Hi all.
I am having ongoing starting issues.
Some history:
The battery was moved to the boot as one of my first mods. (1980's) It has a 10mm wire to the front.
This has worked fine for many years.
The starter motor has been rebuilt.
It has a humongous battery.
 
With the batt fully charged it cranks no probs.
however what i have narrowed down is when it get warm it won't always start.
The solenoid clicks and if the starter engages it makes a nasty grrrrr noise.
All the earths are good.
The neg strap from batt to body and body to engine are 8mm.
 
batt shows 13.3v
Then when it doesn't crank drops to like 9.0
 
Any ideas?
seems to be hit and miss. eg:
drop of at wheel aligners - won't restart.
Pick up - starts fine.
I called in at folks - wont restart. have a coffee for 1/2 hour starts fine.
Drive home - do some tuning - starts fine for rest of evening.
 
thanks

sounds like a real head-scratcher.
 
Unfortunately I'm of no help - do you know of any autoelectricians whose brains you can pick?

one - but i need really to get the oil leaks under control before i go running around too much.

that sounds like a small feed from teh boot battery to the starter BUT you say it has worked before for a long time.  Bear in mind that as the wire gets hotter (ambient air temp rises) the current holding potential of the wire reduces.
 
Other than that, I too am scratching my head............

MK1_Ozcurrent holding potential

Current carrying capacity
I would be running 25mm square minimum from boot to battery and battery to body/engine block. There's some on ebay, good value @ $7 a metre. If the starter has just been rebuilt, take it back for them to have a look at. Also get the battery tested at autobarn etc. Process of elimination.

ok.
when i first encountered this issue i took the starter motor back and they load tested it and it came up fine.
I took the battery back and they load tested it n stuff and said its fine. (it is a big battery)
 
What i don't understand is if the wire was too small then it is too small - why the intermittency? when it does start it starts fine.
I went home last night and started it fine. warmed it up - mucked around with tuning (i think i got no 3 back with a idle mix compressor blow.)
I had no trouble starting it several time even warm with the battery not recently charged
 
The reason i bought this humongous battery was to eliminat this very issue.
 
Is it possible to be the contacts in the starter switching?

What about the ground wire?  I have two on mine just to be sure.
 
Matt 

the next time it happens i'm gonna hook up my jum leads for extra ground - but as i said - if the ground was too small then why does it start fine most times.

Intermittent faults are a PITA

Wow! Sounds like the exact same issue I am having.
Mine is running a standard 1600 with 2L weber carby. Carby was thorougly cleaned with carby cleaner a few months before symptoms started.
I had the battery in the boot and worked fine for years. As part of my trouble shooting I moved it back to the engine bay.
I have new (all less than 1 year old): battery, coil, points, condensor, dizzy cap, plugs, leads, start motor (new not rebuild).
 
The symptoms are:

• starer motor engaging but not turning the motor with enough force
• or starter motor not quite engaging and getting the whirring sound (pinion free spinning or slightly engaging)
• intermittent voltage drops while cranking (may be causing the above)

I left the car off the road for a few weeks until I got a chance to trouble shoot it. The night before I charged up the battery. Come morning I tried to start it with various throttle positions. Gave up and added some WD40 down the carby throat and it started to kick. Finally got it started.
It has now been starting every morning and evening with a little persuation. It dies the first time it fires up about 50% of the time, then fires up fine the next go. Left over the weekend it sometimes needs some WD40 to get going but then it is good for the week.
If I stop the car and try and start it 15-20 minutes later it wont start. An hour or so and it is good.
 
The voltage dropping makes me think it is electrical so I want to try replacing the solonoid and/or ignition switch but haven't got around to it. The solonoid is separate to the starter motor on the 1600.
Other ideas I have are possible compression loss in 1 or more cylinders. I have tested with one of those press-to-seal type gauges but I don't think I was getting a good enough seal. I have borrow a screw in gauge and have yet to try it out.
 
The car runs and idles fine once it is warm with no smoke when starting or accelerating.
I will report back with any more test results as I get around to it.
 
Good luck.