LJ78 L2TE Engine not starting | Filter light ON | Pre Heat light OFF (2 Viewers)

[GTSSportCoupe]

Just to clarify - My primary focus is on the spill control valve power cable. There is no voltage on the cable.

I have attached a photo - the cable marked in blue is the culprit.

Any ideas why there is no power on the cable?

View attachment 2978578

Just FYI: The spill valve never gets a constant voltage. It is pulsed by the ECU to end the injection (spill) event for each cylinder. This how the ECU controls fuel quantity. If a constant voltage is forced on the spill valve, it ruins it. Some people do this by mistake as it would be correct procedure on a mechanical diesel for testing the fuel shut off solenoid.

Can you post a picture of the ground at your battery that goes to the body (specifically, the body end)? If you have a bad ground there, you won't see the right voltages while testing the electrical at relays etc.

There is a Denso ECD-V3 manual that explains how the electronic diesel works. It's really helpful for this sort of troubleshooting. It's actually really simple once you learn it. No worse than a same year gas motor for example.

Here is the Denso manual:

Here is the LJ7x Electrical schematic:

 

[nomadtribe]

Just FYI: The spill valve never gets a constant voltage. It is pulsed by the ECU to end the injection (spill) event for each cylinder. This how the ECU controls fuel quantity. If a constant voltage is forced on the spill valve, it ruins it. Some people do this by mistake as it would be correct procedure on a mechanical diesel for testing the fuel shut off solenoid.

Can you post a picture of the ground at your battery that goes to the body (specifically, the body end)? If you have a bad ground there, you won't see the right voltages while testing the electrical at relays etc.

There is a Denso ECD-V3 manual that explains how the electronic diesel works. It's really helpful for this sort of troubleshooting. It's actually really simple once you learn it. No worse than a same year gas motor for example.

Here is the Denso manual:

Here is the LJ7x Electrical schematic:

Thank you for the reply and manuals! This is great.

I will be working on the truck tomorrow and will take a photo of the connection and ohm reading.

I have ordered 2 x new main relays and will double check the working order of all the relays - just to make double sure

 

[nomadtribe]

Thank you for the reply and manuals! This is great.

I will be working on the truck tomorrow and will take a photo of the connection and ohm reading.

I have ordered 2 x new main relays and will double check the working order of all the relays - just to make double sure

Just FYI: The spill valve never gets a constant voltage. It is pulsed by the ECU to end the injection (spill) event for each cylinder. This how the ECU controls fuel quantity. If a constant voltage is forced on the spill valve, it ruins it. Some people do this by mistake as it would be correct procedure on a mechanical diesel for testing the fuel shut off solenoid.

Can you post a picture of the ground at your battery that goes to the body (specifically, the body end)? If you have a bad ground there, you won't see the right voltages while testing the electrical at relays etc.

There is a Denso ECD-V3 manual that explains how the electronic diesel works. It's really helpful for this sort of troubleshooting. It's actually really simple once you learn it. No worse than a same year gas motor for example.

Here is the Denso manual:

Here is the LJ7x Electrical schematic:

I have attached a few photos for reference. This include the 3 x ground points on the side walls.

All contacts seems clean and in good order.

After rechecking this morning, both Main Relays are dead.

Starter and glow is working perfectly.

Any ideas why the 2 x main ECD relays will go (at the same time)?

 

[GTSSportCoupe]

Thanks for the pictures. I'm concerned with the fresh paint under all those grounds they're not actually making good contact. You need bare metal on bare metal to get good contact. Likely the bolt hole threads are even painted, making an insulating barrier? You're going to have to do something to clean away the paint and I bet you're problems will go away.

 

[GTSSportCoupe]

The engine ground is probably good still which is why some things are fine. I bet your ECD relays are actually fine and not the problem. Painting a vehicle doesn't make things like that fail.

 

[AirheadNut]

For the painted grounds, run a tap through the threaded holes in the body (maybe even a little wire brush like you would find in a gun cleaning kit) to clean the threads down to bare metal, then make sure that the bolt is shiny too. I have had relays like that fail with age and corrosion, but it is unlikely that both ECD relays would fail at the same time. Did you bench test them per the FSM?

 

[nomadtribe]

For the painted grounds, run a tap through the threaded holes in the body (maybe even a little wire brush like you would find in a gun cleaning kit) to clean the threads down to bare metal, then make sure that the bolt is shiny too. I have had relays like that fail with age and corrosion, but it is unlikely that both ECD relays would fail at the same time. Did you bench test them per the FSM?

Thank you all for the replies. I will make double sure the points are clean (no paint) and bare to bare metal.

Yes, I have tested as per FSM by reading ohm and tested with 12v power supply. No click sound and no ohm reading on small pins and large pins when power is connected.

I have order 2 new ones.

Due to most of the power cables still disconnected due to the paint job and panel removal, I will only attempt starting again once all cables are reconnected.

Will keep you posted. Parts should arrive in 3 weeks

 

[nomadtribe]

Here we go again

New 2 x ECD main relays fitted and all grounds cleaned to perfection with new bolts.

Unfortunately the problem still exists.

Problems:

- 2 x Glow Plug relays are not working when fitted to electric wiring and powering on. Bench testing works perfectly and no issues with relays.
- Diesel pump solenoid not opening when powering on and cranking. Ohm reading is 1.6 ohm that indicates a working solenoid. Only 1 x new ECD main relay is kicking in. The second one does nothing. It seems this is the one for the diesel pump solenoid.
- No diesel flow to injector pipes when cranking.

Can this issue be related to an immobilizer? Not sure if one is fitted and no immobilizer light...

Will be taking the ECU in this week for testing.

I am a bit stuck.

Any thoughts?

 

[nomadtribe]

Update on progress:

I have tested continuity on the wires (harness) going back into the ECU. All wires are good (Highlighted in green - photo).

One of the test related to the Pre-Heat Glow Light. The light has a ground to the ECU. I got 12v going to the light, but no ground when the ECU is plugged in.
Other tests included testing volts to the Red/White wire on the harness and testing 2 x ground points. All is good for power and ground through the harness.

With the help of friends, we got the engine to start through manually hardwiring the connections.

Power is flowing from the relay to the glow plug rail and spill control valve, but no connection is provided from the ECU to kick in the relays.

Sending off the ECU again for testing.

Hope this will help those with a similar issue.

 

[nomadtribe]

Quick update regarding the fix - it was a faulty relay connector. One wire was loose in the main ECD plug. All is working perfectly now