2005 VW Passat 2.0 BHW TDI Nightmare Hotline Ref. #4056170

Vehicle is a crank no start condition but only when the vehicle has been fully warmed up, driven hard, and heat soaks for 5 minutes. After 2-4 very long cranks (resting in between to cool starter), vehicle will stumble to life, run poorly for the first 30 seconds, and then clear up. If vehicle is cold and has been started, it has no problem starting at all. The symptoms are very near that of air being in the fuel system

Note: Timing belt has been done in the last month and problem did not start until timing belt was done.

TESTS

-Placed vehicle in service mode once again and ensured my crank tool and camshaft tool slide into their spots correctly. Also removed tandem pump and ensured the cam lock tool will slide into slot on back of camshaft!!! Timing is good, and torsion value is at 0.5KW

-When problem is persisting, vehicle will fire and run with diesel starting fluid introduced into intake manifold.

-Ensured intake flap is not staying stuck closed or EGR valve sticking open. Did find major carbon build up, so I removed intake manifold and cleaned everything well and no difference was found.

-Measured 15 PSI to the tandem pump after the filter and get approximately 60mL of diesel in one key cycle. While vehicle is running, the PSI from lift pump stays at 15 PSI.

-Replaced fuel filter and thermostatic T to see no change in vehicle's status.

-Removed plug on back of Tandem pump and ran vehicle to see PSI jumping from 50-130 psi at idle. Replaced Tandem pump and saw correct flow of about 50 psi at idle and 120 at

Injector pulse- Used a noid light and an oscilloscope to ensure I have Injector pulse at the Cylinder head jack for the injector harness and saw a very dim noid light. Tested resistance on injectors and found all of them to be high (about 4.4 ohms). So i removed valve cover and simply tested the common ground from the cylinder head jack to the splice at the end of the harness and found the resistance there at 4.4, while all the injectors themselves had about 0.5-0.7ohms. Replaced the harness under cylinder head and issue still persists

-Timing. I removed front bumper and checked static timing and the timing tools slide into the crank first (yes the correct arrow and timing tool for crank were used) and then the rig pin slides easily into the bore in the cylinder head through the camshaft hub as well. Arrow for tensioner is perfectly in the middle of the indicator and Torsion value is 0.5KW when vehicle is fully up to temperature.

Air: I placed two clear hoses at the fuel filter. One is the supply line from the filter to the tandem. That line stays clear no gas bubbles the entire time. The other line I put on the return side from the tandem pump to the filter and it begins clear but after 20 minutes of idling small bubbles begin to form. Once the vehicle is fully up to operating temp there is a steady stream of bubbles on the return line! It's actually just foam there is so much air. You then shut the vehicle off and see the air rush back towards the tandem pump.

-I have checked Oil levels and quality to ensure that there oil level is not increasing or smelling like diesel due to fuel leaking into crankcase

I have checked cranking speed Via VCDS and see the RPM's are identical to when the engine is stone cold versus when the problem is persisting, which is 270RPM. Since they are identical, I do not believe it is the starter

-Replaced crankshaft positioning sensor on a whim due to running out of test solutions and that brought no results

-I ensured all temperature sensors are reading within 10 degrees of each other when vehicle has not been started and sat over night.

-Checked cranking compression and got cyl 1: 490, cyl 2: 450 cyl 3: 475 cyl 4: 480

-Put smoke machine on intake and found no false air/vacuum leaks.

-When problem persists I also Remove all 4 glow plugs and turn the engine over for 10 seconds and rest, then repeat 4 times and do not see any fuel mist coming out of glow plug ports.

-I have also unplugged the Coolant temp sensor to force glow plugs into self test mode and I found no difference.

-Ensured turbo is not seized causing an exhaust restriction

-Mvb 13 torque values: we need zero. positive is adding fuel, negative is reducing fuel 2 minutes after cold start 1: +0.1mg/str 2: -0.47 3: +0.13 4: +0.14

After vehicle has warmed up to 93deg C and heat soaked, i started vehicle (after an extremely long crank) and saw these values for the first 30 seconds of operation.:

1: -0.92 2: -0.33 3: +0.314: +0.71

Repeated these tests. Cold start I saw these numbers:

1: -0.852: +0.123:+0.074: +0.64 Again warmed up the vehicle and went on test drive

1:-1.29 2: -0.453:+0.754: +0.78

Oddly during some parts of the test drive saw these numbers:

1: +0.052: +0.003:+0.214: -0.28

-Fuel cooler is clear of debris

-Performed a tandem pump wear test on the new pump. I pulled the return line going to the filter and placed it in container. I then pulled connector off lift pump and applied power directly to pin 1 & 4 and allowed lift pump to run for 60seconds and measured 85mL of fluid. Other specs I have read said 25mL is max and excessive flow indicates a bad pump or failure of the supply fuel pressure limiter. Replaced tandem pump TWICE and have had no success.

-Due to odd torque adjustment on cylinder 1, I swapped injectors 1&4 and replaced all associated seals and gaskets. I was hoping the deviation would follow the injector to cylinder 4 but it did not. The negative numbers are still present on cylinder 1 and are around the same numbers I've provided for you in the past (1:-1.29 2: -0.453:+0.754: +0.78). I also replaced washers and seals on cylinders 2&3 injectors to ensure no odd man was left out.

Look at MVB 18 solenoid valve status. They should all read 0.0 means error free regulation 0.4 low injection quantity solenoid failure 16 means injector signal out of control window 64 is converter error 0.2 control at start 0.8 max current reached 32 number of readings too low-indicating it does not see an error 128 no BIP evaluation possible beginning of injection period

Cold and hot values on MVB 18 showed 0.0 the entire duration. The only time I get a change in value is when I am at a raised RPM and I let off the throttle, all solenoid values go to 4, then 128, then back to 0. That process takes less than a second when I let off the throttle and seems to be perfectly normal when taking fuel away rapidly by letting off the throttle.

I have replaced both return and supply hoses from the fuel filter to the tandem pump, and from the tandem pump to the filter and saw no change in air in return line.

Performed block test due to slightly low coolant level compared to when vehicle arrived. Block test showed a very subtle, but noticeable change in color from blue to green. This points me in the direction that

Conrad Jobst
Owner
B&B Automotive, inc.
Aberdeen, Washington, USA