glow plugs

[ringo]

In the back of the head, on the water heater outlet stub, usually... I think it's dual purpose and feeds the water temp gauge too... (same part is possibly used as an oil temp gauge on some engines )

Temp Sender 049 919 501 (0~125 C) 1 pin, Black

... as opposed to the Temp 'Switch' 251 919 521 (104 C) 1 pin, Grey - that fits into the coolant stub exiting side of engine around cyl. No. 3 going to water pump, amongst others

Clive, i dont suppose you know the part no for the outlet stub?

Mine broke i replaced it with one without the sender in (off a 1Y).

At the moment my light never goes off (helps starting when warm) but i want to change it back.

Cheers

Ringo

[HarryMann]

(Up to ChNo.) >> F 24 K 064 850 it's 068 121 145 K
(From ChNo.) F 24 K 064 851 >> it's 068 121 145 Q

but suspect only one will be current and available, which might turn out to be

068 121 144, replacement for 068 121 145 Q

The K part comes up at a really silly price, so see what they say the 144 is for, if it looks right and is tapped M10x1 for the sender, it'll be less than a tenner I reckon.

[Syncro G]

Theres 2 styles of sender. Early I think is threaded, late is a big black thing (with green marking) held in with a clip and has 2 pin terminals. I guess if you want to swap early for late you'll need to change the pipes. The senders are the same for the heaterplug and temp guage but there is a seperate sender for each, they don't share.

[HarryMann]

Yes, it's a dual sender stub for the heater hose...
Not sure what part no suffix letter corresponds though... you certainly don't want the Golf/Passat nylon one though. This one is circa 1988, Ch. No 24-K-112-210

[img:800:600]https://club8090.co.uk/wiki/images/JX_He ... b(800).jpg[/img]

Glen, the relay seems to have 258 in large white numbers on it...

[Syncro G]

Glen , the relay seems to have 258 in large white numbers on it...

Cheers, will keep an eye out for one of them, then I can test it and see what the difference is.
The LT pages on ETKA lists the later type as having afterglow when you start the engine so maybe thats the difference - suppose it could allow the engine to start sooner and knock less but I don't think I'd like it afterglowing if the engine is hot so maybe it is bad running them without a temp sender? (rather than just irritating as its not perfect)

you certainly don't want the Golf/Passat nylon one though.

Being very late mines got nylon pipes, is that bad? One cracked when I swapped it over but it was old and had been bodge fitted. Readily avalable and cheep though, lots of senders avalable for them too as every modern VW seems to use a variant of the 20mm senders (and they are all almost indistinguishable, especally when fitted, nice one!)

[HarryMann]

Maybe I'm jumping the gun, I've just heard of so many of them cracking, but that's maybe old ones...

Once mine's started I leave it to settle down for 10 or 20 seconds before bringing the speed up, so don't get so much of that initial knocking... hadn't heard of afterglow, or not in that context anyway

I think part of the IDI concept is to have the glow plug incandescent to better vaporise the fuel as it swirls within the pre-chamber under normal running, effectively a permanent hotspot, but maybe that's only when fully warmed or running under load.

Clivee

[Syncro G]

I think part of the IDI concept is to have the glow plug incandescent to better vaporise the fuel as it swirls within the pre-chamber under normal running, effectively a permanent hotspot, but maybe that's only when fully warmed or running under load.

Clivee

Didn't think the plugs do much after the engine is up to temp, only to get enough temp for it to fire, slightly low temp would delay fireing creating more knock so afterglow could help keep temp up and prevent stalling while the advance cable keeps it smooth and closer to time. The plugs seem to cool down much quicker than I'd have thought a bit of metal sumular size would so I wouldn't have thought they help keep a hotspot on a running engine. The swerl chamber does that on its own, especally when the engine is compressing at its running speed rather than starter speed (My landy likes alot of heat as its a really old design but if you bump start it so the engine is being started at 2krpm instead of starter speed it'll fire instantly even on a cold day, as the block can't absorb the heat quick enough - a bit violent though so like starting it with electric assistance as designed (never tried the starting handle but I suspect its completely useless, works well on a petrol though!)). You only get heaterplugs on small capacity IDI engines as bigger stuff and DI stuff has less relative surface area in the piston to absorb the heat so they usally have enough from compression alone, even at really low cranking speed.

[HarryMann]

The swirl chamber does that on its own

Well, that as you say has a lot of surface area in contact with the coolant, whereas the glow is being re-heated at every combustion stroke with no-where to dump it's heat. I'll consult Harry's bible again, after all, he designed the Comet chamber but I may have misread or misinterpreted him there.

You're right on surface area to volume ratio on these smaller IDIs of course; cranking speed too, from memory he said there was an optimum (400 rpm maybe, seems high though), I'll have to re-visit that as well, as I'm sure there is a reason why too high also has a downside for cold-starting

[Syncro G]

Well tested my old relay which I think is faulty, only doing full heat rather than vary (ie coldstart).

Its a "102" 191 911 261C

Can't find any referance to them being fitted to a JX but as mines really late? Did they fit them?

Preheat - Warning lamp for 11sec, plugs run for 20sec.
Afterglow - Yes it does, for about 3 minutes! Maybe on an actual engine with temp sender wired up (I bench tested if off a mains pack) it'll cut out sooner as driving heats the coolent sender and during hot starting it'll do less, but as my coolent sensor didn't seem to be working it'll have been doing this 3 minute thing every time I restarted the van, even when hot, for atleast the last year! Worth looking out for!

So, I'm not convinced you shouldn't run a 102 relay if its not working 100%, next thing to find out is how long it afterglows for on a working engine with the sender setup. On the plus side, after the engine first fires, it quickly becomes happy and not really rough like my landy, perhaps this is why. The landy has fully manual heaterplugs so maybe I'll keep the key on a bit after starting it to see if it does much.

I'm running another 102 relay currently but this one seems to work better (though I haven't used it much to test).