I had my meter set on the upside down horse shoe and 20k
get reading of
00.05
00.04
00.06
00.00

does this mean number 4 if dead, or have i not used the meter right?

i thought that was lowest setting but just noticed its got 2000 and a 200 too

Number 4 would appear to be open circuit Dave, try switching down the Ohms scale while connected to the glow-plug connectors, see what changes, if anything.

Upside down horseshoe... It took me a while to work it out - Ohms. A measure of resistance.

Zero ohms is a short circuit, not an open.

It sounds like they're all pretty much shorts though, as a wire coil would be (if that's what a glow plug is - I dunno).

Doofer said:

Upside down horseshoe... It took me a while to work it out - Ohms. A measure of resistance.

Zero ohms is a short circuit, not an open.It sounds like they're all pretty much shorts though, as a wire coil would be (if that's what a glow plug is - I dunno).

Click to expand...

Thats just wrong... switch on your multi-meter & look at the readings with nothing touching the probes, what do you see? 00:00 thats zero ohms = no resistance = O/C.
The glow-plugs should have a low resistance & heat up as a consequence, a dead short should blow a fuse...

On the range Dave was using if he had his fat sausages on the metal probes that would screw up the measurements.

Ffoxy said:

Thats just wrong... switch on your multi-meter & look at the readings with nothing touching the probes, what do you see? 00:00 thats zero ohms = no resistance = O/C.

Click to expand...

***cough***with nothing touching the probes you should get an infinite resistance, with the probes firmly touching each other you should get zero***cough***

No resistance = short circuit

Infinite resistance = open circuit.

Number four plug is dead, the others sound about right

Sorry to be a pedant

No such thing as zero resistance, well not in car electrics anyway, maybe close with superconductors but we can ignore that (get that cough seen to)

For the purpose of this test for Dave.

00:00 = open circuit. I'll bet anyone the injector isnt short circuit.
The other 3 injectors have resistance.

Edit. On my Fluke Multimeter I get an "OL" indication for a short circuit & 00:00 for an open circuit, I dont know what meters Dave or you other guys have... but mine is a proper professional tool.

Anyhow, Dave... There are two basic types of injectors.
Low impedance injectors with a resistance of around 2.5-3 ohms, and high impedance injectors of around 12 ohms.

Either way, as I said before the pedants chimed in, number 4 looks dead.

if i just turn it on i get a 1 if i touch the ends i get 0.00

i have a happy shopper meter

dave said:

if i just turn it on i get a 1 if i toutch the ends i get 0.00

i have a happy shopper meter

Click to expand...

Lol... get or borrow a decent one Dave, with car electrics as with any other, accuracy is key! Especially if you get looking into Multiplexed signalling systems.

I doubt any meter displays zero for an open, as that's the reading you get for a short. It will display something else for an open - I think mine shows ---.

Yes, zero ohms doesn't really exist, but it means it's below the lowest resistance it can display on the selected range. If you touch the probes together on any meter, on any range, you should get zero ohms displayed.

Given the values (less than 1 ohm) and the range used (20kOhm), you can't conclude anything from the original measurements. They are all very low resistances, near the bottom of what the meter can detect. You might get a clearer result from using the lowest resistance range.

There's nothing pedantic about stating that something is completely wrong!

FFoxy - are you sure you're not talking about the diode testing or continuity mode? (where it beeps)

i am worrying about my other problem atm, have to come back to glow plugs when ive sorted that

I've got a ***cough*** as well

Maybe Ffoxy is using an analogue multimeter and using the wrong scale. (these work back-to-front

As for Dave's meter it is clearly a digital meter. These will (in most cases) show 1.blank blank blank for overrange or overload, or possible OL.

I expect Telford's resident electronics expert will be along shortly to apologise for any confusion caused and the sharp comments.

Back on topic - if glow plugs are coils (and I don't know they are - I'm only assuming) then they may behave differently under load to how they look with a resistance meter. An inductive load may appear to be a short with the piddly voltage applied by the meter.

Doofer said:

If glow plugs are coils

Click to expand...

They generally are. Just an aside while we're talking about glow plugs, the modern plugs should under no circumstances be subjected to the old-fashioned method of direct connection to a battery to see if the end heats up. The reason for this is twofold; the plugs have a 'pulsed' current applied to them to avoid overheating (i.e. it takes time to heat up the combustion area at a constant heat so the current is switched on and off to keep the plug in the right temperature range), also if the plug being tested genuinely has shorted out then the battery may explode

where should i be taking a reading from glow plug and earth, like i did or glow plug and its lead?

today they are reading as
1/ is 0.11
2/ is 0.09
3/ is 0.09
4/ is 0.01

with a hot engine

new plug is reading 0.00 in the kitchen

Does this help?

http://www.ngk-dpower.com/index.php?id=31&L=2

not sure i just tried on the ones in the kitchen and they are 01.5 now

I have a whole new set so hopefully be ok, ive not taken the old ones out, so i'll see what readings are when i take them out

new ones all fitted. took 5 minutes

readings from old ones now i am doing it properly(?) with them removed are...

1.1
62.0
78.6
91.7

am i right in thinking the 3 with the high numbers are all dead, and the one that reads 1.1 is only one worth keeping for a spare?

the 2 end ones came out dry the middle 2 came out wet i dont know if that is normal or not?

found a guy on youtube testing by volts

This will only test for an open circit glow plug.

The input impedance of a multimeter on a low voltage range (0-50V) will be at least 1M Ohms if not 10M Ohms or more (10 million ohms).

In your case with (assuming you are right in your readings) a 1 ohm to 100 ohm glow plug resistance then you will still see battery volts (12.5V in the case of this video).

Glow plugs require current to produce heat.

At 1 ohm and 12V current = 12 Amps. Watts = volts times amps = 144 Watts
At 50 ohm and 12V cuttent = 0.24 Amps. Watts = volts times amps = 2.88 Watts

As glow plugs need to get to around 1000 degrees centigrade quickly then a 2.88 Watt heater is going to be far far below the performance of a 144 Watt heater.

In testing glow plugs a simple current clamp meter is a very good and easy place to start. One can test all 4 plug currents simply by clamping the meter on (if a single lead with block/head return parth) and noting each current (allow for cooling between each test). I would expect 5 to 12 or 15 amps (possibly more) per plug. I would guess a +/-25% tolerance across the range so if the average was 10 Amps then I would expect the lowest to be around 7.5 Amps.

Note! I've never tested or had glow plug problems myself but am just trying to applying some simple logic / rational to the problem.

"And on that statement he slowly sank to the bottom of the ocean"

Whoa whoa whoa this is getting way out of hand, turn ignition on feel for heat on the lowest part of the glow plug you can get to in the block, or remove them get a set of jump leads and test them, no heat it's dead, or better still just replace them after 20k/2years.