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my 1999 audi A 6 will not start.
Car: Audi, A6, 1999 - Back to Fix-It - Audi Repair Manuals
Q.my 1999 audi A 6 will not start. it cranks and occasionally fires but does not start. it was running fine with no roughness.
I already checked/done: just tried to start it. cranked intermittently for about 5 minutes until the battery was weak.
Answer The 1998 - 2001 2.8L 30 valve motors (ATQ, AHA) are prone to "flooding" when cold. This condition is typically brought on after a short drive cycle on a cold engine. A classic example would be starting the vehicle cold, pulling it out of the garage, and shutting it off, attempting to start the next morning. When attempting to start cold in the a. M. the engine will be difficult to start, and run poorly if at all. This is usually caused by carbon particles (byproduct of combustion) getting stuck on the valve seats and not allowing them to seal. The reduction in compression does not provide sufficient pressure and the combustion event can not occur so fuel is unburned and the cylinders become "flooded" with unburned fuel.
This condition can be worsened if the vehicle is run on substandard fuel for an extended period. This engine is designed to run on premium "top tier" fuel. It can be run on mid-grade "top tier" fuel with reduced performance. Only "top tier" fuels have sufficient detergents to prevent the build up of carbon and fuel deposits in the injection system and combustion chambers. See toptiergas. Com for more details.
If this cold start/run condition is caught in the early stages, you can disconnect the fuel pump fuse (in the fuse panel on left of dash) it should be the third fuse from the bottom (blue/15) on the first row. There is a fuse legend on the inside of the cover to confirm location. Then try cranking over the engine for some time with the accelerator pedal to the floor, possibly almost one minuet and see if it begins to catch. If so reinstall the fuse while still cranking. If it does start try and maintain the RPMs at about 2,500 until it clears up. The vehicle must be driven and allowed to fully warm-up before shutting down.
If the cylinders are suspected of excessive carbon build up the Audi dealer should have a fuel injection cleaning system that uses Wynn's cleaning solution. It is run through the injector rail on a running motor in place of the vehicles fuel system which has been disabled. This cleans the injectors, the back sides of the intake valves, and the combustion chambers to some extent. When combustion chambers have excessive carbon buildup you can remove the spark plugs and poor the solution directly into the cylinders and let it soak for several hours, after which time it is expelled and the vehicle is restored to running order. As an owner I DO NOT recommend you try to do this yourself, there are many steps and precautions that are best left to a professional. What you could do would be to periodically run a can of fuel injector cleaner through the fuel tank to help reduce deposits.
If the vehicle is very flooded, I suggest after removing and drying the spark plugs, you disconnect the fuel pump fuse when starting it as described above. I have had instances where I had to remove and dry the plugs a couple of times. When you do have the spark plugs out, if you have a air blow gun with a long nozzle, I suggest blowing out the cylinders in an attempt to dry them. Then its just a matter of waiting for the carbon particles to clear from the valve seats. It also helps to have a strong jumper battery (not a charger) hooked up for this extended cranking.
Another possibility would be a failed fuel pump. Typically when the fuel pumps fail it is after sitting for some time, usually cold. Typically the car may fire and run or sputter for a few seconds then die and not start at all (does this sound familiar?).
If it is a "carbon flooding" issue as described above the vehicle will typically start, run poorly and stall, then will crank faster than normal and intermitently backfire and fire, but never quite catch.
If the vehicle won't start have someone else crank over the starter while you go back to the area of the right rear door, listen underneath the car for a "buzzing" of the fuel pump. If you hear the pump and it is still not starting the fuel pump is likely not the cause. If however you DO NOT hear the "buzzing", bang on the bottom of the fuel tank with your hand or if you have a big rubber or plastic hammer that works better. Often this will giggle the electrical brush contacts of the fuel pump enough to allow the motor to start, as should the engine at this time.
Addition I removed a spark plug and there was quite a lot of motor oil in the plug area. Does not look good. The car ran fine until yesterday. The day before I pulled it out of the garage to clean the floor, pulled the car back in, left it overnight and tried to start it yesterday with no luck. The oil can't be a good sign. What do you think happened.
Answer If there is oil in the spark plug holes around the outside of the spark plug, this is due to the valve cover gasket leaking and does not effect performance, but as you say "it's not good", it should be corrected. The wet spark plugs (inside the cylinder) are unburned fuel. This is what must be cleaned and dried out (or replaced) to attempt a restart.
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