UPDATE: Car is working. The problem is caused by a wiring issue with the ECU to relay on when the car gets loaded the coil wire directly to the ecu failed.

I'm making this post over here to try to help a friend with this V8 swapped Cruiser.

Engine:1UZ-FE non VVTi from 97' LS400 ECU: 89661- 50310 Manual swap.

This engine was pulled from a working V8 swap with all the wiring and modifications already made: Manual conversion, immo emulator, simplified wiring. Worked for a few months without issues.

Problem:
The engine start ups fine, revs fine. If you floor it in neutral, the fuel pump goes ON/OFF/OFF/ON you hear it bog and the you get up to the rev limiter. With load (gear selected) the car shuts down completele. If you are able to slowly get moving, flooring it same behaviour of on off off. (The ECU commands the pump to shut off). The engine can rev fine if you get the reves slow.

What was done:
Swapped parts fron another LS400 TPS (body), O2, MAF, ignito, crank sensor. New spark plugs, and so on.
Recap the ECU witth sugested caps from forum (old caps were LCR tested (ESR and capacity) was within spec.
Swap ECU from a 95? LS400 without immo ( interchange the IGN pins): Engine runs but as soon as reaches the first cut at revlimiter shutdowns completely. Kind of same things as the other ECU.
Force the Pump to run /relay byapass). Car runs fine on any load but after a while I think the engine stops and then don't let you turn it on for a while.
Test multiple sensor at the ECU pin with osciloscope:
Crank shaft : Varies frequency with speed.
Cam shafts: Both signal interlock 90º?
O2 sensors: At idle get's richer and corrects "normal way", you floor it goes rich and corrects. Both banks the same.
AF increases with TPS fine.
Knock Sensor: Increases with RPM both sides the same.

Couldn't connect to this ECU nor a stock LS400 from 97' with any scan tool . Only use the flashing lights (I'll get what that numbers ere).

Anything else to try?

 

My suggestion is to refer you to "gloverman" on the lextreme forums aka CartuneNZ on youtube. He does UZ engine swaps for a living and he has years of experience.
I doubt you will get much help on this forum as it is more focused on the LS as a complete car.

 

I sent an email before writing over here.

Also I've got access to a LS400 97', But can't connect any scan tool to it. All gave communication error on the port at the engine.

 

this is interesting. why would the engine stop and not turn of for awhile if it's bypassed? this leads me to question the pump itself. is it the pump from the cruiser or the LS400?

 

I don't remember exactly, but I think it's a bosch external pump over the passenger side wing. Wired directly to a relay on a custom relay box, and car ground (not battery). The relay signal from ECU (sink current), if you rev it slowly on neutral the pump is always on up to the rev limiter, but if you open the throtle suddenly (more load), the ECU stops the relay ( pin 2 relay goes 12V), and then ECU pull it down, So you have the boggint effect, with "ON, OFF, ON OFF".

Some guy did a bypass on the pump (always on) and the car worked fine but after a undefined ammount of time the car stop and didn't want to turn on again.

The Pump green/black wire from 16 PIN connector, goes directly to a custom connector (solder join) then to the relay of the pump. That's what I check.

 

What do you mean by this? Engine stalls and won't start?

 

The engine stalls and after that If I remember correctly what I was told, the engine didn't start. Even after leaving the ECU unplugged.
I have some clues but I'm not sure:

 

I just fix the issue, such a weird problem, The signal from the ECU to enable the Fuel Pump relay when load was applied the ECU signal goes high
Engine bay : Green wire to Fuel Pump Relay, ground from pump. ---> The pump signal went high when engine load was present and back when release.
ECU pin: 16 pin connector 1st wire. Fuel Pump coil pin. ---> First same behavour inside the car.
Cable resistance was tested before and thougth OK.

pump relay ECU signal (engine bay)

Then the fuel pump relay was bypassed and controlled remotely and wen to a drive test:
Car worked without issues and the Relay signal from ECU was tested outside with the same kind of behaviour even staying more "off 12V signal". When inside choosing body ground under glovebox I wasn't getting the issue in the same way. The IGSW nice 12V signal was present, but then the issue was not exactly the same as before:

As you can see the level goes to 0V instead of the ecu load. Meaning the wire was the one to blame. Instead of any sensor.

Disconnected the bypass, use a direct wire from Fuel Relay coil to ECU pin and solved the issue.

 

so was it a bad ground? or wrong connection altogether? or bad wire itself?

 

The signal is connected to "ground" through the ECU. I have to pull the wire out of the loom, but my guess would be the wire is broken inside.
You have two sides of the wire: From custom relaybox to ECU. and from ECU to custom relay box.
When the wire "disconnects" in the middle:
---> if you measure from the relay box all you see is the 12V being applied to the coil.
----> if you measure from the ECU you measure an open circuit.

 

We need to know 3 important basic issues.
1, The fuel pump relay is only used to bypass the fuel pump resistor which reduces the current to the fuel pump.
2, It is the circuit opening relay that enables or disables the fuel pump.
3, European ECUs for non US/Canada LS400 are not OBD-II compatible. You need to use a scanner which is OK with Toyota K line protocol system or a Techstream.

 

I need to add these 2 for the quicker trouble shootings although these are for a 98-00 but things are almost the same with a 97.
https://www.clublexus.com/forums/ls-...l#post11245833
https://www.clublexus.com/forums/ls-...l#post11245866

 

First of all the car is working right now issue was fixed. I'll update first post.

1,2 This is a custom relay board for the fuel pump. The power to the coil is controlled by another relay controlled by IGSW. If IGSW you get 12V on PIN 1 16pin ECU. This is direct connection, the pump it's placed on engine bay.
3. Yes this engine has the DLC1 connector with K-line. I couldn't connect to this engine neither a stock LS400.
I tried with Techstream with the proper adapter and I got error in comuunication, Choose the right model.
I also tried with a Multiscan Hanatech powered directlyu through the DLC1, choose UC20 engine and communication error.

Next step is to connect directly to the K-line and test the protocol by hand if I get any response.