Hot start problems with new airbox

[xvivalve]

...because the hot starter draws too much current to spin the engine over and thus diminishes the spark?

I don't know to be honest, but I suffered exactly the same symptoms a few years ago, changed the starter for a recon unit and had no further problems.

[Jon Tilson]

I an accept that when its hot various bits of the starter will perform less well than when cold. But this will result in the starter turning over
more slowly than it does when cold. If the battery doesnt have sufficient capacity to maintain the voltage in the ignition system then starting performance
will clearly be impaired. In general hot engines take less effort to turn than cold ones because of lower oil drag.

To stop the car from firing you have to drop the voltage down to about 6-8 volts I would have thought. With that degree of drop you will certainly notice
the starter struggling.

In general cars WILL still start with a slow turning starter if volts are maintained in the ignition circuit. After all we used to start cars with starting handles...

I'm not saying its not the starter, but we dont yet have enough data to recommend replacement before doing the easier stuff IMHO.
Changing a Sprint starter is a bit of a mare after all...

I'd like to see what happens with a measurement of coil + volts when cranking....

Jonners

[Edin Dundee]

Hmmm.
In 1982 I called out the AA to my Dolly 1850, the engine turned away merrily but wouldn't fire.
The patrolman placed his inspection lamp on the battery and found the loose battery connector.
Tightened that, no more problems.
So, starters can take all of the available current and spin very fast indeed, leaving no power for the rest of the car. Current, like water, will always take the easiest path.
I never take anything for granted with car batteries and circuits......

[Jon Tilson]

So that defies ohm's law....

Ye cannae change the laws of physics cap'n.

Try and start your car with the lights on. You will see the lights dim, but don't go out.

Motors do behave strangely with all sorts of complex back e.m.f.'s and time dependance under load etc. But a turning motor will not take ALL the current
or a car would never start...

Jonners

[alolympic]

I keep the battery charged and disconnect the live cable whenever it sits in the garage.
I will try and start with the lights on though.
If it is merely a poor connection somewhere I will be very happy.
I guess I need to get hold of a multimeter to start checking current. Something else to learn.....

Thanks for all of the suggestions guys, I will run through all in order of cost and effort and hope to get to the source asap.

[Jon Tilson]

Lol no I didnt mean YOU should try and start with your lights on. It was just an illustration that not all
current goes to the motor...

I guess it could help show up a dirty connection though...

Jonners

[alolympic]

So, let's talk hypothetically that the plugs were gapped too large, do you think that could contribute to poor hot starting? although cold starting was fine.
I went for a drive this evening, and once home, with the engine hot, I started the car up again, and it started straight away. Repeated 3 times.
Only change I made beforehand was to re gap the plugs.
The mixture is too rich, has been for a while, with the plugs getting pretty black in between cleaning. The plugs are also getting oily.
I wonder if the rich mixture, combined with too big a plug gap could be the source?

[epcot_pete]

Not sure if this is any help, but my MGB had a similar hot start problem about a month ago. I have a set of those clear red plastic tubes that fit onto the plugs and leads fit onto other end. When hot problems occurred it was quite noticeable that the spark was very dim, when left for 10 mins to cool down the spark was very bright and car started immediately. New coil fitted and problem solved.
So lack of power gave poor spark that was not enough to ignite fuel.

[80Sprint]

I hope plugs sort it but my money is with Jonners as I had a similar hot start issue. New Bosch coil and external ballast had it sorted.

[alolympic]

Going to take it for a drive this weekend to try for a 2nd time. Fingers crossed it will be okay, as per the last drive, so fingers crossed the re gapping of the plugs was all that was required.
The coil was replaced a few weeks back before I started driving the car again -non ballast type. Still seeing the same issues after that, so a faulty coil is out of the equation.

[Jon Tilson]

Come to the Ace and I will bring my meter....

Jonners