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prb78

Diesel starting problems!!

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Hi All,

I have been a starting problem with my 2000, 1.9tdi (90hp) Octavia for nearly a year now. So far i have replaced all 4 glow plugs, and yesterday i replaced the coolant temp sensor (green cap type). Nothing has cured my problem. Any suggestions please? I am now running out of patience.

The glow plug light in the car is coming on but doesn't seem to stay lit for very long on a cold morning, and sometimes on a hot day the glow plug light stays lit for ages and she fires up easily! Once she gets running on a morning there is a noticable misfire at around 1500 rpm, very lumpy! You can hear the glow plug relay clicking in and out on acceleration so i didn't suspect this, or could it still be at fault?? Also she has recently become abit smoky on regular driving. She has 100k on the clock and regularly gets blasted up and down the A1.

Please help me!!!!

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Based on the behaviour of my car (and one my dad used to have), I think the problem may be with the glowplug control box, or possibly the main engine management computer if the car's smoking.

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Thanks for the reply. Is the glow plug control box the same as the relay? or is that something totally different? Could Vag com software tell me if it is faulty?

If so, is there anyone with this software near Newcastle upon tyne?

If it is the control box, is it expensive to renew?

Cheers

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Hi PRB78 -

I don't want to sound as if I am knocking this forum , but I asked almost exactly the same question a couple of days ago and have had Zilch answer.

I am surprised as there is a number of queries in the archive with much the same symptoms, and no-one has come up with the answer to where this damn relay is - or in deed if there is such a thing as the "Glow Plug Relay".

Come on chaps, there are guys out here with a problem - surely someone can come up with a definitive answer.

Slightly p*****d off

Rob

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The control box is exactly that, a control box. I'm an amateur, with a bit of knowledge, so I don't know exactly where it lives.

Rob, I'm just back from 2 weeks hols, and only read today and yesterday new posts.

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When I start my car and drive off for the first mile or so I get a relay click at around the 1500rpm mark and then another one around 2000rpm (iirc). After a few miles this stops happening. Not sure what relay is doing this, but the sound comes from the fuse box area - not sure if that is of any help.....

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Sorry to hear that Rob.

Most users, myself included, search under "new posts". If you don't get time to read them all, then they disappear next time you click "new posts".

It might be good to :bump: the thread if you don't receive a reply!

For the starting problem, does sound like a temperature sender at fault. Where abouts in the country are you? There might be a friendly Briskodian nearby with VAGCOM who can do a diagnostics scan for you.

Hope you both get your problems sorted.

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Sorry to pull the spotlight off rob but after all it is my original post!!

I have changed my temp sensor to the green cap type and it is still the same. Do i need to disconnect the battery to reset the ECU after fitting the sensor? Temp guage now behaving itself, but still runs like a bag of poo, and won't start very easily on cold mornings!

Has anyone in Newcastle area got vag com that could help me out!!!!!!!!!!!!

Help Please !!!!!!!!!!!!!!!!!!!!!!!!

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My sincere apologies, PRB78 - I regret I didn't read your mail properly and just assumed that it matched mine and was the relay, but your's sounds as if it OK as you can hear it operating. I certainly didn't mean to highjack the post and was just trying to stir up an answer !

Just out of interest - and it may not be related at all to the poor running, but have you tried replacing the Mass Air Sensor. It's very easy to do and does have quite a significant affect on the mid range revs. It doesn't seem to contribute to poor starting unfortunatly in my experience.

Rob

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:)Once you've got it running and the misfire has cleared does it go alright? Is the performance up to scratch? Is the fuel consumption OK? Does the engine burn oil or sound noisier than usual? Has it been serviced, fuel filter been replaced? When was the cam belt last changed...might have slipped a tooth maybe?

To anyone that knows better than me....should the glow plug relay be clicking in and out on acceleration? That doesn't sound normal to me....I'd have thought it was a cold starting device rather than something that should cut in and out during acceleration?

Hi All,

I have been a starting problem with my 2000, 1.9tdi (90hp) Octavia for nearly a year now. So far i have replaced all 4 glow plugs, and yesterday i replaced the coolant temp sensor (green cap type). Nothing has cured my problem. Any suggestions please? I am now running out of patience.

The glow plug light in the car is coming on but doesn't seem to stay lit for very long on a cold morning, and sometimes on a hot day the glow plug light stays lit for ages and she fires up easily! Once she gets running on a morning there is a noticable misfire at around 1500 rpm, very lumpy! You can hear the glow plug relay clicking in and out on acceleration so i didn't suspect this, or could it still be at fault?? Also she has recently become abit smoky on regular driving. She has 100k on the clock and regularly gets blasted up and down the A1.

Please help me!!!!

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Actually Dave, and this might help someone, I don't get the relay clicking sounds that Matt reports, and I've been listening since he first raised the issue. He's a mate, specifically the one who introduced me to Briskoda.

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The relay is not a control box. Control of the glow plugs is goverened by a map in the ecu, ABOVE 9c they do NOT come on. The brief 1 second glow plug light is not a glow plug light, but an indication that the ECU has power. If it's over 9c and the glow plug light is staying on, wiring or temp sensor is likely issue.

Clicking when cold may be due to the glow plugs coming on for afterglow which afik is only at low revs.

You NEED a full fault scan or it's like probing a patient with a needle blind.

It's also easy to test the glow plugs via resistance test, in situ. Likewise easy to test power to glow plugs, providing that the engine is cold below 9c outside.

It's also possible to alter the map via adaptation in vag-com to alter the glow plug period. I set them to come on longer and even at much warmer temps for my customers with biodiesel/oil powered cars that don't start as well as diesel.

Greg.

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The relay is not a control box. Control of the glow plugs is goverened by a map in the ecu, below 9c they do NOT come on. The brief 1 second glow plug light is not a glow plug light, but an indication that the ECU has power. If it's over 9c and the glow plug light is staying on, wiring or temp sensor is likely issue.]

Greg - can I query why you are saying "below 9C they do NOT come on". Is it possible you've written that the wrong way round ? That is "above 9C they do not come on" !!

This is all rather confusing as regardless of temperature, the vehicle starting is not good - ie it's been OK through the summer but definitely poor the last two months.

We haven't really got to many days below 9C but regardless the starting is poor and results in a cloud of oil fumes when it does fire up. My instinct was that the plugs were not doing their thing but you are seemingly stating that only when the days grow distinctly colder do they kick in.

Any chance of you giving some suggestions as to what to look for. Mileage is 67K on an X reg 1.9Tdi.

Cheers

Rob

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Hi again,

I have changed my temp sensor and the temp guage now behaves itself. When the car is cold, regardless of if it is summer or winter, it is a pig to get going (worse in winter though for obvious reasons!) when it does cough into life it spews white diesel smoke out the back and between 1000 & 2000 rpm it has a real misfire so you have to rev it to pull away without stalling. I intermitantly hear the relay clicking, but not all the time from cold. When the problem first started i changed the glow plugs, this also had no effect.

Should i start by changing the relay? or should i get someone to run a fault scan? If it is a fault in the ecu can it be fixed? or does it mean a new ecu? If so how much are they?

Sorry so many questions but i want to solve this problem! its driving me crazy! apart from that i cannot fault the car, it has been great! racked up over 50k in the last 18 months no problem!

Cheers

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Hey rob, yes I apologise I was tired I mean ABOVE 9c they do not come on!!! thanks!

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Ive just had similar problems to those described on a Golf mark4 TDi 90bhp.

The problem now appears to be cleared

We changed relay 109 from the fitted black relay to the new grey one.

We also noticed that their was a large amount of air bubbles in the diesel supply line. After investigating this we changed the fuel filter and also the small valve which plugs in the top.

After changing the valve in the top the number and size of the air bubbles reduced significantly.

I understand it is normal for some air bubbles to be present, but in our case these were more than normal.

Hope this helps others with starting problems

Dougal

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Dougal

What source of information do you have that identifies relay 109 ? And what part number is it - equally is there a parts list available somewhere?

I will admit to a degree of confusion as did get information copied from an Autodata manual that suggested that the white relay '103' was the relevent item. This has been written on as being the 'Fuel pump and glow plug relay'.

Rob

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The part number of relay 109 is 1J0 906 381A and is listed as being in position 12.

It is a well known problem on the TDi's and it is recomended that you change it if it is the black one. Just do a google search for relay 109.

Did you look at the amount of air bubbles in the fuel line, I think our problem was caused by the valve in the plastic tee piece in the top of the fuel filter.

Dougal

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I had a duff relay 109 on my 1998 TDI which caused the engine to occasionally cut out (usually at the most inconvenient time!). After a short time the engine would restart and run fine. The problem was diagnosed by my neighbour who was at the time a VAG mechanic, as a common fault caused by the failure of a PCB track. Close examination of the old relay after replacement confirmed this.

However, this would not have caused the starting problems described in earlier postings.

Coincidentally, my Octavia became gradually more and more sluggish on the starter motor, turning over extremely slowly in cold conditions, a problem which still has not been solved to this day by the present owner, my son. Indeed, as I post this message he is still trying to get to the bottom of it. A new battery did not provide a solution.

However it may be of interest to others to point out that some little time ago, when the car was serviced by a local garage it was reported by them that the glow plugs were loose and they had tightened them up. My son noted that starting did improve. Nonetheless, the starter motor did not spin the engine over very quickly (not that he expected tightening the glow plugs to affect this anyway!)

Has anyone else had the "sluggish starter motor" problem? Any help would be appreciated.

Dave

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OK, a summary of all what I'm getting from this thread !

The glow plug time is controlled by the ECU - above 9 C the glow plugs do not operate. Under normal summer conditions the glowplug light is just an indication of ECU operability, but does light longer in the winter, which it is now doing.

Relay 109 has been seen as a culprit, but as this controls the ECU - ie causes cut-outs if it is faulty - and I don't have any problems in that area, that's not the problem. And my one is not the black type.

What is still not clear is which relay is driven by the ECU to switch on the glow plugs. I have investigated the relays in the relay block below the steering wheel and they all seem to switch with the ignition switch.

I haven't pursued the bubbles in the fuel line yet, partly because, now that it is colder, the engine is starting better ! It wasn't made clear in my original post that once started the engine runs fine, and fuel consumption is the normal 11 to 12 miles to the litre.

There is no problem with the starter motor or battery.

Cheers

Rob

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