Guide: Testing Glow Plugs

[Jenkosowls]

When glow plugs fail or start to cold starting becomes difficult as diesel need the glow plugs to start the combustion cycle. once warm its not much of a problem as heat in contained within the engine.

The tests are real simple but its always advisable to replace a whole set of plugs rather than just 1 as shortly after often the rest fail.

1) You need a voltmeter the first thing you do is measure the voltage along your battery take note as this is the figure you use to test your plugs.


2) Next you need to remove the power rail along all 4 plugs.


3) Now leave the positive prob on the positive terminal of the battery and then place the negative prob on the end of the glow plugs where the power rail attaches. Make sure you get good contact and dont use the point as this can give false readings if the contact is dirty.


4) If the Glow plug is ok you will get a reading roughly the same as the battery reading


5) If the plug is dead you wont get a reading back if its failing you may get a lower reading in my case 1 plug was dead the other was failing with a reading of 4.5v


6) To confirm the plug is dead you can use jump leads to test them first of connect the the leads to the battery terminals as normal then place the positive clamp onto the end of the glow plug


Then place the negative onto the body/shaft of the plug. A working plug will give off a small amount of smoke as it starts to work this is just crap being burnt off. Be careful this is extremely hot and remains hot a lot while longer.


If your at this stage you may as well have just put new in but its always nice to know you've got spares in the event you need one.