My Xmas would be even better if my car worked!

Hi guys,

BACKGROUND

I have owned my 89 cab since 2004 now and loved it everyday.  In 2010 the gearbox packed up so instead of fixing the old girl back to standard I decided to do the AGU engine conversion.  I started to gather all the bitties and get stuck in.  It has a smooth running AGU, box from 93 mk3 diesel, the Qpeng management along with all sorts of other bits in between.

PROBLEM

It ran great for 18 months, even had it at the Nurembergring (did kill a box but that's fair) always been very reliable until last summer there was a whole load of us up climbing Ben Nevis, drove up there perfect but upon starting the car to come home it did not want to fire, turned over well/fast but would not fire until the third attempt at the key and it started up fine. Drove for over 100miles great, we stopped for some food then back out to the cars expecting the car to start instantly but the same, it took three long turns of the key for it to fire.  
Since then I have removed and cleaned all the earth connections and connections to batt, starter and alternator.  I have fitted a brand new battery.  Still the same.
If you hook the car up to another battery with jump leads it fires instantly but as soon as you only give it one battery then it goes back to the the third key turn starting.  I have tried yet another battery with no success.   

It goes without saying this is doing my head it.

Had one guy saying it could be the starter pulling to many amps and starving the ignition of power?

Any help would be greatly appreciated.

put a jump lead from the battery -ve to one of the bolts holdign the starter on, see if that helps. if it does your engien earth is poor. on the mk1 and early mk2 this runs to a bracket on the gearbox which was a poor location, later mk2 and mk3 instead use a stud on the end of one of the gearbox -> engien mounting bolts. get yourself down the scrappy and nick a set of battery and alternator cables from a mk3 golf as they're much chunkier than mk1/2 then fit them see if it helps at all. you'll see what i mean about the bolt!

only issue with the mk3 battery -ve is it wont reach the earth point on the mk1 chassis leg, so you'll need to make up a short earth for this. what I did on my cabrio was get another mk3 battery cabe and cut the end off so i had a length with a ring on each end. 1 end to chassis leg, andthe other to the spare ring on the battery -ve cable. you'll see what I mean!