2l-te Main Relay remains on with key off (1 Viewer)

Dec 12, 2020
Auckland, NZ
A charity I am connected with has a 1993 Toyota Hiace Super Custom (12 seater) with a 2lte motor. 2 years ago they cooked it and cracked the head. I eventually decided to help them out and in between breaking my arm and wrecking my back, finally got it ready to light up late last year. But it wouldn't start. Initially I was not getting diesel to the injectors. But the seals in the injector pump had dried out (diesel squirting out the sides) and I had to remove it and replace them. Now I have diesel to the injectors, and it occasionally bursts into life, only, it seems, as I turn the key back from start. When it does start there is no throttle control and the revs start racing with engine knock and bulk smoke, but turning the key off stops it, thankfully! I noticed that after turning the key off and removing it, the battery went flat over a day or two. I checked things out and found the SPV Relay was hot to touch, with the key out, and was clicking on and off as I pulled it out and put it back in. Not until I pulled the Main Relay, which also clicked on removal, or disconnected the battery, did it turn off. So I decided the ECU must be crook and sent it for repairs. Leaking capacitors were replaced, and the ECU reinstalled. No different. I then had an auto electrician spend 3 hours on it and he decided it was an ECU problem. I contacted the guy who fixed it and he lent me another one to try, but the same problem. I gave the computer to a mate who works in a repair shop and he said he tested it and it is fine. When I check codes it comes up 1, no problem. I have just checked voltages at the connection terminals at the ECU (still plugged in) with the key on and off, even with the key out altogether.
IGSW 12.6v (Key on) 1v (Key off)
M-REL 11.6v (Key on) 2v (Key off)
FSR 4.5v (Key on) 3v (Key off)
BATT 12.6v (Key on) 12.6v (Key off)

The replacement ECU I was given is worse with 2v at the IGSW with the key off. It seems to me that there must be sufficient voltage going to the M-REL from the BATT when the key is off/out to trigger it or at least keep it on and therefore trigger the FSR (Spill Valve Relay) as well. I am foxed. I am a motor mechanic, but electronic stuff I have never learnt formally, although I have managed to fix a few things in my time. Once I disconnect the plug into the ECU with the IGSW connection with the key off, it also disconnects the battery as well of course, the relays open. When I connect the plug again, they don't close again. Also, turning the key off and pulling the Main Relay seems to reset the ECU. It does not click on when refitted. Once there is no drain on the tranny that switches the M-REL, the tranny seems to switch off again, and the IGSW volts go back to zero as well.

Any ideas anyone?

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