LS400 ignition and CPU wiring help

[elliotaw]

Hi, sorry to keep posting questions on here every step of the way on my project. the reason is that I only get about an hour at a time to work on my engine which is sitting outside on a frame and usually in the dar, wet and cold so my fault finding process is barely working when I need it to.

Anyway, I have the cpu wired up and connected to the main engine wiring loom. I have the starter motor circuit exactly as per lexus manual with the circuit including the neutral/P position switch from the transmission.
My problem is that I have no output from the CPU on the Black/Orange wire, pin 4B (MREL) to operate the EFI relay.
I have tested +12v to 26B on the cpu which should be the main cpu supply.
I assume there must be some other signal I am missing at the CPU to trigger the relay.
Anyone got any ideas? I am wondering if it might be something to do with the Neutral/Park signal which should be present at 14A(NSW) ??

Elliot

 

[madmont]

26 B is the power feed from the efi fuse .Ignition goes to 1A so you should have 12v there when ignition turned on. 12 and 13A should have 12v when ignition on and efi main relay operating [turned on by 4B] 13D and 26D should be earthed.

 

[elliotaw]

I'll check that out, cheers

Elliot

 

[elliotaw]

Still no joy.

I have +12v at 26B

I have a good earth connection from 13 and 26D

output at 12A and 13A are only 0.08v with ignition switched on

I also have nothing at 1A


I stripped my whole setup and rewired it again from scratch using the original diagram including the circuit opening relay, oroginal ignition relay, efi relay and fuel pump relay for for the sake of ruling something out but still the same result.

Apart from the 4 connectors which hook upto the computer, I also have 3 other connectors which come from the engine/transmission loom. One white connector and 2 grey ones. The white one is not connected to anything at all, and of the 2 grey connectors I have only used two of the wires, one to run power to the starter and the other to power the ignitors. I have a feeling there must be more of these wires which might need connecting???? any ideas?

Elliot

 

[madmont]

You should be supplying 12v from the ignition switch to 1a to turn everything on

 

[elliotaw]

tried that, but still nothing at 12 and 13A

Elliot

 

[elliotaw]

Recked my wiring again today and still the same result even with a 12v supply from the ignition switch to 1A.

One thing I did notice is that the previous owner of the car when it was on the road has removed the 2 sub o2 sensors and plugged the holes in the exhaust with exhaust filler. The engine was running in the 1/2 cut when it arrived at my place so I'm wondering where he ran the wires for these sensors?

If these sensors are not used, what do I do with their connections at the computer? leave them disconnected? run them direct to an earth? or though a resistor? what ohmage? how will this affect the performance of the engine once it's finally up and running.

Just a wild stab in the dark that the engine will not start because the computer isnt getting any input from the sensors? Anyone ?

Elliot

 

[Peewee]

Just leave them.
The secondary o2 sensors will not affect the running/starting of the car

 

[Peewee]

Just looking at how I wired up my Soarer ECU.
(I don't have 12A, 13B etc so I'll go by names)

BATT gets constant +12V
IG SW gets +12v from Ignition Switch.
These coupled with earths should enable M-REL to output +12V
Which inturn should input +12 back to +B and +B1

This should happen regardless of tranny position.


Just a further thing, Ignition Relay (or the old circuit opening relay), is triggered by START and IG SW.
IG SW goes through the coil with more resistance.
The Ignition Relay triggers +12v to the injectors and the ignitors/coils. The ISCV is powered by +B,+B1.

Like I said, this is for the Soarer ECU, but I can't see the Celsior ECU running any differently, just different pins.

 

[elliotaw]

Ok, thanks for your help. One more step further ahead than I was.

I was getting spurious readings with the circuit opening relay so, I rewired it yet again without it. I've run ignition relay output to +b +b1 as suggested (i didnt cut the main wire at the computer, but removed the outer insulation and wrapped onto it). Not sure if I'm supposed to cut it or not???

Anyway, finally, I have +12v at BATT and IG SW
M-Rel is outputting 12 volts and relaying back to +B, +B1.

When the motor is cranking, I have a spark at the plugs, 12v at ignitors and coils.

Fuel pump is working, the engine is cranking over nice and quick, but not even a hint that it will fire up.

I'm not sure where the ISCV is, but I'm assuming it is one of the 3 units just before the plenum chamber on the air inlet. Voltage to the 2 units at the front of the inlet (towards the front of the engine)are only 5 volts. There are no volts at all at the unit behind (towards the rear of the engine) at any of the pins.

I am also still concerned that there are numerous wires on one of the engine loom connectors not connected. there are a few large sized wires on there, surely they must be needed for something? One very large black wire and 2 other mid sized wires which are black with a red stripe from memory.....

Sorry to keep being a pain......it's just so frustrating being so close but yet so far

Elliot

 

[Peewee]

Big black unit at the front is the ISCV. Centre 2 wires should have +12v (and are directly connected to +B in the Diagnostic box)
Not sure what other 2 units you are talking about thought.
Only things I can think of, are;
Green 2 wire plug - ECU temp sensor
Brown 2 wire plug - CSI temp sensor/switch
White 1 wire plug - Dash temp sender
Black 2 wire unit - Coil

Other than that there is the AFM, and the TPS.
If the motor has traction control you'll have a 2nd TPS (main TPS is on the closed butterfly), and a traction control motor (controls the traction butterfly). You can leave these both unplugged.
The CSI is under the plenum, and you may have a VSV controlling the Charcoal canister breather.

In the valley are 2 knock sensors, and a starter (big 2/4 gauge thick wire, and 12 guage wire).

Each cam has a cam angle sensor under it, and there is also a crank angle sensor at the bottom.

Apart from that there is no other electrics on the motor (besides the other coil and the 8 injectors)


Check for spark, smell for fuel.
Make sure the ignitors are grounded.

 

[Zuffen]

It sounds suspiciously like the injectors aren't operating.

Check you have voltage at the injectors when yo crank the motor. Why not also check they are earthed.

 

[elliotaw]

When shes cranking theres unburnt fuel coming spraying from each of the exhaust ports so I assmue the injectors must be working ?

 

[MaxPower]

have you used a timing light to verify spark is hapening when it should? If you have fuel out the exhaust ports, spark at each plug and there are no obstructions in the intake it should be trying to fire. Not flooded is it?? If still in doubt of fuel delivery, spray some aero-start in the throttle body, should atleast try and fire if spark is ok. If you dont have aero-start use some other flammable spray, got my 2t-g running on brake cleaner the other day, got it firing while the carbs filled with fuel.

EDIT: and like peewee said, make sure your ignitors are earthed.

 

[madmont]

Also make sure the earth wire coming off the loom on the back of the motor behind the throttle body is earthed.

 

[elliotaw]

Ok, found a bad connection in my wiring and now that's fixed up and checked all the earths as suggested, the engine now fires but wont run!!!!!

It probably fires about 8 or 10 times and then immediately dies. It will do the same over and over again........not quite sure whats wrong there ?

Anyway, I'm thinking maybe its a breather connection or something like that maybe?

I have yet to fill the coolant and attach a few bits but have no pictures or anything to go by, so need a little help here......

Radiator expansion tank.

Bottom vertical connection pipe goes to where ?
Bottom forward facing connection goes to where ?
Pipe at rear of tank goes to where ?

I have a small vacuum hose emerging from around the oil filler cap area which runs to a solid chromed pipe which in turn runs back to the middle connection on a small vacuum unit looking type thing on top of the engine and is the to the right of two other vacuum units.

At the back of the engine is a largish hose coming from the plenum chamber which does a u turn and runs to the right. I think this is the brake servo pipe. is that right ?

Lastly, the round emmisions filter thing that sits at the front of the engine bay. has a breather on top, and two other pipes, one on top and one on the bottom. I have no clue where they go to either....lol

I should have paid more attention when I stripped the motor from the half cut....lesson learned the hard way as usual.

If anyone can help I would be v greatful.....

Elliot

 

[Peewee]

Check your injectors are working.
Its probably running off the Cold Start Injector.

 

[elliotaw]

Its runs ! I had left one of the ignitor plugs off after testing it. My neighbours will be loving me today since the motor has no headers on it at the mo.....

Still desperately needing info on the pipework on the above thread if anyone has time to stick their head under their bonnet, cheers for everyones help

Elliot

 

[Peewee]

Radiator expansion tank is only used if the radiator cap on your cars radiator is below the bolt on top of the thermostat housing.
On 90% of conversions the radiator is higher up than the motor, so there is no need to use the expansion tank.


Ok, at the back of the plenum there are 2 ports.
The small one gets blocked off, the big one goes to the brake servo.

On the throttle body there is one port.
This runs around the front of the plenum via those hard pipes, normally to a VSV on the side of the plenum (opposite side to throttle body), and then from VSV over the cam cover to the Charcoal canister.
The charcoal canister has 2 ports on top, one on bottom.
One of the top ones comes from this VSV, the other comes from the fuel tank (vapour)
If you have converted from Carby to EFI, you won't have this pipe on the car.
The bottom port vents to atmosphere.
The VSV is completely optional. If you use it, it has to be plugged in.
But you can connect the charcoal canister to the throttle body port with no worries.

On the front of the plenum, there is the ISCV, and 2 ports.
The smaller port runs to the hardpipe, and then to the FPR (fuel pressure regulator) on the front of the fuel rail.
The bigger port runs down to the power steering pump.

From the power steering pump the other hose goes to the intake pipe, the same place where the ISCV hose bridges off.


That should cover everything.

 

[elliotaw]

Cheers for that, you've saved me quite a bit of grief.

I will probably still have to use the expansion tank, will have to see how it all sits in the engine bay once the rad has been in installed.

Elliot