Glow Plugs

Wirroff · Senior Member

Glow Plugs

Yuglamron · Guru

Nothing technical about my answer on this subject. A friend has a sprinter I think it's around the 2004 vintage. Bought from new and travels from Qld south to Sydney and Melbourne. on business runs. Has some huge mileage over 300.000K's and to my knowledge very rarely gets serviced. Just taken in when it breaks down. The glow plug light on it comes on after you have started it and theirs stays on for ten minutes or so afterwards.
Why I have no idea, and when the Mercedes service agents were told they never fixed it and it's still going. No recommendation not to have it checked but I am sure someone will have first hand knowledge to give you an answer.

oldbobsbus · Guru

Hi Paul and Val,
Let me try to answer your Q's one at a time in no particular order..
1. A faulty GP has NO detrimental affect on your motor it is only a heating element for cold starts NOT needed in your case..

2. If you can locate the lead that supplies power to the plugs and disconnect it preferably at the relay end or if you take it off the GP end then insulate the end (it is live for a short time when starting)and the light no longer stays on then the problem could well be that one or more of the GP's are faulty.

3.If the light continues to stay on then the problem is in the relay. and you would need to have the ECU read by someone with a suitable Scantool and that would tell them the fault that is causing the problem.

4. The other thing that could cause the problem is if the lead from the relay to the GP's is shorting to earth, but I believe if that was the case then it would have blown the relay fuse.

5. By the look of what I can read on the net it is a fairly common problem and it doesn't have any detrimental effect on the motor..

If you are still worried then give me a ring ..

-- Edited by oldbobsbus on Saturday 7th of December 2013 10:13:33 AM

Aus-Kiwi · Guru

What does it do if you wait 10 to 30 seconds after turning key on ??
My old Fuso would do what you said if started without giving glow plugs time to warm up..
We are lucky really not cold in Australia to effect most diesel motors starting ..
We take it for granted .. Maybe snowy mountains ?
Tmk the gp won't have any adverse effects on engine. They are fitted to make engine start easier..
Diesel fuel is arguable better at starting these days..Better refinery than older diesel fuel

-- Edited by Aus-Kiwi on Saturday 7th of December 2013 10:26:58 AM

-- Edited by Aus-Kiwi on Saturday 7th of December 2013 10:27:52 AM

Wirroff · Senior Member

Thanks folks (Bob, your knowledge never fails to astound me!). I'm not too worried about it as I know we don't really need the glow plugs here anyway. I will try having the key in position 2 for 30 seconds to see if it happens without starting the engine.

Thanks once again folks, you lot on here are just pure gold!

justcruisin01 · Guru

Wirroff wrote:
Thanks folks (Bob, your knowledge never fails to astound me!). I'm not too worried about it as I know we don't really need the glow plugs here anyway. I will try having the key in position 2 for 30 seconds to see if it happens without starting the engine.
Thanks once again folks, you lot on here are just pure gold!

IF the vehicle is srarting ok then the glow plugs are working, many these days only stay on for a few seconds & not 15/20 like the older systems.

You may think that they are not needed but thay are, as I said they only on for a couple seconds & are off before you know it, longer in cold climate.

I would beleive that the prob is the glow plug timmer relay, this controles the time frame the plugs stay on for. Excessive run time is not good for the plugs.

JC.

Wirroff · Senior Member

The thing is; when I now go to turn the engine on, the glow plug light doesn't light (it used to, as you say, for about 3 seconds). It now only lights AFTER the engine is fired and then stays on for approx 20 seconds. I did try activating all the electrics as suggested (aux position) but the light still didn't come on. The engine starts fine anyway so, after re-assurance from my learned friends, I'm not too concerned at this stage.

Cheers!

native pepper · Senior Member

Wirroff wrote:
The thing is; when I now go to turn the engine on, the glow plug light doesn't light (it used to, as you say, for about 3 seconds). It now only lights AFTER the engine is fired and then stays on for approx 20 seconds. I did try activating all the electrics as suggested (aux position) but the light still didn't come on. The engine starts fine anyway so, after re-assurance from my learned friends, I'm not too concerned at this stage.
Cheers!

If you've got a multimeter, get someone to start your engine and have the multimeter attached to the glow plugs, it will tell you you if power is going to them before starting, how long after and when the light is one. Theoretically, your glow plugs should continue to operate for a few seconds after the engine fires, to keep temperature in the engine for proper combustion. This is only for indirect injection, direct injection engines don't need glow plugs, although a number of engines have then. The Isuzu in our bus is direct injection, yet it has glow plugs, which we've only used once to check they are working.

03_troopy · Guru

It looks more like a case of the preheat cycle is not functioning properly. From what I have read only, glow plugs have a preheat and postheat cycle. The preheat cycle is to bring the temperature of the cylinders up to ignition temperature before the engine starts. The post heat cycle is to maintain the temperature for a short while after ignition and is at a lower current via a resistor or is pulsed at a lower duty cycle than preheat. If the preheat isn't working, it might also affect the post heat cycle by keeping it on longer? What actually determines the pre/post timing is a bit of a mystery to me at this stage, weather it is purely time based or temperature based via a sensor and the information fed to the ECU maybe? But from what I can gather, in not so extreme climates, the only problem is the excess of toxic emission that are produced from incomplete burning for a short while after startup.

03_troopy · Guru

There is a good read here if you haven't seen it already Sprinter Source Gets a bit technical in places, but a bit more involved than I originally thought.

Plendo · Guru

Paul & Val,

I do not know the Mercedes dash protocols, but the way it is appearing, and also the reference to the person who is running their's as a commercial with limited servicing makes it sound as if it may have nothing to do with the glow plug, but just an indicator that a service is overdue, and or that there are fault codes that need to rectified.

Given the age of the vehicle it will be OBD2 compliant, so it could be worth spending a few dollars (less than 20) to get an OBD2 interface, and check the fault codes, depending what it is the interface may also give you the ability to clear the code. Certainly cheaper than taking it to a Merc dealer.

BTW, a list of codes and their meanings are available.

Feral Errol · Veteran Member

Most modern diesels have a post-start glow cycle to help reduce emissions post start.

When first started, the heat provided by compressing the air in the pre-combustion chamber or combustion chamber (depending on engine design) may be insufficient to ensure complete/even combustion of the fuel injected. By adding heat from the glow plug, the chamber temperature is increased and the engine is able to burn all/most of the fuel injected and runs much smoother while reducing emissions.

The post start cycle can be of either fixed or variable duration. In some engines such as the late 80's Ford 6 litre turbo/diesel the post start cycle is a series of 4 second pulses. Some other engines use a variable length continuous glow cycle. The length of glow cycle is usually determined by coolant temperature in the block.

-- Edited by Feral Errol on Sunday 8th of December 2013 10:11:36 AM

Wirroff · Senior Member

Plendo wrote:
Paul & Val,
I do not know the Mercedes dash protocols, but the way it is appearing, and also the reference to the person who is running their's as a commercial with limited servicing makes it sound as if it may have nothing to do with the glow plug, but just an indicator that a service is overdue, and or that there are fault codes that need to rectified.
Given the age of the vehicle it will be OBD2 compliant, so it could be worth spending a few dollars (less than 20) to get an OBD2 interface, and check the fault codes, depending what it is the interface may also give you the ability to clear the code. Certainly cheaper than taking it to a Merc dealer.
BTW, a list of codes and their meanings are available.

Hi folks, we're not very 'mechanically minded' and so please excuse our ignorance; what is an OBD2 interface, how does it work, can we do it ourselves? Etc Etc. Once again, sorry for our ignorance.........
PS What are the code listings, is there a website link to them?
Cheers!

Plendo · Guru

Hi Paul and Val,

apologies, I assumed a degree of technical knowledge which was of course completely unfair of me.

ODBII is a standard mandated by the American government back in the 90s, which forces car manufacturers selling cars in America to add an interface (a standard plug somewhere under the dash) which allows anyone with a standard ODBII tool can access the vehicle diagnostics.

Back in the 90s a tool to read ODBII data cost thousands of dollars, but it was a great tool for the independent motor vehicle repairers, who could invest in one tool, and then use this with any car. This was of course the intention of the standard.

Recently (last 4 years) there have been a number of simple interfaces designed to be used with a laptop appear on the market, these plug into the socket under the dash, and connect to the PC either with a USB cable, or via bluetooth. I bought mine for $12. There is also simple software available to use these interfaces, I use an Android tool caller Torque, which cost about $4 from memory.

So no longer are you limited to the manufacturers workshop, now practically any repairer can read and interpret the diagnostic data.

While the standard defines what the manufacturer must make available via the interface, it does not define the codes, and manufacturers use their own error codes, which they then have to publish.

I suspect it is not a tool you would use yourself, but you could go to your local friendly mechanic, and they could read the codes for you.

rockylizard · Guru

Gday...

Correct term is OBDII .... On Board Diagnostics Version 2

This gives a full description of the what it is and the history.

http://en.wikipedia.org/wiki/On-board_diagnostics

Cheers - John

DeBe · Guru

This is a cheep OBD scanner, were around $15 that I use. & a picture of what the socket on the vehicle looks like. It will be with in reach of the drivers position under the dash usualy by the fuse block. It will read codes & erase them.

DeBe · Guru

Another reader which was around $30 you can plug into a laptop USB & read codes & erase, also gives real time data when engine running & very easy to use. ELM 327 reader. Pictures are on A Ford BA Falcon with the engine running.

DeBe · Guru

Couple more pics,

Santa · Guru

Plendo wrote:
Hi Paul and Val,
apologies, I assumed a degree of technical knowledge which was of course completely unfair of me.
ODBII is a standard mandated by the American government back in the 90s, which forces car manufacturers selling cars in America to add an interface (a standard plug somewhere under the dash) which allows anyone with a standard ODBII tool can access the vehicle diagnostics.
Back in the 90s a tool to read ODBII data cost thousands of dollars, but it was a great tool for the independent motor vehicle repairers, who could invest in one tool, and then use this with any car. This was of course the intention of the standard.
Recently (last 4 years) there have been a number of simple interfaces designed to be used with a laptop appear on the market, these plug into the socket under the dash, and connect to the PC either with a USB cable, or via bluetooth. I bought mine for $12. There is also simple software available to use these interfaces, I use an Android tool caller Torque, which cost about $4 from memory.
So no longer are you limited to the manufacturers workshop, now practically any repairer can read and interpret the diagnostic data.
While the standard defines what the manufacturer must make available via the interface, it does not define the codes, and manufacturers use their own error codes, which they then have to publish.
I suspect it is not a tool you would use yourself, but you could go to your local friendly mechanic, and they could read the codes for you.

Thanks Plendo, while I'm only too aware of the fact that workshops have diagnostic tools I didn't know there were cheaper versions available.

Will have to look around for one to suit the Transit, are there different models to suit various vehicles or are they a one size fits all arrangement? smile

oldbobsbus · Guru

Just a point to remember,...
All OBD II scantools dont read ALL vehicles..
I have a VT commodore and a 2002 Pulsar and I bought a cheap Scantool OBD II and it wouldn't read the codes in either car...
When I contacted the seller he then told me it would only read European vehicles..
He refunded me and I put a bit more with it and got one that would do the job.

Santa · Guru

oldbobsbus wrote:
Just a point to remember,...
All OBD II scantools dont read ALL vehicles..
I have a VT commodore and a 2002 Pulsar and I bought a cheap Scantool OBD II and it wouldn't read the codes in either car...
When I contacted the seller he then told me it would only read European vehicles..
He refunded me and I put a bit more with it and got one that would do the job.

Thanks Bob, I had a feeling this may be the case, will have to do some research. smile

Plendo · Guru

I have had two units, the first a usb interface, and the second a bluetooth unit both worked well across a number of cars, including Hyundai, Toyota, and Mitsubishi. Have not tried it on the Land Rover yet.

DeBe · Guru

They will read pretty mutch any thing after 2005 Asian & Ausie vehicles. Anything before 2005 is hit & miss, but at $15 its not a huge outlay.

Wirroff · Senior Member

Hi folks, sorry we've been out of contact for a few days as we crossed the Nullarbor (thankfully now arrived in Norseman!). Really appreciate all your kind assistance and helpful suggestions. What I have noticed is that the glow plug light does not come on AT ALL now before the engine is fired and then comes on for 30 seconds AFTER that. I have also noticed that the engine, from cold, is more difficult to start now without that glow plug light on. I'll have to get it checked out when we get to Esperance tomorrow.

Once again, you are so kind with your assistance.

mr glassies · Guru

ok for the rest of the merk owners let us know what it was please.

just for the record there is an air heater in side the intake manifold of some diesels they dont have glow plugs.

dibs

jims troopy has glow plugs a m8

Wirroff · Senior Member

OK folks, time for an update. After a couple of days in Esperance, we found it harder and harder to start the engine (the ambient temperature would not have been an issue). The engine was turning over but not firing. The glow plug light still only comes on AFTER the engine has started. One day, after 10 minutes, it finally started!

I took it to two mechanics who between them, tried 4 different diagnostic tools plugged in and not one could communicate with the Merc! (They both suggested I take it to a Mercedes Dealer who, unfortunately, happens to be 700kms away!). Anyway, one morning I really struggled to get it to fire and only after a huge amount of throttle would it do so. I took it to a mechanic (again still in Esperance) and he noted that there was fuel visible around the top of the injectors that shouldn't be there. His assumption was that the 'return fuel lines' were perished and had been leaking out under pressure and so he replaced them (they are on top of the engine at the injectors). Anyway, the next day, after 12 hours idle, it started fine and I thought the problem had been fixed. However, the very next day and the same problem has arisen (the top of the injectors look fine and dry). The engine turns over but REFUSES to fire without a heap of throttle. I'm now at a loss as to what to do. I still believe the issue is with the glow plug relay module and I told the mechanic this but he didn't seem to know a lot about them....

If anyone has any ideas as to why there should be fuel around the top of the injectors, then all advice will be taken as this is driving me insane!

Thanks in anticipation......

native pepper · Senior Member

Wirroff wrote:
OK folks, time for an update. After a couple of days in Esperance, we found it harder and harder to start the engine (the ambient temperature would not have been an issue). The engine was turning over but not firing. The glow plug light still only comes on AFTER the engine has started. One day, after 10 minutes, it finally started!
I took it to two mechanics who between them, tried 4 different diagnostic tools plugged in and not one could communicate with the Merc! (They both suggested I take it to a Mercedes Dealer who, unfortunately, happens to be 700kms away!). Anyway, one morning I really struggled to get it to fire and only after a huge amount of throttle would it do so. I took it to a mechanic (again still in Esperance) and he noted that there was fuel visible around the top of the injectors that shouldn't be there. His assumption was that the 'return fuel lines' were perished and had been leaking out under pressure and so he replaced them (they are on top of the engine at the injectors). Anyway, the next day, after 12 hours idle, it started fine and I thought the problem had been fixed. However, the very next day and the same problem has arisen (the top of the injectors look fine and dry). The engine turns over but REFUSES to fire without a heap of throttle. I'm now at a loss as to what to do. I still believe the issue is with the glow plug relay module and I told the mechanic this but he didn't seem to know a lot about them....
If anyone has any ideas as to why there should be fuel around the top of the injectors, then all advice will be taken as this is driving me insane!
Thanks in anticipation......

G'ady cobber, you're having a terrible time with this problem. It now sounds like the IP is playing up and either delivering large amounts of fuel, or none at all. If your engine is Di, then it should start without glow plugs where you are if it is getting the right fuel amount and not flooding the injectors. Does it drive alright, if so then it could be an intermittent blockage in your fuel system, which settles when the car is sitting.

If you can, start running through your fuel system and checking fuel is getting through properly all the way through. You may even have to crack an injector to see what's occurring. Sadly most mechanics of today, have no idea and can only work with their plug in diagnostic tools. That's another reason we drive pre 90's vehicles, if something goes wrong, you can trace it through the system on the side of the road, just like you can with the electrics.

oldbobsbus · Guru

There should be a pressure sensitive valve in the form of a banjo bolt on the top of the injector pump on the fuel return .. If it has a bit of **** under the ball that restricts the flow of fuel back to the tank then the pump would drain and the sensor would tell the OBC that there was no fuel pressure hence the glow plug light..
Maybe you need to get this valve checked out and have it cleaned...
Also the supply line into the pump should have a large hole in the Banjo bolt and the return line should have a very small hole in it with a restriction spring and ball, just be sure someone at some stage hasn't put the wrong bolt into the wrong banjo connector..

Thats the only thing that I can think of that could be causing the problem..

Wirroff · Senior Member

Hi Bob, as you know we're not very mechanically minded, could you show where the injector pump and the 'banjo bolt' would be situated? I've taken a photo of the engine bay and you can clearly see where the mechanic replaced the fuel return lines (in flouro yellow!). If you could show us where to look, we'd be grateful and have a go at cleaning it...

oldbobsbus · Guru

Hi Paul,
Follow those steel lines from the injectors down to under the manifold and you will find the pump...
I am thinking it is something you should run past a diesel mechanic..
Maybe goto Repco and ask them where the closest Diesel Injector Service is...
Repco Esperance.
Lot 138 Norseman Rd, Esperance WA 6450
(08) 9071 7260..