I have a UK 1998 Audi A6 with the 2.5 V6 TDI engine, with 140,000 miles.
The engine does not start particularly easily when cold (even in summer) and often requires several goes on the starter motor until it catches on enough cylinders for the engine to run. Once running, the engine performance and fuel consumption is normal. If I try to restart the car 3 or 4 hours after it was last used, it starts perfectly.
Any informed ideas would be gratefully received. My own thinking is tired glow-plugs, but the a number of sources have said that these will only affect starting below freezing.
Dave
|
|
Glowplugs(or other systems)are needed to start diesels at all ambient temperatures;so you could well be right.
|
Agreed - I'd change the glowplugs and see how it goes.
|
|
A direct-injection diesel like yours shouldn't need glow plugs at all during the summer months. It sounds more like air ingress in the fuel line, or if the oil hadn't been changed often enough, bad compression when the cylinders are cold.
|
Actually, I read sean's comment that glow-plugs are not needed on VAG engines above +2 deg C ambient as AndyT suggests.
www.honestjohn.co.uk/forum/post/index.htm?v=e&t=15...3
He should be along tomorrow to suggest likely remedies. (He is the resident VAG guru). I bet he will say it is probably due to air getting into the system. And I would agree. (So does AndyT).
|
I am also reliably informed that there is a sensor named G62 which measures the coolant temperature. Apparently, this temperature reading is used to inject the fuel earlier in the cycle when the engine is cold. If the sensor is faulty then I guess this could also cause the problems I'm experiencing.
I would welcome comments from the resident VAG guru as to whether it is worth changing this sensor on a speculative basis?
|
Dunno if I would change the sensor on a speculative basis, it might (and probably will be) damned expensive, knowing Audi!
|
|
|
|
Big Dave,
I attach a print-out from VagCom of possibles:
VIN Number: WVWPD63B21P133337 License Plate: ABC 1234
Mileage: 99991 Repair Order: R30402001
Control Module Part Number: 4B0 906 018 CL
Component and/or Version: 1.8L R4/5VT G01 0001
Software Coding: 16551
Additional Info: WVWPD63B21P133337 VWZ7Z0Y3224122
10 Faults Found:
17931 - Crash Signal from Airbag Controller: Implausible Signal
P1523 - 35-00 - -
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent
16622 - Manifold Pressure / Boost Sensor (G31): Signal too High
P0238 - 35-00 - -
18320 - Pressure Sensor for Brake Boost (G294): Short to Plus
P1912 - 35-00 - -
17069 - ECM Power Relay Control Circuit (J271): Open
P0685 - 35-00 - -
18034 - Powertrain Data Bus: Missing Message from TCU
P1626 - 35-00 - -
18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 35-00 - -
18058 - Powertrain Data Bus: Missing Message from Instrument Cluster
P1650 - 35-00 - -
16497 - Intake Air Temp. Sensor (G42): Signal too High
P0113 - 35-00 - -
16502 - Engine Coolant Temp. Sensor (G62): Signal too High
P0118 - 35-00 - -
So, G62 is there, BUT:
If I were you I'd nip to the local VAG dealer and bung the fitter a fiver to get the diagnostics on it (2 mins work).
OR:
Go around the fuel system, looking for air leaks into the fuel. Try especially around the clear fuel pipe in the engine bay from filter to engine. Has it got air bubbles in it?
Glow plugs not in use at this time of year for a highly efficient, direct injection engine.
Let us know how matters progress.
|
Sean,
I actually know a friend of a friend who has the 3rd party VAG-COM software & cable on his laptop, so I'll have to speak nicely. He previously helped me diagnose a faulty Air Mass Sensor on my 98 Passat TDI in return for beer.
If he plugs in a VAG-COM, will it immediately diagnose that one of the sensors is faulty, or will it require interpretation of the readings to know that one is miss-reading?
Where is the diagnostic socket on an A6?
Of some of the faults you mention (e.g. signal from airbag controller), I don't understand how this would affect cold starting - or am I missing your point?
Kind Regards,
Dave
|
Big Dave,
I'm going to get into all sorts of trouble now.
I posted all this nonsense to show you how dealers make money out of people.
Look at the Pug-Cit post a bit deeper, a couple of postings above, and you will see the real solution to your problem.
It's air in the fuel and none of this malarkey.
I'm not giving you a direct answer, so look and learn. You'll feel a VERY warm glow when you fix it.
If you really can't, write back and I'll help you.
|
Oh, and Dave,
Get yourself a tub of Vaseline.
!!!!!!!
|
Sean,
Can you give me any pointers as to where in the engine bay I might find the fuel line on the 2.5 TDI engine. There are many different hoses and lines, but none of them appear to be clear on first inspection?
Dave
|
Big Dave,
You might think that I'm teasing you. I'm not. I'm trying to establish how much experience you have.
Yours is quite a common fault on most diesel-engined cars, of all makes.
Look for a canister, like an oil filter. You will see 1/2" diameter pipepork on the top. You should see a blue clip with pipework immediately under it.
These pipes are your fuel lines, and one should be black and one clear plastic from the filter to the rotary pump.
Never mind if they are black rubber, it just means that they may have been changed.
What you need to do is go round all of these pipe joints, where rubber meets metal, plastic etc, and smear your Vaseline over the interface to prevent air ingress.
Yours is one of my last posts here. I return to Germany on Friday night. Some may miss me, others won't.
Good luck mate.
|
|
Sean, they have got the internet in Germany, haven't they? Why no more BR just 'cause you're living it up on the continent? (I am one of the former. You make this place even more interesting.)
|
If this is the typical VW group diesel filter, it will be as Sean said, a cannister about 6" tall and 3" dia.
On top of the filter will be two right-angled metal pipes for fuel in and out, and also a tee fitting (for fuel return/recycle)made of plastic with a hose on either end. This tee piece has an O-ring seal and is held in place by an R clip.
I would say that this tee fitting has the most potential to let in air. As has been said, smother it in Vaseline and see if that helps.
|
AndyT,
I took the engine cover off yesterday and traced the fuel line round the engine bay to the fuel pump. As Sean indicated, the hose is transparent for the last stretch between filter and pump.
I could see a single (very) small air bubble in the line, so I don't know whether this was significant.
In any case, I smeared some petroleum jelly as best I could round all the joints along the fuel line. It was also noticeable that I could tighten one of the o-ring seals by about 4 complete turns of a screwdriver, so maybe this was the culprit.
I'll have to wait until starting the car tmrw before I know whether it has made any difference.
Dave
|
|
|
|
>I return to Germany on Friday night. Some may miss me, others won't.
Sean me ole fruit, *I* will miss you.
Even tho you are a Tyke.
|
|
|
|
|
