What have I got?

Yes as mentioned use engine oil in the gearbox and transfer case. In addition to the reasons given related to the oil pump modern gear oils (EP90 inparticular) have additives that can eat phosphor bronze bits inside the gearbox.

Also - if the oil pressure light did not go out I would not have run the engine - it is just too risky - for sure most likely a sender issue but maybe not and not worth damaging the engine. Before running again I would get the sender checked/changed so you know for sure what oil pressure is doing.

Great to hear that you have got a pretty good vehicle [smilebigeye]

Garry

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Originally Posted by garrycol

Yes as mentioned use engine oil in the gearbox and transfer case. In addition to the reasons given related to the oil pump modern gear oils (EP90 inparticular) have additives that can eat phosphor bronze bits inside the gearbox.

Also - if the oil pressure light did not go out I would not have run the engine - it is just too risky - for sure most likely a sender issue but maybe not and not worth damaging the engine. Before running again I would get the sender checked/changed so you know for sure what oil pressure is doing.

Great to hear that you have got a pretty good vehicle [smilebigeye]

Garry

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Thanks Garry,

I went out there now and did locate the switch at the rear RHS of the block tucked up and away. The rubber cover was a sticky disintegrated black mess, - thanks!
I disconnected the two bullet plugs on the wires to the switch.
Started it again and the light remnained on.

According to the fault finding section of my newly acquired (V8) manual, under 'warning lights / instruments (where fitted)'...
"Oil warning light does not go out / a)... Lack of oil... b)...Oil warning light faulty or pressure failure. Remove wire from switch ...if light stays on, there is a fault in the wiring. If light goes out there is a fault in the switch or the high pressure system..."
I know that is the V8 engine, but is it reasonable to assume the switch is wired the same way on both?
I've found a switch on line for $16.00, but will see if I can get something locally first, just to be sure.
However if the manual is correct, it's probably a wiring issue. And, since the wiring was interfered with when the bulkhead was repaired and repainted, and the instrument cluster is still hanging forward, then I suspect something isn't connected or isn't earthed etc....
Hopefully I didn't do any damage, but I do get your point. Will try and sort that ASAP.
cheers,
Rob.

I don't know if it applies to the stage 1, but the Isuzu 110 has two pressure switches - one works the warninf light, the other inhibits the reversing light if the engine is not running. Obviously, if the one you found is the reversing light one, disconnecting it will do nothing to the pressure warning light.

Apart from this, the comments on the V8 should apply equally.

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Originally Posted by JDNSW

I don't know if it applies to the stage 1, but the Isuzu 110 has two pressure switches - one works the warninf light, the other inhibits the reversing light if the engine is not running. Obviously, if the one you found is the reversing light one, disconnecting it will do nothing to the pressure warning light.

Apart from this, the comments on the V8 should apply equally.

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Thanks John.
As I have no rear lights yet I can't tell either. It took me a while to find the switch I did. I didn't see any others.
The wiring diagram in the 3.9 owners manual only showed the one oil pressure switch and it was wired from the secondary relay which I noticed was on the engine side of the fire wall. That helped me find it. Hopefully it's the only one.
But as they say.. a little knowledge can be dangerous so it might be time for some professional input. However I suspect good mechanics who know this 35yr old version of a 4bd1 inside out and, can be bothered getting involved might me a bit thin on the ground.
I'll look at the wiring, replace the switch and do the oil / filter changes first.
Rob.

Read here: https://www.aulro.com/afvb/the-isuzu...ml#post2699906

The wiring diagram in the manual is not correct.

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Originally Posted by Red90

So it is now fixed. The power feed wire had a break.

What is missing in the wiring diagram is the power feed wire. It is a brown wire that runs through the engine harness to the starter.

The relay is a dual contact relay.

Terminals at relay.
- Brown (unfused constant power from starter) connects to input for reverse light contact.
- Green (to reverse light switch) connects to output of first contact. Closed when energized.

- Brown (jumper from other brown wire) connects to coil input.
- Slate (to low pressure switch) connects to coil output.
- Other side of switch goes to ground.

- White/Brown (from dash light) connect to second contact input.
- Black (to ground) connects to second contact output. Open when energized.

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Thanks Red 90 and all the other advice. My oil pressure warning light is now sorted.
From Red90's diagram and his separate tread on the subject, together with my diagram and the trouble shooting note which suggested a wiring issue; I went searching the engine bay with some printouts and a multimeter.
I tested the slate wire going to the switch and got full power... (more than 12v).
That made me chase the earth.... among the spagetti sitting below the relay I almost immediately noticed a loose black wire with a ring terminal. It was only long enough to reach the clutch master cylinder bracket cover plate which started to make sense as that has been removed and is still to be refitted following a clutch master replacement by the PO. I screwed on the earth wire...started her up... no more oil warning light!...
So glad to know I wasnt doing any damage and it was an easy fix.
It's not easy picking up someone else's project to finish and trying to work out what was disturbed, what's been done, what hasn't and where it's up to.
Here's the switch location and the Series III 3.9 manual wiring diagram for reference. (also posted in Red90's thread)
cheers,
Rob.

OK, Now that the oil pressue warning light is fixed. (a little embarrassingly)....
I removed the wiper washer bottle for a look at the starter in the process and wondered what this is?
It looks like a resistor pack being aluminium with all the fins, it has 3 screw terminals but can't see any wiring for it...
Mounted on the left inside guard under the water bottle adjacent to the starter.
Any ideas?
Rob.

Hard to see. Might be a battery isolator.

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Originally Posted by Red90

Hard to see. Might be a battery isolator.

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Not with those fins.
I'd suggest electronic ignition module but too few terminals.

Quote:

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Originally Posted by Red90

Hard to see. Might be a battery isolator.

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Correct. In the good old days of low power alternators your battery isolator was a pair of high(ish) current diodes in a finned box like that. It split the alternator output to two independent batteries. One input terminal, two output terminals, probably can handle 40A or so.