No glow plug light

Hi All
Sorry if this is in wrong place. Got a TD5 Defender 55 plate (2.5 diesel).
Been running great. This morning got in turned key and no glow plug light or engine light. Temp gauge flies over to edge of red. Engine turns but not starting. I’ve looked for causes but struggling. I’ve removed the three relays under driver seat and cleaned terminals. Checked fuses all look good. Any suggestion most welcome.

Hope this might shed some light....
https://www.landyzone.co.uk/land-rover/td5-defender-non-start-no-glow-plug-engine-light.204320/

Thanks Marmaduke
Yes I’ve read this thread. I’ve removed and cleaned the relays, checked fuses as instructed but to no avail. Not looked under bonnet yet though. Was hoping it might just be one relay but I’ve got fears about the ECU now. Think I’m gonna have to get a diagnostic on it. Any recommendations on a worthy DIY diagnostic kit?

If your anywhere near north devon I have the relays you will need to test? To me it sounds like relay?

Discodevon said:

If your anywhere near north devon I have the relays you will need to test? To me it sounds like relay?

Click to expand...

Thanks. I’m a long way from Devon (Yorkshire Dales). My local garage do a lot of Landy work for Farmers and local owners. They’re really good lads. They might let me borrow one to test with. There’s two yellow relays and a black one under the driver seat and I’m gonna have to look up which is which. Appreciate your help.

Discodevon said:

If your anywhere near north devon I have the relays you will need to test? To me it sounds like relay?

Click to expand...

Just checked my Haynes manual and it says the relay/timer is on the engine compartment bulkhead. It’s bolted on so it says. Do you know where it is? Thanks

It's highly unlikely that the fault lies with the glow plug relay. On the Td5 engine in the Defender the relay is triggered by the engine ECU. The relay only controls the current to the glow plugs.
The glow plug "tell-tale" light is driven from the ECU too, but on a different output directly to the dashboard..
Unlike the 300 tdi engine which uses a timer for the glow plugs, the Td5 in both the Defender and the Disco use an electronic circuit inside the ECU to measure the coolant temperature and apply the glow plug heating for a period depending on how hot or cold the engine is. The "tell-tale" doesn't actually confirm that the glow plugs are heating, only that a signal has been sent to the relay coil.
The ECU on the Td5 engine is "voltage sensitive" which means that if the battery volts drop below 10.5 volts or so while the engine is cranking, the ECU will not operate.
Sometimes the action of removing the plugs to the ECU and giving them a bit of a squirt of switch cleaner and putting them back again can clear a problem of tarnish developing on the pins over time.

Thanks for the help. I’ve cleaned the plugs to the ECU. The engine cranks pretty quickly so I think the battery is good. Today I’m going to remove the ECU and have a look. Also trace wiring and check for defects for poor earth. I’ve discovered that the relay is beneath the driver seat and might be able to try a spare just to rule it out. I’m thinking it’s gonna be an ECU fault but let’s find out.

Mine did something similar in the autumn of 2016 - engine cranked but there was no engine check light or glow plug light - and it turned out to be the ECU. Also, it wouldn't communicate with my Nanocom. However, if the fault code reader can't read it, that points to the ECU as being at fault, so it tells you something!

Brown said:

Mine did something similar in the autumn of 2016 - engine cranked but there was no engine check light or glow plug light - and it turned out to be the ECU. Also, it wouldn't communicate with my Nanocom. However, if the fault code reader can't read it, that points to the ECU as being at fault, so it tells you something!

Click to expand...

Thanks. I’ve spoken to a highly respected local Land Rover boffin. He told me to put a jump lead from the negative battery terminal across the the earth stud next to the ECU and relays. He thinks it could be an earth issue. I’ll try it in the morning. If this fails he has a spare ECU with whichbto test mine. He’s got a good diagnostic kit and will come if needed. I’m feeling more optimistic about resolving it and I’ll post updates.

Problem solved.
Simple continuity test showed broken or detached wire in crimped joint from bulkhead inertia switch. It caused no live to main relay fuse. Job sorted.

Oh good, that was nice and easy then. Yes, one of my diagnostic tests is to unplug the multiplugs from those underbonnet switches to see if it makes a difference to the symptoms, the lights that light up on the instrument panel and so on. At least it helps rule them out.