Glow plugs 101 ***Ver. 2.0***

Alex,

I don't know for sure about the GP's in the CR engines, yet. However, I doubt if you are having any GP related issues at all in a car that new?

993er said:

Do these glow plugs operate at different voltages based on model year?

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YES !!

If you try to "test" a 5-volt glow plug by putting 12 volts across it, you'll simply burn it out... in a hurry... (there are also 7 volt (nominal) glow plugs in addition to the original 11 volt (nominal) units...) Using the car's glow plug controller to supply the operating current through the harness is safe. (You can disconnect the temperature sensor to force a longer glow time...)


Yuri

r90sKirk said:

Alex,

I don't know for sure about the GP's in the CR engines, yet. However, I doubt if you are having any GP related issues at all in a car that new?

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I only asked about the current draw because I have a HP 6267B 0-40V, 0-10A DC Power Supply that I can use to test my glow plugs when the need arises.

No issues now (better not have any this soon), but I just received my tube of Beru GFK01 glow plug grease that is used on the shaft and threads of the glow plugs as recommended by Beru. This to avoid cursing at some later date as I have already seen on this forum. The grease by the way is white in color. I would have expected something similar to an anti-seize compound.

ymz said:

YES !!

If you try to "test" a 5-volt glow plug by putting 12 volts across it, you'll simply burn it out... in a hurry... (there are also 7 volt (nominal) glow plugs in addition to the original 11 volt (nominal) units...) Using the car's glow plug controller to supply the operating current through the harness is safe. (You can disconnect the temperature sensor to force a longer glow time...)


Yuri

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Hi Yuri,

Which I should be able to do with my HP DC power supply, provided they do not draw more than 10A at 4.4V.

Like a bulb filament, I would assume initial current draw is a spike due to lower resistance and a split second later, current draw would be far less as the GP heats up.

They are also pulse-width-modulated... which adds another dimension to figuring out power draw etc.

Vince Waldon said:

They are also pulse-width-modulated... which adds another dimension to figuring out power draw etc.

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They sure like to over-complicate things.

I guess I'll keep it simple. Set the V to 4.4V and turn the current limiting up gradually.

True, although I get why they do it... and it does give me a reason to dig my oscilloscope out of retirement every now and then.

Vince Waldon said:

True, although I get why they do it... and it does give me a reason to dig my oscilloscope out of retirement every now and then.

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I don't.

If they are going to have a variable time for the GPs to be on, based on temperature (1s, 2s, 3s...etc) why PWM it unless you want to vary the power.

I'll leave my TEK 2445B in the cabinet for now. I've got too much on the go at the moment.

993er said:

why PWM it unless you want to vary the power.

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Yup, and that's exactly why... they *do* want to vary the power, and PWM is the most efficient way to do it.

For example: Full power (50 amps or so) for starts...much less power for after-glow. On my pre-PWM system they can't run all the coolant plugs when in after-glow mode because the glow plugs are still demanding full power. If it had a later system this would be possible.

Or the 100A in-car electric heater later models with PWM glowplugs have.

And so on...

Vince Waldon said:

Yup, and that's exactly why... they *do* want to vary the power, and PWM is the most efficient way to do it.

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Which is why I when the electric vest I use when motorcycling used a large bi-metallic thermostat to control the heat.

I came up with a PWM controller switching a FET (no heat sink required) to vary the heat. Soon thereafter, manufacturers were doing the same.

By the way, where is that GP controller located? Is it a separate module and it must be solid state I would think.

...and then sometimes all the plugs meter out good even though the car doesn't think they do. I had this problem recently. Last July I finally troubleshot my fault down to the glowplug harness. After changing that out all was well until November rolled around and the #3 GP fault returned. I metered the plugs and all read very close to one another. I thought I would need to change the loom again. Just for kicks I swapped the #4 and #3 plugs. The fault followed that plug. I metered them all again and found all to be similar. The supposed bad one even read the same as the plug in the #1 position. I changed out that bad plug and the code is gone! I wish VW hadn't made this system so damn sensitive. Really, the GP system should've just been designed to be "dumb" and not throw codes at all. Sometimes I think those Germans make some things complex for the sake of complexity. But that is just one mechanics opinion.

454k30 said:

Sometimes I think those Germans make some things complex for the sake of complexity.

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But I do have to hand it to them in certain areas.

At least on a BMW 3-series and a Mk6 Jetta, they know where to put the oil filter.

Not only is the location perfect, put it is a drop in cartridge for a no-mess installation compared to the sideways-mounted-out-under-the-car-under-the-intake-manifold location.

Yes, the oil filter is of a good design. Everybody gets one!

Hi
Just bought a 2005 Golf TDI, It has cold start up issues so I started digging into the engine. I found the glow plugs were from the ALH engine (obviously shorter) I replaced these with the proper ones. When testing the harness with the temp sensor disconnected I got 7.5 volts at the harness. The voltage immediately drops to 2.5 volts and the entire cycle lasts under 10 seconds. Is this normal?

Wingnut said:

One thing to try is to bridge the 2 harness wires together. This will eliminate the possibility of the ECM detecting a variation in the plugs as they will all be on the same circuit instead of 2 seperate ones. If that fixes the CEL, then you know the problem is the plugs or the harness. If it doesn't fix the CEL, then the problem is between the harness & the relay.
It is a mickey mouse way of fixing the problem, but if you are not worried about monitoring the GP's, then you can leave the wires bridged and that will permenantly elininate the GP CEL. You will just have to check your plugs with a multimeter every fall before the cold temps set in to ensure they are OK so you won't have winter starting problems.

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I'm trying to get my car to pass emissions in Ontario with the CEL on due to glowplugs. I've read a few times in this forum about bridging the two wires to keep the CEL off by insuring that the difference in resistance isn't registered.
What I want to know is, for the purpose of emissions, do I really have to do this? What if I just clear the code then unplug the glow plugs for a few days, then get the test done? Am I correct to presume that the CEL wouldn't come on since the resistance will be the same for both wires (i.e. infinite) since the wires aren't on the glowplugs?

Great Diagnostic Idea... Greg Scruton

Thanks Greg Scruton... Your diagnostic idea is simple... but better yet "brilliant" ! I'll have to try this my next opportunity !
Sam Ross

Greg Scruton said:

Am I correct to presume that the CEL wouldn't come on since the resistance will be the same for both wires (i.e. infinite) since the wires aren't on the glowplugs?

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You can try it and see, but as far as I know the system looks for open glow plugs as well as glowplugs with a different resistance than the rest, and thus your CEL will come on next time you start the car.

As per the discussion on your other thread on this, the permanent way to fix this IMHO is to treat your car to a new $74CND harness...since IIRC you've already bought the new plugs.

Hey everybody, I'm wondering if anyone is using Bosch Duraterm glow plugs on their MK4 tdi?

I found a set but not sure if these are better to use then standard glow plugs (beru)?

My babies get nothing but Bosch Duraterms.

Vince Waldon said:

My babies get nothing but Bosch Duraterms.

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What I am trying to understand is, is there some kind of difference between the normal ones and these? I can't seem to find much info on the web regarding these which has me concerned that they are not as popular.

The duratherms are the undisputed champion of glow plugs in the MK1 world. They have lasted three times as long as the autolite ones from a big box parts store on my 1.6. I would definitely buy them again.

tjsean0308 said:

The duratherms are the undisputed champion of glow plugs in the MK1 world. They have lasted three times as long as the autolite ones from a big box parts store on my 1.6. I would definitely buy them again.

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What I recall reading is that they light up longer then the normal ones. Also I saw people mention that there are shot and long relays. Not sure how that would affect MK4's since I've never heard of a long/short relay on these cars.

I know with VCDs you can extend the GP time so it lights up longer but didn't think that glow plugs by themselves could be set to light longer.

"Short" and "long" are concepts from VW's IDI engines back in the mid-eighties when glowplug technology was changing, and different relays were needed depending on the version of glow plug you bought.

On your engine there's no fast or slow... the glow plug system determines how long to pre-glow and post-glow and a glow plug is a glow plug timing-wise; it can't decide how long to run on its own.

I don't know that anyone could prove Bosch are better or worse than Beru... both claim to have the best design, and you probably can't go wrong with either.

Autolite and Champion plugs, on the other hand, have a terrible reputation and I'd stay well clear, personally.

The only thing to remember is that your glow plugs run a couple minutes every time you start the engine, summer or winter, so in my humble opinion worth buying good ones that last. A quality brand, like Bosch or Beru, is probably a safe bet. The rest is probably bragging rights.

Well I made the jump and purchased the Bosch Duraterm glow plugs from here:
http://www.ebay.com/itm/151083420540?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

IMO the pricing seems pretty good, about 12.00 a plug.

My next worry/challenge is removing the old glow plugs...so nervous and worried about them stripping and/or breaking off in the head (the old ones)

I've been having problems with starting my caddy 2k 1.9tdi bls engine when cold or hot.

Glow plug 3 comes up on vagcom as being open.

I've just followed your procedure on post 1.

Glow plugs all read 2.4 using multimeter using ground where the battery connects and the positive on the tips of the plugs.

I then disconnected the coolant sensor to the right of the engine which kick starts the fans when ignition on.

I tested the glow plug wiring loom and only reading approx 2.60 across the 4 which all drop to 0.16

Does this sound like the relay?


My van only starts after constant cranking

mrrhtuner said:

My next worry/challenge is removing the old glow plugs...so nervous and worried about them stripping and/or breaking off in the head (the old ones)

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Soak the threads of the old GPlugs with wd40 or ANY oil you choose, let sit overnight, (hopefully no rain that night), then the next day get a long extenion for your deep-socket (IIRC 11mm) socket, then tighten glowplugs until you just make a little squeek with the oil, then reverse the pawl on the ratchet, and the glowplugs should be free. When doing this, you are 'breaking' the seize, and by going in a clockwize direction, you just tighten a teeny bit, but it breaks the rust/alloy chemical bond.

The heating / cooling of the GlowPlugs (Steel Bolt) in an Alloy(Aluminum) block does the 'freezing' of the bolts into the head.

Apply Liberal amounts of 'Anti-Seize' compound on the thread only of the NEW Glow Plug , and torque to the required amount. (Sorry can't remember , while cold beer is beside me..... the exact torq spec for the GlowPlugs).

Piece of Cake!

mrrhtuner said:

My next worry/challenge is removing the old glow plugs...so nervous and worried about them stripping and/or breaking off in the head (the old ones)

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Which is why I removed them on my new 2013 Jetta this past June to clean the threads and then apply Beru GFK01 Glow Plug Mounting Grease to the shafts and threads of the glow plugs, as per Beru glow plug mounting instructions.

A torque wrench was used to remove and install them as well, as per Beru glow plug installation instructions. They were installed on the loose side by the factory.

I'll be doing this every few years.

i have a 2000 jetta 5 spd. i bought it in june. since it has started to get a little colder in indiana, ive noticed my glowplug light only comes on for maybe 2 secs. (same as it did all summer) its getting hard to start and its 60 degrees out!! Can anyone point me in the right direction. this isnt my first diesel, but my cummins has a grid heater. Thanks!!!

If it's 60 degrees (F) your glow plugs are still not designed to come into operation for starting the car... I'd guess retarded timing... have you had your timing belt system changed yet? It's good policy on any new-to-you TDI to make sure that everything in that system (belt(s), tensioner, 3 iders, water pump, a bunch of single-use bolts) has been recently and properly changed... (with good quality parts, I shouldn't need to add... avoid a certain vendor from North Carolina...)

Yuri

I have a 2000 jetta. The flow plug light is only coming on for a couple seconds. When i disconnect the temp sensor it did come on for 20 or so. I do show voltage to the plugs then. Did this mean my relay is bad? I can't seem to find the relay this manual doesn't show it. Thanks!