Glow plug light only shows for a short time?

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Joined: April 11th, 2015, 9:21 am

Glow plug light only shows for a short time?

Unread post by skid65 » April 25th, 2016, 7:08 am

I have a 2000 GU series 2 which was originally a 3Ltr but the previous owner converted it to a 4.2Ltr being a 4.2 silvertop, the problem I have is when I glow the plugs, the light stays on for about 3 seconds, if the motor is already warm the light will only stay on for a second, where and how to I make adjustments to make the plugs glow longer?
Also when I start the motor regardless if the motor is hot or cold, the is a cloud of blackish/greyish smoke, I really notice at night if I put my foot down going up a hill and there is a car behind me, it looks like I have flicked a switch to turn on smoke screen mode!!!! during the day if I put the foot down sometimes I can see a bit of black smoke. The motor has done 320000, other than the above problems/concerns it runs well

Peter Aawen
Posts: 20898
Joined: June 17th, 2005, 8:01 pm

Re: Glow plug light only shows for a short time?

Unread post by Peter Aawen » April 25th, 2016, 12:13 pm

The glow light is just an indicator, there is a glow control timer that attempts to send power to the glow plugs for far longer than however long the light shines regardless of your light timer working/shining or not!! So ignore how long the light shines for, it might not have anything to do with what the glow control timer is doing - altho given the engine change-over, it might have some relationship & it might even mean you have the wrong glow timer, ie the one that's meant for the 3.0l motor, so it's trying (unsuccessfully) to work correctly & glow the plugs long enough for the 4.2 litre motor!! The smoke on start up could well be suggesting that your engine isn't getting enough glow plug time - the big 6 cyl does need more than the little 4cyl.... And how long the light shines really means squat!!

What you need to do is get hold of a workshop manual for the engine/model & test the glow plugs AND the power delivery to the glow plugs - the workshop manual should specify how long & at what levels the plugs need to get power; the duration depends on block & coolant temps (there's a sensor for those) as well as the basic key driven & glow light related display. You need to check that the plugs work properly first, & then that they work for long enough (& that means for far longer than the light will EVER show!) A Gregory's or Haines w/shop manual should be OK for that, best $50 or so you'll ever spend!!

While whitish/greyish smoke only on start-up suggests a dodgy glow plug or two &/or a dodgy glow timer; the black component to that smoke could well be an indication that your fuel pump has been wound up too much & that the engine is over-fuelling - does it over run hot on long hills &/or when you try to keep up to speed in fifth gear or a high gear with dropping boost & revs.... Or it could be that your oil rings &/or valve stem seals are getting tired, does it use much oil between scheduled changes?
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