2.5TDI Glow Plug/Starting Problem

[Zinraf]

Hello!

I've been having an unusual problem with starting my 2004 A6 2.5TDI Quattro for a while now, which I believe to be related to the glow plugs.

When the engine is completely cold (Not been driven for a day or so), I turn the ignition and the glow plugs run for about 10seconds, and then the car starts spot on. If I go to start my car up within a few minutes of switching it off, again it'll start fine. However if I go to start the car after it has being sat for a couple of hours (So engine is almost completely cold - but I'm guessing still a tiny amount of residual heat), the glow plug light comes on, and then goes off after about half a second (Even if I try running it a few times). At this point when I go to start my car it takes approximately 30-60seconds of turning over for it to start! (Which I find very disconcerting, especially when the start motor starts spinning slower and slower...).

I've read about a glow plug relay causing starting issues, but it was all vague information in a different forum, so hopefully someone here might be able to help me solve this issue (Especially now that winter is coming.)

Many Thanks,
Jon

[grant19841]

Hello!

I've been having an unusual problem with starting my 2004 A6 2.5TDI Quattro for a while now, which I believe to be related to the glow plugs.

When the engine is completely cold (Not been driven for a day or so), I turn the ignition and the glow plugs run for about 10seconds, and then the car starts spot on. If I go to start my car up within a few minutes of switching it off, again it'll start fine. However if I go to start the car after it has being sat for a couple of hours (So engine is almost completely cold - but I'm guessing still a tiny amount of residual heat), the glow plug light comes on, and then goes off after about half a second (Even if I try running it a few times). At this point when I go to start my car it takes approximately 30-60seconds of turning over for it to start! (Which I find very disconcerting, especially when the start motor starts spinning slower and slower...).

I've read about a glow plug relay causing starting issues, but it was all vague information in a different forum, so hopefully someone here might be able to help me solve this issue (Especially now that winter is coming.)

Many Thanks,
Jon

The starter turns slower on the final 30-60 seconds attempt,

I would say check the battery voltage first with a multimeter, as old battery cells die in the cold wether. You should see 12.5-14.5 volts on a good battery for start up.

I know you say the car starts first time every morning but I'm wondering if the car battery losses charge fast on short journeys rather than long, so give a multimeter a try first to rule out the battery.

Also a worn starter can withdraw too much current and spin the starter motor slowly preventing the engine turning fast enough, so you could check that current too which will be between 13.5-14.5 for a decent healthy current.

The other problem is it could the glowplugs, when worn they take longer to heat up but usually the light stays on longer and actually modern combustion engines are very rarely affected by the gp's nowadays as the combustion chambers create plenty of heat those self.

I'm thinking more along the lines of the battery or starter motor.


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[grant19841]

Also check all connections between the battery and starter are clean and good


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[bluezie]

A TDI engine should start without glow plugs unless the air temperature is well below freezing. If it needs glow plugs, then they are masking another fault.
No TDI I have owned, or used or been driven in has needed glow plugs.
My A6 AKE engine glow plugs have all blown, and been like that for many years, and it starts virtually smoke free every time first go. It does take a couple of goes to start it when minus 5 or colder!

[amiram]

Hello!

I've been having an unusual problem with starting my 2004 A6 2.5TDI Quattro for a while now, which I believe to be related to the glow plugs.

When the engine is completely cold (Not been driven for a day or so), I turn the ignition and the glow plugs run for about 10seconds, and then the car starts spot on. If I go to start my car up within a few minutes of switching it off, again it'll start fine. However if I go to start the car after it has being sat for a couple of hours (So engine is almost completely cold - but I'm guessing still a tiny amount of residual heat), the glow plug light comes on, and then goes off after about half a second (Even if I try running it a few times). At this point when I go to start my car it takes approximately 30-60seconds of turning over for it to start! (Which I find very disconcerting, especially when the start motor starts spinning slower and slower...).

I've read about a glow plug relay causing starting issues, but it was all vague information in a different forum, so hopefully someone here might be able to help me solve this issue (Especially now that winter is coming.)

Many Thanks,
Jon

I do not think it's a problem of glow plugs, It is more likely that the Ignition timing valve in the Injection pump Gets stuck.

[ametlib]

It is more likely that the Ignition timing valve in the Injection pump Gets stuck.

But when he starts from cold the timing piston works fine ? I,ve had exactly this fault and it turned out to be a faulty VP44 injection pump. .
The one thing you can do is to advance the timing a couple of degrees and check the fuel supply to the injection pump ( tank pick up, fuel filter, thermostatic valve on filter) If that don't do it, you need a new injection pump ( or at least new seals in the old one)

[Vagnuts]

A TDI engine should start without glow plugs unless the air temperature is well below freezing. If it needs glow plugs, then they are masking another fault.
No TDI I have owned, or used or been driven in has needed glow plugs.
My A6 AKE engine glow plugs have all blown, and been like that for many years, and it starts virtually smoke free every time first go. It does take a couple of goes to start it when minus 5 or colder!

althought the glow plug light comes on all of the time--they dont start to heat unless it is below 5*

[niall campbell]

For me its back to basics and tonights UK wide frost will be a good test

1) Check battery for dud cell (s) for free
2) Check cranking speed of starter
3) Consider new glow plugs ...................... the light should not stay on for 10 seconds