Engine Conversion Wiring Basics

[Impurist]

I'm having trouble wiring up my engine conversion and unfortunately the combination of before engine and after engine seems fairly undocumented, everyone starting with an Australia 5M-E goes straight to a 7M-GTE while I'm trying to do a 7M-GE. I haven't even been able to confirm whether I have the right pinout for the '91 Cressie Grande engine I'm working with.

Despite all my reading, I'm still stuck trying to figure things out. I know I'm not going to get a simple pin-to-pin conversion guide, so I need to actually understand what I'm doing.. something that's a bit lacking in most guides which are more of a comprehensive step by step without a detailed explanation of why pin x on plug 1 goes to pin y on plug 2.

Right now as far as my limited understanding of EFI, Celica-Supra circuits & 7Ms goes, I should be fine with:

• connect ECU to Fuel Pump via standard MA61 circuit (ie, wire fuel pump via 7M AFM signal)
• connect ECU to Battery
• connect ECU to Ignition circuit
• possibly something to fool the ECU into thinking the auto gearbox its expecting is behaving right

Once the ECU gets power, the 7M harness should take care of spark, injectors and sensors, the only thing missing from the equation is the fuel pump, which CrUZida explains in the sort of detail I like here.

Am I missing something here?

[George]

The fuel pump is the easiest thing out of your checklist. You may temporarily connect it to ignition key circuit, so the pump would always run when ignition is on.
Having no wiring diagram it's difficult to say how it goes with your engine. Different circuits exist. The most common circuit is that:
- Ignition system is powered right off ignition key circuit (+IG)
- Said +IG signal engages the main relay (directly or by means of ECU, so ECU would receive +IG signal and if everything ok engage the MREL)
- Main relay powers up injectors, sensors and ECU (though some ECU pins are powered right off the battery)
- Main relay also provides +12V to fuel pump. This line is broken with fuel pump relay
- Fuel pump relay is controlled by ECU

As for your missing something there, well yes you did. You must make sure +12V is delivered to injectors,ignition system and the sensors that need it. These power lines are already in your loom but it's unlikely the harness you have is that complete. I mean, power distribution is usually made in the body loom, not engine loom.

[wilbo666]

I know I don't cover 7m (yet ), but if you read some of my wiring info on my wiki it explains what the pins on the engine ecu do, and how you need to connect them...

i.e. JZS147 2JZGTE
wilbo666 2JZ-GTE JZS147 Aristo Engine Wiring


This thread covers the M-REL pin / ISCV wiring in some detail...
http://www.toymods.org.au/forums/tec...el-wiring.html

Also Automotive Training and Resource Site has a lot of docs that are helpful for understanding

Do you have the part number off your 7mge engine ECU?



Cheers
Wilbo

[DX20VT]

Some ECU's have the pin labelled inside the ECU, but not all.

Pull the top off and have a look.
If the abbreviations are in there and you dont knowwhat they mean post them up and someone will tell you.
I know most of them from memory.

[thechuckster]

I did a 7MGE into the MZ10 - hardest part was working out the chassis-inter-connect plug (followed closely by the wiper stalk as i'd trashed all the cabin looms) as each model uses a different plug layout..

My approach is to conceptually:
- identify what in the engine loom needs to go directly to the chassis loom (e.g. bypasses the ECU)
- identify what signals the ECU needs from the chassis loom
- identify what signals the ECU sends to the chassis loom

Then spend a few hours looking at what's in the various looms and what they connect to (e.g. on the engine locate the plugs for oil pressure, temp, cold-start time switch, tps, CLT, AFM, TVIS or other induction-changing that are driven by VSVs, etc. On the chassis side locate the alt, power for inj and spark, tacho, a/c, etc)

Then visit the wiring diagrams to see what colours/parts will probably match to the above - and then check against your actual wiring. After a few back-and-forth steps you refine your docs and eliminate most of the errors. Write down what you think things do and where they go and most importantly if you have a question to resolve.

For instance, you identify what temp/pressure sensors are on the motor, note down the colours and importantly whether they have their own earth or use the engine. Try to identify them against a dash wiring diagram (toyota tends to use colours consistently). Try to locate them on the chassis interconnect plug. If in doubt, hook up a multimeter to the sensor plug and check where it appears on the larger plugs.

This is how I'm documenting the RA65 wiring.

fwiw, wiring in the C/O relay in the RA65, I'm simply replacing the part of that circuit that would normally go to the AFM to trigger the fuel pump and making the megasquirt ECU do that switch instead (with a low-current relay). The rest of the C/O circuitry is left intact as behaves as per previous.

[BLK_20v]

My approach is to conceptually:
- identify what in the engine loom needs to go directly to the chassis loom (e.g. bypasses the ECU)
- identify what signals the ECU needs from the chassis loom
- identify what signals the ECU sends to the chassis loom

Couldn't agree with this more... When converting i tend to use the original fuse box that came with the car, not the one with the loom. Just have always found it easier that way. I'll expand a little on things if you are rewiring a car and retaining the stock loom / ecu.

Fuel Pump Relay

If the car is map sensored, the ecu normally controls the fuel pump relay via the earth, if it is afm, the afm controlls it via the same earth wire. The exception is when you are starting it, the second side of the relay when it gets 10-12v input will fire up the fuel pump.

Alternator

Charge wire - Big ass one back to the battery
Ign - Switched power
Constant - Non Switched power
Charge light - The alternator earths the charge light on the dash, turns off when it is functioning correctly
Sense - For internally regulated alternators, needs to know what voltage is being put out, can be hooked to constant power.

Starter

For auto cars working out the inhibitor switch can be a pain for some people, but the gear selector is just a switch at the end of the day. Most ecus like to know when the car is starting, which is just a 12v input. Normally the starter wire is spliced to ecu, Fuel circuit relay and starter relay and switched at the igniton barrel.

Injectors / Coil / Ignitor

Most ecus earth out the injectors so they will fire. Constant power is fed from the EFI relay to the 3. All you should concern yourself with on these is giving it the 12v switched ignition power unless using an after market ecu as the rest of the wires will connect into the ecu.

Earths

Critical to hook up, if you have both sides of the engine earthed with decent wire you shouldn't have any problems.

Dash Gauges

Check engine light - The ecu provides the earth to the light and switches it on.
Temp gauge - if you see the temp skyrocket as soon as it starts to get a reading, your gauge most likely isn't earthed. Normally located on the engine near the thermostat.
Alternator Charge light - goes to charge wire on alternator
Oil pressure switch / guague - Earths out when no oil pressure, goes away when you have pressure / reading
Tacho - From ignitor usually or negative coil wire. Most common these days from ignitor

ECU Inputs

Idleups - brake lights on, cooling fan etc - MOST of these are 12v inputs

Hope this helps someone somewhere someday

[Impurist]

Thanks everyone, there's a lot of good suggestions in here, it's helping me approach the situation a bit more systematically now. I finally lucked into a good set of pinouts for the plugs on my harness too. I found a good guide that suggests tapping into the wires coming off the main plugs off the engine/ecu harness that originally went to the chassis and instruments, which seems pretty obvious in retrospect since that's exactly the functionality I need to replicate. (Sadly my plugs have quite a few wires cut short immediately behind them, but that's a seperate issue to consider.)

Wilbo, I grabbed the serial number off the ECU when I was out at the car earlier, 89661-22210. It's off an '89-'91(?) Auto Cressida. I have plenty of resources now to work from though. If you're planning on documenting 7M stuff on your wiki let me know because I have a bunch of links, diagrams and an 89 Cressida wiring manual now.