Having a bit of a hard start issue once the car sits for more than 5-8 minutes, warm or cold.

Test scenario:
Car running at idle, I see 45-48psi at the fuel filter fitting. This seems about right. When I turn the car off, pressure drops to zero within 5 seconds. While I'm new to the Porsche, I am not new to fuel injection. This seems a bit odd to me. Even with the pump off, my Lexus and Toyota cars manage to hold 30-40psi in the rails after sitting over night. There are a few more things I want to check before I start looking for a leaking part, but wanted to run it across some of the great minds here.

Does this fuel pressure bleed off issue seem inconstant with other 996 Turbos? If so, I presume I need to look at the fuel system front to rear. Which means, pull the pump, replace the commonly faulty hoses and work to the back of the car. I don't believe injectors to be leaking, as I don't smell raw fuel, nor do I have a once cylinder rich issue (based on the plug readings)

Thanks in advance!

-Brad

 

Brad, if you don't have a leaking injector then it is likely the fuel pressure regulator that is allowing fuel pressure to bleed off...if you turn on the key and wait 5-10 seconds for fuel pressure to come back up before you crank the engine does it start right away?

 

It could possibly be that awful rubber line in the tank, but usually when I see that problem the car doesn't run. Does it drive properly once started? An as stated above f/p regulator as well.

 

Chuck: Yes, in most cases it will start up as expected if I bump the engine over and leave the key in the 'run' position for 5-8 seconds. There are no fuel system leaks that are external. So bypass regulator or front hose are the most likely candidates. An injector leaking that fast would show all sorts of external signs.


Zeppelin: The car runs/operates at expected. I'm planning on changing that hose in the tank very shortly. The car is 8 years old now and I see no record of having this hose changed. Known ticking time bombs scare me; especially when related to fuel systems on a forced induction car.

Anyone have a known good stock regulator laying around? If it were cheap enough, I'd swap it out simply to rule it out.

 

another thought...if it was the regulator bleeding pressure it would be to the fuel tank and it would be likely that fuel would remain in the line up to the regulator and the car would still start pretty quickly...I'm leaning toward a small hole in the fuel hose at this point since the engine is starved for fuel when first cranking but it will still run..could be a pre-cursor of a complete hose failure and then you will be stranded...a good Porsche mechanic will know if the symptoms are more indicative of a failure of the regulator or the hose...good luck

 

Did the rest of the testing on it this morning. Hook the fuel pressure gauge up, I see zero pressure. turn the key on, it bumps to about 10psi. Crank the car over, the pressure slowly rises until it gets around 45-48psi and then fires right up.
Based on this, I'm the line up front. It'll only take me 10 minutes to get the pump assembly out, so it's worthy of the inspection. The fuel filter was replaced on the car about 6 months ago, so I don't suspect that's the issue.

IF that checks good, I'll check the amperage draw on the pump and pressure/bleed down at the pump. I just need to find the quick connector for these lines.

 

Found it. Looks like it was a rubbed pin-hole marked by the end of my key. Fuel pressure rests at 42psi now with the car off, idles at 48 when cold. I had 200psi 5/16" fuel line laying around, which did the trick. I'll find a better quality solution sometime this week. Total repair time was just at 45 minutes with cleanup. I'll post photos of removing the tank sending unit in this thread this evening.




Which is part of this one, not the rubber hose circled, but the "J" shaped hose connected to it that goes straight up:

 

good job...I like happy endings..

 

awesome man.

 

This is a quick writeup of pulling the sending unit out and repair process:

Remove the 4 10mm nuts on this cover:


Press the grey & green buttons on the fuel lines to unclip. **Note**, if you've not released the pressure in the fuel system, this will make a mess. Depressurize the system or have towels to catch the fuel spray and prevent it from getting on your carpet.



This large retaining ring simply unscrews. I have always used a blunt screwdriver on the ridge and tapped it until it can be removed. I suspect there is a proper tool for this piece, but I've never bothered to look.


All connectors and clips unhooked. One simply needs to lift the sending unit out enough to reach the quick connectors on the fuel lines (under the ones you released) and the fuel pump wires.





Once the fuel sending unit is removed, everything is pretty visible. However, it's wise to start with a near empty tank of fuel so that you don't end up having to find gasoline safe gloves to stick your hands down into the fuel. As all things "Porsche" They have really missed the point of the KISS rule. There are hose/wires running everywhere. Fortunately, I was able to see my hose up top and get to everything without removing all the bits & pieces below. I cut the factory crimp-clamps off the check valve and quick connect, sliced the broken line and removed it. From there, I replaced with a high pressure fuel injection hose and high pressure hose clamps. (5/16" line hose for those searching)

Total cost for this repair was about $10.00 and about 45 minutes time with a few clean-ups and photograph time. Ideally, I'd like to find a suitable replacement for the factory lines. I'm not real keen on rubber with all the alcohol content in our current gasoline, nor an over priced set of Porsche lines that are prone to failure and don't do much better than quality rubber hose that normally holds up for over a decade in this environment. Anyone have any solid suggestions?

 

very helpful thread, thank you.