300tdi conversion - Glow plugs and cooked wiring..

Morning all,

I recently did a 300tdi conversion from a 2.5na, all went well as I connected a single glowplug to the original brown cable (used on the 2.5na)

Anyway, its been chugging when started from cold with a bit of smoke - so thought id connect up the other glow plugs and see if it got any better - bad idea! Ive melted the first yellow/black cable to the second glow plug, and after disconnecting the others (just one left connected) the light just stays on the dash when engine is running

Done a bit of reading up and i might have fried my ignition switch, kind of makes sense as when i turn the engine off I can hear the starter motor kicking in - great

So the question is, it I get a replacement ignition switch and the correct timer relay from a Disco for glowplugs, should I need anything else?

Thanks guys

Chris

According to my book of worms, the Y/B feed for the glows goes to tthe No. 4 and out from there.
Which pllug did you connect to?
I would ask the question of why the fuse didn't blow?

chriswood6725 said:

Morning all,

I recently did a 300tdi conversion from a 2.5na, all went well as I connected a single glowplug to the original brown cable (used on the 2.5na)

Anyway, its been chugging when started from cold with a bit of smoke - so thought id connect up the other glow plugs and see if it got any better - bad idea! Ive melted the first yellow/black cable to the second glow plug, and after disconnecting the others (just one left connected) the light just stays on the dash when engine is running

Done a bit of reading up and i might have fried my ignition switch, kind of makes sense as when i turn the engine off I can hear the starter motor kicking in - great

So the question is, it I get a replacement ignition switch and the correct timer relay from a Disco for glowplugs, should I need anything else?

Thanks guys

Chris

Click to expand...

My first BIG question would be why did it fry - by any chance has one of your terminals or GP wires made contact with the block?

The 2.5NA did not have a fuse for the GP circuit.

If it was me, I would run a dedicated supply from the starter positive terminal, a short distance to a dedicated fuse - I would say about 60A - then from there to a 80-100A relay, then onto the GP's - I would then either take a feed from the GP position on the ignition, and wire it to the relay to activate it - this keeps it fairly seamless.

However if the ignition switch is toast, is it only toast on the GP position, i.e. still OK to start and run? If so then I would just take an ignition live, via a small push to make switch on the steering column and just have a GP switch you can press. Also good on cold mornings as you can hold the GP's on after the engine has started.

I would also however ask the question of why does your engine need GP's at this time of the year - both 300tdi's I had/have didn't even need it in the winter. A good starter on a good engine should light these engines up no bother.

My apologies as I tend to stick fuses on everything ... just in case!
However, we don't know how much of the 300 TD1 was changed over.

I did what @discomania did around 12 yes ago.
New switch is cheap (£12?) Bit of a faff to get at the screws holding it on to the barrel or take the whole barrel and switch off complete. Knock the security heads round with a chisel.
Don't bother with a timer it's just something else to go wrong.. make sure you buy the diesel switch, the petrol one doesn't have the pre heat position.

Don't think you should need glow plugs this time of year - the 200 doesn't even in winter. Check your fuel connections, particularly the return.

chriswood6725 said:

Morning all,

I recently did a 300tdi conversion from a 2.5na, all went well as I connected a single glowplug to the original brown cable (used on the 2.5na)

Anyway, its been chugging when started from cold with a bit of smoke - so thought id connect up the other glow plugs and see if it got any better - bad idea! Ive melted the first yellow/black cable to the second glow plug, and after disconnecting the others (just one left connected) the light just stays on the dash when engine is running

Done a bit of reading up and i might have fried my ignition switch, kind of makes sense as when i turn the engine off I can hear the starter motor kicking in - great

So the question is, it I get a replacement ignition switch and the correct timer relay from a Disco for glowplugs, should I need anything else?

Thanks guys

Chris

Click to expand...

it shouldnt have fried the wire unless the second plug is shorted or your wiring was

Thanks for all replies, I have so far ordered up the following:

New ignition switch - sounds fairly easy to change over, although never done it before
Timer relay from a disco - will wire up in same manor as intended, so the dash light will go out when ready
Replacement wiring to link plugs - thinking about it, they must have shorted out on the block - it was a mess!
New glow plugs - no idea how old the current ones are, and it gives me piece of mind

Need to order up replacement wire for supply wire to relay from starter motor

I understand about Tdi not requiring glow plugs this time of year, but I do get a bit of smoke and rough idle for the first 20-30 seconds. I think this next bit is a separate issue but when cold I get lots of blue smoke on overrun... tried a good service with Lucas oil stabilizer without success - suspect the pump timing next perhaps?

Any thoughts to the above?

Cheers again

Chris

Bit of smoke and rough idle for a few secs is fine. Glow plugs will stop the black stuff on start up or at least cut it down a bit. Timer - just count to ten and then start.

chriswood6725 said:

Thanks for all replies, I have so far ordered up the following:

New ignition switch - sounds fairly easy to change over, although never done it before
Timer relay from a disco - will wire up in same manor as intended, so the dash light will go out when ready
Replacement wiring to link plugs - thinking about it, they must have shorted out on the block - it was a mess!
New glow plugs - no idea how old the current ones are, and it gives me piece of mind

Need to order up replacement wire for supply wire to relay from starter motor

I understand about Tdi not requiring glow plugs this time of year, but I do get a bit of smoke and rough idle for the first 20-30 seconds. I think this next bit is a separate issue but when cold I get lots of blue smoke on overrun... tried a good service with Lucas oil stabilizer without success - suspect the pump timing next perhaps?

Any thoughts to the above?

Cheers again

Chris

Click to expand...

Regarding the glow plugs it all sounds good to me - make sure your wiring is spot on, proper terminals and crimps, heat-shrink sleeve over exposed metal or wire etc. the glow plugs pull some decent current and you don't want any high impedance joints that could then get red hot.

Smoke and rough idle could be a few issues, such as worn injectors, or bad timing, or decreased compression - the blue smoke which is burning oil makes me think along the lines of worn engine parts. If on overrun it could be the bit of vacuum on the intake (turbo not blowing to pressurise) so any route into the intake system from oily bits of the engine could be to blame, sucking oil down the valve guides is common, if the seals are worn and the guides may also then be worn, if this is all worn then there is the possibility that your valves could do with being lapped in - if they are not making a good seal that could then explain your rough smokey idle at first.

Ignition switch pack is 'easy' to swap out....the tiny screw on the bulkhead side of the barrel is a faff to get at.

As mentioned, it may be easier to get a couple of new anti-tamper bolts and break off the old old ones with a chisel or drill and extractor set. take the whole barrel and switch out complete, replace the switch pack and then replace the whole lot with new anti-tamper bolts.

My experience with the cheaper switch pack was after 6 months it fell to bits (maybe I got a duff one) in the end I just replaced the whole ignition barrel and switch pack for an OEM one (was around £100 or so) but never had a problem with it since!