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Matt
Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 22166
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi Matt, warm start problems with 2004 Audi A6 2.5 Tdi V6

Customer Question

Hi Matt, warm start problems with 2004 Audi A6 2.5 Tdi V6 (163). Car has 93,000 Miles, full Main Dealer Audi Service history, last serviced by audi at 90,000. MultiTronic Gearbox. Battery is new and cranking speed is fine.

The fuel tank is full, cold starts are fine but warm starts take 3 attempts and lots of cranking

After a long run I can turn engine off, and re-start no problem. I can leave it 10-15mins and still re-start no problem. Leave it a couple of hours and lots of cranking required.

Submitted: 3 years ago.
Category: Audi
Expert:  Matt replied 3 years ago.
Hello

I'd check that you're getting full power to the glow-plugs, they pull a lot of current so take care when checking but see if the relay is clicking when the ignition is turned on first and also check the fuse if this is OK check to see if the engine earth strap is also OK.

If the plugs haven't been changed in the last 20K then they may have to be replaced.
You can test the glow-plugs with a multimeter by measuring the resistance across the plug ( between the power connection and the body) it should be around 4-8ohms if its tending to infinity / open circuit the plug is faulty or by using a clip on current clamp, either on the supply wire to glow plugs or onto engine earth, with glow plug light on you should see 15-20amps for each glow plug fitted, 4 cylinders would be approximately 60-80amps.

it’s also worth considering fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.