996 C4 died on freeway last night, wont start
09-16-2009, 08:45 PM
#32
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great pictures of 996/4 fuel tank - now I can see what I am dealing with ...
http://www.6speedonline.com/forums/9...-pictures.html
relevant quote from the link above
"It seems that one of the fuel pressure failure can be on those venturi tubes, if one fail, all fuel pressure goes to that pipe and back to the fuel tank and you get almost no pressure to the injectors. So it is a good time to inspect them if you remove your fuel pump from the tank."
Given I am getting bubbles blowing from the passenger side venturi tube, and RAC's comment about his car dying due to a failed "fuel pick up jet" I think thats the component I'll focus on.
http://www.6speedonline.com/forums/9...-pictures.html
relevant quote from the link above
"It seems that one of the fuel pressure failure can be on those venturi tubes, if one fail, all fuel pressure goes to that pipe and back to the fuel tank and you get almost no pressure to the injectors. So it is a good time to inspect them if you remove your fuel pump from the tank."
Given I am getting bubbles blowing from the passenger side venturi tube, and RAC's comment about his car dying due to a failed "fuel pick up jet" I think thats the component I'll focus on.
09-16-2009, 11:46 PM
#33
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great pictures of 996/4 fuel tank - now I can see what I am dealing with ...
http://www.6speedonline.com/forums/9...-pictures.html
relevant quote from the link above
"It seems that one of the fuel pressure failure can be on those venturi tubes, if one fail, all fuel pressure goes to that pipe and back to the fuel tank and you get almost no pressure to the injectors. So it is a good time to inspect them if you remove your fuel pump from the tank."
Given I am getting bubbles blowing from the passenger side venturi tube, and RAC's comment about his car dying due to a failed "fuel pick up jet" I think thats the component I'll focus on.
http://www.6speedonline.com/forums/9...-pictures.html
relevant quote from the link above
"It seems that one of the fuel pressure failure can be on those venturi tubes, if one fail, all fuel pressure goes to that pipe and back to the fuel tank and you get almost no pressure to the injectors. So it is a good time to inspect them if you remove your fuel pump from the tank."
Given I am getting bubbles blowing from the passenger side venturi tube, and RAC's comment about his car dying due to a failed "fuel pick up jet" I think thats the component I'll focus on.
Good luck. It appears that you are approaching your troubleshooting very systematically.
09-17-2009, 10:30 AM
#34
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Agree - flooded usuallly means no spark but I have concluded that "must be flooded" was a bad diagnosis on my part, based mainly on my nose telling me that if I smelled gas in the exhaust it must be flooded. Later tests, specifically the spraying of carb cleaner in the intake and the engine briefly running on the carb cleaner convinced me it is a fuel starvation issue. Subsequent test results (ie can't drain fuel tank past top of fuel pump/surge tank followed by bubbling in the vicinity of passenger side venturi/pickup) continue to bolster the diagnosis of a fuel delivery problem. I hope to tear into the fuel tank plumbing later today. I'll let you know how it plays out.
09-17-2009, 10:48 AM
#35
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RAC - 996.620.113.00 is indeed the part I suspect has failed, it is the "Venturi Tube". Costs $331.50 for a plastic tube!! I could simply add a second in tank pump to provide fuel pickup from the fuel tank's "corner pockets" - for less than $100. All those venturi tubes do is move fuel from the lower recesses of the tank into the surge tank, where the high pressure pump then pulls fuel from for delivery to the injector rails. The 4 wheel drive cars have a funky shaped tank compared to 2 wheel drive models and need these venturi tubes to get at all the fuel whereas the two wheel drive models do not need or have them. IMHO the Porsche engineers got a little too clever when simpler solutions were available.
09-17-2009, 12:12 PM
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A little digging and I found many Porsche shop manuals, including the 996 manual, online here ...
http://www.cannell.co.uk/Manuals.htm
Although the 996 manual does not cover the 4wd models.
http://www.cannell.co.uk/Manuals.htm
Although the 996 manual does not cover the 4wd models.
09-17-2009, 01:33 PM
#37
My guess is that once you dissasemble the tank, you will find a loose or cracked line that should be quite obvious.
09-17-2009, 08:38 PM
#38
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RAC - 996.620.113.00 is indeed the part I suspect has failed, it is the "Venturi Tube". Costs $331.50 for a plastic tube!! I could simply add a second in tank pump to provide fuel pickup from the fuel tank's "corner pockets" - for less than $100. All those venturi tubes do is move fuel from the lower recesses of the tank into the surge tank, where the high pressure pump then pulls fuel from for delivery to the injector rails. The 4 wheel drive cars have a funky shaped tank compared to 2 wheel drive models and need these venturi tubes to get at all the fuel whereas the two wheel drive models do not need or have them. IMHO the Porsche engineers got a little too clever when simpler solutions were available.
09-17-2009, 08:50 PM
#39
Race Director
RAC - 996.620.113.00 is indeed the part I suspect has failed, it is the "Venturi Tube". Costs $331.50 for a plastic tube!! I could simply add a second in tank pump to provide fuel pickup from the fuel tank's "corner pockets" - for less than $100. All those venturi tubes do is move fuel from the lower recesses of the tank into the surge tank, where the high pressure pump then pulls fuel from for delivery to the injector rails. The 4 wheel drive cars have a funky shaped tank compared to 2 wheel drive models and need these venturi tubes to get at all the fuel whereas the two wheel drive models do not need or have them. IMHO the Porsche engineers got a little too clever when simpler solutions were available.
The design looks too clever but it is just clever enough to deal with a gas tank that has an odd shape/configuration to accomodate the front differential.
Don't try to improve the tank pump, just fix it with proper parts then button tank up with no leaks.
Sincerely,
Macster.
09-18-2009, 03:02 PM
#40
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update
OK - got into the tank this morning, not very hard. First I drained the tank completely using an external fuel pump with a siphon hose. I removed the passenger side Venturi Tube and as I suspected the end cap was missing. I found it lying loose in the lowest part of the passenger side of the fuel tank. Best I can tell it could never have been snapped in properly. I snapped it in place and it very positively clicked into place. I reassembled everything except for the outlet of the fuel filter. I connected a host to the fuel filter outlet and tested fuel flow and found it to be flowing at a much higher velocity than in prior testing. I then connected the fuel filter outlet and fired up the engine. Or rather I tried to. Still would not start. I went back into the tank suspecting the little cover on the end of the venturi had popped off again but instead found the fuel line connnector had popped off, presumably due to the fuel pressure. It appears the little retaining clip that is part of the connector has lost its oomph. Went to Autozone, Napa, then finally Hilton Head Porsche and no one had the part. HHP told me I would have to buy new fuel lines but I am no where near ready to accept that diagnosis/solution. Does anyone have a source for these little widgets? I found them for domestic cars at the local autozone but could not find them for anything remotely Porsche, ie Audi, Volkswagen.
09-18-2009, 04:15 PM
#41
Race Director
OK - got into the tank this morning, not very hard. First I drained the tank completely using an external fuel pump with a siphon hose. I removed the passenger side Venturi Tube and as I suspected the end cap was missing. I found it lying loose in the lowest part of the passenger side of the fuel tank. Best I can tell it could never have been snapped in properly. I snapped it in place and it very positively clicked into place. I reassembled everything except for the outlet of the fuel filter. I connected a host to the fuel filter outlet and tested fuel flow and found it to be flowing at a much higher velocity than in prior testing. I then connected the fuel filter outlet and fired up the engine. Or rather I tried to. Still would not start. I went back into the tank suspecting the little cover on the end of the venturi had popped off again but instead found the fuel line connnector had popped off, presumably due to the fuel pressure. It appears the little retaining clip that is part of the connector has lost its oomph. Went to Autozone, Napa, then finally Hilton Head Porsche and no one had the part. HHP told me I would have to buy new fuel lines but I am no where near ready to accept that diagnosis/solution. Does anyone have a source for these little widgets? I found them for domestic cars at the local autozone but could not find them for anything remotely Porsche, ie Audi, Volkswagen.
Even if you do source just the clips you will have the worry of if the clips are actually going to work long term (like "forever").
That said I suspect there is a lot of commonality at the fuel line/fuel clip level. Can't imagine Porsche paying some manufacturer for custom clips.
Take the clip to a VW parts counter and see if parts counter guy can help you source a suitable (maybe exact) clip from his VW parts bin.
If unsuccessful, visit an Audi dealer. Or BMW or Mercedes. But I suspect you'll have good luck at either a VW or Audi parts counter.
Oh, you might try one of the companies that sell Porsches parts over the 'net. Pelican? Suncoast? etc.
Sincerely,
Macster.
09-18-2009, 04:18 PM
#42
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2 shadetree methods:
1. Use 0.032" or 0.040" safety wire around the slots where the clip fastens.
2. Put original clip back on and put a small hose clamp around it so it cannot release.
Of course later get the right clip!
1. Use 0.032" or 0.040" safety wire around the slots where the clip fastens.
2. Put original clip back on and put a small hose clamp around it so it cannot release.
Of course later get the right clip!
09-18-2009, 09:00 PM
#44
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OK - the end cap on the Venturi Hose popped off again so my guess that it was never well seated to start with was wrong. I secured it ( as well as the driver side Venturi end cap for good measure) with a zip tie and now the hose feeding it is popping off at the quick disconnect! Its like the gopher game!! what a PIA! Two different disconnects in the tank are popping off due to "weak" clips. I have to believe they either chose a plastic that was not well suited to gasoline OR ethanol is at work. Either way, the clips are failing. Needless to say I am getting very annoyed at my quick disconnects quickly disconnecting on their own! And annoyed that no one sells them! I haver no reason to believe that even if the OOOO cars use the same disconnects that they will sell the clips standalone. There is a manufacturer's mark "RAY" on them but google yields nothing relevant. Tippy, I like your thinking!
09-18-2009, 09:03 PM
#45
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FYI, I died a few miles from home on a test drive because teh passenger ventyuri high pressure hose popped off at teh quickdisconnect. Quick solution was to swap the clips from outside the tank (ie never exposed to fuel) with the ones failing inside the tank (ie the ones soaking in fuel their whole life). Got me home but I sure would like to fine some new replacements.