svfr@scanvaegt.no

i Have recently bought a 95 Audi a8 2,8 Quattro it was running fine for a few week and one morning it did not start... i have troubleshooting this for one month now and it still wont start.
The symptom is No spark and no fuel to the cylinder, fuel pump is ok but no signal to the injector.
i have tried the following with no result.
Vagcom show no problem...
have replace main battery and tried with jump start cable.
Tried new ECU
New Cam position censor .
Checked the fuel pump relay,
have check the grounding all around and it seems ok.
have measure Crankshaft censor (800 Ohm)
Have check all fuses =ok
it look like the ECU don't send the correct signal to the ignition module and the fuel system but i am not sure.
i suspect it maybe cold bee a problem whit some short circut in the system causing the voltage to the ECU Drop but i cant find it..
any steps for further fault seeking is highly welcome..

the_duke

I don't know anything about a 95 but on a newer car I would replace the crankshaft position sensor. If that is bad you get no spark or fuel because the ecu doesn't know the engine is turning.

svfr@scanvaegt.no

i Have remove and measure the Crank Shaft censor and i am getting Ca 950 ohm. and i am 90% sure it is working...
but something i was reading on another forum get my attention. There is a pin on the flywheel the crankshaft censor need to determine if the engine is running.
Sometime this pin fall off.

quattroworld.com Forums: UrS4/UrS6/S2/RS2

if this pin is missing i will get the same symptom as a bad crank shaft censor.
i have try to use a inspection camera in the hole for the crank shaft censor but i cant decide 100% if this the pin is missing or not.
i will try to remove starter motor to get a better look.

Articus

I would just replace the crankshaft position sensor, is it still original from factory?
They can be had for $50, bosch oem equivalent.

MikkiJayne

That's only for the early engines, and that thread in particular for the 5 cylinder. Your V6 does not have a pin - the crank position sensor counts the flywheel teeth.

Does VCDS show any rpm while cranking?

svfr@scanvaegt.no

cant see any rpm on vagcom, when i use the inspection camera in the hole for the Sensor, i cant see the teeth on the flywheel, i can only see solid metal an at one point some marking that has some different texture, it may be a pin a magnetic field or i maybe wrong... i have order a new Crankshaft sensor to be sure this is not the problem, will receive it an about 8-10 days, will wait for if before i try anything more.
The old sensor is the original Audi sensor and is 20 years old, i sure hope this is the problem-

MikkiJayne

This is what the flywheel looks like:



The sensor is looking at the slotted ring and will produce a signal each time one of the teeth between the slots goes past. The gap tells it that it is at TDC. This is known as a 60-2 timing wheel and is very common.

The torque converter sits inside this ring, so that may be what you're seeing if you're not looking perfectly down the centre of the sensor hole.

Hope the new sensor fixes it

jfrahm

You should be able to see pulses from the CPS with a decent multimeter, at least some AC volts. It's more often the wiring to the sensor that gets some breaks in it. If you can look for voltage or pulses at the ECU that is a helpful test. Also look for an alarm and a disabler line from the alarm module to the ECU.

rbjones17

I had this problem on my A8 D2 a few weeks ago. It drove me nuts. Turned out it was the wiring from the Crankshaft position sensor just behind the drivers side camshaft where the actual part wires into its harness just below the rear of the hood at the firewall area. I realized this was the problem because when I would turn the key on, I couldn't hear the fuel pump kick on but when I wiggled the crankshaft position sensor wiring I could hear the fuel pump intermittently kick on and then it would start right up. I zip tied the wire on top and reattached it properly and now all is well again.

svfr@scanvaegt.no

i have replace the crankshaft sensor. i use a multi-meter to compare it to my old sensor, and it is clear the old sensor was defect. the new sensor show 950 ohm but when i touch the magnetic end with some metal it shows over 10 M Ohm, the old sensor did not show any reaction.
But the car still not start, no spark and no fuel to the cylinder.

i have connect Vagcom but now i cant connect to the ECU. i get error 59 connection error. (i have tried both of my ECU)
I suspect sometime in my fault seeking i have done something stupid resulting in the ECU don`t working. i have check all the fuses and connector and cant find any fault.
now i am googling for wiring diagram of the ECU, i will check power and grounding to the ECU and any relay that might causing the ecu to not respond.