank your car when hot and you measure the voltage at the coil. This will probably tell you where or if you have an electrical situation. al zim
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marcsherriff
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Re: Hot Starting Problems

#20 Post by marcsherriff »

Thank you all for the helpful tips.
After all this, it has actually turned out to be a fuel problem. Seems the stuff just disappears from the carbs when hot!
Is dumping a tonne of the stuff in there with the accelerator pedal the smartest/only solution?
Maybe one of those Autoprime things I read about will help?
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Mervyn Hyde
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Re: Hot Starting Problems

#21 Post by Mervyn Hyde »

Marc you think it is fuel starvation when hot? Normally, priming is only needed when cold (pumping the pedal or using a separate inline electric pump like the Airtex), not when hot. A single, partial depression of the pedal while cranking should do the job when hot. What fuel pump do you have on the car now? You have Webers I see, but is there some excessive heat sink effect with the mounting of those (as others have said)? My experience only runs to Zeniths.
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David Jones
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Re: Hot Starting Problems

#22 Post by David Jones »

Marc, hot starting is an issue that is exacerbated by using weber manifolds with out the phenolic heat insulating spacers but if it is as you say above 38*c then it is going to be even worse. The problem is partly with modern gasoline because it is more volatile than the gasoline that was in use when these cars were new. Once the engine is hot and in your case hotter than it may be in other countries, as soon as you stop and turn off the engine the heat of the engine naturally rises once the fan ceases turning. On top of this the manifolds without the spacers transfer heat to the carbs in an already hot and getting hotter engine compartment. This boils off a significant portion of the fuel in the carbs, the vapors of which being heavier than air immediately collect in the intake manifold thereby creating a super rich mixture which will not ignite when you spin the engine over. On top of this the fuel in the line has also probably turned to vapour so the pump cannot fill the carbs again until raw fuel reaches the fuel pump. By the time it does it is likely you have decided it is not going to start and give up until it cools down. One answer is the fuel primer bulb or an electric pump close to the tank. The electric pump or the primer bulb will also help by running cooler fuel through the fuel system which will help to cool everything down and improve the chance of starting the engine. On really hot days here in the midwest and also as a mater of habit with a hot engine I hold the gas pedal down to the boards for a hot start and spin the engine over until I see oil pressure. By that time I am sure I have scoured the rich mixture out of the intake manifolds and usually the carbs have refilled with cool fuel and it fires right up. I also always let it idle for a minute before turning off so the engine has a chance to cool off a little and I try to park in the shade so it does not cook in direct sunlight.
I hope these comments help you.
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Chuck House
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Re: Hot Starting Problems

#23 Post by Chuck House »

marcsherriff wrote:
The car will bump start straight away, just not key start.
The above symptom is inconsistent with a fuel problem.
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Re: Hot Starting Problems

#24 Post by marcsherriff »

Chuck, Noooooooo!!!!
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Dick Weiss
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Re: Hot Starting Problems

#25 Post by Dick Weiss »

Adding grease to the starter bushing? Sure, you could add a little, but not worth modifying the trans. bell housing for a ball bearing--Max. clearance between the bushing ID and shaft OD is .008" and it'll be worn oval.

The bushing could/should be an oil-light version which has lube already in it. There's no room for a ball bearing unless the ID for the bushing in the trans. bell housing is enlarged, but there's less than 1/8" wall thickness on 1-side of the ID!

Finally, you could use the hi-power starter which has its own shaft end-support & not using the bushing mentioned above.

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Thomas Sottile
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Re: Hot Starting Problems

#26 Post by Thomas Sottile »

Thanks Dick. Tom

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Mervyn Hyde
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Re: Hot Starting Problems

#27 Post by Mervyn Hyde »

+ on what Fred said (and I asked earlier) about the coil. It may be new Marc, but that doesn't mean its perfect. Try another one to check.
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Chuck House
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Re: Hot Starting Problems

#28 Post by Chuck House »

marcsherriff wrote:
The car will bump start straight away, just not key start.
If the above symptom statement is indeed true, I would suspect the electronic distributor may have a heat related fault which makes it susceptible to low voltage. Try putting the original distributor back in.
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Re: Hot Starting Problems

#29 Post by Mervyn Hyde »

Marc, if it helps give me a call. Will send you an email. I may have some spares that you could try to identify this troublesome issue for you.

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John Brooks
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Re: Hot Starting Problems

#30 Post by John Brooks »

My 2 Cents. I think the fuel is fine.

Since it will start cold, then jump start fine when hot, I would look at the ignition switch. The run and start positions share a contact inside the switch. First time you start they work fine. Then again when you bump or jump start it HOT, It's starts fine, because the starter contact is not used and the voltage to the coil is closer battery Voltage.

But the ignition contacts are dirty or corroded they heat up when the starter current is passed through the ignition switch, to the Starter solenoid. When cranking the starter, it draws allot of power, the voltage to the coil drops a couple volts since they are parallel at the switch when cranking.

I bet if you check the + side of the coil, the voltage drops to 4-5V when the starter is cranking when hot. Less voltage = less current = less spark, that means no start. With "ignition on" you should see the battery voltage, Same as voltage as Bat on the regulator post. Then crank and watch the drop drop at the coil.

Check the voltage at both the switch and the coil. Some times its just the bullet connector on the switch. But more than likely it internal to the switch.

The fix is overhaul/repair the switch or Put a relay on the starter solenoid circuit to reduce the current draw when cranking. And while you are at it, I highly recommend to wire a momentary push button switch to the relay coil and the regulator "Bat" so you can crank the engine from the back of the car when doing maintenance or when it decides not to start when hot. Then you can open the deck lid crank it and work the carbs from the back of the car. Also a jumper wire from "Bat" to "Coil +" allows you to hot wire the car and eliminate the key switch.
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John Brooks

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