Can Glow Plugs Only Function Partially??

[Genesis]

Good question.

However, not really all that material since the other cylinders start firing almost immediately. The first one that fires kicks the RPM up enough to lift compression heat sufficiently to light the others; it does not take long at all -- just a couple of revolutions.

 

[WolfgangVW]

Tis the season......

A quick and simple way of checking that glow plugs are heating, on a cold snowy day is to throw a little snow on each glowplug and then glow the plugs with the ignition switch without starting the car. You will see the snow starting to melt around the base of any glowplugs that are working.
We regularily start our tdi's no problem down to about -25c without being "plugged in".
We do use oil pan heaters to assist in very cold temps, not usualy necessary but they definately help.
As Oilhammer said above...."Other things beside the glow system can cause a long crank time and hard starts. "

So I tried the snow trick. It wasn't optimal conditions as its warmed up here lots. But it looked like GP#4 wasn't melting the snow. That being said it's GP#3 that's bad. I seem to remember someone mentioning that the GP's are paired so that can effect more than just the bad plug. How does this work? Does GP3 effect the GP4?? If so is there a work around?

 

[maxmoo]

So I tried the snow trick. It wasn't optimal conditions as its warmed up here lots. But it looked like GP#4 wasn't melting the snow. That being said it's GP#3 that's bad. I seem to remember someone mentioning that the GP's are paired so that can effect more than just the bad plug. How does this work? Does GP3 effect the GP4?? If so is there a work around?

A non working glow plug will not have any effect on any other glow plugs.
But you may have a bad glow plug harness that is not transmitting power to one or more glow plugs.
You can try cleaning the contact area inside the harness with a tiny screw driver and some contact cleaner also some people have had luck wraping a tiny piece of tinfoil over the contact area on the glow plug and then reinstalling the harness. This helps to make a better connection if it was loose.
But the best way is to simply replace the harness....they are just under $100 and all the venders carry them.
Hope this helps.

 

[Tdijarhead]

Glow plugs are paired in the older systems. In 02 vw went to a 4 wire system so if yours is the 03 in your signature yours are not paired.

Cleaning the connectors works for me every 6 to 8 months when they throw a code. I use a 22 cal wire bore brush. Eventually I’ll have to replace the harness.

 

[realslimshaver]

After cleaning Add dielectric grease( the high voltage spark plug stuff will do from auto parts stores or get some from an electronic store ) this prevents corrosion by not allowing water to get to it

 

[UhOh]

If after testing and cleaning everything appears fine but you might still be getting a code I'd suggest stuffing some tin foil over the top of the offending GP and snapping the harness back on. This has solved one such problem I ran across. The connectors start to weaken and this results in the harness breaking down (increases resistance, which then generates more heat in the harness).

 

[turbovan+tdi]

Did you extend the gp time? I found that fixed my wife's ALH cold start issues.
As for my BEW, its started over Xmas at a ski resort, -25 deg C and she was NOT plugged in. I also left the interior light on so the battery was weak, but she started, coughed, bucked, smooth out and good to go.

 

[WolfgangVW]

A non working glow plug will not have any effect on any other glow plugs.
But you may have a bad glow plug harness that is not transmitting power to one or more glow plugs.
You can try cleaning the contact area inside the harness with a tiny screw driver and some contact cleaner also some people have had luck wraping a tiny piece of tinfoil over the contact area on the glow plug and then reinstalling the harness. This helps to make a better connection if it was loose.
But the best way is to simply replace the harness....they are just under $100 and all the venders carry them.
Hope this helps.

I will try cleaning the harness. Is there a way to test the harness with a multimeter?

 

[WolfgangVW]

Did you extend the gp time? I found that fixed my wife's ALH cold start issues.
As for my BEW, its started over Xmas at a ski resort, -25 deg C and she was NOT plugged in. I also left the interior light on so the battery was weak, but she started, coughed, bucked, smooth out and good to go.

How long did the car sit there in -25C??

I didn't extend the glow time. Just pre heat multiple times.

 

[WolfgangVW]

Glow plugs are paired in the older systems. In 02 vw went to a 4 wire system so if yours is the 03 in your signature yours are not paired.

Cleaning the connectors works for me every 6 to 8 months when they throw a code. I use a 22 cal wire bore brush. Eventually I’ll have to replace the harness.

Ya mine is the 2003. In replacing the harness do you just splice the new one on or is there a connector?

 

[realslimshaver]

I will try cleaning the harness. Is there a way to test the harness with a multimeter?

it is thick wire. If you disconnect it entirely the resistance shoud be under .5 ohm and preferably closer to .1 ohm

 

[Tdijarhead]

Splice and butt connectors.

 

[maxmoo]

I will try cleaning the harness. Is there a way to test the harness with a multimeter?

You can test for 12v at each of the 4 connectors that attach to the glow plugs while the key is turned on and glow plug light is still on, which you probably have but the problem is because of a worn, loose or corroded connector in your harness that 12v will not reach your glow plug.
Just cut and splice new harness, many use a but connector but I prefer to solder and shrik wrap.....there is a fair bit of current going to these glow plugs.

see....
https://www.idparts.com/glow-plug-harness-a4-late-p-606.html
https://www.youtube.com/watch?v=omezWFuSUEk

 

[turbovan+tdi]

If the gp's are new and working and still getting codes, replace the harness. They break down and even if they seem good, when all the amperage goes thru it, it shows up bad.

How long did the car sit there in -25C??
I didn't extend the glow time. Just pre heat multiple times.

It sat for 15 hours.

Extend the GP time, you'll be amazed how much better it starts.

 

[WolfgangVW]

You can test for 12v at each of the 4 connectors that attach to the glow plugs while the key is turned on and glow plug light is still on, which you probably have but the problem is because of a worn, loose or corroded connector in your harness that 12v will not reach your glow plug.
Just cut and splice new harness, many use a but connector but I prefer to solder and shrik wrap.....there is a fair bit of current going to these glow plugs.

see....
https://www.idparts.com/glow-plug-harness-a4-late-p-606.html
https://www.youtube.com/watch?v=omezWFuSUEk

Excellent thanks for this maxmoo! Do you by chance know if NAPA carries the harness and if they're ok to use?? I get a decent discount there is why i'm asking...

 

[WolfgangVW]

If the gp's are new and working and still getting codes, replace the harness. They break down and even if they seem good, when all the amperage goes thru it, it shows up bad.



It sat for 15 hours.

Extend the GP time, you'll be amazed how much better it starts.

I always have a CEL as my one plug is bad and stripped in the head.

15 hours thats not bad!! To extend the time i would need VCDS??

 

[Tdijarhead]

Yes you will need vcds.

http://forums.tdiclub.com/showthread.php?t=123304

 

[Genesis]

Ya mine is the 2003. In replacing the harness do you just splice the new one on or is there a connector?

There is a connector; it's a pain in the tush to get to however, as it's in the plenum under the battery. You have to remove the battery and airbox; you'll see a long, black plenum under there -- remove the cover (it just unsnaps) and the connector is in there.

BEST OPTION is to disconnect it. It's a SEVERE pain in the neck to actually unthread the cable run itself; what I did with my car was cut it off where it gets wrapped into the harness on both ends and then use a piece of corrugated wire loom to run the replacement and wire-tie it into place.

Why do this instead of splicing the new one in? Because this is a high-current connection and splicing in is just asking for more trouble down the road. I replaced mine something like 7-8 years ago and the replacement is still going strong.

 

[WolfgangVW]

Yes you will need vcds.

http://forums.tdiclub.com/showthread.php?t=123304

Thanks for this. Just a quick question, whats the advantage of extending glow time vs just multiple preheats??

 

[WolfgangVW]

There is a connector; it's a pain in the tush to get to however, as it's in the plenum under the battery. You have to remove the battery and airbox; you'll see a long, black plenum under there -- remove the cover (it just unsnaps) and the connector is in there.
BEST OPTION is to disconnect it. It's a SEVERE pain in the neck to actually unthread the cable run itself; what I did with my car was cut it off where it gets wrapped into the harness on both ends and then use a piece of corrugated wire loom to run the replacement and wire-tie it into place.
Why do this instead of splicing the new one in? Because this is a high-current connection and splicing in is just asking for more trouble down the road. I replaced mine something like 7-8 years ago and the replacement is still going strong.

Thanks Genesis. I saw in the vid ya there is a connector and it seems like alot of work. We'll see what i do and i'll post back .

 

[turbovan+tdi]

Thanks for this. Just a quick question, whats the advantage of extending glow time vs just multiple preheats??

Convenience, wear and tear on the ignition lock cylinder, less thermal shock to the electrical system, anyone can start the car without special instructions.

 

[WolfgangVW]

Convenience, wear and tear on the ignition lock cylinder, less thermal shock to the electrical system, anyone can start the car without special instructions.

Alright good to know. Thanks for this