I have owned my 1.4TDCI Mk6 Fiesta since 2008 and this as always been very difficult to start in cold weather. The glow plug warning light doesn't illuminate unless the weather is extremely cold, and even then it only stays on for for a couple of seconds. I have posted questions on this subject many times over the years but have never found an answer.

Today, whilst having my battery and charging circuits tested, I was taking to my mechanic friend about this problem and he was saying that although the glow plug warning light extinguishes the glow plugs are still operational as long as the key is turned to that position? He has advised that I leave the key turned to that position for some extra time before attempting to start the engine, which in turn should alleviate this problem.

I have never come across this before and always understood that the glow plugs are only operational whist the glow plug light is illuminated. Anyone else have any experience of this?

whilst I have not proved it by testing with a voltmeter etc, I have always been under the impression that on modern diesels including my previous 2007 fiesta that the glow plugs do stay on longer than the light does, including when the engine has actually started but has not warmed up at all yet (to help it run smoother and smoke free). 

On my 2007 1.6tdci I reckon I only saw the light come on max 10 times a year and then only for no more then 2 seconds each time. 

On my current 1.5tdci i do see it more often but it's only one for a second or two.

I guess it needs one of us to put a voltmeter on a glowplug terminal. then turn ignition on, start the engine and see when the voltmeter goes back to zero, comparing it to the light. If they were easier to get to I would.  It's much easier on a 1.8tdci where you open the bonnet and they are there right in front of you. 

 

8 minutes ago, isetta said:

whilst I have not proved it by testing with a voltmeter etc, I have always been under the impression that on modern diesels including my previous 2007 fiesta that the glow plugs do stay on longer than the light does, including when the engine has actually started but has not warmed up at all yet (to help it run smoother and smoke free). 

On my 2007 1.6tdci I reckon I only saw the light come on max 10 times a year and then only for no more then 2 seconds each time. 

On my current 1.5tdci i do see it more often but it's only one for a second or two.

I guess it needs one of us to put a voltmeter on a glowplug terminal. then turn ignition on, start the engine and see when the voltmeter goes back to zero, comparing it to the light. If they were easier to get to I would.  It's much easier on a 1.8tdci where you open the bonnet and they are there right in front of you. 

 

Wow. He must have been correct then? I just had no idea about this. The glow plugs are situated at the rear under the air cleaner / inlet manifold. If the weather is kind I will just have to remove this and pop a multi-meter across them to see whats going on? I might just change them as a matter of course at the same time?

The glow plugs can remain energised for upto 20 seconds after the light goes out and also extended time when in cold conditions 

Yeah I believe the glow plugs still come on even if the light doesn't come on. 

On the 1.6 and likely the 1.4 (using my 1.6 TDCI as a reference) I notice the glow plug light comes on for an astro second if the temperature outside is lower than 5 degrees. I think once when it was -2 degrees it came on for a second. I think the car tends to start a little better when you have the key in the ignition for a few seconds as it allows the glow plugs to heat up fully. 

17 minutes ago, zain611 said:

Yeah I believe the glow plugs still come on even if the light doesn't come on. 

On the 1.6 and likely the 1.4 (using my 1.6 TDCI as a reference) I notice the glow plug light comes on for an astro second if the temperature outside is lower than 5 degrees. I think once when it was -2 degrees it came on for a second. I think the car tends to start a little better when you have the key in the ignition for a few seconds as it allows the glow plugs to heat up fully. 

I will give that a try next time its cold. I wish someone had mentioned this during my previous posts? Thanks guys

You mention that you might change them. They do sometimes snap when trying to remove them. And then you will wish you never started. If the car is usable as is I might be reluctant to try. If you take connector off each one you can test the resistance on each between the live terminal and earth(engine block) to see if any dead. Maybe Relay problem

Can agree with @isetta here if you do change the glow plugs. My dad changed mine and it took him an hour per plug as he did not want to snap any. It might help the symptoms your having putting new ones in. 

12 hours ago, zain611 said:

............... I think the car tends to start a little better when you have the key in the ignition for a few seconds as it allows the glow plugs to heat up fully. 

Right. It was reasonably cold this morning. No glow plug lights illuminated when turning the key so I left the ignition key in the pre-start position for around 10 - 15 seconds. Still took an age for it to start. I'll keep trying this but I don't think it'll make too much difference. I don't really want to change the glow plugs for the reasons mentioned, but if I have to then so be it.!!

3 minutes ago, chris301up said:

Right. It was reasonably cold this morning. No glow plug lights illuminated when turning the key so I left the ignition key in the pre-start position for around 10 - 15 seconds. Still took an age for it to start. I'll keep trying this but I don't think it'll make too much difference. I don't really want to change the glow plugs for the reasons mentioned, but if I have to then so be it.!!

Might be the glow plugs then losing efficiency. I know on mine if the car reads less than 5 degree the light flashes instantly and if it reads less than 0 degrees it's comes on slightly longer. 

Well, on my TDCi Mondeo, the glowplugs are energised for 30 seconds whenever the ignition key is turned to on. And they stay energised while the engine is running too. (goes off after the 30 secs) Also, do you realise they're a bit like light bulbs and have a heating element in them, and like light bulbs, they don't last forever! Sometimes mine only last 12 months. Easy to check their resistance with a multimeter.. should read very low Ohms if good. If you want to replace them, buy the Beru (or Ford) ones, as some of the other makes are not as robustly made (as I've found out... snapped stuck tip in cylinder head) If you do decide to change any, then doing it on a really hot engine is your best chance of not running into trouble as the alloy cyl head expands at a greater rate than the glowplug metal, so less likely to damage the cyl head.or snap off the glowplug. When I do mine, I get the engine really hot, then whip 2 out before the engine cools down too much, then run the engine up again, and change the other 2. It takes longer but it has been noted that usually its the last one to get changed that seizes up. (engine having cooled down the most by then) Also, put some copperslip (or copper ease) on the threads of the new ones which will make it easier to remove  them the next time you change them. As I said already, they don't last forever, treat them as consumables.. The glowplug light on the dash is dual function, it flashes or stays on steady if there's a fault detected by the ECU, (nothing to do with a glowplug failure, btw) and it comes on initially at switch on as part of the systems check. Again, the glowplugs remain energised for 30 secs after switch on, and really put a strain on the battery if you're having to crank it lots. If a glowplug is burnt out, the only way to check is by testing it with a meter. If the car is hard to start in cold weather then that could be a clue that 1 or more gp has failed. 

8 minutes ago, nicam49 said:

Well, on my TDCi Mondeo, the glowplugs are energised for 30 seconds whenever the ignition key is turned to on. And they stay energised while the engine is running too. (goes off after the 30 secs) Also, do you realise they're a bit like light bulbs and have a heating element in them, and they don't last forever! Sometimes mine only last 12 months. Easy to check their resistance with a multimeter.. should read very low Ohms if good. If you want to replace them, buy the Beru (or Ford) ones, as some of the other makes are not as robustly made (as I've found out... snapped stuck tip in cylinder head) If you do decide to change any, then doing it on a really hot engine is your best chance of not running into trouble as the alloy cyl head expands at a greater rate than the glowplug metal, so less likely to damage the cyl head.or snap off the glowplug. When I do mine, I get the engine really hot, then whip 2 out before the engine cools down too much, then run the engine up again, and change the other 2. It takes longer but it has been noted that usually its the last one to get changed that seizes up. (engine having cooled down the most by then) Also, put some coppers lip on the threads of the new ones to ease them out the next time you change them. As I said already, they don't last forever, treat them as consumables.. The glowplug light on the dash is dual function, it flashes or stays on steady if there's a fault detected by the ECU, (nothing to do with a glowplug failure, btw) and it comes on initially at switch on as part of the systems check. Again, the glowplugs remain energised for 30 secs after switch on, and really put a strain on the battery if you're having to crank it lots. End if brain dump! 

Thanks for the advice. Your comments are very comprehensive and will bear this in mind. One thing I will mention is that the glow plug warning light does not illuminate at switch on. The only time I see it is when its very cold, and then its so brief that it goes off almost immediately. 

Hi, have another read of my post as I edited extra bits in while you where reading it! Interesting about your gp light only coming on v. briefly and then only when cold. Does the handbook explain its function? 

16 hours ago, isetta said:

I guess it needs one of us to put a voltmeter on a glowplug terminal. then turn ignition on, start the engine and see when the voltmeter goes back to zero, comparing it to the light. If they were easier to get to I would.  It's much easier on a 1.8tdci where you open the bonnet and they are there right in front of you. 

 

You can watch the glowplugs on Forscan live data...saves getting your hands dirty under the bonnet!  

The plugs generally pulse on and off every few seconds once running for the first few minutes.  I do have a screenshot of this but can't find it.

 

And yes, just to clarify, the glow plug light on these isn't connected to the plugs in any way.  It's purely timed by the ECU, dependant on temperatures.  @chris301up I wonder if you have a temperature sensor fault, so the ECU thinks it's warmer than it actually is...  I'm not sure how many temp inputs it uses, obviously coolant temp, but also exterior temp or intake air temp as well.  If it's IAT, you may not notice that being faulty from the drivers seat.

From the manual it looks like this is the way it's supposed to be. Apparently, when cold, the engine could turn over for up to 25 seconds before the engine starts. Also, it says, switch the ignition on and wait for the glow plug light to go out, which of course doesn't happen