Passat diesel AWX firstlook need interpretation

Ask for and share advice on using the PicoScope kit to fix vehicles here.
Post Reply
GENU40
OneWave
OneWave
Posts: 12
Joined: Tue May 17, 2016 5:18 pm

Passat diesel AWX firstlook need interpretation

Post by GENU40 »

HI
I took some measurement with the firstlook sensor on the above engine.
I have previously unplugged the crankshaft sensor so the engine will not start.

The issue that I have with this car is that after a minute from starting at idle it start balancing the whole car.

I replaced the flywheel along with the clutch kit. But it is still doing it. After 4 or 5 minutes it will stop and the car will run normally. I have also checked the injectors with vag com. One of them on cylinder four had 1.8 compensation. I replaced it with another one, not new, and now I have 1.0 compensation on that injector.
Now I suspect a mechanical issue with the engine. So I tried firstlook diagnostic pulse sensor.
First I took a measurement at the oil dipstick with the engine cold and cranking. Then a measurement at the exhaust , same conditions. Then I plugged back the crank sensor run the engine and took the same measurement at the oil dipstick and at the exhaust. I will try to attach the wave forms.

I need some help in the wave forms inetrpretation. Unfortunately I do not have the reference for the number one cylinder on the screen. But an honest opinion with the integrity of the engine can be done. I can see the waveforms are not even.

Thank you.
Attachments
Diesel_20180602-0001 DIESEL EXHAUST AWX COLD CRANK.psdata
(2.29 MiB) Downloaded 522 times

GENU40
OneWave
OneWave
Posts: 12
Joined: Tue May 17, 2016 5:18 pm

Re: Passat diesel AWX firstlook need interpretation

Post by GENU40 »

Hello everybody
I did a relative compression test with an amp clamp. Looked ok. So I start looking in a different direction.
Meanwhile the client told me that when the fuel tank is below half of the capacity the car starts and works better.
So I brought him a brand new original fuel tank cap having in mind that the old one was probably causing vacuum inside. After that , and this is for the past week, the car works fine.
I noticed the part number for the fuel tank cap was replaced three times.
At this point I asked him if he wants to check the fuel pump which he agreed. I imagined that it could be worn out after running for so long in difficult conditions.
So I am attaching the waveform of the above diesel fuel pump. I asked a friend of mine who works in a VW dealership and he told me that I should expect 7 to 8 amps of current. Unfortunately the waveform shows 2.5 to 5 amps of current. I used the 60 amp clamp with the 20 amps of current setting. I used a jumper on the fuse 28 on the side panel inside the car of 20 amps.
What I am asking is for a second opinion. Looking at the waveform I would say the pump is worn.
If anybody came across this issue a second opinion would be appreciated.
THX
Attachments
20181103-0001 PASSAT AWX.psdata
(6.93 MiB) Downloaded 403 times

landroverman1958
OneWave
OneWave
Posts: 43
Joined: Thu Dec 04, 2014 7:53 pm

Re: Passat diesel AWX firstlook need interpretation

Post by landroverman1958 »

Hi I would say the amperage is lower than i would expect,i would agree that your friend is correct of the amps drawn on a good pump,that is to say if the powers and grounds prove to be good at the pump,also what pressure at the intermediate pump?any sign of aeration in the supply to the engine?check volume of supply of fuel.and of course when was the filter last replaced?Any bits of foreign materials in the filter housing.

GENU40
OneWave
OneWave
Posts: 12
Joined: Tue May 17, 2016 5:18 pm

Re: Passat diesel AWX firstlook need interpretation

Post by GENU40 »

Thank you for your quick response.
Next week I will try to measure the pressure at the intermediate pump. I need a special tool from VW but I know someone who has it and he will most probably help me out.

GENU40
OneWave
OneWave
Posts: 12
Joined: Tue May 17, 2016 5:18 pm

Re: Passat diesel AWX firstlook need interpretation

Post by GENU40 »

Finally I discovered that the car had not the right fuel filter So I replaced the filter with the right one.
Now the car works fine.
Thank you for help.

Post Reply