Why not replace the whole deal, including the pump?

 

Look closely at the intake plenum assembly on top of your motor, your problem sounds like a vacuum leak. Look at the rubber boots that join the aluminum housing containing the intake butterfly valve. If the rubber boots are torn, that is your leak.

 

Safety wire might be a solution. I thought about suggesting it before but I prefer whenever possible to use the exact same parts to repair something. Especially if this something buried down in the bowels of the gas tank.

Besides I do not have the assembly in front of me and the hose and its mating fitting may *not* be safety wire compatible. I'm not talking about material incompatability (though that's a consideration) but mechanically the wire may not hold be able to hold the hose secure and leaks might happen with variable and therefore hard to diagnose symptoms from the engine. The hose may move around and after awhile a fracture of the fitting may occur.

Or maybe not. But one way to avoid the unknowns is to use the same style clip to replace the one that's not working for you.

Safety wire wants to be a type that won't rust, too.

As someone else asked -- and it is a very good question -- what's the cost of a new assembly? Doesn't take many visits to the insides of the gas tank in my book to warrant just replacing the whole assembly with something new (and possibly improved) and fixing the thing once and for all.

Sincerely,

Macster.

 

Glad it turned out to be so minor! Sucks about the clips and the venturi price, but in the grand scheme of porsche repair bills I think you're still doing all right.

Question, is the pressure / flow rate significantly above spec when you snap the loose part in place? While I don't have a schematic or spec on the venturi tube itself, the way they operate is by difference in internal diameter from one end to the other right? Ignore me if I'm crazy but could deposits/ debris or deterioration or other damage have altered this enough to increase pressure while operating? Would this increased pressure cause the cascading failures you're seeing in other places in the system? Just food for thought.

Hans

 

good thread!

try ebay!

http://cgi.ebay.com/ebaymotors/PORSC...=p4506.c0.m245

http://cgi.ebay.com/ebaymotors/Porsc...=p4506.c0.m245

 

HTNY - I had the same thought as you - that if the venturi jet were clogged the pressure increase could cause the venturi assembly's end cap to blow off - in fact it might have been designed to do that. The jet diameter is maybe 0.025" which, best I can tell, is driven directly off the fuel pump with no pressure regulation. I just can't see that the jet being clogged or not would change the pressure that end cap is exposed to enought to make a difference. But I am tempted to test the theory. Note that I have not seen any filter in the system which protects that 0.025" jet from debri. There is a small grate/filter where the supply from the pump terminates at the venturi assembly but the grate size sure looks to be much larger than the jet diameter.

 

That would be too easy! Where's the challenge in that? Besides, the only problem is a few 10 cent plastic clips.

 

Both those pumps are used so almost certainly the quick disconnect clips are in the same shape as mine. So far my best solution is to buy new fuel filters as they cost $30/each and come with one clip. But I intend to contact Porsche factory (Porsche USA has no tech support, or so I am told when I called customer service. Actually, they referred me to the local dealer, not exactly what I would call factory tech support) to get a line on the connector manufacturer. Ja, Ich spreche eine bitte deutsch!

I am baffled as to why I seem to be the only one with this issue with the quick disconnect clips. It seems like there would be more buzz about them in the forums and/or they would be sold by pelican parts or others if they failed as often as mine seem to be failing. And its not that I have excess pressure in the system. I slide the connector on, I feel a solid click, but then if I pull with only minimal force they pop right off. Its a head scratcher.

 

Porsche clips are usually a b!tch... to take off and are solid (especially the non moving type, Eg: clips for the tranny end links). Maybe your pump assembly has been dismantled before

 

I agree that it sounds like you found the problem, but whenever something which "should" act one way but acts another, I always take a step back and make sure I diagnosed the issue properly. It's easy to loose perspective once you find what you think is the problem, and become biased toward it, not seeing other possible causes. Is it really worn clips, or did something else get tweeked during the troubleshooting that is causing this?
This isn't a slam. I'm just an engineer, and have been down the aforementioned road way too many times.

BTW, I'm bookmarking this thread so I've got the answer should this ever happen to me. Thanks for reporting all the research and updates!

 

I am a electrical engineer and spun my wheels more than once due to tunnel vision. In this instance, I swapped a fuel disconect clip from a vapor return fitting on top of the tank (ie never exposed to fuel and under no pressure) with the one that was popping off inside the tank (ie always exposed to fuel and under pressure) and the problem was solved. I think that definitively points to the clips as the failed component. I have a call in to Porsche Stuttgart to locate replacement clips. They are working on it - stay tuned.

 

Here are some pictures of the project. Anyone know how I can add captions/text with each picture?

 

Nice! This thread should be copied and pasted over on RennTech too, super good info/picts.
My bad, I did read that you swapped the clips in the thread, but didn't realize that it worked. Order up 100 clips and you can be our Go-To Guy for these things. Mark them up double or triple if you want.

BTW, I'm an electrical engineer too.

 

Ha...that looks awefully familiar. When I had the issue with my car not taking gas I had to pull all of that apart to perform the TSB from Porsche which consisted of adding zip-ties to secure the brown hoses to the tank gauge in order to keep them away from the flapper valve in the tank.

Good times.

Glad to see you're getting this sorted by yourself.

Andy

 

You're kidding me?! Zip ties?! Haaa!!
Well it looks like maybe Porsche knew their factory clips could fatigue and ultimately let loose.