Hello,
I have a glow plug question.
Car: A4 tdi 90BHP 1996 Non-PD 1Z engine.
The glow plugs only seem to stay on for a second, may be two at the most, which makes (made) starting a real pain first thing.
I have checked all the glow plugs and they are working fine, I know the plugs are only staying for a couple of seconds because I have put my multmeter across them.
Now, IF I disconnect the coolant temp sensor from by the thermostat the plugs stay on for approx 20 seconds regardless...this makes me suspect the sensor is faulty, however how do I check for sure?
I have a VAG-com unit but are only running the free software. I have taken a look and checked all the coolant parameters and they appear to be reading correctly....does anyone know if the thermostat sensor is 'just for the glow plugs' Will it have any adverse effect if the sensor is disconnected whilst driving?
I plan to get another sensor shortly but I wanted to check I had covered all my bases before getting one.
Also, injection pump timing, a while ago I was told these are 'adjustable' and has an effect on the car starting (screwloose was it you?).....I will be doing the cam belt week....
Thanks
H
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hm
Yes; TDi timing is adjustable on the injection pump pulley - but only if there's three small bolts in slots. You should be able to check it dynamically using VAG-Com on the adjustable ones. If the timing is out of range, then it makes them a pig to start cold.
The glow-timing is controlled from the engine ECU. If the ECU is showing a correct coolant temp reading, but still switching off the glow-plugs' relay too early, then it looks like a software issue..... Odd.
The ECU coolant sensor affects the fuelling map too. The ECU can then modify the amount injected.
Don't forget a new seal and clip when buying your [colour-coded] sensor.
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screwloose,
If the coolant sensor a common fault...if it is faulty would it upset the balance of the car? I do not think the timing is out because I simply would not cause the plugs to go out so fast?
I only have the free version VAG com so I do not think I ca check the timing anyway.
I find it very hard to belive the software is wrong......I guess the best thing is to get a temp sensor, but I still can not understand why the temp reading the VAG look about right unless VAG looks at another sensor for the reading?
Do you know if GSF do the sensors?
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Eurocarparts do the sensors for about £16. I'd just replace it and be done with it. The new one comes with the O-Ring. Be careful not to break the clip, otherwise you can't drive the car to get a new one. Take the lid off the coolant tank to release the pressure, then put it back on before you pull the sensor. (to stop it emptying)
To see the diagram, register on ...
www.vagcat.com
then go straight to
www.vagcat.com/epc/cat/au/A4Q/1996/157/49/1767219/
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Thanks you so much....man I love this website, everyone is so helpful..I have just been on a popular Landrover site...the only help I get there are smart comments and no real assistant at all.....
Will post my question here.
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hm
Coolant temp sensor is a very common fault. Both the gauge half [erratic dash gauge] and the ECU sensor half [bad cold starting etc.]
If the sensor is reading correctly on VAG-Com, that is the ECU sensor half that it's reading; but is that with engine hot or cold? Very common for it to go doolally at one extreme or other, but read OK otherwise. Agreed; software issue is very unlikely.
Don't know if GSF do one; I'll never use anything but dealer parts - been there; know better now!
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Glow plugs only work below 5 degrees don't they?
When you fudge the GPs into operation does the car start better?
Has the car had a timing belt fitted recently? They're known for jumping teeth on the pump after a few thousand miles, bosch belts in particular.
Have you checked for fuel draining back into the tank after standing for a while? Look for poor pipe connections and crazed fuel lines.....This lead me a dance for 9 months
Does the engine turn over fast enough to start? An aging battery, poor battery, earth connections or worn starter will give poor cold starting
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I have a petrol A4 where the engine management light came on and was diagnosed as the coolant temp sensor. No effect on temp gauge but, although I thought the car was driving all right, it is much more responsive now atl ow revs so obviously affecting the fueling.
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Aretas
That would fit; it's a double [4-pin] sensor on most VAG cars - one thermistor for the gauge and a separate one for the ECU [and the CAN network on the later ones.]
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