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10th October 2014, 08:09 AM
#1
MQ(260) glow plugs
So my MQ fitted with a 2.8 turbo diesel, is a little rough at idle when starting from cold
I've read that people have fitted 4.2 glow plugs ?
Just trying to understand if mine are 12 0r 6 volt ? Or if they have a post glow system ?
Any idea where the glow plug relay(s) are located ?
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10th October 2014 08:09 AM
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12th October 2014, 08:23 PM
#2
Hi all,
Can someone explain to me how this system works?
I have 2 sets of 3 plugs fitted to my 2.8 diesel turbo
There are 2 relays, and 2 contacts strips as show in the pics
The one relay activates all 6 glow plugs
The second relay only activates 3 of the plugs
Is it best to scrap this system, and just have 6 standard glowplugs?
All 3 plugs that have the double contact don't work, so I'm guessing they are unreliable ?!image.jpgimage.jpg
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12th October 2014, 09:04 PM
#3
When the engine is cold relay 1 is switched on and supplies 12 volts to the long busbar that connects all 6 glow plugs.
3 of the glow plugs are earthed via the engine. The other 3 glow plugs (double contacts ones) are earth via relay 2.
When the glow plug control module determines it's time to turn on the after glow (post glow) It will turn relay 1 off and turn relay 2 on. This supplies 12 volts to the small busbar. Now the two lots of glow plugs are in series so 6 volts is dropped across each lot allowing them to run at around half the temperature.
To test the double contact glow plugs you need to measure the resistance between the 2 contacts. There should be an open circuit to the body of the glow plug.
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13th October 2014, 12:46 AM
#4
Cheers.... That's starting to make some sense now !
Would you recommend ditching the post glow system and converting to 4.2 plugs like others have done ?
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13th October 2014, 02:28 PM
#5
If your old glow plugs are faulty it will work out cheaper to change them over to the 4.2 ones.
Have you tested your old glow plugs? Have you checked the glow plug electrical circuit?. I take it you are having starting issues?. If your old glow plug circuit is working correctly and the glow plugs are heating up fitting the 4.2 glow plugs won't solve your starting problem. How's your injector pump and injectors?, engine compression?, battery condition?, is the starter motor cranking the engine fast enough?
If you do convert to the 4.2 ones you will loose the after glow function unless you also fit a universal glow plug timer. There are a few on Ebay.
Or you could still just fit the momentary switch in the dash. Then you could manually push the button before starting the vehicle and if needed you could push it again once the engine was running.
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15th October 2014, 05:35 AM
#6
I check the 3 standard contact plugs by putting them across the battery, one of them was dead, one didn't heat up quickly.
One of the double contact plugs was dead too.
Bought some 4.2 plugs, fitted them tonight , but the engine was still warm. Will have to see how it starts in the morning
I've disconnect the second relay, the first relay gives the plugs 12v for about 6 seconds.
So as usual say I dont have the after glow, and the glow plug light flashes for a few minutes ?
Hopefully no clouds of smoke in the morning !
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15th October 2014, 03:15 PM
#7
Hopefully they stay on longer then 6 seconds when the engine is cold.
If there not staying on long enough you might need to look at installing the manual switch in the dash. You only need a momentary push switch and some wire to do this. You can still use the original relay.
The glow plug light flashing is just telling you that there is a problem with the after-glow, because it's disconnected. It will keep flashing until the engine temperature heats up to a certain temperature or you drive the vehicle above a certain speed.
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16th October 2014, 02:26 AM
#8
Originally Posted by
Yendor
Hopefully they stay on longer then 6 seconds when the engine is cold.
If there not staying on long enough you might need to look at installing the manual switch in the dash. You only need a momentary push switch and some wire to do this. You can still use the original relay.
The glow plug light flashing is just telling you that there is a problem with the after-glow, because it's disconnected. It will keep flashing until the engine temperature heats up to a certain temperature or you drive the vehicle above a certain speed.
Started great... But then ran rough as the glow plugs had gone out
I don't want to fit a manual switch if I can help it, will either replace the 1st relay with a timed relay, or see if I can use the second relay to operate the glow plugs until the engine has warmed
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16th October 2014, 05:05 AM
#9
Can seem to use the second relay, does anyone know where the glowplug control unit is located ?
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16th October 2014, 07:29 AM
#10
You should be able to use the second relay. You will need to cut the large black wire (earth) at the second relay and tape both ends up. Then just connect the other wire that was connected to the short busbar onto the long busbar at the glow plugs.
I think the glow plug warning light will still flash during after glow.
Not sure where the glow plug ECU is. Have a look in the drivers side kick panel or on the firewall below the glovebox.
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