Engine Mechanical problem
1998 Audi A8 V8 Four Wheel Drive Automatic
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Hello, I have 1998 Audi A8, and one day I parked my car and turned off the engine, and the next day went to go start it, but it would not start. I also have another one and took the computer from the other one, and put it in to my working A8, and it worked, so the computer in it is fine. I checked the fuel injectors harness, and there is no power in it. What could have possibly happend?

theres a few possibilitys, first thing to do is check for key on power. with the key on the power terminal should have +12v constant, you can check that with a test light.

next step if that is there is to check for a pulsing ground signal which completes the circuit and fires the injector, if you have a noid light hook it up and crank, the light should flash. if not its lacking one of the above.

are you getting spark and good fuel pressure to the rail?

Hello, I hooked up the noid light, and nothing was flashing. But I have have fuel pressure and good spark.

unhook all the injectors and check again for a pulse when cranking.

do you get a real fast blip when turning the key to on?

are you getting +12v to the injectors with key on? or none.

can you mark down all the injector colors and what cylinders and post them here?

you want to check for pulse on all cylinders also.

Hello again, I tried everything you told me to do, but none of the injectors have any pulse. I want to know where the pulse is supposed to come from (ignition coil, a relay etc.), basically what causes the pulse to happen.

you get the pulse from the computer first of all but what it gets the information from for pulse is the camshaft position sensor.

its located on the rear of the left cylinder head. unhook it and try to start the vehicle, you may have to crank it for 10-15 seconds, and it should fire up if the camshaft sensor is at fault, but it still could be bad and the vehicle not start with it unplugged.

also i forgot to mention can you have it scanned for codes to see if thers any issues before we get too advanced?

I scanned the car for some codes, and I got a code of P1856.

P1856

Throttle/Pedal Pos.Sensor A Circ. Error Message from Engine Contr.

i would like you to check the TPS voltages closed and wide open throttle. post them back here.

also disconnect the tps then try to recheck for a pulse. anything?

try disconnecting cam sensor and seeing.

if that doesnt do it chances are thers a damage in a harness somewhere, try wiggling the connectors around and see if anything. if not its time for a pin to pin test and a pin to ground test.