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Turnover but no fire until throttle applied


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I have read lots of threads that say you should not apply the throttle until the engine fires as this would affect the engines cold start.

It was -3 C this morning when I tried to start the 300 tdi - the engine turns over fine with the starter but without any throttle is very reluctant to fire.

Has new battery, new starter, new earths to chassis, bellhousing, starter and block....

Would be very grateful for some counsel....

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Thanks K88 MUD that's what I was thinking - there are some a set of 4x NGKY-729U glow plugs for a reasonable £32.78 on Fleabay here if anyone else is having the some problem with their 300 TDi

http://cgi.ebay.co.uk/NGK-GLOW-PLUGS-Y-729U-Y729U-STOCK-CODE-2203-/310268183493?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item483d6cc3c5

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A 300tdi should fire up at -3C w/o pre-glowing at all. It only has a little rougher idle for the first few seconds (at least mine one has). How many miles do you have on the injectors?

Robert

PS: Check the glow plugs before you replace them (disconnect them and check on continuity to ground).

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...

It was -3 C this morning when I tried to start the 300 tdi - the engine turns over fine with the starter but without any throttle is very reluctant to fire.

You are implying that it fires with markedly less reluctance if you give it a bit of throttle, did you mean to imply that? Or were you just wondering whether to try a bit of throttle?
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Hi David -thanks for your help and post

Sequence was as follows

1) turn ign to Pos II and wait for glow plugs light to go out

2) turn from ign Pos II to III the starter motor engages and cranks the engine - this goes on for about 5 seconds - then I reset

3) repeated 1 and 2 and got the same

4) repeated 1 and 2 and lightly feathered throttle this time - engine fires roughly and then after about 5 seconds is OK

Once started like this first thing in the day - its starts on the turn at all other times

I gather that it should be possible to get a 300 tdi to fire without the use of glow plugs in theory - but cant reconcile why they are fitted if this is true.

Also wrt the injectors - truck has only been ours for 4 months - but has been well serviced and maintained - done 90k.

You are implying that it fires with markedly less reluctance if you give it a bit of throttle, did you mean to imply that? Or were you just wondering whether to try a bit of throttle?

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Ok.

In the light of that I'd just go with starting with a touch of throttle in cold conditions.

I suggest the initial running rough is either a lazy glow plug, or a badly spraying injector. Once the combustion chamber has warmed up a tad the sprayed fuel is burning OK, and it sounds as though the engine is retaining enough heat while standing during the day to give better initial firing conditions, thus the defect isn't noticable.

Removing, testing, and changing whichever glow plug is found faulty is probably the cheapest way forward, but it might be worthwhile looking out for somewhere that will test the injectors.

Best if you can take them out and arrive with them in your hand, but that does depend on you having other transport available, and the workshop ability + kit to remove and injectors. Don't forget any fire washers that might need extracting separately.

If you believe the 'should fire without glow plugs' story, then that makes the fault either poor spray pattern due to faulty injectors or low pressure from the fuel pump, or the battery and starter circuit isn't good enough, causing the starter to not spin the engine fast enough to generate the heat due to compression that the fuel needs in order to burn.

Worn bores and rings could also be a cause of poor compression when cold.

Personally I'd say 'some do, some don't' when it comes to starting without glow plugs, so I wouldn't class the need to use glow plugs as a fault.

HTH

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Thanks David

Just braved the -4 C outside currently at 17:30 - to have a closer look.

Did the resistance check across them and only showed 16 kohm which I think equates to 0.016 ohm - so something to be concerned about.

Whipped a couple of them out - both look thick with oil and on the poor end of the spectrum - Beru components - tried to pass 12v across the top terminal and casing as earth of a spare 12v car battery - dead as a dodo - both of them.

Tried this again using the new battery in the truck same result.

So no wonder the poor thing is struggling to start with no "help" at all.

Guess what I'm buying on the morning ! Thanks again this forum is fantastic.

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I remember about a year ago having V.cold day start problemss with my 300 Disco.

Tested and found only one of four working! :o

Changing all to new made a massive difference without altering anything else. Still ok today and that's even though I've yet to sort out an overnight fuel or oild seepage - so they're soaked in cr*p as well!!

If working they really do glow bright red hot when connected and grounded held with insulated pliers. I had not seen them working in 'real life' before and took advice from this forum and did the job. Thought better of the cheaper 'eblag' ones in favour of Bosch from local factors - never looked back HTH a Little.

Paul. :)

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Now that's a good thought - can anyone advise me on where I can find the sensor - had a look on RAVE but did not find it... thanks

On the top of the inlet manifold is a sensor, this is as far as i'm aware the cold start sensor.......... which basically richens up the fuelling when stone cold..... maybe that needs changing.....

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Well I'm glad I am not going mad!!

On othe defender fora there is mention of the cold start advance that is part of the Bosch injector head. Have been trying to find out more .... Can any wise person point me in the right direction please ? Am really quite intrigued as to what it is and how it works.

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Thanks Western that's really kind of you.

So - does this function only with the EGR - or does it have a function to control the cold start advance facility on the Bosch pump head ?

it'll be for the EGR system IIRC. Item 31 on the attached microcat parts info page below, also used on Td5 as the cooling system temp sensor.

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