LJ78 L2TE Engine not starting | Filter light ON | Pre Heat light OFF

[nomadtribe]

So, here I am.

About 3 months ago, I decided to strip the LJ78 down for a respray. To date, things are going well and started with the reassembly this weekend.

Battery was fully charged and all cables reconnected (that I know of...).

Prior to starting the engine; the Filter light is ON and the Pre Heat light is OFF. I can however hear the relay click after 6/7 seconds.

I have pumped the diesel filter and drained to check for any dirt. All is clean and the sensor cable is connected.

The Pre Heat light stays off for the entire time.

When starting the engine, it turns, but no diesel is pumped. I have checked by removing the out hose of the diesel filter. The Pre Heat Light stays off.

Any ideas or where I can check?

Your wisdom will be greatly appreciated.

 

[AirheadNut]

When you say the out hose on the filter, is that the return line from the injector pump, or the hose leading to the injector pump? There is no lift pump, the injector pump pulls fuel through the filter.

Is it possible that the Glow and Filter lights got switched by mistake?

 

[nomadtribe]

When you say the out hose on the filter, is that the return line from the injector pump, or the hose leading to the injector pump? There is no lift pump, the injector pump pulls fuel through the filter.

Is it possible that the Glow and Filter lights got switched by mistake?

Thanks for the reply.

I have not yet took the dash apart, so all the lights are still as-is.

In the attached picture, the red hose allows diesel to flow when manually pumping the diesel filter (hose detached), but when the engine is started, there is no suction when the pipe is removed and when I place my finger over the pipe in order to check the injector pump suction.

The orange pipe has suction and allow diesel to flow into the filter when manually pumping.

When the diesel filter is manually pumped until full, it looses the pressure when the engine is cranked.

None of the injector pump wires were removed during my dismantle... I think so

 

[Felde]

Most probably a "no fuel" issue / air in fuel line.
Not likely to be an issue of the lights, so don't take your dash apart for probably nothing.
Work your way systematically through the fuel lines from tank over filters to injector pump and bleed the sections. I used a big syringe and clear tube to pull fuel trough and check for bubbles.
Consult maintenance manual for bleeding procedure.
Your last spot to check will be the fuel cutoff solenoid. Make sure it's open. That might be the only spot where the electric may interfere.
Primer pump needs to get real hard.
I understand you bled the lines to the filter already. So air might be in the injector pump and lines.
Latest advice on that was to take out the glow plugs and bleed by cranking without engine pressure.
You might find the respective advice by searching the forum. It was posted within only one or two month ago.

 

[nomadtribe]

Most probably a "no fuel" issue / air in fuel line.
Not likely to be an issue of the lights, so don't take your dash apart for probably nothing.
Work your way systematically through the fuel lines from tank over filters to injector pump and bleed the sections. I used a big syringe and clear tube to pull fuel trough and check for bubbles.
Consult maintenance manual for bleeding procedure.
Your last spot to check will be the fuel cutoff solenoid. Make sure it's open. That might be the only spot where the electric may interfere.
Primer pump needs to get real hard.
I understand you bled the lines to the filter already. So air might be in the injector pump and lines.
Latest advice on that was to take out the glow plugs and bleed by cranking without engine pressure.
You might find the respective advice by searching the forum. It was posted within only one or two month ago.

Thank you. Will continue working on it later today and update the post.

 

[nomadtribe]

Okay, some progress today.

I have removed the diesel nozzle pipe (one unit sitting on top of the injectors), but the first injector started coming loose from the engine. This was a bit strange.

In the diagram, when cranking, I get diesel coming out of the green tube.

Diesel is not flowing through the orange tubes when manually pumping. Is this correct?

I have ordered a few new parts and will assemble and test again in two to three weeks when they arrive.

Thank you for all the feedback to date.

Off raptor painting the inside of the truck

 

[Felde]

Diesel is not flowing through the orange tubes when manually pumping. Is this correct?

Those orange lines are the injectors into the cylinder (as far as I see from the pic). Fuel will be supplied here from the injector pump (IP). I think, you can't manually pump fuel trough the IP to the injectors using the priming pump. It is designed to distribute the fuel only as needed. With the engine not cranking, by design, no fuel is needed .... so... But it should give fuel there when cranking the engine with the starter.
I can't figure from the picture what the green line is and where it should connect. Main feed line? Return line? Priming must rsp. may bring fuel here..

 

[nomadtribe]

Those orange lines are the injectors into the cylinder (as far as I see from the pic). Fuel will be supplied here from the injector pump (IP). I think, you can't manually pump fuel trough the IP to the injectors using the priming pump. It is designed to distribute the fuel only as needed. With the engine not cranking, by design, no fuel is needed .... so... But it should give fuel there when cranking the engine with the starter.
I can't figure from the picture what the green line is and where it should connect. Main feed line? Return line? Priming must rsp. may bring fuel here..

Thank you.

The green line connects the long diesel nozzle pipe that sits on-top of the injectors to the pump.

Will keep the post updated once the parts are installed.

 

[nomadtribe]

I had a few hours to troubleshoot today and narrowed the issue down to the glow plugs.

Test performed:

- Glow plug ohm reading - no issues
- 2 x relays tested as per manual - no issues
- glow plug voltage test with meter (ground to body) - no issues
- Checked all fuses - success

However glow plugs are not glowing

Does anyone know where the pre-heat timer is located in an LJ78?

Any thoughts?

 

[AirheadNut]

Pretty sure that the glow plug timer function is built in to the engine ECU on the LJ. It should be controlled by the reading from the engine temperature sensor, so perhaps the issue is there?

 

[GTSSportCoupe]

The ECU won't work if the smaller gnd wire from battery to body is not a clean good gnd. Make sure to check and clean it. This is voice of experience.

 

[nomadtribe]

Pretty sure that the glow plug timer function is built in to the engine ECU on the LJ. It should be controlled by the reading from the engine temperature sensor, so perhaps the issue is there?
View attachment 2976617

Thank you for the diagram. The temp sensor seems to be hidden at the bottom of the intake manifold. No easy way to reach it

The ECU won't work if the smaller gnd wire from battery to body is not a clean good gnd. Make sure to check and clean it. This is voice of experience.

Thank you. I will check this first . Have pulled out the ECU, but cant find any blown components...

 

[nomadtribe]

Okay. Over the weekend and this evening I did some more testing, including cleaning all the ground points.

The solenoid shows an ohm reading of 1.6. From other forums, this seems to indicate a working solenoid.

However, there is no voltage reading on the solenoid power cable.

All other readings as above remains the same.

I have also checked all fuses on the driver side - no issues there.

As per the diagram above, the LJ seems to have a spill valve relay. This will be the next check point.

I removed the ECU today but cannot find any blown components / burn marks / burn smell. All seems okay.

Any thoughts?

 

[AirheadNut]

I may have lost track of what’s going on; which solenoid are you testing?

 

[nomadtribe]

I may have lost track of what’s going on; which solenoid are you testing?

The one located on the injector pump

 

[Squash]

Keep in mind your glow plugs like mine will only light up when told to!
Above Zero degrees my dash will not light up and neither does the relay.

 

[nomadtribe]

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?

 

[nomadtribe]

Keep in mind your glow plugs like mine will only light up when told to!
Above Zero degrees my dash will not light up and neither does the relay.

Thanks. That actually makes sense. Some people (forum posts) notice the pre-heat light only on for a second or two in cold weather.

 

[nomadtribe]

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

There is another article here that describes the SCV. However measuring the voltage on the cable with a multimeter is not recommended - 2LTE Spill Control Valve - https://forum.ih8mud.com/threads/2lte-spill-control-valve.374649/.

Therefore my test may not be correct...

 

[nomadtribe]

The issue has been isolated to the main ECD relay - 85915-60030

Relay has been tested and no click or ohm reading on pins when power is applied.

There are 2 x Main ECD relays, both having the same part number.

On the working relay, I get a reading of +11 volts on the harness and the relay kicks in.

However on the broken relay wiring, I am getting a reading of 0.2 volts on the harness. The truck is in park (P) and not sure if this has an impact on the voltage provided?

Any thoughts? Can the low voltage reading be correct?