Glow plugs again? Xantia mk1

[aerodynamica]

Auld Katy the mk1 xantia has been difficult to start of late. It fires on one cylinder and a lot of gray smoke then soon two cylinders and eventually fires up. Takes a few minutes. I checked fuel delivery and the glow plug relay - both fine. Checked the volts at the glow plugs and it's getting the power that cuts off after the timer. The measured voltage seems a little high at 12v - shouldn't it be about 9v with the resistances of the plugs?

I can't recall the expected reading. Anyway I only changed these plugs last year and the car has quite light use. I know plugs can just give up but am I going nuts? Would 3 of them die at the same time? Seems unlikely.

I can't recall what make they were but certain they were not the recommended Bosch brand.

There goes my Saturday afternoon!

[ekjdm14]

Ugh, yes sounds like they may have gone south... Beru or Bosch I've heard are the ones to go for if you don't enjoy fiddling behind the injector pump every few months

[elma]

Check the resistance on the plugs. Then you can have a very good idea if they are OK or not without all the spannering. Can't remember the correct values but Google knows.

12v is normal, 9v would worry me.

[white exec]

Hi Graeme

To save taking the plugs out to test them individually -
Disconnect the feed at each plug, so just the supply cable remains live.
Connect a voltmeter to the supply cable, and note its voltage (should be battery voltage).
Connect just one plug at a time, one by one, and check the voltage drop you get on the supply cable.
Any non-working plug will not draw current (usually about 11amp apiece), and should show up in this test.

You might have to switched the IGN on/off a few times during all this, because the GP relay will time out.

As said, BERU are best.

[aerodynamica]

Cheers chaps I went and got a full set of plugs anyway and they're beru brand. I think the set fitted last year were actually ngk and perhaps are bad. It's been starting B&B on the button all day today though apart from this morning. That's odd because even when heated up it always needs the plugs. Ill test then each in situ anyway. Thanks again!

[elma]

I found the difference between beru and ngk substantial myself.
Hopefully that's you sorted with plugs for the next 5yrs or so.

[CitroJim]

I found the difference between beru and ngk substantial myself.

I do too... Beru for me have always been streets ahead...

[white exec]

Will be interesting to see how those not-so-old GPs test on the bench, Graeme.

[demag]

The NGK are probably just out of warranty. [emoji16]

Sent from my Wileyfox Swift using Tapatalk

[aerodynamica]

Ha probably would have been!

So I discovered that the 'failed ' plugs were in fact a set of Bosch plugs (don't know what's worse, my terrible memory or that a set of Bosch plugs failed..) I Think the ngk plugs I wad thinking of were fitted in the silver mk1 I had before this xantia.... maybe...

And it looks like they are actually alright. I haven't done the 'glow ' test for each yet but all 4 have a resistance of 1.3 ohm that I think is about right. They're certainly all the same reading. There's no single plug that's different. I checked them against the new set of beru plugs that also read at about the same resistance. So I expect the outgoing set will each glow readily when hooked up.

But what went wrong? I tested the voltage to the bridging wire and got full battery volts. It cut off after the timer so I reckon the relay is ok. I checked the supply at each plug and again got volts though they varied a bit in their reading. I made the stupid mistake of measuring between the plug supply and the battery negative that of course eliminates the voltage drop over the plug itself - I should have measured between the plug and the cylinder head so that should have shown up differences between each. Still no answer.

New plugs in, dropped one of the nuts down behind diesel pump as per standard. The ring connectors for each plug from the bridging cable were all quite dirty so cleaned the full thing up and refitted the lot. Started and ran well but the acid test was this morning and the thing started immediately on about half a crank of the engine.

I have a funny feeling the plugs were fine and it was bad connections at each of the ring connectors... I might have spotted that if I'd measured the volts properly!

[CitroJim]

It's a good point you make about measuring the volts Graeme...

Pleased all is now good!

Blu-Tak is a good way to guard against loosing your nuts. As is stuffing a load of rag down by the pump to catch any escapees

[lexi]

Would love to know the reason why NGK are not rated here for French cars. I mean the actual technical reason, as I rate all NGK and Nippon Denso stuff highly.
I had Ngk glow plugs in many Jap Diesels and they are long lasting. Just curious

[CitroJim]

Maybe one should only ever use Jap glowplugs in Jap engines and European glowplugs in European engines Lexi

[white exec]

The only problem I've ever had with Toyota (=Denso) GPs is that they really do not like low available battery voltage - eg a battery in less than a good state. I needlessly replaced a set of OE Denso's years ago (with Blueprint GPs), only to discover it was a battery issue.

Graeme,
Glad you've got it sorted. Had similar problem on XM several years ago, where I found that as well as dirty GP ring connectors, Citroen had - in their infinite wisdom - replaced the earlier twin-cable feed from GP relay to GPs (i.e. one cable feeding just two GPs, another cable feeding the other two) with a single cable only. OK, but they hadn't uprated this cable to match!!! A really stout 6mm2 cable fed the GP relay main contacts from the battery, but something much smaller left it, and headed off to the GPs. My improvement was to run a second cable alongside the existing one, thus doubling the feed capacity. Result was that current delivered to the GPs increased from 55A to 75A, with cold starting now always very first tweak of the key.
Early XM diagrams show two cables; later ones just one.

[lexi]

Maybe one should only ever use Jap glowplugs in Jap engines and European glowplugs in European engines Lexi

Well FWIW I fitted the Beru in the C5................go with the flow