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Porsche Crest Attn. CIS Guru's!!!!

Hey guys,

This is going to be one of my longest posts yet because I think I have a difficult problem to fix.

I have a 77 930 that is running poorly to say the least. It is a 3 litre car that is now a 3.2 running on European CIS. The car is a Euro car.

This problem started intermittantly around a year ago and has become worse over the last 1000 miles or so to the point it is full time.

When you drive around once at normal operating temp it seems to be fine when you are less then 15% throttle. Once you get beyond 15% and get into ANY kind of boost the car falls on its face, smokes black out of the tail pipes, shutters and wants to almost die. Once you lift off the throttle it is fine. So really I have NO driveability at this point at all.

When the engine is cold is the only time it will even kind of idle smoothly and after warm up when at idle I am having to keep my foot on the throttle to keep it running or it will load up and die.

I recently made a post about a frequency valve that I thought was issue but just found out tonight that my car never had a frequency valve or an oxygen sensor for that matter. I have wondered since I bought this car what the blue box with absolutely NO labels on it was for in the rear of the car near the lower seet cushion on the vertical surface there. I am leaning towards the thought that it is a fuel enrichment device from someone. I would think Andial would have put a label on theirs but who knows. It looks pretty old. Looks like early 80's to me.

I will post pictures of the box. I am hoping that someone has some kind of idea as to what this is. I have not got to the point of tracing wires yet but I do see something in the engine bay zip tied to the WUR. It appears to be a frequency valve. Is it possible that this blue box controls it to manipulate the WUR? Please help???

I am very confused and just want my baby to run like it used to!

Thanks in advance for any help here. If I didnt post all the info I should have please ask me questions as I would be glad to answer any and all of them I can.

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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 04-16-2007, 10:41 PM
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The blue box is not the Andial FEU - at least completely different than the one I had way back.

Have you started with basic fuel pressure test? Ignition test?
What happens when you simply rev up the engine without load (in neutral)?
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Old 04-17-2007, 07:05 AM
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It will rev no problem it has the problem only under load and boost situations.

I will get pressure numbers this weekend. As for ignition, everything checks out ok.

So are you saying that this looks like an enrichment unit to you?
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 04-17-2007, 07:57 AM
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Chris,

In general, 2 types of enrichment units exist - one where a fuel pressure regulator has a diaphram that is acted upon by manifold pressure in that it retards the flow of fuel back to the tank as manifold pressure increases. In the aftermarket supercharger market this is called an FMU (fuel management unit), and in our cars the WUR does somewhat serve in this capacity - the actual fuel pressure regulator for the CIS system is in the CIS box/fuel head unit, and the WUR acts to further limit fuel return (thereby increasing fuel pressure and therefore increasing the amount of fuel injected at any given metering rod setting) when the manifold vacuum line connected to it is under pressure (boost). This is a totally passive (non - electronic) system, and as I said it is widely used in the aftermarket superchager kits.

The second unit uses a fuel injector (frequency valve) to add fuel either to the manifold directly or to the CIS fuel system by again limiting the fuel return and increasing pressure in the system. This electronic unit would also measure manifold air pressure and use this to prescribe the frequency valve pulse to either add fuel to the intake or slow/stop fuel return flow to increase pressue in the CIS system. This will have some connection to the MAP/boost sending unit (or a stand alone MAP sensor), the frequency valve plumbed either into the intake or in-line after the WUR, and the controller board. It 'appears' as though you have something of this nature, but without seeing all of it in place I can't offer much more than that.

If it is used as such to build pressure in the CIS system by augmenting the WUR operation (limiting fuel return to increase pressure) and the frequency valve is not opening correctly it could cause a 'super-rich' condition under even slight boost that would result in the symptoms you've described. Again, this is only speculation based on what you've shown/described, and I don't want to be part of you leaning out your mixture and killing a motor when this is removed/disconnected. I would tread very carefully if you remove parts.....

Pat Kelley

Last edited by kellcats521; 04-17-2007 at 09:21 AM..
Old 04-17-2007, 09:19 AM
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Check Pressures then the WUR. If the WUR isn't within spec nothing else works correctly.

Does the oil smell like gas at the oil fill tube or does it run hot?
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Old 04-17-2007, 10:38 AM
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Oil doesnt smell like fuel but Im sure with any mileage it would. Pipes and bumper are charcoal black. Engine never runs hot.
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 04-17-2007, 10:59 AM
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I would check the pressures and then the WUR. I've seen the exact same symptoms with a defective WUR.

Do you know the AFR?
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Old 04-17-2007, 12:26 PM
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Dont know the AFR as I dont have a wideband set up in the car yet.
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 04-17-2007, 12:39 PM
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Hey my old 1982 930 (euro CIS also) had a white colored box that looked identical to that, that was located in the same area of the car.

I always wondered what that was. And after this posts, it looks like we still don't know....

But that is interesting!

Brian
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Old 04-17-2007, 01:13 PM
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Check your fuel pressure at the wur, more control pressure is leaner, less control pressure is richer. The frequency valve is used to reduce the CONTROL pressure to make the mixture richer.

Dan
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Old 04-17-2007, 04:46 PM
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ignition will break up under load also, take a spray bottle with water and add table salt to the water and spray the ignition system down (wires,cap) see if you get misfires at idle. the salt in the water will give ignition leaks a better path to ground. good luck
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Old 04-17-2007, 04:57 PM
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The description of your engine does not indicate a need for additional fueling.
I replied in the thread you posted in the 911BBS that if this were my engine I would strip off the CIS and build it back, component by component, checking them all along the way. I would also leave off anything not essential to your driving habits or needs. When finished run an A/F check throughout the range and adjust accordingly.
You will then know exactly what you have and will be confident in its operation.
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Old 04-18-2007, 06:55 AM
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Quote:
Originally posted by briankeithsmith
Hey my old 1982 930 (euro CIS also) had a white colored box that looked identical to that, that was located in the same area of the car.

I always wondered what that was. And after this posts, it looks like we still don't know....

But that is interesting!
Brian
My 82 Euro still has the decal on it. It is a K-Jetronic box. My shop just told me that it was put in as part of the Federalization setup to help meet emissions and to (if possible) remove it and reconnect any wires it may have bypassed and spliced into. I'll see if I can trace it when I get time next week.
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Old 04-18-2007, 01:10 PM
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Interesting Gary, I had been thinking about that thing?
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Old 04-18-2007, 01:33 PM
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hey you find the problem yet?
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Old 04-19-2007, 05:09 PM
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No, I will be checking pressures this weekend and I will post asap. Depending on what we find then I might just decide to make the jump to EFI !
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77 930 "P Zilla" 3.2 Litre w / EFI conversion
Old 04-19-2007, 06:12 PM
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what do you have to do to convert to efi?
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Old 04-20-2007, 09:31 AM
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Old 04-24-2007, 02:34 PM
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i really dont mind cis injection, i had enough cis rabbits and golfs
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Old 04-24-2007, 05:01 PM
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