How Long Do Glow Plugs Last For?

13 Sep 2010
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Wrong side of The Channel
United Kingdom
I have an old shape 2004 Fiat Scudo 2.0 jtd van. As far as I'm aware, the glow plugs are the originals. Do they degrade like spark plugs and need replacing after a certain time, or should they last the life of the engine (95,000 miles at present)? Can they be tested?

The van starts perfectly all year apart from winter when the the temps get near or below freezing, then it can take a fair bit of turning over to kick into life. If it's really cold the battery can go flat or almost flat, before it starts. Today the battery went flat before it would start and the resting volts on battery were 12.5 after it flattened. I've got it on charge now. The battery is a heavy duty 096 Lucas calcium which is the standard size according to spec. Are diesels always a pig to start in winter - it's my first? The battery was replaced about 4 or 5 years ago.

Any help and advice appreciated.
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You probably have 4 glow plugs in your van and the symptoms may mean that at least one of them has failed and the remaining ones struggle to start the van in the cold.

If you are mechanically competent/confident then changing them is relatively straight forward (access is usually the issue) as they “simply” unscrew with an appropriately sized spanner.

If not, try an independent garage to give it a once over and price up.

Might be worth checking your battery as well as mine failed on my previous car and was only 5 years old - a new one fitted from the RAC was only around £50-60 so not too bad.
PS. On your dashboard when you turn the key to position II - ignition on but not trying to star the car, you should get a glow plug light on the dash. See how long it takes to go out. When out, the van should start.
To test your glowplugs, disconnect them and check one by are looking for a resistance of around one ohm.
Its impossible to say how long they will last - some last forever, some fail at early mileages. Even when you look at them once unscrewed, they may look clean but also they may have cracks or even a chunk missing. The issue is getting the things out in the first place - some come out easily enough, some snap off :eek: If yours come out, renew them anyway.
Check your battery when the engine is cranking - it shouldn't fall below around 11 volts. This is my main suspect so far.
A thinner grade of engine oil may help too.
John :)
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Mines starting to do the same thing in the cold weather, but I had the glow plugs changed about 3 years ago (well 3 of them, they couldn't get the 4th out), so I'll update you next week when the garage has had a look at it.

But they can last about 100K, so at 95K, I'd say they'd be the first thing to change.
Are diesels always a pig to start in winter - it's my first? The battery was replaced about 4 or 5 years ago.

Any help and advice appreciated.

No, a properly working diesel should start within a few seconds of cranking even in winter (after glowplugs have heated fully).

I've barely seen the glowplug light on our Kuga (2l PSA engine), never had any problems starting even in sub zero temps.

5 years on the battery might warrant an new one, they don't last as long as they used to and Diesels require a lot more cranking effort due to higher compression.
An easy way to test them without removing them is to disconnect the wires on them. Then, using a test lamp connected to the POSITIVE terminal of the battery, touch the probe onto the glow plug terminal. If it lights up, it’s okay. If not, it’s ****ed so replace it. They either work or they don’t so I only replace all 4 if three have gone, which is rare. Just one not working can give you starting problems.
..or if you have a multi meter check the resistance from the top terminal to earth, should read around 1 ohm. I may be wrong but is that not a Peugeot Hdi engine? I know that the Multipla uses one, if that is the case its a common rail which should start OK without the glow plugs, the most likely reason for it not starting in that case is a weak battery or starter motor, they need to spin quite fast to start.

Does sound like the Glow plugs have failed. The symptoms you describe are the same as the ones as a mate had on his van - the same van as yours. The plugs are reasonbly priced but can be a pig to fit. They are at the back of the engine and you have to (re)move coolant expansion tank and the remove the inlet ducting along lots of other engine acillaries.
Thanks for all of your replies - really appreciated.

The dash light for the plugs comes on for a very brief time - 2 to 3 seconds. If I can get to the plugs, I will test them with my meter for amps/continuity - when the snow stops.

I'm wondering if it may be the battery. When it failed to start yesterday, I gave it a two hour charge then it started instantly. I had a short drive and afterwards the battery voltage was 12.4 volts. Today I tested the battery and the reading was 12.2 volts. I haven't tried to start it today - just put it on charge again to give it a really full charge. The reason the van originally failed to start may be down to the fact that I have recently done lots of short town trips, usually with headlights and blower on most of the time. Maybe it's just run down or poss getting weak. Will monitor and see how it goes.

And to PerterN - yes, I believe it is a Peugeot HDI engine. Great engine, but access for most things in the engine bay is difficult.

I use Mobil 10w40 oil.
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12.2 volts is practically half-charged. I’d charge it up if I were you and get it tested. Sounds like it could need replacing, especially this time of year.
OK thanks. Put the charger on at 2pm today and will let it charge to this evening. Will take a reading then, and another in the morning to see how it held it's charge overnight. Then poss take a reading when it's cranking and one with engine running.

I'll report back.
I changed my 5 year old Evoque battery last week. Showed up fully charged but didn’t have the guts to turn the engine over. I also changed the one in our diesel Golf too - it was 8 years old and with winter apon us, I just felt it wise to do so. If your battery is 5 years old, what have you got left in it - £20? Is it worth trying to eke that out another year to save that £20 considering the aggro you’ll have if it just lets you down just once? A quick way to check (if you have no specialist test tools and providing you can remove the battery caps), is to spin it over until the engine starts to go slow or stops and with someone keeping the key held round in the start position, have a look in the cells. If one is fizzing like it’s got an Alka Seltzer in it, it’s dead. Replace the battery. Use a torch to look in the cell, not a naked flame though!
12+ with no load doesn't mean much, an almost flat battery will read 12v you need a load tester, the starter will do, see what the battery reads with the starter engaged, much less than 10 volts and the battery has had it.

May be worth checking the alternator output, it should cope with doing short runs. Not like dynamos in the old days.
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