Help! Octavia 1.9 TDi. Starting problem!

ukchriss

:jI have a 2002 Octavia 1.9 TDi. Starting wasn't a problem until Monday of this week and now...

Symptoms:

1. engine turns over but doesn't fire up
2. noticable that pre-heat (glowplug) light is not showing on dash (it's cold at the moment so I'd expect something)

Checks done:

1. multimeter between glowplug and lead - no current
2. battery fully charged and voltage checked (>11.5v)
3. sprayed wd40 on wire connections
4. fuses (facia and battery areas) checked OK
5. tried with spare key - still no start
6. Witnessed fuel flowing through clear fuel feed pipe after ignition turned
7. (seemingly) no other problems

Other info:

I charged battery yesterday and put back in car at at about 16:00. Car started (with a little trouble initially) . Tried shortly again afterwards and car started OK (and saw pre-heat light on the dashboard). Tried again this morning and car wouldn't start

My thoughts:

• car has started and it may be temp thing. My understanding is that below about 4 degrees C glowplugs are necessary since insufficient heat generated through compression. This would explain non start in cold and start in late afternoon with a fully charged battery
• no current to glowplugs when I would expect to see one leads me to believe that the issue is possibly:
  • coolant temp sensor
  • relay
  • wiring

I've been reading posts on the web which have been helpful, but I've been left with the following questions -

1. How do I check whether the coolant temp sensor is working?
2. If the relay is failing, wouldn't that affect other things as well?
3. Can someone confirm which relay is used by the glowplugs?
4. How can you test a relay?
5. Wiring - eek any ideas?

I've got the car booked in to the dealers but they can't see me until next week and I've been quoted in excess of £120 just to get the car there

Can anyone Help with Ideas of what might be wrong and what I could try to get it going?

Many thanks

harveybobbles

Glowplugs would be the first thing to check, but upon reading your post a second time I started to think towards maybe a timing issue? We had a Passat TDi that wouldn't always start. Similar issues to yours. Turned out tp be the belt that was a tooth out. So simple. Yet so annoying. Lol...

Pew_Pew_Pew_Lasers!

You say you measured the current between glowplug and lead - did you measure amps in series, or amps in parallel - because you can't do the latter. You can only measure voltage in parallel.

You need to disconnect each glowplug and measure the resistance between the plug and the chassis. If the resistance is infinite then that glow plug is open circuit and faulty. Normally a working glow plug will exhibit a low resistance, a few ohms.

If your vehicle has a glow plug relay circuit (the glow plug connectors will all terminate there) then you should investigate that relay to see if it is still functioning correctly, or if it has any internal fuses.

Spraying WD40 on electrical connections is pointless. Also a fully charged battery may well show full voltage but that will not be a reliable indicator as to its ability to store charge. If its the original battery it may be time to replace it anyway. Is it cranking at full speed or going slowly?

ukchriss

Pew_Pew_Pew_Lasers! wrote: »

Spraying WD40 on electrical connections is pointless. Also a fully charged battery may well show full voltage but that will not be a reliable indicator as to its ability to store charge. If its the original battery it may be time to replace it anyway. Is it cranking at full speed or going slowly?

Thanks for your reply, I have recharged the battery and Is it cranking at full speed

Conor_3

Probably the glowplug relay that's gone if you're getting no voltage across the glowplug supply rail and the light isn't going on. It has a built in timer and also illuminates the dashboard indicator. I'd go to an autoelectricians and get them to swap it which will determine whether or not that's where the problem lies.