PD 1.9 BXE Intermittent Cold Start Problem

[CombatWombat]

Hi,

This fault is actually on a Skoda Superb II, but as this engine type is massively more popular in the Octavia , I thought I'd cheekily post it here in case someone's suffered similar with an Octavia 1.9  PD BXE.   

 

The car's covered 148,000 miles.  It generally starts and runs absolutely fine, hot or cold, but once or twice in the last few months it has been reluctant to fire up. 

The first time this happened, a few months back, I did a VCDS scan and a defective glowplug (the first one to fail on this car) was shown.  I metered this - it was indeed duff, and I replaced it.

 

But, a few days back, the day after a very long motorway journey, the car wasn't quite 'catching' on attempting a (very) cold startup; the first first in a long while.  The engine was turning over OK though.  After about 5 attempts it started and ran fine for the rest of the day's startups. Although the following day's similarly cold start went with no problems at all - near instant.

 

I have checked for new codes with VCDS and there are none.

 

My thought is that the glowplug controller (where is it?) has some ageing, pitted contacts and is intermittently not cleanly switching the glowplugs up to full current.  Any thoughts?  If there is a contoller/relay, is it easily opened up to clean the contacts it has ( I have a diamond-faced spatula, and have done similar on other non-automotive equipment)?

 

The battery seems AOK and the motor spins at a decent speed on the starter.  I have had the car for 9 years, it is all standard.

 

Thanks in advance!

Edited 26 January, 2023 by CombatWombat

[J.R.]

It is not a relay switching the glowplugs but a pulse width modulation (PWM) integrated circuit, the voltage drop is monitored which is how the ECU can report a failed or out of limits failing glowplug.

 

A quick and dirty way of ensuring the glowplugs are working is to use a voltmeter across the battery or the accessory socket and watch the voltage drop while the glowplug light is illuminated and the consequent rise after it goes out.

 

I have a voltmeter in the centre console, I use it to check the battery state of charge by looking through the window when the car has not been used for several days, if it is getting low I also watch it while the glowplugs are heating, if it drops too low then if I have time I would abort the start and charge the battery for 30 minutes.

 

It also reassures me that the glowplugs are working but any failure should generate a fault code as long as I regularly connect VCDS.

[CombatWombat]

Thanks for the quick reply!

 

Ah! - pulse width modulation!  I see now!

 

From looking over a friend's Kia a long while back, I was vaguely aware that some cars have 12v glowplugs, and some other cars were definitely not using 12v on their glowplugs.  I can see where the PWM comes in now.

 

I've got a DVM or two in the house.  I have a cigarette lighter voltmeter as well - I'll retrieve it from my next door neighbour, so I can more easily check what's happening.

 

If there is an intermittent glowplug 'non-operation', as there seems to be, where does the controller live?  Are there any corrosion-vulnerable connections to check?

 

I have a clamp-on DC ammeter, too, If that is any use in this situation.

 

Cheers!

 

 

 

Edited 26 January, 2023 by CombatWombat

[Guest]

As has been stated in other posts, glow plugs aren't necessary on a PD engine unless the temperature is lower than approximately -5C.

Edited 26 January, 2023 by MicMac