Glow Plugs

[Rogan]

Hi, new member here..
I have been chasing a glow plug issue.  When I first turn the key on, the glow plug light comes on then goes out about .5-1 second later.  The engine is a little hard to start, but not hateful.
If I plugged the CTS and the light stayed on for about 20 sec, so I replaced the CTS.  No change.
I have no codes, so I'm not really sure where to go from here..  any ideas?

Thanks

[theman53]

Even when it is -15f my alh light doesn't stay on for more than 10 seconds. If it is warmer, now in the 90f range, it does not stay on for 1 second. I think what you are describing is fine. Also, once the engine is warm no matter how cold outside, the light goes out very quickly.

[Rogan]

I understand that the glowplug circuit is not needed once engine is warm.  Not to sound snotty, but having owned multiple Dodge Cummins trucks, so I'm well versed in that aspect.
However, i am definitely new to the VW side of glowplug operation.  Even with coolant temps (first start) in the 60*F range, Id expect the glowplug circuit to activate, at least for more than a second or two..

But then again, that's why i am here

[theman53]

Nope, the light doesn't even mean the glowplugs are on, it is just a timer. Anything above 50f for sure I have never seen the light on for more than 2 seconds if that. These vw's are much better built than what you are used to.

[Rogan]

Better built?    that's opinionated. The two are not comparable beyond the fuel they use.
i appreciate your help and input on this matter, however.  I'll continue to monitor the glowplug circuit as this past winter, it was all but functional.  Test results pointed to the CTS and ive since replaced it. So i guess we'll see.
Thanks again, fine sir! 

[vanbcguy]

Worth mentioning that the GP light is only a "Ready to start" light. For instance on my car the GPs come on when you close the driver's door before you've even put the key in, stay on after the light has gone out for a while and then come on after the engine has started and stay on for several minutes. The GP light isn't on for most of that.

[theman53]

with no codes it and it is operating fine, I would say you have no issue at all. If one glow plugs resistance is off a bit I get a code. The plug still works, but if the resistance is too far off from the rest it throws a code quite easily.

I should say better built engine stuff. The electronics are suspect sometimes. All forged internals and pretty much the same bosch fuel systems depending on years, I will stand by the better built statement.

[Rogan]

theman and vanbc,
thanks to both of you for your responses.
I'll do some more testing/investigating..

With what I'm used to (Dodge grid heater), the light on the dash operates in conjunction with the glow plug relay circuit..  Meaning, that if the light is on, the grid heater is active..

The car still is cranks a little more than it should on even warm mornings ( 70f) first start..  Takes about 5-8 sec. of cranking to get it to fire.  The GP light on the dash illuminates exactly the same manner, whether it's 30F or 100F.

[theman53]

You may have a little fuel line sucking air. On the mkiv have a recirculation thing on the fuel filter that has some orings that like to leak air but never diesel. The recirculation thing is plastic, so it can break and leak. If you just got the car then anything is suspect. The fuel lines, pump seals, return lines < the injector return lines love to leak and go undetected. Many run clear fuel lines to see if any air is present. All of these things cause a loss in pressure and longer start times on these cars.

[libbydiesel]

As has been mentioned, the glow plug light is not an indication of whether or not the glow plugs are ON or more accurately, when it goes out is not an indication of when the stop being powered. 

I would check your clear supply line for air and I would install a clear return line and check it for air infiltration. 

[Caroi]

I have a 1999 L3410. The glow plugs do not preheat
when the switch is turned on. The tractors starts
fine -just takes a little longer, especially when
it is cold. I have been told this will not hurt
the engine. It has been suggested that the glow
plug controller needs to be replaced. How
difficult is this procedure?

[745 turbogreasel]

I should say better built engine stuff. The electronics are suspect sometimes. All forged internals and pretty much the same bosch fuel systems depending on years, I will stand by the better built statement.

I will  put this head to head with any timing belt VW ever built.  In 230,000 miles it has required no service or adjustment whatsoever.

[ORCoaster]

745   That looks a lot like my wife's food processor.  With an alternator.   Sometimes I have to swing to the engineered and built in USA is better than Germany.  But when I look at the 1981 car I have and then my 1996 I still think the VW is the winner.  If I look at more recent cars I may have to say the USA finally is catching up.  So maybe better built by era might be a consideration. 

[StrogovaSeta]

this is my first ever diesel.. Very sluggish on starting in the cold. Battery/earths, etc OK. How do you check glow plugs all I know is the yellow heater light comes on and goes out after 5 seconds. Do they 'wear', get clogged, or what.
What is cost of replacements ?

thanks

Hello. And Bye.