TDI Newbie, not diesel newbie, glow plug question`

I recently bought a 97 TDI Jetta to drive to work 35 miles a day, great on fuel. But have one major question.

I always used to drive older non TDI, or computer controlled diesel VW's mostly rabbits. Of course on them you would pull out the glow plug cable to engage the glow plugs before starting it. The glowplugs would engage in ANY weather since it was just an electrical connection you were making with the cable.

It was nice because on cool mornings (50-60 degrees) it would always ensure a nice smooth start by pre warming the cylinders a bit with the glow plugs.

But my TDI does not do this AT ALL. On a cool morning or evening when I turn the key and watch for the glow plug light on the dash, it comes on for just less then a second and turns right off. Basically the glowplugs aren't coming on. Since it is still warm enough to start, it starts, but is very rough and shaky for a minute or so till it warms up, not smooth at startup at all like my older diesels.

I'm worried that there may be something wrong with my glow plug system and would like to know of this is normal for a TDI? I have heard that computer controlled TDIs don't turn their glowplugs on till the temperature of the coolant is below 40 degrees, but that seems crazy.

If this is normal, then I'll live with it, but if this isn't would someone please let me know. Because while summer is still here I would really need to get this looked at before winter hits, or be stuck with a non starting car.

Any help would be extremely appreciated.

Thanks,

-Joe

Yes it is true, the glowplugs do not come on when the ambient temp is 40 F. If your car is running rough at cold start, it could be that your timing is slightly off. Another possible cause is that your injectors are not clean, and they aren't giving you an optimum spray pattern.

I've only seen any kind of significant light-on time when the temps were in the 30s. Above that, the glow plug light more or less "flashes on, then off" one time.

But don't be fooled into thinking at the plugs aren't on. The light is only to remind you to wait-to-start.

My F350 (7.3 PS) ALWAYS turns on the glow plugs lights regardless if it's warm or not.

JP

to quickly check, just unplug the engine coolant temp sender. its located on the coolant manifold bolted to the head(when you open the hood and find where the top rad hose meets the head). the ecu will run the glow plugs just not sure how long.

Best have your timing checked by someone w/ Vag-Com. Make sure it is near the top (advanced) end of the graph. If that is as it should be and you are still getting a rough start, follow some of the other advice about nozzles possibley being gunked up. Also may want to do a compression test, not hard w/ the right adapter.

I don't think the GPs on the VWs are on unless the light is on. The initial flash you see is the test of the circuit. Below 40, on, above off...The way it is designed. There was a thread some time ago about lengthening the GP time (may have included increasing the temp setting, can't recall ATM...) Search "extend glowplug time"

Check this: http://forums.tdiclub.com/showthread.php?t=123304&highlight=extend+glowplug+time

chromeBuddha said:

I don't think the GPs on the VWs are on unless the light is on.

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Not totally accurate... when it's cold, the glow plugs stay on a bit longer than indicated by the light... you can tell by the brightness of the interior dome light (if you leave the door open)... Also, for emission control, the glow plugs come on while driving when the engine's on the cool side, without any indication from the dashboard light...

Yuri.

I can hear the relay clicking on & off when it's cold out, depending on the RPM of the engine. The light remains off at that time.

JP

ymz said:

Not totally accurate... when it's cold, the glow plugs stay on a bit longer than indicated by the light... you can tell by the brightness of the interior dome light (if you leave the door open)... Also, for emission control, the glow plugs come on while driving when the engine's on the cool side, without any indication from the dashboard light...

Yuri.

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