MK4 Golf TDI starts from cold with temp sender disconnected

[peteheat]

Hi,

I have a MK4 golf TDI (110bhp) on a 1998 plate that has problems starting from cold but not when warm. Glow plugs and battery are new.
When cold the glow plug symbol on the dash goes out just as quickly as when it is warm and the car struggles to start. However if I disconnect the coolant temperature sender the symbol stays lit for some time. When it finally goes out the car starts absolutely fine.
I assumed therefore that the coolant temperature sender is not working and bought a replacement. This has not rectified the problem and the car starts first time in the cold only when the sender is disconnected.
Does anyone have any ideas on what is causing this problem?

Many thanks in advance!

[andy-b]

Hi,

I have a MK4 golf TDI (110bhp) on a 1998 plate that has problems starting from cold but not when warm. Glow plugs and battery are new.
When cold the glow plug symbol on the dash goes out just as quickly as when it is warm and the car struggles to start. However if I disconnect the coolant temperature sender the symbol stays lit for some time. When it finally goes out the car starts absolutely fine.
I assumed therefore that the coolant temperature sender is not working and bought a replacement. This has not rectified the problem and the car starts first time in the cold only when the sender is disconnected.
Does anyone have any ideas on what is causing this problem?

Many thanks in advance!

i had the same problem, and i sprayed contact cleaner into the water temp sender plug as two pins looked rusty. it worked a treat.

[Crasher]

If you have a fault code read done you will find you have a faulty coolant temp sender code stored. Have this code deleted and see if this helps.

[Alex Himself]

Hi,

Wouldn't mind checking for rust with mine also. sometimes when cold it can struggle a little. Where abouts is the water temp sender plug? And, is it easy enough to just remove and plug back in?

Cheers

Alex

[andy-b]

Hi,

Wouldn't mind checking for rust with mine also. sometimes when cold it can struggle a little. Where abouts is the water temp sender plug? And, is it easy enough to just remove and plug back in?

Cheers

Alex

well i have an AHF engine in mine and it's at the right hand rear of the engine. (blue 4 pin plug in thermo housing). you just need to hold two clips on the plug and remove. easy to put back on too. mine was shait at starting when cold. took 3 or 4 turns. but since i done that with the plug it starts first turn when hot or cold.

[Alex Himself]

Andy,

Many thanks for the reply

Alex

[Alex Himself]

Had a quick look at this on mine and can't see a blue 4 pin plug. Should I be able to see this without removing anything?

Cheers

Alex

[andy-b]

Had a quick look at this on mine and can't see a blue 4 pin plug. Should I be able to see this without removing anything?

Cheers

Alex

yes its visible without taking anything off. unless you have a different engine type, but mine is an AHF.

[Crasher]

Alex, what year and engine is your car?

[Alex Himself]

Bora TDI 110bhp 1999

Cheers

[Crasher]

For 99 it changed slightly. The sender is still on the left side of the engine (viewed from inside the car) over the top of the gearbox and under the servo vacuum pump. It is located in a black plastic water outlet and in 99 the switch changed to being green (although originals are sometimes black with a green paint mark) and the wiring connection changed from the square type with a metal clip and ears sticking out that you squeeze to release, to a D shaped connector with no visible release clip. If you don’t know how to release these connectors, you can break the retaining clip. If you look closely at it you will see a raised section with a flat vertical (to the line of the connector) lip at the back, if you push the connector down and pull back and down the lip at the same time, it will come away. Do not force the connector or you will break it and it is a specialised job to replace.

[Alex Himself]

Hi,

I have just driven my Bora for 30 mins, which then makes it 4 to 5 seconds starting (warm). I then disconnected the sensor and it starts instantly. There are 4 metal contacts on the plug itself, 2 of which are rusty, 2 are completely fine. The glow plug light on the dashboard stays on for 3 times as long, about 6 or 7 seconds rather than 2 with the plug fitted.

Where does the fault lie, or do I need to check anything else?

Cheers

Alex

[andy-b]

Hi,

I have just driven my Bora for 30 mins, which then makes it 4 to 5 seconds starting (warm). I then disconnected the sensor and it starts instantly. There are 4 metal contacts on the plug itself, 2 of which are rusty, 2 are completely fine. The glow plug light on the dashboard stays on for 3 times as long, about 6 or 7 seconds rather than 2 with the plug fitted.

Where does the fault lie, or do I need to check anything else?

Cheers

Alex


spray some wd40 on the plug and try it like i did.

[Alex Himself]

Hi,

Doesn't seem to have done the trick on mine, still got the delay.

Any ideas?

Cheers

Alex

[Crasher]

Is it generating a fault code to do with the coolant temp sender.

[Alex Himself]

Hi,

Thanks for the response.

Last time I took my car for work at my local guy there were no fault codes then, about a year ago, and the problem has been present for about 3 years i've owned the car.
He doesn't use VAG COM however, I asked him today and it's a version for all cars he said. Would this make a difference?

I don't have the VAG COM programme.

Cheers

Alex

[andy-b]

Hi,

Thanks for the response.

Last time I took my car for work at my local guy there were no fault codes then, about a year ago, and the problem has been present for about 3 years i've owned the car.
He doesn't use VAG COM however, I asked him today and it's a version for all cars he said. Would this make a difference?

I don't have the VAG COM programme.

Cheers

Alex


if it worked ok whilst the plug being off i would say the temp sensor is faulty. the sensor must be giving out wrong signals. worth a try mate.

[Crasher]

The connectors in the plug are very awkward to change but really they should be if they are corroded.

[Alex Himself]

Hi,

Just been out and taken a few photos.

Is that rust or is is meant to be that copper colour?
http://i165.photobucket.com/albums/u75/alexb1985/Plug2.jpg

http://i165.photobucket.com/albums/u75/alexb1985/Plug4.jpg

http://i165.photobucket.com/albums/u75/alexb1985/Plug1.jpg

http://i165.photobucket.com/albums/u75/alexb1985/Plug3.jpg

[andy-b]

my plug was like that with two pins a copper colour. i would change temp switch to be honest. sounds like the switch is putting different signals to the ecu thus causing the car to take a while to start whilst warm thinking the engine is cold.

[Alex Himself]

Thanks for the help, has any one replaced this before, or know how to?

Is in the green part you are refering to?

Cheers

Alex

[Crasher]

That is the early plug, pre mid 99 and so the connectors are easier to change. I can't tell if that is rust, copper grease (which it looks suspiciously like on the plug) or gold plating. If I change those terminals, I always use gold plated versions. If you try and buy them from VW you get a terminal fitted to a piece of yellow wire which is supposed to be soldered in as they don't trust spanner monkeys to do the job properly, with good reason. I buy the terminals from Würth (they are made by AMP) and I crimp them on. Those earlier ones are much easier to do than the later micro timer connections.

[Alex Himself]

Hi,

Thanks for all the replies, much appreciated.

Would you reccommend that I get the green part and see how that goes, what is that part called? Also what is the correct name for the plug itself?
Is is a case of removing the current part and simply plugging a new one in? Would I need to disconnect the battery and drain some coolant from the engine?

Regards

Alex

[Crasher]

PM me your reg or chassis number and I will post the part numbers.

[Crasher]

That is the wrong sensor and plug for a 99 Bora, the sensor you have there is not the 059 919 501 A it should have and neither is it the earlier 059 919 501. Can you take it out and have a look to see what the VW part number is? Also, peel back that insulation on the wiring; I have a feeling there will be some soldering not far back, that isn't the original covering.

[Alex Himself]

Didn't have any luck removing that green part, does it just pull out, I gave it some stick. Should I expect coolant to pour out, its Horizontally orientated. Will try again in morn.

[Crasher]

You did slide out the clip? It then just pulls out and yes some coolant will be lost.

[Alex Himself]

Will have another crack when im off again. Car is booked in for Cam Belt, Break discs, pads, water pump and service next week. Bank balance won't be happy, but will have peace of mind. :D

Cheers

Alex

[Alex Himself]

Right, finally had a few minutes to have a go at this, the numbers on the green plug are - 059 919 501 (07-03) EH2 12V-140ma

As for the wiring, it goes back inside a plastic housing. Do I need to check this for soldering?

Cheers

Alex

[DEL_BOI]

i have this exact problem on my golf 115 2000, can someone tell me where my sensor is so i can check it please......

thanks

[Alex Himself]

On my '99 Bora its as per below. About halfway down into the engine. On mine it's a square type plug, as per photo on previous page and has metal clips either side which are squeezed together to release. (Photo is not my car BTW)

http://i165.photobucket.com/albums/u75/alexb1985/png.jpg

[andy-b]

i have this exact problem on my golf 115 2000, can someone tell me where my sensor is so i can check it please......

thanks


it should be on the rear right side looking at your engine. attached to a black plastic housing. should be a blue sensor with metal clips holding it on. the multi-plug on it should be a 4 pin one.

[DEL_BOI]

thanks for the help i shall check that out and see how it goes;)

[DEL_BOI]

well i tried this and it didnt really help me the light stayed on for longer and i thought i was on to something but sadly not......:zx11: the car still took a 2 attempts to start...

also found out that its misfiring on one cylinder when starting from cold it came up on vagcom as a fault id say it takes about 30 seconds before the last chamber ignites.....

[Crasher]

What was the fault code number?

[redmax90]

i have got a bit of hard to start problem from cold. I have a 90 ALH engine and usuually it takes a couple of turns before the car starts when its cold. i have no other problems with the car it runs great and starts ont he button when warm. ive had the coolant temp sensor replaced a while ago but it still can be a little troublesome to fire up int he morning. any ideas ? :confused:

[Crasher]

Does it pump black smoke out when it eventually fires up? If it does, fit a new set of glow plugs.

[redmax90]

well more greyish smoke. its odd because it would sounds like a car thats far past its best in the morning ..but its so not :p. you think i should try the glowplugs? ..i kno these things dont really use the plugs to start unless its below 5 degrees.

[Crasher]

They are used more than you think.

[DEL_BOI]

eh will get that fault code at the weekend cant remember it offhand.....and for the record ive replaced my glow plugs, oil, oil filter, and fuel filter... and mine can be a bit smoky to on cold mornings but its definatly not black smoke...

[DEL_BOI]

VAG-COM Version: Release 409.1-US
Control Module Part Number: 038 906 019 CJ
Component and/or Version: 1,9l R4 EDC 0000SG 1086
Software Coding: 00002
Work Shop Code: WSC 00012
2 Faults Found:
17664 - Engine Coolant Temp Sensor (G62): Open or Short to Plus
P1256 - 35-10 - - - Intermittent
16688 - Shareware Version. To Decode all DTCs
P0304 - 35-00 - Please Register/Activate


there you go just searched right now for faults and thats what came up...

[Crasher]

Have you replaced the coolant temp sender?

16688 is a misfire on cylinder 4, probably a faulty head harness.

[DEL_BOI]

ive not replaced the coolant sensor yet but im going to change it..... dont mean to sound stupid but whats a head harness....am i right in saying its the glow plug harness..:confused:

[Crasher]

The head harness is a wiring harness which runs inside the head on a PD providing power connection to the injectors from the plug on the side of the head. It is part number 038 971 600 and costs £42.17 from VW. It is quite easy to swap, you just have to remove the cam cover and disconnect the main harness from the side of the head.

[redmax90]

hey my car isnt a PD ..i dunno it kinda bothers me these lumpy starts ..once the car starts it runs fine. it just sometimes takes a few turns to fire up ..it starts perfect from warm. we've checked the timing and its fine..and the coolant temp sensor has been replaced..what else:confused:

[Crasher]

Take the glow plugs out and test them.

[redmax90]

ill do that ..it needs serviced soon anyway. ill get my mech to stick some new glow plugs in. hes a master tech from vw ..he reckons the older cars startin problems are sometimes down to the fuel temp sensor int he distribution pump. any ideas ? :p

[Crasher]

fuel temp sensor int he distribution pump

If it doesn’t come up as a fault code, “17570P1162 Fuel temperature sender-G81 Short to earth” or “17571P1163 Fuel temperature sender-G81 Open circuit/short to positive” it can be checked in Measuring Blocks 08, display group 007, display zone 001 where the reading should be approximately ambient temperature. A faulty fuel temperature senor makes it impossible to set the Commencement Of Injection (COI) timing.

[DEL_BOI]

right ill try changing the coolant sensor and if that doesnt work then ill try the head harness....

thanks for your help

[peteh23]

any luck with your problems guys?

as i seem to be having a similar problem.

[DEL_BOI]

Changed my coolent temp sensor last weekend and no luck:zx11: so am going to order a head harness next and see if this works....will keep yas updated ;)

[tony19]

i got same problem with my car. when is cold it struggle to start. and the glow plug light goes off in a sec.
someone told me that it could be the glow plug relay.
does anyone knows??

[tony19]

Will have another crack when im off again. Car is booked in for Cam Belt, Break discs, pads, water pump and service next week. Bank balance won't be happy, but will have peace of mind. :D

Cheers

Alex
any luck with your cold start problem alex??

[DEL_BOI]

ok update i have replaced my head harness and it has made no differance, im all out of ideas, ive turned to testing the heater plugs again and they dont receive any power on cold starts, i did a test for power when the orange light is on by dissconecting the temp sender and they get power ok but when the sender is connected and the engine is cold the light doesnt stay on long enough for power to heat the plugs. my dad is convinced it is the temp sensor but as i said earlier i replaced it with a genuine green vw one from VW SPEED. should i have bought one from the dealer????? or have i maybe got bigger problems than i thought :(

[redmax90]

hi, your glow plugs dont recieve enough power to heat them because the ecu recieves temperature signals from the temp sender that are above the threshold level. ie. the temp isnt cold enough to require glow plugs for your start. The glow plugs on the TDI engine are used for initial cold engine running in cold conditions, they are they to insure improved combustion and improve the emmissions when the engine is very cold. they are not used as a starting aid unless the coolant temperture is below 5 degrees i think. Anyway ..it seems your problem lies within the static timing of the fuel pump. Have the car checked on vag com..it will show the injection time in relation to the fuel temperature. It sounds like your car is a little retarded.. this causes no problem when the car runs because the ecu can adjust this..however the cold start requires the fuel to be injected at the exact time to insure a clean start. The TDI engine has a window of injection time and has a prefered injection time. I suggest you talk to your mechanic and consider having this altered. To do it properly while u have the car stripped..its wise to change the timing belt and tensioner and maybe the water pump if u want or if its needed. Im quite sure this is the base of your cause. Mechanic's may sometimes try to shy away from adjusting the timing staticaly because it can be quite a timing consuming job..changing the pump sproket postion..and checking via vag come and repeating until its correct. If you look for 'hard start' on www.tdiclub.com (http://www.tdiclub.com) im sure you'll understand more wat im getting at. But honestly..thats where your problem is. :)

[redmax90]

i beg your pardon ...:( ive just noticed your have a PD engine ..the advice ive given above only applies to thos with an older generation original TDI ..sorry

[veedub76]

Hi,
I have a TDI 110 AHF.I've had cold starting problems with my car.Had the battery tested that was fine.Had it serviced and hooked up to VAG-COM and no codes stored at all.Really bugged me for weeks.Being as i just bought it too i thought i'd been ripped off,but my mechanic said the glow plugs don't really need changing etc,so i thought i'd change them anyway and it worked .The car starts fine and i nearly went and paid for a new starter motor!!
Maybe glowplugs do more than you think and should be changed as they don't last forever.My car has 131k on the clock and the glowplugs were well knackered!
for £28 it was worth the try:D

[tony19]

hi.

i found out that we need to extend the glow time with vag com.

i will try this on my car as soon as i find a vag com

http://forums.tdiclub.com/showthread.php?t=123304

hope it helps guys.:D

[DEL_BOI]

ive got some more advice and ive been told to try the crank sensor!! so willing to give it a go an see. anyone had any problems with crank sensors?

oh and how do you extend the glow time?? as i have vag-com

[DEL_BOI]

oh i missed the link:Blush2:

:D

[tony19]

Did you try to extend the glow time DEL-BOI?

if yes let us know please.

[ini]

Extending the main glow phase, increasing startup fueling or coding as an auto box should only be used as a last resort, otherwise you are only masking the underlying problem.

[Alex Himself]

any luck with your cold start problem alex??

Sorry for the late reply Tony,

But no i've not done anything since replacing the coolant temp sensor, which had no luck, still got the 4 sec warm start delay.

Alex

[poor1]

Hot start has been a problem for a number of years. You will probably be aware of the hundreds of posts on the subject in TDI Club Forum. It is generally attributed to a mapping problem in the Engine Management System, which can be circumvented by by temporarily taking the temperature sensor out of circuit during the starting process, either by a manual switch or a relay arrangement. I am endeavouring to do this without cutting into the wiring harness by inserting a link between the sensor socket and sensor plug, but I need to get obtain a compatible socket & plug. You allude to "Wurth" connectors where can I get such connectors please?

The question regarding the connectors referred to above is directed to Crasher the cat man.

[Crasher]

You called :D

[poor1]

Please see my post Number 64. I was wondering whether you could assist. I have now found the Wurth web site and sent them a picture of the male and female plugs in the hope that they may be able to supply them. Having said that the socket into which the sensor is fitted appears to be a VW/Audi part, so without any further information as to the actual manufacturer of the part I am not raising my hopes that they will be able to assist, unless they are the actual manufacturers.

[Crasher]

Würth will want you to buy in silly numbers; I may have what you need in stock or be able to get them for you. Würth prices can make your eyes bleed!

[poor1]

Any progress with the plugs please?.

[Crasher]

The plug and pins for both sides are no problem; the socket to replicate the sensor is proving to be an issue.

[Crasher]

357 919 754 £3.76 is the plug, I have the pins for both sides in stock but I think you will have to cut up a temperature sender for the other half.

[poor1]

Excellent PM me. I have a temp sensor.

[Alex Himself]

Hi,

Woohay, my warm start problem has completely dissapeared! :fing02:

When I start now, hot or cold, it fires up instantly!

Symptoms: Good start from cold, 3-4 seconds, or so, from warm.
With temp sensor disconnected at warm, it started perfectly. Replaced sensor to no avail.

Fix: New battery (previous one was 10 years old).

Hope this helps, as it is a very common problem and an easy fix, if you have not changed this already.

Regards

Alex

[Crasher]

The trouble with these modern starter motors is that they crank over on a flat battery and confuse the diagnosis. I have known V6 4M’s crank over quite happily but with such low battery voltage the engine will not start.