Strange Glow Plug Problem

[SolarSteve]

I just installed new glow plugs when I changed out the head on my 1.6 N/A last week.  When the motor is stone cold the glow plug light comes on when I turn the key forward and they appear to be working.  After I drive the car and shut it off and then go to re-start it and it cools off a bit but is not stone cold, the glow plug light does not come on and they don't appear to work due to the long cranking time and white smoke.  Before the head swap the glow plugs would light during a start attemp even if the motor was only shut off for a few minutes after being hot.

I have a Bentley but it does not descibe this type of problem.  Does anyone know what's going on with this?

Thanks

[derekp]

I'd take a peek at your temperature sender just to make sure you didnt disconnect the sender accidently?
Outside of checking all the connections on the glows, not much else comes to mind though
I know theres "fast" and "slow" glow plugs and you arent supposed to mix the type of plug improperly with "fast" or "slow" relays but I dont know how to tell the difference.
Maybe you bought the wrong type (fast vs. slow)?

[SolarSteve]

I tried swapping the temp senor for the plugs and the temp gauge and nothing changed.  I bought the same pug that I had in it previously, but I gues they could have given me the wrong ones.  I don't know how to check that, though.  They were the same lenght, size and shape.

I am wondering if the sensor itself might be bad, but I don't know how to check it.

I will continue to check the connetions in the system.

thanks

[Possum79]

I would pull the sensor wire then try and start it. If I understand correctly that mAkes it like it's stone cold so they should stAy on long.

[arb]

You might want to pimp your glow plugs like so many of us have. Its in the FAQ... here a direct link:

http://vincewaldon.com/index.php?option=com_content&task=view&id=30&Itemid=28

[SolarSteve]

I would pull the sensor wire then try and start it. If I understand correctly that mAkes it like it's stone cold so they should stAy on long.

Yes, pulling the connector will make it think it is cold, but I would like to know what is wrong so that I can fix it and not have to pop the hood to unplug and re-plug in the connector under the certain conditions that I am experiencing this problem.  Also, just leaving that connection off will cause the glow plugs to glow for the longest amount of time every time I go to start the car causing them to burn out much faster.

[SolarSteve]

You might want to pimp your glow plugs like so many of us have. Its in the FAQ... here a direct link:

http://vincewaldon.com/index.php?option=com_content&task=view&id=30&Itemid=28

Thta is a nice link, but I don't believe it will cure the problem I am experiencing.  Also, it does looks very nice, but what exactly do you benefit by performing this?

[92EcoDiesel Jetta]

You might want to pimp your glow plugs like so many of us have. Its in the FAQ... here a direct link:

http://vincewaldon.com/index.php?option=com_content&task=view&id=30&Itemid=28

Thta is a nice link, but I don't believe it will cure the problem I am experiencing.  Also, it does looks very nice, but what exactly do you benefit by performing this?

Have you read everything in that link? Here are the benefits:

IMHO there are several weaknesses in the original VW IDI glowplug harness, including:

the full amperage of the circuit (50 amps or so) passes thru the firewall and thru the connectors in the fuseblock
the copper buss bar makes removing the glow plugs a pain since you have to completely remove the 8mm nuts
the copper buss bar makes troubleshooting a pain since all plugs are connected in parallel
the 50A fuse is prone to hairline fractures that takes out all your glowplugs
the glowplug relay itself is *extremely* expensive
the length and gauge of the factory wiring results in a reasonably significant voltage drop to the glow plugs... I've measured below 9V at the plugs when the battery was delivering 12.5V
 

 

Ergo, this design has the following features:

el-cheapo garden tractor relay carries all the current and protects the contacts of the expensive glow plug relay
all the heavy duty current travels via short wires in the engine compartment to minimize voltage drops
all the heavy duty current travels via over-designed wire gauges to minimze voltage drops
separate fuses provide individual protection and prevent all plugs from being disabled at once
separate and easy-to-remove fuses  make it quick to continuity or current-test each glow plug individually
color-coded wires make it easy to trace which glow plug is which
modified connectors at the glowplug allow removal without removing the 8mm glow plug terminal nut

In a previous post, I pointed out to you that the 2 senders on the coolant flange are different. You stated yours are the same. Well that may be a cause of your problem.  I think you also said you do not have an ohmmeter. If that's true, it may be difficult in troubleshooting the problem, unless you are content with replacing parts by trial and error.

[Possum79]

Let me clarify what I was getting at. I was on an iphone and I cant type for crap on it. If you pull the wire and let them stay on for 20 seconds then try and start it. If it starts good you know your plugs are getting good glow and that sensor is probably toast. If it still doesnt start for crap then your sensor is probably fine. If it still starts like crap check out your gp fuse and make sure you actually get power to the bus bar. Easiest way to tell if they work is pull the injectors and watch them glow. if you still get power and everything then your relay could be crapping out timing wise.

Please correct me if Im wrong but thats what I have been lead to understand.

[92EcoDiesel Jetta]

Pulling the connector is a good test. Clipping a test light across the glow plugs will let you see exacly what's happening.

[SolarSteve]

In a previous post, I pointed out to you that the 2 senders on the coolant flange are different. You stated yours are the same. Well that may be a cause of your problem.  I think you also said you do not have an ohmmeter. If that's true, it may be difficult in troubleshooting the problem, unless you are content with replacing parts by trial and error.

I never told you that I did not have an ohmmeter.  I never said that the 2 sensors were "the same", but that the connectors will fit in each position.  I don't replace parts by trial and error and I try to troubleshoot as much as I can before posting, which is most certainly something you should try to do once in a while.  

I only posted this glow plug problem because I have found nothing like it in any of the FAQ's.  On top of that I have been extemely busy lately and thought that there might be a simple solution to this problem.

[SolarSteve]

Let me clarify what I was getting at. I was on an iphone and I cant type for crap on it. If you pull the wire and let them stay on for 20 seconds then try and start it. If it starts good you know your plugs are getting good glow and that sensor is probably toast. If it still doesnt start for crap then your sensor is probably fine. If it still starts like crap check out your gp fuse and make sure you actually get power to the bus bar. Easiest way to tell if they work is pull the injectors and watch them glow. if you still get power and everything then your relay could be crapping out timing wise.

Please correct me if Im wrong but thats what I have been lead to understand.

Thank you for your input.

I will try your suggestion the next time this occurs, but I felt like the fuse and bus bar are ok due to the fact that it works fine when cold and I checked the fuse.  I have not had the time to mess with this much lately because I have been very busy and the car is running, but I think it is going to be a sensor or relay issue.  Being that it only happens when "warm" I am leaning more towards the sensor, but I want to be sure before I pull it.

[maxfax]

If I remeber correctly the resistance for the temp sender for the glow plugs should be from around 270 ohm cold to about 150 ohm @ operating temp (around 190 deg F)... These reading where taking from a MK1 but should be about the same though the years..     

Acutally it sounds like the glow plug system is doing as it should possibly..  About how long is it sitting till you restart? Normally once the coolant temp is around 130 the glow plugs no longer cycle..

[SolarSteve]

If I remeber correctly the resistance for the temp sender for the glow plugs should be from around 270 ohm cold to about 150 ohm @ operating temp (around 190 deg F)... These reading where taking from a MK1 but should be about the same though the years..     

Acutally it sounds like the glow plug system is doing as it should possibly..  About how long is it sitting till you restart? Normally once the coolant temp is around 130 the glow plugs no longer cycle..

This problem only reallyt happened once where it was very noticable.  I drove the car to a diner last Monday.  By the time I got there it was at full operating temp.  I ate and left.  It was probably sitting for about 30 minutes.  When I went to start it, I noticed the glow plug light did not come on, which it normally would have after that long of a stop.  I pressed on and went for a start and experienced the very long crank time and lots of white smoke.

I think this may have happened one other time, but the stop time was shorter so it was as dramatic.

Thank you for the ohms for the sensor, I will ring it out as soon as I can.