Hot Starting Problems

[marcsherriff]

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.
Please avoid witless remarks, unless very entertaining.

[Erik Thomas]

Marc:

Is the starter a real 356 4 brush starter, or a 2 brush smaller wattage VW unit? when is the last time the starter bushing in the bell housing was replaced? Measure resistance of cable from battery to starter?

My BT-5 is not a good hot starter either, and I have ordered the fancy 6V modern starter from the UK. I have not installed it yet. I will give a report as soon as that happens.

[John Brooks]

Contact Godfrey Everett, have him take a look, I don't have is number, but he is local. tootie@iinet.net.au

[marcsherriff]

John, Thanks for the tip on Godfrey. I know him well. His response is take it to the mechanic we currently share! The mechanic is also going through the elimination process, thought I'd see if there was a time saving solution out there.

Erik, It is a real, 4 bush starter, reconditioned. Due to it's willingness to start the car cold, I have not invested a lot of time in the starter part of the problem. Will do so.

[Mervyn Hyde]

Too hot to drive in summer in WA Marc? In Qld we have had many days in the mid to high 30's and the 356 is out there 8)

Now how long between starts? That is how long from the drive/stop to the re-start? Also are you holding the pedal down somewhat on the re-start (viz., Handbook)?

The 123 isn't the problem? Did you change the coil when you installed the 123 dizzy?

[marcsherriff]

Merv,
Thanks for the response.
Basically, if I turn the car off, any time trying to start it again from straight away, to needle back at zero point on gauge, I have the hot start problem.
I have tried pedal to the metal (well timber) on restart.
Maybe those big windows on a T6 let more air in than my T5. I've even disconnected the heater cans, but the cabin gets stifling. Then again, you might just be tougher than me !

[Phil Planck]

You probably have the steel Weber manifold adapters with no phenolic spacers to reduce heat soak to the carbs. Also, hot electric motors run slower than cold ones. And, as said above, what is condition of the starter bushing? Too much shaft clearance will cause the starter motor to run slower than normal.

[David Jones]

Marc, if the car cranks slowly then it is likely that at the same time the battery is being dragged down to a low voltage and you consequently have either a weak or no spark. This is borne out by your observation that it will start easily on a push start. I suspect your starter bushing is the culprit though it could be the starter motor, but even a VW starter with a good battery should crank the engine fast enough to start it even when hot. Having been fooled myself by a bad bushing I would suggest you replace that first but check the starter to see if it is a VW or Porsche style. If a VW it is going to be a more difficult fit than the Porsche style due to the orientation of the solenoid. In order to test for volts drop in the system it is not that difficult to access the starter solenoid by removing the right rear wheel and reaching under the car and shorting the terminals from solenoid hot to the solenoid spade terminal and see if the engine will then crank quickly. I use a small coin such as a US quarter to do this. Many years ago I did this on an almost daily basis when I had issues with my 914 starter.

[Adam Wright]

I had this problem too, also have a T5. On hot start the starter would turn very slow. I cleaned all my grounds, the one from the battery was pretty cruddy, fixed it right up.

[Jeffrey Leeds]

+1 on starter bushing.

[Steve Douglas]

I have had that problem show up a few times, even when they had new bushings and starters. I made up a "test lead", a wire 3 feet long #16awg, with large alligator clips on the end. When the car won't start try "hot wiring" the ignition, one end of the test lead to the + side of the coil the other to the BAT terminal on the regulator. The red and green lights on the dash should light up even with the key off. Then try and start the car, if it starts then it's in the ignition switch, fuses or a bad connection elsewhere, if it won't start start looking at the coil or the isolation of the distributor points or condenser. Temperature can make a difference in the circuits, sometimes "shorted" to ground, other times just open or partially open. A voltage test on the hot side of the coil may show low, less than 3 volts may not fire the coil when cranking, while push/bump starting it will be fine as the starter isn't drawing the power from the coil. Clean the fuses, look at each one carefully as they may look intact but can have a crack in the conductor which when cold works but in heat of passing current may expand enough to reduce the current to the coil. Ignition switches and bullet connectors can also be temp sensitive due to poor contact, burnt/worn contacts within the switch can be good when cold and bad when heated. I recommend cleaning the cables and starter connections well, ground strap at starter, and install a starter relay, such as Joe Leoni's.

[Chuck House]

Marc,

I'm with Steve and others, your problem is electrical. If it won't start by the starter when hot but fires right off by push/bump starting, it is a classic case of weak spark likely caused by voltage drop through too much resistance at one or multiple connections. Our 6V cars are more sensitive to poor connections as the current is twice that of 12V and thus twice the voltage drop through any resistance - and the resistance and thus the voltage drop increases with heat. Use the test jumper that Steve Douglas mentioned to verify it is a weak spark problem and then clean the battery connections, including the ground at the chassis and the transmission ground strap , fuse box, etc.. Sometimes the resistance is in the ignition switch which necessitates rebuilding the switch although as Steve also mentions, Joe Leoni's relay kit will usually take care of this. Good luck.

[Mervyn Hyde]

I think most of us have had the same experience at some stage Marc. I agree with Chuck, it seems electrical. Earth straps and grounds are critical but you have checked that. I have even added extra (modern non-woven type) earth connectors. I also made up a starter relay on Joe L's diagram, and changed the starter bushing.

However, did you check that coil? It might be breaking down somewhat when hot.

[marcsherriff]

Thanks for the responses everyone.
I have replaced the starter outside bushing, in the Tranny case.
I’ll check out the brass strip too, between the solenoid, and the starter case.
All other Earths have been cleaned.
I am not convinced I have a starter problem though. I think it is more to do with the motor itself. My reasoning is that I would have thought that if the starter does the job pretty effortlessly when cold, it should do it any time, as I would have thought this would have been the most strain on the starter with cold oil in the motor, most resistance etc..
Also, to me, if what I have stated above is true, it will be drawing the most current then, hence reducing available current to the coil, but again, this is not a problem starting cold.
The coil is the Bosch one supplied direct from 123Ignition, when they supplied the Dizzy. The car ran beautifully, from the moment it was installed. Still does. Just does not ignite when hot.
Logically, this means it must be a fuel or ignition problem. I believe the ignition problem is eliminated, through my point above. Either that, or I have a joint somewhere hanging by a thread, when everything expands hot, then joins nice when cooled down?
Fortunately, I lack the hair that I’d otherwise pull out!
I will pursue alligator clip test.
Car does not have weber adaptor plates, but weber manifolds. Fuel evap has not been eliminated as a problem yet. I am doing all this trial and testing on my own, so somewhat of a challenge cranking the car and working in the engine bay.

[David Jones]

Marc, you have eliminated the hard start problem caused by fuel because you said it starts on a bump. If it was fuel related it would not start any better on a bump start. My 64 coupe also started easily cold and turned over much faster on the starter when cold. I thought the problem was the starter because I was sure the starter bushing was good. After going through three starter motors one of which worked perfectly in my "A" coupe I had to accept the bushing was at fault. Put a new one in and after that the car spun over fast enough when hot with full throttle to blow the over rich mixture out and restart the car. If there is any misalignment of the starter motor armature with the starter coils the starter will tend to grind over slowly. When cold the misalignment could be less allowing the starter to turn easily. You could perhaps procure another starter motor and try it if you are 100% certain the starter bushing is OK.