Miniscule attemp at hard labour? All people in my year define hard labour as washing the dishes or bringing the shopping in

The wall was 20m by 15m, two high (500 each). The aussie sun wasn't forgiving that day and about 5 or so years ago I was pushing a diesel compactor doing the pad for that house (oh and driving my dad's bobcat).
Best to ignore my verbal diarrhea on occasions DD. (It's a kiwi thing. ..... Just like my compatriot - Dougal, I also like to engage in baiting from time to time.)
...The PO was a diesel mech and he works on trucks and heavy machinery. It could of been him that installed the pre-heat system which is just a switch and a relay connected to the glow plugs .......... That might be my next thing on my list. Getting the glow system same as how it was stock.
I like things to be stock but I must admit that the "superglow" preheat system the factory installed on your truck does give trouble and it was an early step towards treating landcruiser owners as "impatient dummies". .... In other words, Toyota tried to speed up the preheating process, and tried also to take the control of it away from the person sitting in the driver's seat (by making its workings automatic).
So in your shoes I'm not sure which way I'd go either. (Stock or modified.)
..First priority is EDIC. Today I took apart the fuel controller (EDIC relay or whatever you want to call it) to inspect it. There was no corrosion or anything on the board. One thing that I might do is check the resistance across the motor pins. As far as I know, there a 4 coloured cables leading to the motor and they are the yellow, green, red and blue. Question; the cable that goes to the oil pressure switch has got 5v on it (colour code YB). I'm just trying to pin-point the problem. Thanks guys for all the help
Firstly
Looking at my info here I see your EDIC relay (aka Fuel Control Relay) should be part number 28590-57010. (Have a look and see if you find this number on it.)
This relay was apparently used on the following Aug 1980 to June 1985 12 volt landcruisers:
BJ40, BJ42, HJ47 (B, 3B and 2H engines)
(and also found on an Aug 80 to April 82 2B-powered 12 volt BB10 Coaster)
In your pm you asked about whether the relay from a HJ60 would work.... Well it appears that relay is 28590-56090 (assuming its a 12V cruiser) so, because the part number is different, I doubt it.
Secondly
That wire to the oil switch (that you measure 5V on) gets "shorted to earth" whenever your oil pressure drops below around 3-5 psi. In other words, your oil switch opens on rising pressure and closes on falling pressure.
(So if your engine loses oil pressure during a journey, that wire will become earthed and cause your EDIC system to stop your engine.)
Thirdly
Your EDIC relay is different to my earlier one and I've kept only info relating to mine. So I'm afraid I'm not much help in diagnosing whether yours is faulty or not or what each component in yours does.
If it looks fine, perhaps you should take a peak inside your EDIC gearhousing. At the top there you'll find electrical contacts. Grease or other muck sometimes gets in the way to stop them operating correctly.
It is these contacts that tell the relay when the arm has reached the "set point" dictated by the conditions (and thereby stop further power getting fed to the motor that would otherwise make it turn too far).
By "set point" I mean these three positions:
- Fuel shut-off (aka "stop")
- Engine run
- Overinject (aka "start")
Hope this helps
