High pressure fuel pump failure symptoms

[Joedatsun]

After doing a carbon cleaning and replacing a intake manifold with broken flaps, Im still experiencing a extended crank before starting.
The car also refused to rev over 2500rpm without breaking up and totally falling on its face. Does this sound like a high pressure fuel pump issue?
I also just replaced the coils and plugs. My inexpensive scanner says fuel rail pressure at idle is 600-640 Kpa.

[jfojtik]

I’d smell your oil. A quick sign is if it smells really bad like gas, meaning the seal is broken and gas is getting into the oil.

[xxxaudixxx]

I’d smell your oil. A quick sign is if it smells really bad like gas, meaning the seal is broken and gas is getting into the oil.

this ^

[hahnmgh63]

From the shop manual: Specification: approx. 5.5 bar (4.5 ... 6.5 bar). Are you getting a check engine light CEL? A scan with Vagcom should tell you which if either bank is running lean and the cause would most likely be your HPFP. Shouldn't run the engine with a high percentage of fuel in the Oil.

[Joedatsun]

No Cel. Replaced in tank pump, fuel pump driver as well as both HP pumps. On first start up fuel pressure was perfect. After restarting fuel pressure dropped back to low again. What am I missing? High pressure sensor under intake? Didn’t replace that.


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[hahnmgh63]

Are you sure the intake manifold flaps are opening?

[Joedatsun]

I replaced the entire intake manifold as well. I don’t believe the flaps are the problem. Intermittently, the fuel pressure has risen to normal (2600 KPa) as per Vag com. When this occurs the car runs perfectly with lots of power throughout the rev range…..but when I turn off the car and try to restart it the pressure is down to 500-600 KPa, runs rough and won’t rev at all.

[TontoLoidRS5]

I guess it would have to affect both banks and maybe it is a long shot:

oxygen sensors? heard sometimes it doesnt throw errors for this. was a similar story a few years back on the audi revolution forum, i think.

[TontoLoidRS5]

might have been on here, actually: https://www.audizine.com/forum/showt...sue-Help/page3

[TontoLoidRS5]

long story short, but I recommend you read the thread above: first get vcds reading of, then try clean (electric cleaner spray on on wires) and then move around the camshaft position sensors, then try replacing them if needed. If I remember right they come off a lot easier with with engine warm. Then try MAP sensor and finally the control module for fuel (see the thread). after that maybe do the o2 sensors as I mentioned above. I think they did PCV as well (might be due). symptoms of pcv include oil consumption and non-constant fuel consumption

[TontoLoidRS5]

I am mean clean the connectors of below with electrics spray cleaner.. and what seems to have been needed in the end check wiring harness feeding HPFP and CPS.

[Yamaha]

I had the same problem of falling on its face and long cranking with no codes for almost a year before it finally failed and caused a cascade of chaos. So, my car randomly threw epc, cel, starting running rough, stalled, and then threw everything else from parking brake to sport diff to tpms, yea, the entire dash was on and the message screen was crazy. My vcds log had 20 faults for just the engine section. Most were short to ground or open circuit. I replaced just the HPFP sensors and replaced a 15a fuse in the ecu’s housing and all of that is gone. The car runs great, feels fast again, yada yada. The important thing for me during winter, the replacement sensors were $70 for the pair. I’m still going to replace the hpfp’s this spring/summer since one had some metal flakes behind the sensor.