Glow plugs

[California Dreamin]

Like I say...I've never owned a JX but for the life if me, I never remember them taking anything like 20 seconds back in the day. I was on the shop floor for some years back in the mid/late 80's and I regularly worked on VAG Diesels although rice burners weren't as common as they are now. Glow plug systems/indirect injection of that era did take time but really...20 - 30 seconds!!
There must be some info on this somewhere.....temp/time glow plug graph?

Martin

[Oldiebut goodie]

Testing - from VW diesel handbook. Max times. Gives a rough idea.

[Smcknighty]

How do we upgrade to the quick glow system!

[Oldiebut goodie]

I direct the honourable member to the reply that I gave earlier!

[Smcknighty]

Ah ok. It's no more than a marginal annoyance for me - although I do feel my neighbours think I've lapsed into a micro sleep as I sit there hand on key for 30 seconds staring vacantly at the dash. I've noticed it's finally got cold enough for the wife's seat to need it's glow plugs, normally can just turn the key and it starts, now if you make that mistake it spins for five seconds then starts. That's modern emission dodging technology for you. We are still waiting with bated breath to find out what vw's 'fix' is going to be on the seat for its supposed problems, they can't make it any slower surely.

[dogbreath100]

I think my glow plugs are on the way out .
Had a look around to see how difficult
It is to change them . Can anyone
Point me in the right direction ,
Thanks

[California Dreamin]

Oldiebutgoodie ...that's most enlightening and sort of backs up what I was saying...if those are maximum times then one would presume they are for the extremes of temperatures that we don't necessarily see in this country.

Still I can't ever remember waiting for anything more than 7 - 9 seconds for the light to go out and usually much less. I would still like to see a temp graph (time in relationship to temp) to see exactly what temperatures these longer times are associated with.
Given the dramatic difference in those times I feel sorry for anyone with an 'older' system fitted although I would assume any new replacement glow plugs will be of the 'quick glow' variety, I've seen replacements from 'Bosch' advertised as such.




Martin

[Oldiebut goodie]

The thing is you would need to change the glow plug relay also as that is specific to each type of plug.
The time can be varied with the water temp sensor for the plugs so if the sensor is out of spec this will affect the time as much as the relay.

[California Dreamin]

I'm honestly not sure how the relay works in relation to load. Whether the relay is SMART only in relation to 'temp/time' ? however, I always thought that ageing glow plugs resulted in higher resistance, poorer cold start performance and so longer glow times? If this is right then the relay must be altering that time in relation to load?


Martin

[Oldiebut goodie]

As far as I am aware the relay only varies the time according to the sensor resistance, the load not coming into the equation.
Can't find a table for temp/resistance/and time relationship. The book of words only mentions max time.

[California Dreamin]

OK...liking it...so looking at the resistance on the left it's 'increase' definitely isn't linear as it rises sharply the colder it gets. If the assumption was made (and I say if) that resistance to time is linear (exponential) with this relay, then the time would 'sharply' increase towards the lower temperatures

-10 being 3.500 - 5.500 ohms and -15 jumping to a massive 6.000 to 11.000 ohms (there about's) lower down the temperature range the resistance change is minuscule for the same 5 degree change.

Than all makes sense in the bigger picture of how fuel is ignited in an indirect injection combustion chamber with its heat sapping internal surfaces.

Martin

[California Dreamin]

OK...liking it...so looking at the resistance on the left it's 'increase' definitely isn't linear as it rises sharply the colder it gets. If the assumption was made (and I say if) that resistance to time is linear (exponential) with this relay, then the time would 'sharply' increase towards the lower temperatures

-10 being 3.500 - 5.500 ohms and -15 jumping to a massive 6.000 to 11.000 ohms (there about's). Higher up the temperature range the resistance change is minuscule for a similar 5 degree change.

That all makes sense in the bigger picture of how fuel is ignited in an indirect injection combustion chamber with its heat sapping internal surfaces.

Martin

[windy]

The water temp senders (same part number as the glow plug sender) are a lucky dip as far as quality goes these days.
The cheap generic ones are useless, sometimes lasting only a week or 2.
I've just managed to get around 12 months use out of a supposedly original equipment supplier Febi one, but now it seems that needs replacing too.