2016 VW Golf 1.8 Hard Start Runs Rich at Idle

While it is running try removing the oil cap. If it is really hard to remove the cap the crankcase breather has failed. It should have a slight vacuum at oil cap.

There's about 1inch of vacuum measured at the dipstick tube but it does run better with the oil filler cap removed but then it started smoking severely burning oil?

High pressure fuel pump leaking into crankcase?

I thought of that but not that I can tell as I just changed the oil and filter. It was not contaminated and not overfill. If it was leaking I would have expected it to run good for a few minutes but it was basically the same as before replacing the injectors and cleaning the carbon.

You can measure the rail pressure after turning the engine off, that will let you know if the high pressure is actually bleeding off. Do you have a manometer to measure crankcase negative pressure?

Here's some live data to compare Philip. forums​.​ross-tech​.​com/index​.​php?thre… Hth, Sean

Thanks that helps a lot. One thing I noted was Actual low pressure fuel pressure and Specified low pressure fuel pressure were 11bar actual and 5 bar desired. Seems the 11bar actual is normal. I don't think it has a low pressure sensor. The link you sent me showed the same values for low pressure but my high pressure is nearly double what this example shows at 90bar at idle. Off idle it drops to…

The fuel rail pressure does actually climb as it should during a hot soak. I measured crankcase pressure at tge dipstick tube and it measures 1 inch of vacuum at the dip stick tube. It does seem to run better with the oil filler cap removed. I'm wondering if the high pressure pump is actually leaking internally and the crankcase breather is drawing the fuel into the intake.

Phillip I have seen the HPFP leak internally and you can still see a rise in rail pressure with engine off. Generally a failed crankcase breather will cause a lean condition on these engines. I suspect it runs better with the oil cap removed because that causes a lean condition and your running so rich….

Take the HPFP off Philip, dry it all off, attach the fuel pipes and place a paper towel under the pump. Activate the low pressure supply pump and watch for any fuel leaking onto the towel. It might not be instant, give it a few minutes.

Sean, He might see something using this idea but there is no pumping action and the pressure is very low compared to running operation.

True Bill, but they normally show up like this if leaking at all. Done one two weeks ago and it had a few drips after about 90 seconds.

No leaks at 85 to 90 psi running the low pressure fuel pump.

I'll give that a try for sure.

How does it start with the high pressure pump's solenoid (normally open) disconnected?

Hard starting and runs rough the same with the pressure regulator disconnected. Do you know if the PID High Fuel Pressure Specified Value is the desired fuel pressure or just another way of displaying the actual high pressure fuel pressure. I'm starting to wonder if the HPFP sensor is falsely reporting the fuel pressure. When I disconnected the regulator both PIDs read 8 BAR. I would think that…

Specified pressure is the desired pressure Philip. When you disconnect the pressure reg the system defaults to max low pressure only so desired is 8 bar. Hth Sean

Specified is the desired value. With only low pressure system active the pcm switches to the default value, the 8 bars you see on the scanner.

Hi dont forget to test timing.. What is your lambda value is it in fuel control ..? what your maf values..? yes injectors leak and evap solenoid stuck open on these..

E85 fuel in it perhaps? causing ECU to add more fuel to keep it running? just a thought.

I thought of that and tried running it on alternate fuel using an injector flusher supplying fuel to the HPFP at 85psi while I had the low pressure line disconnected and capped with a pressure gage.

Evap leak? Sucking fumes from gas tank?

I checked the purge solenoid and plugged off the purge line, thanks for the suggestion.

Dynamic compression test ?

Phillip using your VCDS take a look at the camshaft data there will be actual and specified valves for you to use. You can see intake actuator command as well make sure it's not cycling… you have posted a lot of data but unless I am overlooking it I don't see this has been verified.

Yes we had one here that had a stretched timing chain that would cause high fuel pressure at idle. It chugged just like that. Bassicaly the high pressure pump regulator pumping strokes were all over the place and the regulator could not control the fuel pressure. Did a timing chain, guides and tensioner and all worked good after. However did also have another that the engine oil pump was worn…

Desired and actual intake and exhaust cam timing pads match when running.

Only time I have ever seen those figures on VW TSI is when the valve timing is incorrect. Incorrect valve timing equals incorrect high pressure pump timing.

The used car dealer is installing a used engine into the VW. I'm hoping to get the original for a teardown and I will follow-up with what I find at that time. Thanks for all the suggestions it is very much appreciated.