The vehicle I am referring to is a 2009 L320 2.7 fitted with a P10 Head up display showing engine temperature..ebay item eBay Item No. 256379951819
When it is cold around 0 c the engine is hard to start and produces a lot of smoke.
The reason is that below 0 c the fuelling is increased and with 6 good glow plugs it will start down to -25 c.
However if all the glow plugs are not all working it floods supressing combustion . When you do start it the surplus fuel shows as a clouds of black smoke.

Glow plug function.

It is useful but not essential to check how many glow plugs you have working. The simple way is to measure the glow plug current ..about 12 A per plug. In the under bonnet fuse box are 3 fuses ,one for each pair of plugs ..top left in the box. Remove the fuses and join the terminals with a 300mm length of
wire fitted with Lucar connectors. Use a clamp on Ammeter around the wire to measure the current.
Ebay item eBay Item No. 234933885169 is suitable but be careful to check the spec that it will do DC current many cheap ones only do AC.
On mine only one fuse location showed 25A so I have 2 glow plugs working. the others showed zero current. Changing the plugs is not easy with bits breaking off and falling into the cylinders..beware.

Hot Water Start.

One trick is to pour hot water onto the engine temp sensor ( in top hose by air flow meter)
With the engine at 2 c pouring the water on raised the engine temp on the P10 to 9 c and the engine started.
So we know have a base line.

Fitting a resistor to the temp sender.

We have all seen on the net about fitting a 10 k ohm resistor across the temp sender ..Tried that and the ECU though the engine was at 56 c. did not start too high for me.
Measuring the resistance of the temp sender showed about 16k at 3c and 3k at 86c.
Calculations showed that fitting a 220k resistor would drop the 16k to about 13.7k.
This raised the engine temp from 8 to 24 deg .engine started and ran well.A rise of 16 deg. Considering temps in UK rarely go below -10c I think that 220 could go up to 270k the idea being to fool the ECU to think its over 0c so it dont over fuel.
When the engine temp rises the sender resistance drops to 3k at 86c. Now 220k in parallel with 3k makes very little difference . The normal engine temp of 86 now showed as 88 on the P10 and the dash gauge was still in the middle. So just leave it in place.

Of course what would happen with no glow plugs I cannot tell but in the summer I just hit it so the plugs dont get time to heat up .Considering removing the fuse from the good ones in the summer to extend there life. ( usually blow when first energised) Always listen to old people or when they die you will live on in ignorance.
The avatar is a picture of the man with a big cock.
Learned to 4x4 on 100 mile beach and Frazer Island QLD
Dont spend money on old cars you will never get it back

Interesting solution to the problem. I assume such an approach might be less favourable with the later engines fitted with ever more emissions kit as the glow plugs help with emissions when the engine is warming up (would the lack of glow plugs cause issues with the kit? I have no idea). Not such a problem on a Euro 4 engine, presumably.

My indie changed some glow plugs on my 08MY TDV8 a few years ago without issue, but not sure if there are differences or just luck on my part that they appeared not to be an issue to change. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

OK, that's quite smart but why fiddle with an ad-hoc contraption instead of changing the glow plugs and have the car start as designed? Regards etc.,

Wojtek

---
WAS: 2006 RRS Supercharged
IS: 2010 RRS TDV8 HSE

1. I thought glowplugs were more like 7A each. So your 25A could be all working. Just disconnect the black and brown 3 pin plugs ontop of the engine and measure resistance on the green wires to ground.

Glow plugs are smart. When hot the current drops.

https://www.rrsport.co.uk/forum/topic49539.html?highlight=glow


2. Remove both fuses and see if your engine will start at 0C

Andy they are fused in 3 lots of 2. hence the 3 fuses
They are not smart ..laws of physics ..when they heat up the resistance goes up so the current drops just like a bulb Always listen to old people or when they die you will live on in ignorance.
The avatar is a picture of the man with a big cock.
Learned to 4x4 on 100 mile beach and Frazer Island QLD
Dont spend money on old cars you will never get it back

Weird. The 2005 has a fuse and relay for the left bank.
And same for the right bank.

Edit: I see what you mean. Changed to 3 fuses in 2007?

The 3.0 has a seperate control box with GP failure detection