2003 Jetta cold start problem

bkrahmer · October 27th, 2007, 16:16

Now that it's getting cold, my Jetta is not starting well. I started having this problem last spring, and at that point, I checked the resistance on all of the glow plugs, and they were fine. I am not getting a check engine or MIL. I really dug into it today. A couple years back, when the car was under warranty, the glow plug harness was replaced. I have the 4-wire version. I checked the resistance on all four wires at the loom connector, and there were no open circuits. I believe I had the coolant temp sensor disconnected at that point, and when I checked the power side of the 4 pin connector with a test light, I got nothing. I have a '99 Beetle Bentley manual, but not an '03 Jetta manual. I was hoping to find a 180 relay on the relay panel (as on the 99), but the space is empty. I pulled relays one at a time, and the only one that prevented the glow plug indicator light from coming on at all was the 109 power supply relay. When that one is pulled, the engine won't start at all, because I believe it also powers the ECU.
Is this the same relay that powers the glow plugs? Is it possible that part of the relay is bad causing my problem? IIRC, there were five leads on that relay, but I'm not good enough with relays to test it properly.

thanks,
brian

paramedick · October 27th, 2007, 16:43

First question I have is what is your timing set at? If it's low, it will make the car harder to start.

bkrahmer · October 27th, 2007, 18:46

That's an interesting question, but I think it's unrelated. I already know I have no juice going to the glow plugs. I've never checked the timing, but it starts in about a 1/4th of a second when it's warm.

Mark of Diesel · October 27th, 2007, 19:08

It's actually quite related and very important. Paramedick knows his stuff, honest. This is always one of the first questions asked when cold start problems rear their ugly heads along with the GP questions. If the timing is too retarded, the cranking time gets longer as the temp drops. I'm not sure about your relay questions but if the GPs are working, I'd say check the timing and if needed, adjust to a somewhat more advanced setting and possibly check the function of the coolant temp sensor. Good luck!

Matthew_S · October 27th, 2007, 19:16

The absolute first thing you should always do when there is a cold start problem is check the timing. The reason you don't have power to the glow plugs is probably because it isn't cold enough to need them.

I've talked to so many people that have thrown all kinds of parts at their car trying to fix a cold start problem when all along the timing was off. People replace glow plugs, glow plug harness, glow plug relay, the battery, install a coolant heater, oil pan heater, battery warmer, 0-w30 oil, you name it and they needed was a timing adjustment.

bkrahmer · October 27th, 2007, 19:18

I appreciate the information, but I'm just looking at it from an analytical point of view. I have a cold start problem. The first thing I checked is the GPs, and there is no juice. Why would I start looking at other parts, when I know there is a problem with the GPs?
I know that the temp sensor is working, as when I disconnected it and cycled the key, the glow plug time (indicator light) went from 2 seconds to 15 seconds.
I'm at about 67k miles now, so I wll probably be replacing the timing belt next summer.

thanks,
brian

Matthew_S · October 27th, 2007, 19:20

Did you check for voltage at the glow plugs with the CTS disconected?

bkrahmer · October 27th, 2007, 19:31

In the '99s, glow plugs are used at temps below 48 degrees. I don't know if that's changed. It got below freezing last night, and when I was working on the car, the coolant couldn't have been over 40. As I mentioned, I did do testing with the coolant temp sensor disconnected.
I first just pulled a couple of the GP connectors and checked for voltage. I got 0. Later, I disconnected all 4 connectors, and got 12V, dropping to about 6.25V after the circuit was shut down by the ECU. That was using a DVOM, though, and I think that it was just getting milliamps. That made me think the harness might be bad again, which was when I started digging into the wiring loom. When I got at the loom harness connector, there wasn't enough amperage to light even a small test light. I didn't bother to measure voltage at that point.
I am still just looking for basic info about the relay. Anybody have a Bentley manual with a wiring diagram to confirm that the glow plug circuit runs off the 109 relay?

thanks,
brian

Matthew_S · October 27th, 2007, 19:50

If there is a problem with the glow plugs or glow plug harness it will almost certainly set a code. If relay 109 isn't working the glow plug light will not come on at all and the car won't start. Relay 109 does not power the glow plugs.

It sounds to me like there may not be a problem with the glow plugs. You should find a way to get your timing check before you spend too much time on this. I really think that is your problem.

bkrahmer · October 27th, 2007, 22:18

So what relay powers the glow plugs? I can't explain it any other way. If there's no power at the wiring harness connector, how can it be the wiring harness or the glow plugs? Common sense always comes first. Besides that, I have already tested the harness and the glow plugs. Anybody have a Bentley manual that can answer my question?

Matthew_S · October 27th, 2007, 23:50

2002 and newer have a "glow plug control module" (J370). Here is a thread on a problem very similar to what you are having. The fix was never posted but there is some good information that might help.

http://forums.tdiclub.com/showthread.php?t=128147

bkrahmer · October 28th, 2007, 00:14

Big ups to my main man ... Matthew. I will see if I can locate that 'controller' tomorrow, and do some investigative testing.

thanks,
brian

bkrahmer · October 28th, 2007, 13:29

Well, looks like it wasn't timing after all, eh?

Seriously, though, thank you to everybody for attempting to help. The 'controller' was totally melted, although the connector looks salvagable. From what I can tell, I still am getting a signal from the ECU on one of the pins, I have a ground, and an 8 or 10ga power pin that still has juice. Hopefully they have updated this part with one that won't nearly start a fire if it goes again.

brian

Matthew_S · October 28th, 2007, 13:41

Yeah, but did you check the timing?

vdubdezl · November 4th, 2007, 18:01

where do you check the timing at? With a diagnostic computer or can you check it at the pump?