Glowplug testing

Chris P · Post by **Chris P** » Fri Apr 06, 2007 11:30 am

Perdon my ignorance, but how do I identify which of my glowplugs is dead.

My garage only changed the dead one the last time, and now another one has gone (judging by the black smoke).

It being the Bank holiday, I have the time to prat around myself, but how do I tell which one it is? Spark plugs, I know about... but not glowplugs...

Cheers

Chris

Chris P · Post by **Chris P** » Fri Apr 06, 2007 11:58 am

Lets add stupidity to ignorance...

I did a search on the forum before asking the question, but didn't look in the members only section - there is a section on glowplug testing and replacemen there...

Now I just need to know what an "anti-sieze compound (such as Coppaslip) is"...

Cheers

Chris

Harry · Post by **Harry** » Fri Apr 06, 2007 12:05 pm

Comes in a tube....is copper coloured...bit like a wx mixed with copper...prevents metal parts siezing together at high temps.

Chris P · Post by **Chris P** » Fri Apr 06, 2007 4:26 pm

Thanks Harry - I'll get some in the morning before giving it a go.

Day was so nice that we decided to go out for a picnic in the (black smoking) Bongo, rather than fixing it.

Cheers

Chris

brorabongo · Post by **brorabongo** » Fri Apr 06, 2007 7:34 pm

After replacing my plugs as I was having starting probs, I tested my old ones and three of them were open circuit(no continuity or infinite resistance), and one read 3omns. At the end-of-the-day the plugs are little heater elements so there sould be a resistance between the threaded part at the top and the threaded body.

Chris P · Post by **Chris P** » Sat Apr 07, 2007 7:20 am

brorabongo wrote:After replacing my plugs as I was having starting probs, I tested my old ones and three of them were open circuit...

Interesting on two counts - if they typically go open circuit, I'd rather test for that with my little circuit tester than try powering them to see if they are dead.

Secondly - you had THREE dead ones - how was the starting - mine was really lumpy last time one had gone - how bad is it when three have gone?

Cheers

Chris

brorabongo · Post by **brorabongo** » Sat Apr 07, 2007 9:34 am

Hi Chris.

I replaced them after reading on forum about starting problems, I then tested them with a meter.

I can only think that the bongo was starting as the battery was in good condition and i've got good compression? It would take a couple of attempts to get her going then produce a good cloud of grey smoke

with poor idling for a few seconds. The rest of the day no problems at all. Since replacing glow plugs it's been a dream to start with a steady idle.

grumpo · Post by **grumpo** » Sat Apr 07, 2007 5:27 pm

A Bongo glowplug has a cold resistance of less than 0.01 ohm, so as far as
cheap multimeters are concerned, a good one is a short circuit, and a bad
one is open circuit. As the glowplug warms up it's resistance increases. To
test the cold resistance you need to remove the common bus bar and test
each plug individually to determine which ones are faulty.

At initial switch on, the plug current is extremely high for a few milliseconds
but quickly reduces to about 12 amps after a second or so, after 5 seconds
the current is about 6 amps and after about 15 seconds the current stabilises
to around 4 amps.

If you have an expensive DC clamp meter, all you need to do is switch
on the ignition, with a cold engine, wait for 15 seconds, and measure the
supply current, it should be around 16 amps for 4 good glowplugs, assuming
your battery voltage is around 12.6 volts. If you don't have a DC clamp
meter then you could use a heavy duty series amp meter to measure
the current.