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#1
1st August 2017, 06:21 PM
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TDI hot start issues
Hi guys. I'm wondering if someone could plug their 4.0 or 4.2 TDI in and tell what the RPM of the engine is while cranking. When the 3.0tdi A4 is cranknig it spins over very fast in comparison. (keep forgetting to plug in and see what speed it turns)
My hot starting problem is getting worse and worse and worse. The other day, after having sat on the drive over the weekend it wouldn't even start from cold. The engine sounds slow and gets slower. Tonight after trying to start it I plugged my wee code reader in. On its own battery it started off turning at c150RPM and by the time it decided it wasnt going to start it was only doing c120RPM. With the jump leads on the A4 it started turning over at c170 RPM slowing to the mid 160's. It isnt even starting with a jump until it has sat and cooled for 3-4 hours. Also, I used to be able to start from cold at work, then stop at the supermarket on the way home, by which time the engine had heated up to around 70 degrees and was still able to start it after doing the weeks shopping. Now it takes several attempts and usually needs the booster battery to start. Ive bought a new starter motor for it. I'm not one for blindly throwing replacement parts at a probelm in the hope of fixing a problem but it was really very cheap so i thought i moight as well take a punt. Taking it to the "experts" to have it scanned on dealer level VCDS software gave me no information and the crank sensor did nothing to help so if this doesnt work I'm seriously considering scrapping the thing. gill 
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#2
2nd August 2017, 05:17 PM
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If it cranks faster using another car as a booster, then your battery must be bad.
Try charging it fully, either by a long drive (3-4 hours) or put a charger on at least over night. If the problem doesn't go away, you need a new battery  But as you have thought of yourself, a worn out starter motor will crank considerably slower than a new one.
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06 A8 3,0TDIq My daily driver and project... 97 A4 1,8Tq. Powered by a 4,2 from the '01 S6, full rollcage, FIA seats and 6-point harnesses, B5 RS4 KW Competition race suspension, B6 S4 brakes, 18" Toyo RS1 slicks, carbon fiber roof. V8 trackday racer  14 VW Caddy 1,6TDI from my employer.. (X)00 A8 2,8q, (X)97 A4 1,8Tq, (X)92 S4 2,2Tq, (X)92 80 2,3E
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#4
2nd August 2017, 08:52 PM
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Your symptoms sound exactly like crankshaft position sensor failing which happened on my D3. Only started well when cold and it flattens the battery everyone you crank it without starting. In the end it packed up altogether and the car wouldn't start until it was changed.
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Confidence is the feeling you have before you know better . . . .  Audi A8 D2 3.7 Quattro Sport 1999 FL - Melange 2nd Place Winner - A8-Freunde Annual German Meet 2012 at Edersee 20" x 9" Bentley GTC Wheels with 385mm W12 Front Discs & Bentley Caliper Covers, Front Lowered on Coilovers, Xenons, Combined DRLs and LED Foglights to modified OEM front fog lamp position, Alcantara/Leather, Full Black Alcantara headlining + pillars and blind shelf, Bespoke Flat Bottomed Sports Steering Wheel, Dark Myrtle Wood, Autodim Mirrors, Bose, Blinds, Digital TV, Ski Hatch, Modified rear exhaust section for extra V8 Burble Audi S8 D2 Final Edition 2002, Avus Silver with Red Leather Interior Tiptronic with Sport mode button, Sony rear entertainment package, Bose sound system, Audi Navigation Plus, 20 inch Final Edition alloys, Full Cat Back Stainless Milltek exhaust, giving a great V8 burble Audi A8L D2 4.2 Petrol with LPG - Ebony Black Audi A8L D4 FL 4.0T Petrol twin turbo - Havana Black Audi A2 1.6 FSi Sport - Dolphin Grey with Votex body kit and Red Leather Interior and some other A8's A8L's and Mercs
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#5
3rd August 2017, 06:44 AM
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Quote:
Wasn't clear if the battery had been coded to the car tho.
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1996 A8 4.2 QS. Bose, Solar roof, um...um... rally sport towbar. Now gone to a new home as the Traders 8. Bright yellow bus o love.
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#6
3rd August 2017, 09:23 PM
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It's actually had two new crank sensors. An intermotor one which I thought might have been a fake (cheapo off ebay) and a genuine bosch one straight from the bosch factory.
Its had three new batteries in the last two years as well. The current one was brand new in I think October. I'm beginning to suspect something to do with fuel pressure but without VCDS I cant check. I'm hoping to get it in to my local garage for a scan next week sometime. Cranking speed is definitely low though I think. I'm not going to bother with changing the starter until Ive had the fuel pressure checked. gilll
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Hybrid Mode
