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I have had a hard start problem only under certain conditions - warm parking garage - sitting for between 3hrs to 7hrs - any longer or shorter no problems whatsoever so after some reading on this forum I figured it may be a problem with incorrect fuel pressure being sent to the engine
So I figured I'd try replacing the fuel pressure sensor
Hope this helps someone else
I chose the Bosch version for half price from pelican
Remove battery compartment shroud
Disconnect terminals and in my case strut brace
Remove battery and battery tray
Locate sensor sitting right under the battery tray you removed <br/><br/>Disconnect old sensor and replace - there is no chance of screwing this up <br/><br/>Put everything back together
BTW, the sensor is not measuring the fuel rail pressure. It's measuring the fuel tank vapor pressure solely for evap tests to satisfy OBDII requirements (in case someone misinterprets that). More from the Porsche service manual here:
"20 Tank Venting System
From model year '98, a test for tank system leakage will be
required for vehicles with OBD II. This test can detect leaks
in the tank system measuring up to 1 mm in diameter.
Apart from the already familiar components of the tank venting
system (e.g, carbon canister and tank venting valve), a
pressure sensor for differential pressure in the tank and a
shut-off valve for the purge air line used to seal the tank venting
system are also to be installed to make this new diagnosis
function possible."
Then the manual goes on to describe the sensor and its functionality.
Roadsession,
I have a similar issue like yours where as mine has a small misfire once at normal idle speed. With a rich fuel smell after initial start up and sort of bad fuel consumption. Out of curiosity how did you determine your issue was the fuel tank sensor. Just wondering because I'm at a cross roads between a fuel tank sensor and a possible old MAF. Which I will pull tomorrow and look at again because I cleaned it once before already and car still has that random seldom misfire.
My car is fresh off a refresh disassembly and re-assembly (Dec 2016). I had the issue prior to dissy too my timing is spot on, new timing chain solenoids pads, new coil packs and connectors. New Spark plugs and no "CEL" just a minor and random misfire from time to time in the lower rpm range. No cylinder scoring so I eliminated all those first and I've ran fuel injector cleaner through my system a few times. Just wanted to see if you had any other suggestion or out of the box troubleshooting suggestions before I pull the trigger on buccu $$ parts like a new Bosch MAF and new Fuel tank pressure sensor.
Thanks.
hmmm I didn't have a misfire whilst running, just a hard start condition where the engine wouldn't catch at certain conditions - especially in parking garages after around 5 hrs.
MAF is definitely a common problem - but would usually throw a code. Fuel Pressure Sensor is an inexpensive / relatively cheap fix that doesn't throw any codes....
"I figured it may be a problem with incorrect fuel pressure being sent to the engine"
Glad that replacing the sensor worked(?) on yr car.
Like others I am surprised too. How did you eliminate the Fuel Pressure Regulator as a cause of a heat soak(?) restart problem/fuel pressure problem? Maybe it was just a fortunate guess?
Just asking to help others who search and find this rather common issue.
Thank you. http://www.pelicanparts.com/catalog/...FULFUL_pg2.htm
Hi folks - since replacing the sensor it completely resolved the problem I had (at least for the subsequent 5 months I owned the car after replacing it)
Thanks for the guide & pics roadsession, this helped me with this replacement. Pretty easy overall, hoping it cures my remaining hard start issue. Initial symptoms were frequent hard start, getting progressively worse & infrequent starter squeal. Starter motor & y-cable replacement yielded substantial improvement and now the lone remaining symptom is infrequent hard start (mostly at the garage at work).
Update - daily driving for a week and start behavior appears to be 100% normal. The first start or two after installation were relatively slow, and everything since then has been fast & reliable (hot or cold, same duration to fire it up). It'll take more time to see if it's 100% fixed, but results so far are encouraging.
items replaced:
- fuel pressure sensor
- y-cable
- starter motor
- crank position sensor (done for another issue, but it's possible it influenced behavior change)
lagging issue with warm starts - particularly in the garage at work in the afternoon - appear to be fixed with the FPS.
04-25-2016, 11:25 PM
Fuel pressure sensor replacement guide with pics
