Td4 glow plug testing

Hi all,

2004 Td4 with 115,000 miles.

Starts like a bag of spanners, then runs perfectly well. New injectors fitted before I got it, LP and HP pumps are fine. No codes.

I thought I'd check the glow plugs - removed one, connected to a spare battery, no heating. Went to remove the second, and the nut sheared off the body - the main thread is still seated so I think I'm ok.

Bottom line is - I'd like to replace the remaining two plugs, but instead of risking breaking them off, I want to test them in situ. What resistance value am I looking for? RAVE is no help.

Also, is it easy to extract the seized plug, or should I not bother?

Cheers.

There's a company in Carlisle that can extract them instu for £75 plus I think £35 pound an hour travel as he can come to you the company is called extract engineering look them up

I would think that the plugs should draw about 10 amps. 12 amps at 12 volts is 1 ohm so your resistance would be 1.2 ish ohms. Anything more than 2 to 3 ohms would indicate a dead plug.

I was under the impression that we do not need the glow plugs in this country to start our cars, I never wait for the glow plug light to go out on the dash I just turn key on both my FL and the R40 tourer I had they always seem to start, but it will be interesting to see how you remove the snapped glow plug.

I did my mates TD4 6 weeks ago, first 3 were very tight. Fourth sheared off, so we left it as is. Starts fine on 3. I bought a spare full engine and all four came out dead easy. I need to do mine as it starts and runs like bag of spanners, fair bit of unburnt diesel smoke for a couple of seconds.
Not looking forward to removing them but will do them when engine is at its hottest.

And I have a spare head if it all goes belly up.

Plenty of Plusgas and a few days to allow it to soak in, is the key here.

Thanks all. I'm going to get some of this Plusgas everyone talks about.

Zippy6971 - a nice option in case the worst happens. I think the plug is still seated so I'll just leave it.

Nodge - I'll test resistances and report back.

Arctic2 - I'm blaming the glow plugs for the misfiring and general farting at startup. I hope some new ones will cure it and will report back.

Lowbank - I wondered if the engine should be hot or cold at removal time - I thought you should avoid removing/refitting spark plugs when the engine's hot as there's more risk of stripping the threads, so I tried with engine cold. A spare head is nice to have, but I'd rather not have to swap the damn head just for a pi$$y glow plug...

Glowplug test results:

1 - open circuit/no heating
2 - 414 ohm/no heating
3 - open circuit/broken in head
4 - 1 ohm/good heating

So only no.4 was working. That might well be the reason for the lumpy start. I have ordered some NGK replacements.

For anyone searching this, I will list the resistances of the new plugs, for reference.

Also, you should really soak the plugs for a few days before attempting removal. Then crack them 1/8th turn, spray wd40, and turn the opposite way. Keep easing them back and forth (and spraying), 1/8th turn at a time, with your hand over the head of the ratchet so you can't apply too much torque.

Update: Installed three new NGK plugs. Resistance of these was 1 ohm.

With three working plugs now the car starts up much better, with less cranking and much less farting and coughing.

Update: Installed three new NGK plugs. Resistance of these was 1 ohm

Click to expand...

cheers for that update ..
useful post for future reference
( think my glow-plugs could do with replacing )
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This tool makes removing glow plugs a lot easier.

http://www.lasertools.co.uk/product/6035

This 'tool' makes removing glow plugs even easier:

I always keep a tin of this by me when working on cars. As my Dad says to me, always leave it as you would like to find it. (He was talking about the bog, but you get the idea).

guineafowl21 said:

This 'tool' makes removing glow plugs even easier:

I always keep a tin of this by me when working on cars. As my Dad says to me, always leave it as you would like to find it. (He was talking about the bog, but you get the idea).

Click to expand...

Second time around it does