Rewiring an RA28

[frag_dog]

I've started rewiring my RA28. I've got a good idea of what I want to do (anything is better then the mess it was before). I just want to float the idea here to see if there are any big holes in my plan. Below is a diagram of what I want to do...



Key:
Blue - ECU Outputs (injectors and spark)
Green - ECU Inputs (O2, TPS, Eng Temp, Air Temp, MAF)
Red - From Battery
Orange - Lights, idicators, hazards

For the fusebox I'm thinking of getting something like a VL fusebox, I know they melt but I have a plan. Is it a good idea to mount it in the engine bay, so far away from the battery?

I want to route the ECU to one side and the lights an everything else to the other, this will make engine removal a little easier.

Any pointers or advise is appreciated.

[thechuckster]

i'd swap the battery to the other side of the boot to shorten cable from battery to starter motor.

Am re-wiring my MZ10 from scratch atm, i would suggest not making looms in the car as this add heaps of hassles - just carefully measure the length needed to run looms from various objects then layout on a board - i'll do this for my next car.

Also, check carefully how the wiper/indicator/headlight stalks function - i had to re-think how to wire up headlight relays.

Also 2, draw up the whole thing wire by wire.

I sourced my relays and relay plugs and main fused power distributor from some sort of commode but am using a pair of Nava fuse panels. I'm mounting everything inside the cabin - but that's mostly as the car is for motorsport/thrashing and the interior isn't going to be very exciting.

["Z" UTE]

Could not agree more Mr thechuckster. I have used a large sheet of MDF, with locations of all components marked on the board. Board is also marked with complete colour code, and type of terminals for all ends and junctions. Lotsa nails and zip ties to hold it all on the board for when space gets tight. Old chippies rule applies equally here, "measure twice, cut once" nothing worse than a loom with heaps of needless joins.

Toyota Corona ST/RT13x/14x fuse and relay boxes are plentiful at wreckers. Pull one apart, and you will see a full numbering system inside, which basically tells you what wire is connected to which fuse and relay. Using Toyota stuff really makes life easy.

cheers Chuck.

[LeeRoy]

I'm about half way through wiring my 22 from scratch using a Painless Wiring harness designed for a hot rod. Its a universal harness though so its been ok although testing at times.

Although how youve started with a pretty good direction theres a few things id change.

The board is a good idea but i wouldnt go putting plugs onto wire ends until theyre in the car. However, id run string for where everything needs to go, throw some masking tape on the ends of the string labelling whats what, transfer this to a board, then put the wires on that while grouping them together. Then put that into the car and put the ends on there. Just make sure you clamp wires along bends etc so that when plugs go on and interior goes back in they are all the right length.

As mentioned above id move the battery to the other side. Also hook up a circuit breaker or fuse. Youll then need to run the main power wire to the positive on the starter and then to the alternator. From there a wire can be run to your fusebox. I'd run this through the cabin and then drill a hole next to the gearbox at the bottom of the firewall for it to pop through.

Id change your engine bay wiring a little also and be inclined to mount the fuse box at the front of the car, and id probably look into having another fuse box in the cabin for things like ecu power, some lighting, and other random things like stereo, heater, etc. Get a fuse box from the wreckers, look at whats been mentioned above. These will not only save you a bit of money but will look neat. They also hold all your fuses and relays and with lids will also keep them safe from moisture, heat, and the elements.

I would also probably wire the whole front end and engine bay on one side then group everything together and split it apart once it reaches the engine. This way you can also put a single plug in there so that if you ever need to remove the engine you can quite easily. The coils is better kept on the driver side away from heat though (thats if your running an 18rg or similar with exhaust on pass side. Keeping everything together will also look alot neater.

Id run these wires to the lights with the light wires then down along the rail, up the mount or in front of it, then split everything apart from there.

Were you going to run an isolator (one of those red key thingys) if so where would you mount it.

Were you going to run relays for the lights or keep the standard negative switched setup (which can be eaily improved upon). If you want to use a relay/s then just run a power to them, bridge the power over to pin 85 from pin 30(iirc), and return this wire to your switch which then grounds the relay closes the circuit, and provides power to the lights between pins 30 and 87.

You should probably list everything that you plan on running (some of which ive listed above) as it will help you nail everything at once and not be halfway through wiring it and then go shit i dont have any power for the door switches, reverse lights, dome light, or whatever else.

Youll also need a wire/wires for fuel pump, sender, demister.

Hopefully Mos will read this and chime in. He just partially rewired a 23 with a SR20, pretty much redoing the whole engine bay, ecu, battery relocation, and a few other bits. Before even laying down a single wire he spent a good couple of days drawing plans and diagrams with the end result being a neat and functioning wire up.

Good plans are the key.

Ill think of a few more things and post again.

Good luck

[frag_dog]

Thanks for the response guys!

I'm in 2 minds about the battery. I would like to put it on the other side (as it currently is on the right), however, that would mean closing up the tool area. Where it sits now, its on top of the fuel filler neck.

My current stage in this project is stripping it down. I've pulled all the wires out of the car (except the tail lights, fuel sender, low pressue pump and battery mains. The wiring for the engine bay was such a rock show. There was a huge nest of wires around the engine, infront, behind, and both sides. I figure to make future engine removal easy, I'm going fit one plug on either side that will have all that sides systems running thur it. That way 2 plugs, the starter and alternator and I have the electrical sorted.

The engine is a 3T-GTE with a Wolf 3Dv4, so for the engine loom, I'm just going to buy a loom from Wolf and work off that.

I've been doodling some diagrams of the basic circuits on a notepad, however, before I start to run wires I'm going to get a nice big schmatic together.

Thanks for the MDF idea. The other way I was told was to run string around the inside of the car then pull it out and cut the wires to length.

The reason why I'm thinking of putting the fuse box in the engine bay is I would prefer to have all the fuses in the one place. I think it will make troubleshooting a bit easier, and with the ECU in the footwell, im going to be cramped for space as it is.

[LeeRoy]

Well what do you need for the wolf?

Power for:
- Coils
- Injectors
- Thermo

These can all be fused in your fuse box (and i assure you will take up most if not all space in one) but you will need another one for body related stuff.

[frag_dog]

Well what do you need for the wolf?

Power for:
- Coils
- Injectors
- Thermo

These can all be fused in your fuse box (and i assure you will take up most if not all space in one) but you will need another one for body related stuff.

This is the rough list I have put together for my fuse needs.

Constant Power:
Brake Lights and Reverse Lights
Park Lights (guage lights inc)
Head Lights [R]
High Beams [R]
Hazards, Horn and Indicators
Interior lights

Run:
ECU Power
Coils [R]
Fuel Pumps [R]
Guages and Heater
Wipers and Squirters
Heater

Acc (All off one Relay):
Stereo
Cig Lighter
Power Windows

That puts me at 13 in total. Do the injectors need a fuse?

[Kebin]

I find rewiring the original body toyota loom makes life so much easier.... if it all worked in the begining why change their design? just tidy it up with lots of conduit split tubing, electrical tape and heat shrink.
Though there are 10 million ways in which to rewire a car. Most people opting to hide wiring as their basis.
I would reccomend keeping your engine computer loom seperate to your body electrics loom and battery feeds. Makes life easier when removing the engine and diagnosing future faults.
I have used a corolla ae102 front wiring loom incl. fusebox in the past to rewire an engine bay as the ae102's runs the looms through the guards to "hide it all" and enters the cabin via the kickpanels. I also chopped the fusebox off and extended the loom so the fusebox was hidden under the glovebox. Though this method is long and tedious but still kept within toyota's colour coding.

Best of luck whichever route you take

[o_man_ra23]

Didnt read all BUT!!! Keep your fusebox as close to the battery as humanly possible. The fuses protect the wires in case of a fault (equipment failure or wire short), so the further from the battery your fusebox is, the greater the chance of a fire.

The other option is to have a really big cable (capable of both reducing voltage drop, and sustaining large current draw in the case of a short) and have a fuse or CB rated for the ENTIRE load of the car (plus a bit for good luck) minus starter motor going to a fuse panel elsewhere. Starter cable should be 2guage and there should also be a 2guage earth cable going from the battery negative to the engine, as well as a very short earth cable going to the body in the boot.

I like the peg boarding idea, will have to use that one.

[thechuckster]

while i remember - using sticky paper/masking tape labels is good for quick/dirty identification - but when you have a whole bunch of wires with labels these tend to stick to each other and tear off the wire - and after a while they get fairly brittle and wiping your hand along a clump of them will remove older labels.

Get an electric dymo labelling machine and plenty of white tape (e.g. like this) - i pinched an old one from work.

[LeeRoy]

It would be good practice to fuse everything. An ecu doesnt actually supply power to anything other than sensors, it merely controls their grounds.

[o_man_ra23]

It would be good practice to fuse everything. An ecu doesnt actually supply power to anything other than sensors, it merely controls their grounds.

I thought fusing everything (except possibly starter) was a given??

Another thing which I forgot to mention previously is, give everything in your loom just a little slack. It should all hold in place by ties, not tension. Oh, and buy good plugs. Watertight ones when your outside the cabin will save you a lot of heartache in a few years time when it comes to dirty joins causing faults. Also, route your wires as far away from the exhaust as possible. When you do need to bring them close, get some of that braided heat-proof sheathing (like what you would find originally on an 18R-C temp sensor wire) to help protect it.

[Kebin]

Cheapest option to fuse battery in boot that is resetable is jaycar 100amp circuit breaker
http://www.jaycar.com.au/productView...Max=&SUBCATID=

[thechuckster]

... except that a starter motor on a cold morning will pull more than 100amps when cranking.

[LeeRoy]

That topic cas been comprehensively discussed. Starters will pull well into a few hundred amps (hence the need for batterys larger than 350cca in most cars). However, for short starting periods, an underrated circuit breaker (depending on type) will not trip instantly but will in the case of a short, or in the case of extended cranking.

Anyways back on topic ive been thinking of an approach you could probably take.

Start by grabbing an RA28 diagram taking note of every component in the car. Do this for both the body and the engine but keep them listed seperately. Its probably easier in regards to working out fuse requirements if you group things together like they are from the factory and run the same amperage fuse. ie you might run the instrument lighting, dome light, and stereo on the same fuse.

Now go through this list and cross off things you dont want or add in any extra things you want to add in. ie efi, circuit for injectors, power windows, and whatever else, but keep the engine and body stuff seperate still.

Now start by jotting down where you will run power wire from the battery and to where via where. Then think about where you will grab power from. Depending on where you mount your fuse box you may either power it via the post on the starter where your battery connects or even from the battery in the boot if you decide to mount the fuse box there.

You could even get an isolator rubber and have this attach to somewhere in the engine bay and use the other side (theyre insulated from each other) as a positive terminal and just run everything from there. Even mount fusible links from it if you want and if you change your mind in future and want to add other things in then just chuck another ring terminal on the post, run it to a fuse or fuse box, then power whatever your adding in.

Fuse everything starting at the battery and ending at the smallest components working your way down like a pyramid.

Battery - 150A??? Circuit breaker or fusible link.
First branch - This may have things like alternator, and every component in the car except starter. Fuse this with the total amps of everything on the curcuit following it. Fusible links here as well maybe? Couple of 40A fuses?
Second branch - May go to fuse boxes, which will then be broken down into your 10-30A fuses. After this it reaches the components, they gobble their juice, and then theyre grounded.

Also take note of hot (always powered) components in the car such as your headlights, horn, interior light, brakes and power them accordingly ie dont run power through ign sw. Everything except relay main power will run through ignition switch.

Think about relays and what your going to use them for along with where they will be placed. Youll need one for your thermos, horn, fuel pump, ecu, and one on your headlights.

Dont forget to run a ground wire either equal to that of the current going into the components you are grounding or larger than it. Youll also find that the older celicas use a single (or few) grounds for almost all components. In the 22 everything is grounded via one wire behind the dash. Provided you use a large enough wire you should be able to get away with only a handful of grounds for the entire car.

You planning on installing a car alarm too?

Just out of curiousity what is the car going to be primarily used for, and how much experience do you have on the electrical side of things?

ps sorry about the long winded post