How do you check/change glow plugs?

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p63500sv8
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Joined: 19 Jan 2004, 16:05

How do you check/change glow plugs?

Post by p63500sv8 » 19 Jan 2004, 16:06

I have a 205 turbo diesel which has been fine for the last 2 years.
All of a sudden it was reluctant to start on Friday and would not start at all today.
I do not have the diesel workshop manual so need your help.
1)How can I check that the glowplugs are working ok?
2)How long do I have to keep pressing the button up and down on top of the fuel filter to prime it?
3)What are the procedures for changing the glowplugs?
4)Any other ideas why it won't start? (it turns over ok but does not seem to be firing)
Any help/suggestions would be greatfully received.
Cheers
Michael

Dave Burns
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Joined: 14 May 2001, 05:30
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Post by Dave Burns » 20 Jan 2004, 02:17

What did it start like before, A, if it used to start easey and ran without missfiring then the plugs were fine up to then and probably still are, B, if for some time there has been some missfiring then one or more plugs could be duff.
A sudden total refusal to start is more likely to be either as a result of air getting in to the injection pump or failure of the glow plug relay, especialy so if as in A above.
To prime it, switch the ignition on and pump away untill resistance to pumping is felt.
If air is getting in one of the most common entry points is the injector leakoff pipes.
To test glowplugs, disconect the glowplug bus cable from all plugs and put a ohm meter lead from the terminal of the plug and the other lead to earth on the side of the plug for each plug.
The resistance should be about 0.5 ohm, be sure to test the resistance of the meters leads first by contacting them together and noting the reading, this must be subtracted from the reading of the plugs for a true value, before you go messing about like this be sure to test for the obvious.
What injection pump is fitted Lucas/Rotodiesel or Bosch.
Dave

p63500sv8
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Joined: 19 Jan 2004, 16:05

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Post by p63500sv8 » 20 Jan 2004, 04:58

Hi Dave
Thanks for taking the time to help!
The car has been running fine for the last 2 years, but last Friday when starting in the morning I did not catch it when turning the ignition key and then it was reluctant to start and took a few persistant turns to get it going.
It has a Lucas injection pump but everything seems dry and fine around that.
Where will I find the glow plug relay?
It had blown one of the two 30amp fuses situated next to the battery, could that have been caused by anything?
Cheers
Michael

p63500sv8
Posts: 10
Joined: 19 Jan 2004, 16:05

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Post by p63500sv8 » 20 Jan 2004, 21:51

How can I test the relay?
Is there a way I can bypass it to check if it is faulty?

Dave Burns
Posts: 1916
Joined: 14 May 2001, 05:30
x 2

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Post by Dave Burns » 21 Jan 2004, 01:28

The relay needs to be able to supply current in the order of 50 amps to light all four plugs at once, the easiest way to test its operation is either by a meter or test lamp on its output, this wont however tell you if its delivering the required current, that would require a suitable heavy meter.
All four plugs together should glow a bright orangy red when things are as they should be, so thats the best way to test the current passing capacity of the contacts without the use of special meters.
The relay has several inputs to disengage it under certain conditions, namely throttle position (on some models), engine temperature and an engine running signal, failure of the relay may be down to one of these inputs and not the actual glow relay its self, earthing and other wiring faults are possible causes.
A dry fueling system does'nt necessarily mean that air is not getting in, just that fuel is not getting out, anyone used to diesels will tell you that air can get in without fuel getting out.
Dave

p63500sv8
Posts: 10
Joined: 19 Jan 2004, 16:05

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Post by p63500sv8 » 22 Jan 2004, 04:17

Hi Dave
I bought a test meter (£5 from Maplins) and set about the car today.
I found the glow plug relay in the black box next to the expansion tank and with the ignition turned on I could hear the relay click off so assumed it was working fine.
I then tested each glowplug was receiving current by switching the ignition on and using the test meter could detect 12amps/volts (not sure which!) which would disappear once the relay clicked.
I then turned the car over but it still would not start.
I pulled out one of the glowplugs and it was wet indicating that diesel was getting through.
I popped down to the Chelmsford branch bought a set of new glowplugs, air filter and fuel filter fitted them and the car started up straight away.
It seems strange that all four glowplugs failed at once as in 2 years I have never had a problem starting the car, but there you go!
Thanks for your help.