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Question CIS air/fuel flapper is binding...car is down

Need some advice before I tear into it. Was cruising home from work tonight, and I could tell the car was about to die...gave a hesitation, and I could tell as soon as I took my foot off the gas she'd be dead. So I coasted into a parking lot.

From what I can tell, the fuel metering flapper plate is binding. It doesn't have that "feather touch" to make it move down - takes some force to push down. The car runs VERY ROUGH. Will not idle. Sounds a little bit like it's backfiring through the intake.

I have the following CIS mods:
-Imagine Auto modified fuel head
-Brian Leask WUR
-Brian Leask RPM solenoid
-No smog equipment
-no AAV
-Aftermarket air cleaner...no air box

I checked to be sure that the AFR adjustment spring/screw wasn't binding on my air cleaner, and it's not.

Any ideas? What would cause this? Car was running beautifully.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-27-2007, 06:18 PM
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Okay, I disconnected the fuel line that runs from the top of the fuel filter to the front of the fuel dizzy (head). A pretty good stream of gas shot out. Then the flapper got it's sensitivity back and moved freely up and down with little force. It's almost as if there was too much pressure and or vacuum for the flapper to move. I haven't connected the line and attempted to pressurize the system yet.

The filter was replaced about 8,000 miles ago. Could this be related to the fuel accumulator canistor next to the filter?

Any thoughts?
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-27-2007, 06:39 PM
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I've never experienced such a thing but what it sounds like you are saying is that the return fuel line has become blocked or unable to bleed off excess presure. Can you hook up a gage and check it while keeping the car running?
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 08-27-2007, 06:47 PM
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Is that what line that is? I haven't broken out the workshop manuals yet to look over the schematics. I have the gauges, so I guess some tests are in order.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-27-2007, 07:16 PM
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Okay the line I had disconnected was the actual fuel delivery line to the fuel dizzy (from the fuel filter).

Any way, I re-connected this line, ran the fuel pumps and the CIS flapper (sensor) plate got rock hard! I'd have to apply a decent force to get it to move down!!! So what the hell? A blockage of some sort? The fuel return line from the fuel dizzy has a junction that connects to the bottom of the fuel accumulator. I once read that if you removed the bottom connection to the accumulator and fuel leaked out, that's an indication that the diaphram inside is bad. Is tis true?
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-27-2007, 08:45 PM
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Plan of action today will be to disconnect the fuel return line from the fuel dizzy, run a line from the dizzy into a gas can, run the fuel pumps and see if the binding continues. If it doesn't, then I'll know there must be a blockage in the actual fuel line. If it does, then I guess I have a problem with the fuel head.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 04:55 AM
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Don't forget the WUR controls the fuel pressure in the fuel distributor head. These fuel heads are extremely reliable------don't know about IA Head Mod, but you should give Brian L. and Stephen K. a call. They got some 'splain'in to do.
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Old 08-28-2007, 05:57 AM
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What is your cold or warm pressure vs system pressure?
Your system pressure should be ~90psi while your cold/warm pressure will be much lower. If they are the same .....
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 08-28-2007, 06:50 AM
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Quote:
Originally Posted by WERK-I View Post
Don't forget the WUR controls the fuel pressure in the fuel distributor head. These fuel heads are extremely reliable------don't know about IA Head Mod, but you should give Brian L. and Stephen K. a call. They got some 'splain'in to do.
Thanks so much Werk and Rarly for taking the time to help!

Latest update:
I by-passed all return fuel lines and ran a "home-made" line from the fuel head, main return port, directly into a gas can. With the pumps running, I get a steady and strong stream of gas from the return section. BUT the sensor plate in the meter housing still locks up tighter than a crab's ass!!! So I know I don't have a blockage with the fuel lines...and it appears that gas is flowing in and out of the fuel head just fine. Before I remove the fuel head to check for a stuck piston, I will test the WUR.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 06:52 AM
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More info:
WUR Cold: 2.1 bar
WUR Warm: 4.0 bar

System pressure...NEEDLE ON MY GAUGE WAS BURRIED!!!!! I mean as soon as I switched the ball valve on my CIS pressure test gauges, the pressure just went from 2.1 bar all the way to well past 100 PSI! It would have kept going if my pressure gauge allowed it!

So what the hell is that? Bad WUR? Fuel pump(s)? Did I perform the system pressure check correctly?

I guess there are some more tests I can take, but what's the point?
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-jeff
back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 07:48 AM
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Diagnosis via the internet is a dangerous thing, but it sounds like the iA fuel head has malfunctioned. It would be my guess that the head was set at ~100psi originally, yes?
Give Stephen a call and run your pressure findings and symptoms by him.
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Old 08-28-2007, 09:48 AM
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Quote:
Originally Posted by RarlyL8 View Post
Diagnosis via the internet is a dangerous thing, but it sounds like the iA fuel head has malfunctioned. It would be my guess that the head was set at ~100psi originally, yes?
Give Stephen a call and run your pressure findings and symptoms by him.
I know what you mean about the internet diagnosis. I'll give him a try...THANKS! I didn't have the proper sized fittings to test the fuel supply line the actually feeds the fuel head. I wanted to take a pressure reading before the gas enters the fuel head.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 10:21 AM
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With pressure readings that high, it sounds like the WUR especially since it happened all of a sudden. I assume the flapper moves very freely when there's no fuel pressure?
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Old 08-28-2007, 10:28 AM
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Quote:
Originally Posted by 125shifter View Post
With pressure readings that high, it sounds like the WUR especially since it happened all of a sudden. I assume the flapper moves very freely when there's no fuel pressure?
Yes the flapper moves freely once I've opened a fuel line to remove pressure. The thing is, the WUR does appear to provide decent readings. I think the system pressure test, even though hooked in between the WUR and fuel head, does by-pass the WUR once you move the valve on the pressure test gauges.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 10:40 AM
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I think it's the fuel head. The reason? Even if the fuel pumps haven't run in a couple of hours, if I don't open a fuel line to remove system pressure, the flapper stays locked in place from the pressure. I think if it was a faulty WUR, the problem would only happen with the fuel pumps running.

Is there another check valve on the car some place? Only other thing I can think of is the fuel accumulator.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 11:06 AM
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Before I lose my mind, the CIS sensor plate is supposed to be easy to push down...correct? I just want to be sure I'm barking up the right tree. Mine will go down, but takes force. I remember it being very sensitive, even when the pumps were running.

I've cleaned out all of the ports on the fuel head, still when the fuel pumps have presurized the system, the plate just gets stiff. I guess next will be to pull the head.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 01:17 PM
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The check valve in the accumulator works to slow pressure bleed down once the pumps are shut down. It does not cap the system pressure, that is done by the fuel head. Excess pressure or volume is routed back to the tank.
The check valve in the fuel pump has a similar function in that it slows bleed down for easy starts.
As you have stated, when system pressure is checked the WUR is taken out of the loop.
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Old 08-28-2007, 01:51 PM
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You can pull the regulator out and check the oring and the value. It is on the top of the head on the side right in front to the right. It is either that or the WUR has failed.
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Old 08-28-2007, 01:53 PM
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Quote:
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You can pull the regulator out and check the oring and the value. It is on the top of the head on the side right in front to the right. It is either that or the WUR has failed.
Thanks for stepping up to help, Stephen! I did pull the regulator out of the fuel head and the o-ring looks to be fine..I was sure not to lose any shims that were present...Brian Leask actually mentioned I try this. I plan to button everything back up and see if it'll start. The thing throwing me off was how stiff the plate should be when there's pressure. I guess there is supposed to be some resistance.
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back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 02:01 PM
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All Fixed

Thanks to all for the input, advice, and patience!

The car is back to it's smooth ol' self!

I ended up pulling the fuel head. These things really aren't meant to be disassembled and/or tampered with (unless you're Porschephd)...so I proceeded with care and only cleaned things...know your limits. I think it's possible the workings were just sort of gummed up where the head sits on the metering housing. Also it's possible some shiat came out when I removed the regulator side of the head. Once I re-installed it and pressurized the fuel system, the sensor plate acted with much more sensitivity...the car started right up

As others pointed out, the sensor plate does have some resistance when the fuel is flowing.

MANY THANKS TO ALL!
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-jeff
back in the saddle: '95 993 - just another black C2
*SOLD*: '87 930 GP White - heroin would have been a cheaper addiction...
"Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP)
Old 08-28-2007, 06:36 PM
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