OA 69

and fuel pressure regulator ?
No fuel pressure after 5-6 hrs
Needs new regulator ?
It is 1996 a4 2.8L 200.000 Km

turbo510

What problem are you trying to solve? No check valve after the fuel pump, but I see a test for fuel pressure to stay higher than 32 PSI (220 kPa) for 10 minutes after shutoff. I wouldn't be surprised that you have no pressure after 5-6 hours, there's no accumulator like the old CIS cars, so only a small leak past the pump's check valve, or the regulator, will release all the pressure.

OA 69

Engine Will not start in the morning or after 5-6 hrs.
After 3-4 times cranking it starts normally
Is it fuel pressure regulator problem ?

turbo510

Often a temp bad coolant temp sensor. VAG-COM can show the reading, but if the sensor tells the ECU that the coolant is hot when the engine has cooled off, it won't have a correct mixture for starting.

OA 69

Vag-Com result:
VAG-COM Version: Release 311.2-N


Chassis Type: 8D - Audi A4 B5
Scan: 01,02,03,08,15,17,25,35,45,55,56

Address 01 -------------------------------------------------------
Controller: 8D0 906 266 B
Component: 2,8l V6/2V MPI OBD2 D01
Coding: 01251
Shop #: WSC 04752
No fault code found.

Address 02 -------------------------------------------------------
Controller: 8D0 927 156 J
Component: AG5 01V 2.8l2V US D89
Coding: 00000
Shop #: WSC 00000
1 Fault Found:
00526 - Brake Light Switch-F
27-00 - Implausible Signal

Address 03 -------------------------------------------------------
Controller: 4D0 907 379 J
Component: ABS/EDS BOSCH 5 7679
Coding: 0265109024
Shop #: BB 37679
No fault code found.

Address 08 -------------------------------------------------------
Controller: 8D0 820 043 H
Component: A4-KLIMAVOLLAUTOMAT_D65
Coding: 00160
Shop #: WSC 06335
No fault code found.

Skipping Address 15-Airbags

Address 17 -------------------------------------------------------
Controller: 8D0 919 033 G
Component: B5-KOMBIINSTRUMENT D08
Coding: 00362
Shop #: WSC 00066
No fault code found.

End -------------------------------------------------------

Another detail: -black spark plugs-mixture to rich ????

turbo510

A bad sensor won't necessarily set a fault, you need to let the car fully cool to ambient temp (overnight at least) then step through the various readings (RPM, timing, etc.) until you see temp, which should be about the same as the air temperature. I've had the same symptom on my '96, the temp reading was -50C or something like that. The over-rich mixture makes the engine hard to start and your plugs sooty.

OA 69

Thanks for your advice.I'll start over from coolant temp sensor

Slawomir

600whpA4

Have you tried turning the key on till the pump has stopped before starting the car?

Sounds like the check valve in the pump has gone bad causing all of the pressure to leak off during that 5-6 hrs.

OA 69

Yes,for few times.Fuel pump makes noise for few seconds.After 3th cranking engine will start...

turbo510

The lines are full of fuel, so as soon as the pump starts, the pressure is ready. I left my 2.8 in the garage during vacation for a week, obviously no residual pressure, and it lit immediately on the first crank.