Testing Glow Plugs

Submitted: Saturday, Apr 24, 2010 at 16:12
ThreadID: 77968 Views:4082 Replies:5 FollowUps:2
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Hi everyone, i have done a search, but seeing as the search function on this site is poo, i can't find any bleep ing thing on here. So, my question is as follows: how do you test the glow plugs with a multi-meter while they are still in the vehicle? If it is possible, of course. The vehicle in question is a '91 turbo diesel Hilux Surf
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Reply By: Member - Phil G (SA) - Saturday, Apr 24, 2010 at 16:54

Saturday, Apr 24, 2010 at 16:54
Remove the bar that connects the glow plugs, so they have nothing connected to them. Switch your multimeter to the 200 ohm scale. With the black lead earthed to the cylinder head, touch the red lead on the tip of each glow plug - it should read close to zero (indicates continuity). If it doesn't then that glow plug is dead.
AnswerID: 414143

Reply By: Member - Stuart P (WA) - Saturday, Apr 24, 2010 at 16:54

Saturday, Apr 24, 2010 at 16:54
the only awy to test them is out of the motor, you will only be able to test that you have voltage to the glowplug with a multi meter.
AnswerID: 414144

Reply By: howesy - Saturday, Apr 24, 2010 at 17:21

Saturday, Apr 24, 2010 at 17:21
gotta say i agree with Phil, been using the continuity test as he describes for years and it nails the weak glow plugs every time. Never pulled one out to test it yet. You should get a reading on the 200ohm scale of 0.005 to 0.009 if they are decent. Much above 0.010 and I like to replace it anyway.
AnswerID: 414146

Follow Up By: oldtrack123 - Saturday, Apr 24, 2010 at 19:49

Saturday, Apr 24, 2010 at 19:49
Hi
I agree with Phil & Howesy The usual failure is to go high resistance or open circuit
Should show near zero resistance on any multimeter set to lowest ohms range Probable max of 0.5ohms
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FollowupID: 684388

Follow Up By: Ozhumvee - Sunday, Apr 25, 2010 at 08:38

Sunday, Apr 25, 2010 at 08:38
Yep agree with Phil, I've always tested them by removing the wiring/busbar and then testing with a test lamp.
Connect the fly lead on the test lamp to positive battery and touch the tip to the terminal on top of the glowplug, if the lamp lights up the glowplug is ok, if no light then it is kangaroo edward.
When they blow they 99.99% of the time go open circuit, ie: no continuity or zero on the multimeter.
Peter
1996 Oka Motorhome

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Reply By: Stu-e - Sunday, Apr 25, 2010 at 22:21

Sunday, Apr 25, 2010 at 22:21
with stuart p, the other auto sparky

you can test it like the others said but it wont tell you JS,

if you wish to test them in the vehicle you will need to test for power at the rail you can do this with your meter and test for voltage, if that is ok you can remove the buzz bar, and test for resistance like the others said, this is about as much as you can do with a std mullimeter, to test further in vehicle you will need a ampmeter capable of at least 20amps and connect this form batt pos to the terminal on top observing how many amps are being drawn and how fast they drop away they should be similar but dont power up for longer than 10 sec as you cant see how hot they are getting.

to test them properly you need to remove them from the vehicle
a ampmeter capable of at least 20amps and connect this form batt pos to the terminal on top while holding the hex of the nut on negative observing how many amps are being drawn and how fast they drop away and the time they take to glow cherry red at the tip NOT HALFWAY DOWN they should all be similar, this will give you an indication as to how long the timer should be glowing them for.

if any need replacing do the whole lot its alot easier than doing the same job again next winter

Stu
AnswerID: 414276

Reply By: Dave... Adelaide (SA - Sunday, Apr 25, 2010 at 23:13

Sunday, Apr 25, 2010 at 23:13
Thanks everyone that replied!
Tested the glow plugs the way Phil described and discovered 2 of the plugs were stuffed, Once we had pulled the vehicle apart to change the glow plugs we checked them using a 12 Volt battery...All done now and the mate is happy again!!

Thanks again......Dave
AnswerID: 414284

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