Rough start

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tilly2 said:
A 0.9ohm glow plug will draw around 13 amps, where a 0.5ohm plug will draw twice that. So, four good plugs will draw just over 50amps, and four low resistance ones will draw around 100amps. On a car that isnt running, thats drawing that current straight from the battery, whilst the starter is cranking. Thats quite a load for the battery to take if its not in tip top condition. Might be worth sticking a volt meter across the battery whilst its cranking, to see if the voltage is sustained enough for the engine management to operate correctly.
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You logic is somewhat flawed. The car starts perfectly if i force yhe plug relay on for longer, if i had issues with battery voltage the problem would get worse in this case
 
My final answer, and what I would do next, is replace the glow plugs for a set of good quality compatible new ones.

Although the electrician in me is interested in why theres a 1 volt drop between the relay, and the plugs. Is that under load, or with all plugs disconnected.
 
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I've made some measurements today:
- I've 11.5V at battery when key is in Pos 2. (Pump running, Radio, ECU)
- I've 11.4V at the glow plug relay and glow plug connection itsef (all are disconnected)
- A glow plug has 0.8 Ohm
- When one glow plug is connected I've 1.1 Ohm at the glow plug relay
- When I connect second one 0.9Ohm, third 0.6 Ohm, fourth 0.6 Ohm (the fourth one is working and connector is good, I think my measurement device is not good enough)
- When I'm glowing I start at 10.7V at battery going higher to 10.9V, when glowing is turned off by ECU I've 11.4V again
- The error of my measurement device is 0.2Ohm, so we have to subtract this
- I've Beru glow plugs 2 years old
The ECU is glowing longer than the LED is turned on. It is not glowing when I start at second attempt (warm start of ECU), only when ECU has a cold start glowing sequence started again.
For my issue, I glowed 3x but it started at the second attempt. My conlcusion is for me, the glow plugs are not the root cause of the issue. Glow plugs are running for ~13 seconds at outside temperature of 4°C.

The glow plugs are PTC resistors, I'm not sure about 0.9Ohm if this is the value when they are cold or if this is the value at "operating" temperature.
 
Dont worry about the "glow plug light," its controlled by the ECU, and doesn't follow the actual glow plug on period.
 
sierrafery said:
Ok, what do i know ? if they had 0.5 ohm from from factory which are not mentioned as "after glow capable" and others clearely described and those have 0.9 ohm and that's how the genuine LR ones are, i measured them not once, also they are all designed to work at 11V , this type is the good one https://www.autodoc.co.uk/ngk/7155984 ,
tilly2 said:
My final answer, and what I would do next, is replace the glow plugs for a set of good quality compatible new ones.

Although the electrician in me is interested in why theres a 1 volt drop between the relay, and the plugs. Is that under load, or with all plugs disconnected.
Click to expand...
tilly2 said:
My final answer, and what I would do next, is replace the glow plugs for a set of good quality compatible new ones.

Although the electrician in me is interested in why theres a 1 volt drop between the relay, and the plugs. Is that under load, or with all plugs disconnected.
Click to expand...
Its under load, and measured from battery + to the glowplug connection. The relay i fitted was used, but seemed better than the original. Ive a new one coming tomorrow so ill try that before i throw 60 quid on a new set of plugs. The previous ones were good 'quality' so even with a good make ,it doesnt mean they are any good
Click to expand...
 
Just to bypass the relay, how about shorting the contacts out where the relay N/O terminals are, with a wire and two male spade connectors. That would eliminate the relay out as a cause of high resistance. Not looked at mine to see ifvits possible, just thinking out loud..
 
Mario110 said:
How long?
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It's irrelevant cos the plugs are staying under power regardless of the warning light. You dont have to "force" the relay cos it stays closed anyway untill the ECU ''considers" it's necessary... but to understand that it's mandatory to know how a D2 works compared to a tractor which has a rudimentary glow plug controll :cool:
 
Watch that relay then cos it will not last long, just calculate and you'll see that at 0.5 Ohm each the glow plugs will draw above 80A on first contact while the relay is rated to 70A which is OK for the proper 0.9 Ohm glow plugs, the vehciles which are OK with the 0.5 Ohm plugs have a separate timer unit which is rated to 100A
 
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sierrafery said:
It's irrelevant cos the plugs are staying under power regardless of the warning light. You dont have to "force" the relay cos it stays closed anyway untill the ECU ''considers" it's necessary... but to understand that it's mandatory to know how a D2 works compared to a tractor which has a rudimentary glow plug controll :cool:
Click to expand...
Yes I know, the glow plug LED is not coupled with the glow plug itself. My glow plugs are running for 14 seconds maximal, then they are turned off by ECU, I've measured it. Is that too little?
 
Mario110 said:
Yes I know, the glow plug LED is not coupled with the glow plug itself. My glow plugs are running for 14 seconds maximal, then they are turned off by ECU, I've measured it. Is that too little?
Click to expand...
Depends on ECT input but did you start it ? cos if you don't start it it in a decent time(i dont exactly know how much) after the warning goes out the feed is cut to not drain the battery in vain but if you start the engine they'll keep glowing up to 3 minutes or so untill the ECT reaches the preset limit...iirc 20*C but not 100% sure
 
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Yes, it's a balance between low battery and glowing. On my TD5 it is ~13 seconds, after that time it will stop, like I posted above. So the question is if this amount of time is correct - the procedure behind (also glowing while running to get better emission values, smoother running etc.) is clear to me.
 
That 13 seconds is not a constant time, the colder it is the more it will last and vice-versa... if it was around 5*C outside 13-14 seconds without starting seems OK to me
 
Do you have a diagnostic tool to watch live sensor inputs before a cold start cos if there are erratic inputs especially from ECT or FT sensors it can start harder, also you said the voltage dropped to 10.7V so measure it while cranking too cos if it drops much below 10.5V the inverter in the ECU is mixed up and the common positive feed for injector PWM doesnt reach the desired 85V then it can make all kind of tricks so a good powerfull battery is very important for a ''clean'' cold start
 
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With the measured value while the motor is turning (not at the start of starting) and a starter of 2.2kW the voltage is 11.2V with a real no-load voltage of 12.36V gives me 6 mOhm internal resistance of battery. Currently, the battery is a bit low because of some short distance drives, roughly 15km.

I've make a list:
upload_2021-1-25_11-9-11.png


When issue is starting, there are three different types of starting:
a) Need two attemps, the second attempt start everytime neat:
b) Long cranking with rough idle for some seconds:
c) Pulled down gas pedal to start bleed of injectors

I replaced a lot of things on my TD5....
 
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