testing glow plugs toyota 1HD-T motor

Submitted: Sunday, Jun 10, 2007 at 21:06

ThreadID: 46503 Views:6467 Replies:3 FollowUps:3

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Member - Mal B

went to test my glow plugs today IE see if the system is working,good book says switch motor off for 10s before test ,connect test light to good earth other end to top of plug get sombody to turn on key light should come on for short time,mine stays on for about 30s even if i start the motor [i earthed it direct to battery] wounder if this is my problum, should i earth to motor thanks mal b

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Reply By: Member - 120scruiser (NSW) - Sunday, Jun 10, 2007 at 21:13

Sunday, Jun 10, 2007 at 21:13

Some glow plug circuits continue to run even after the engine starts. They run through a timer. If your test light lights up when you turn the ignition on, you are fine. Earthing direct to the battery or the chassis doesn't matter. I usually earth straight to the battery negative where I can when testing electrical systems.
120scruiser

AnswerID: 245974

Follow Up By: Member - Mal B - Sunday, Jun 10, 2007 at 21:36

Sunday, Jun 10, 2007 at 21:36

thanks next step is test one at a time after i remove the power strap mal b

FollowupID: 506928

Follow Up By: Peter 2 - Sunday, Jun 10, 2007 at 22:42

Sunday, Jun 10, 2007 at 22:42

all you've done at this stage is to test that power is getting to the busbar that feeds the glowplugs.
the next step is to remove the busbar and test each plug individually.
When glowplugs are blown they usually go open circuit.
the easiest way to test them is to use a test lamp with the wire connected to positive battery then touch the testlamp probe to the end of the pin on the plug, if the testlamp lights the plug is ok, no light the plug is blown.

FollowupID: 506939

Reply By: peejay - Monday, Jun 11, 2007 at 01:51

Monday, Jun 11, 2007 at 01:51

With the glow plugs on my jackaroo, one of them was shorted to earth and was blowing the main fuse,in which case attatching a live wire to test it would could cause sparks to fly .I by passed it and all was ok for about six months until another shorted out. So i replaced them all for about $80.and even though the light on the dash is coming on it doesnt mean the glow plugs are working.

AnswerID: 246006

Reply By: Member - Phil G (SA) - Monday, Jun 11, 2007 at 19:07

Monday, Jun 11, 2007 at 19:07

When the engine is cold, they stay on for a while - 30secs is pretty normal, and is the same as mine on most mornings. When the motor is hot, they may not come on at all.

If you are concerned that they are not working, do what Peter says, and test them individually. Once one plug goes open circuit, then the others are more likely to go because they then get higher volts. If you find one or two are gone, I'd replace them as a set of 6, and keep the good ones as spares.

AnswerID: 246131