300tdi hard to start

I have a 300tdi auto '98 and it has been getting worse and worse to start lately.
To start it now it has to be cranked for a few minutes! It started off
with prolonged cranking from about 10 secs now it seems to be getting longer each time!
This ONLY happens when its left over night or long periods, once started it will be fine all day.
It had new glow plugs about 5 months ago and a new battery last year. It was serviced about a year ago and has only done about 8k since that.
When it does finally start there is LOADS of white smoke out the exhaust as it the glow plugs where not working.
I know the glow plugs are getting power with a 12v tester and are pretty confident that they are not all broken within 5 months. I have had disco's for years now and only ever change 3 glow plugs (leave the one behind the ac pump) and all have worked fine including friends ones.
Could the fuel be draining back?
Please help!
Mark.
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Hi Mark,
I had a problem with my TDi havnig starting problems, particularly if parked with engine up a slope. My LR guy changed the fuel lift pump that time, and the problem went away - he said the diaphragm had gone allowing fuel to bleed back.
I have also had a problem where after changing the injectors, I had a similar problem which could be alleviated by bleeding the system. This eventually went away by itself. Theory is that if there is fuel in the lines, the injector pump doesn't need the fuel lift pump - it can suck the fuel through itself. It's only of the lines are empty that the lift pump comes into play. Might be worth checking you have no loose connections on the fuel lines from teh tank.
I would still check the glow plugs. I know that here in Zimbabwe, I live in warmer climes, but glow plugs failing will give you the symptoms you mention. What happened with mine is it kept starting until all 4 had failed! It obviously needed a hot spot in just one cylinder to be able to get everything to fire.
You say you have checked that the plugs are getting 12V. On my Tdi, my voltmeter shows a significant drop in voltage when the glow plugs are on. Turn ignition to first position, get just over 12 volts. Turn to second to get the heaters on and voltage drops to about 11.5 as the heaters draw their current. After the heaters switch off, you should get back to 12V again. If this isn't happening, you've had a duff set of glow plugs.
Good Luck Graham Carter Harare Zimbabwe

longer
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mark i would change the heater plugs as matter of course, just so you know they are definately good ones in there .
also i would tighten the fuel filter up a bit more .
i had this problem with my 300tdi and i had to bleed the injectors a few times to get it started in the course of a week or two after fitting a new fuel filter cannister .
i tightened the filter a bit more and it didnt play up after . if you had changed the filter and undone the water trap bung on tottom for any reason , you may also tighten this up a bit more .
you may have a very small airleak in the system via the fuel filter seals .
fuel filters are only a couple of quid new , so perhaps buy another filter and 4 heater plugs and make sure filter is on tight .
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Assuming it runs fine once it's going then white smoke at start up equals unburnt fuel. Glow plugs are hardly needed at this time of year so it doesn't matter if they are knackered anyway. So if it has fuel but won't start it must be a lack of compression, an air leak or only one cylinder getting fuel and the others not. Therefore it is either an air leak in or a cylinder head fault or a duff injector pump.
Conclusion: As you had it fiddled with in the last 5 months my bet is on an air leak in, probably around one of the glow plugs.
TonyB
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TonyB wrote:

What a load of codswallop - any compression (ie air) leak that's large enough to have an impact on cold starting will make so much noise that nobody in their right mind would drive the vehicle.
--
EMB

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an
I stand corrected then. TonyB
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On or around Mon, 17 Apr 2006 16:34:48 GMT, "Mark C."

could be. however, lots of white smoke on startup is characteristic of lots of fuel in the cylinders and exhaust.
a good TDi doesn't strictly need glow plugs if the battery's good. I'd check that the plugs are working though - might be the glowplug relay is iffy. You can try manually heating the plugs, by clipping a jump lead from the battery + to a handy glow plug terminal for, oh, say 10s or so. If that makes it fire up straight away, then you've found your problem.
You can also test the plugs by pulling 'em out and wiring them up and seeing that the tip gets red hot.
Poor starting on a diesel can also be down to poor compression, though.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"Festina Lente" (Hasten slowly) Suetonius (c.70-c.140) Augustus, 25
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Thanks all, think i will start with the tightness of the fuel filter first, maybe a new one then i will get a jump lead on the glow plug rail then check the glow plugs.
They where after market plugs so possibly suspect.....
I know form experience that these engines will start on 1 glow plug even at 0 degrees in the winter! thats why its so fustrating!
Thanks all for your replies!
If u keep think of any more then keer them coming!
MC.
PS. forgot to say it had a new lift pump fitted 2 yrs ago too. - old one leaking.
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"Mark C." <> Thanks all for your replies!

Fairly topical for me ATM as my P38 began starting badly after I noticed a fuel leak (just a few spots) a couple of weeks ago. It's suprising how long I have to crank it before it starts. (Although curiously it sometimes starts straight away - even after standing overnight).
It goes in for repairs today so I'm hoping they sort out the cause without too much hassle.
- Tom.
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