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A bit of background first. I bought an 89 L Touring Wagon with an EJ22 motor. The wiring was as dodgy as hell, not just the EJ loom but the existing L wiring was hacked to pieces. The engine in my 90 Lib had died so I decided to replace the wiring in the L. Not just the engine loom but ALL the wiring (including the dash). My thinking was that it would solve several problems all at once – temp gauge correct, fans switch on when they’re supposed to, better headlights etc. (sounds really good in theory…..lol …..will do a write up when I’m finished). At this stage I have all the wiring in but have only connected enough to start the engine. And so to the problem(s).

With no key in the ignition, a lot of the pins on the ECU are putting out a small voltage. Some are 0.12V and some are 0.54V.
Only the correct pins are receiving power.
All pins meant to be grounded are actually grounded.
All general wiring ground points are grounded.
When I turn on the ignition, most outputs are as they should be (TPS 7.78V, Knock sensor 3.78V etc).

However pin a7 (temp sensor) is putting out 3.54 volts and the temp gauge jumps straight to 3/4s hot (should be 0.7 – 1.1V).
The fuel pump relay wont cut in, pin b23 (fuel pump relay control) is showing battery voltage 12.8V (on is 0V off is 12V).
Both the original ECU and my donor ECU do exactly the same.
ECU not showing any error codes.

ANY suggestions are most welcome. I am unemployed and cannot afford a mobile auto sparky at the moment so I am relying on you guys right now.

Sorry to be so long winded,

Thanks

With no key in the ignition, a lot of the pins on the ECU are putting out a small voltage. Some are 0.12V and some are 0.54V.
Only the correct pins are receiving power.
All pins meant to be grounded are actually grounded.
All general wiring ground points are grounded.
When I turn on the ignition, most outputs are as they should be (TPS 7.78V, Knock sensor 3.78V etc).

Its probably not a big deal as some electronic components leak a little bit of voltage.

TPS should be somewhere between 0v and 5v, depending on where your throttle is

Knock sensor is a piezoelectric device, so works somewhat like a microphone.

Both of these devices are inputs, not outputs

However pin a7 (temp sensor) is putting out 3.54 volts and the temp gauge jumps straight to 3/4s hot (should be 0.7 – 1.1V).

The water temperature sensor is for telling the ECU the engine temperature, it has 2 wires. It
has nothing to do with the seperate temp gauge sender which has 1 wire

The fuel pump relay wont cut in, pin b23 (fuel pump relay control) is showing battery voltage 12.8V (on is 0V off is 12V).

The fuel pump relay is negative switched by the ECU. This means that one pin of the relay gets 12v from the ignition switch, and the other pin connects to the ECU and the ECU grounds it to turn the relay on.

When you first switch the ignition on, pin 23 should have 0v for a second, then go back to 12v. When you crank the engine, it should fall to 0v again and stay there once the engine is running

Thanks for your help Gannon.

Sorry i've had so many things going thru my head i made a stuff up.
Air Bypass was showing 7.7V not the TPS. Was just trying to point out that these were giving correct readings.

Pin a7 is part of the 2 wire temp sensor unit. Its expected range is between 0.7 (20degC) and 1.1V(80degC). The ECU is putting out 3.54V and i don't understand why. when i disconnected the plug at the sensor to test continuity i tested the voltage again and it jumps to 4.5V ??????

With the fuel pump relay it is not coming on at all. Usually it comes on for a couple of seconds until the fuel system is pressurised and then cuts out, but mine is not coming on at all. It goes straight to 12V and stays there even if i crank the engine.

Thanks again for your help.

Tony

I don't mean to sound like a spoil sport but unless u know what your doing i wouldn't be stuffing with ECU wiring. You will have to be very very careful. I assume you have some sort of automotive electrical knowledge.

Best bit of advice i can give you is to study the ECU wiring in the Gregories Liberty manual and the L series Gregories manual. It says in there what all the measurments and voltages should be.

Dave

Thats ok Dave.

Yes i have a fairly good knowkedge of auto electrics. The problems i'm having aren't covered in the Gregorys manuals nor in the factory workshop manual.

I was hoping that someboy may be able to shed light on whats happening. I'm not stuffing around with the ECU wiring i am just reading voltages to try to solve the problem.

Cheers

Tony

Well i finally solved the problem.

After testing every ECU wire to see if there was any dodgy inputs (none) i tested every wire to see if any were earthed when they shouldn't. Sure enough one wire was earthed. After about 2 hours of tracing said earth it turned out to be the fact that i had plugged a relay into the pink relay connector which sits beside the fuel and ignition relays.

This managed to earth out fuses 15, 16 and i can't remember the other one. It also caused the spurious readings from the ECU. As soon as i unplugged the relay all these problems disappeared. What i want to know is why would plugging this relay in cause so many problems???? I have yet to trace what relay this is supposed to be but when i do i will post it up.

Still one problem to resolve with the fuel pump relay not cutting in so thats my job for tomorrow. Will keep you updated.

SubieMad wrote:Still one problem to resolve with the fuel pump relay not cutting in so thats my job for tomorrow. Will keep you updated.

Did you get this sorted? I'm currently having a similar problem.

Dane.

GOD wrote:Did you get this sorted? I'm currently having a similar problem.

Hope I'm not next! What are you doing with yours to create this probem God?

Cheers

Bennie

I had been running an EJ22 engine with an EJ18 ECU and harness. I'm now trying to get all the 22 stuff in. It's mostly working, but the computer won't turn the fuel pump on, and I can't work out why. Dave maaaate...

Dane.

GOD wrote:I had been running an EJ22 engine with an EJ18 ECU and harness. I'm now trying to get all the 22 stuff in. It's mostly working, but the computer won't turn the fuel pump on, and I can't work out why. Dave maaaate...

Dane.

Ahhhhh.. yes Dane.. EJ18 harness I'm sure they are close but this maybe where the issue lies. Have you got the wiring diagram for both EJ18 and EJ22? I'd study both at see if there is any differences.

RSR 555 wrote:Ahhhhh.. yes Dane.. EJ18 harness I'm sure they are close but this maybe where the issue lies. Have you got the wiring diagram for both EJ18 and EJ22? I'd study both at see if there is any differences.

Had been using EJ18, it's all matching EJ22 stuff in the car now. The two harnesses aren't even close.

Dane.

GOD wrote:Had been using EJ18, it's all matching EJ22 stuff in the car now. The two harnesses aren't even close.

Dane.

oops.. sorry Dane.. I miss read it

Ok.. I'd probably see if Dave is keen to check it out for you?

PM sent Dane. Will try work out a time i can come take a look.

Dave

You the man Dave