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CIS Pressure thread

Guys,
I'm still chasing a rich condition and am now looking at testing all the CIS pressures. So this time I'm going to start a ultimate thread with all the readings and pictures etc..
I want to check my return pressure but don't have an adapter for my CIS pressure kit,, Anyone know where to get an adapter for either one of these spots ? I borrowed the pics from Jonny wishbones leak thread

The one on the left is bigger than anything that came with the kit and the other is a banjo fitting
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-27-2009, 05:25 PM
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Crotchety Old Bastard
 
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The pressure is measured between the WUR and the fuel head.
In the picture below you can see where the inlet line to the WUR has been removed and bolted to the pressure gage. The other end of the pressure gage then bolts back into the WUR.
To check system pressure you turn the in-line lever to deadhead the flow which loops back to the fuel tank.


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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8

Last edited by RarlyL8; 11-27-2009 at 07:11 PM..
Old 11-27-2009, 07:06 PM
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Brian, my intent is to document ALL of the pertinant pressures.. Right now I think my problem may be in the return pressure and I don't know where to get an adapter for either one of the circled areas I want to tap into..
T
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-27-2009, 07:14 PM
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You should be able to measure return (system) pressure as I described. Do you have a problem between the WUR return line and the fuel head return line (in other words a problem inside the fuel head)? What symptom points towards a return/system pressure issue?
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-27-2009, 07:47 PM
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Brian I thought the return pressure was measured between the fuel head as it heads back towards the fuel tank.. that's the two parts I had circled.
Anyway here are the symptoms with no air filter ( in case you may have thought it was an airflow issue) it starts no problem . It idles at 14.5-14.7 AFR
When I rev it up to say 3-4k rpm it instantly goes rich (10-11 AFR or more) with NO BOOST
I've replaced my digital WUR with the stock one,, same issues
Also when I had my DWUR installed it showed control pressure of 4.5 -5 at cruise (should be in the 2.5's or so I believe)
Now I've replaced all of the gaskets on the injection blocks, checked everything for vacuum leaks (done the carb cleaner spray test)..
Oh and I also rebuilt the recirculation valve..
So my conclussion is it's got to be a fuel system issue
What do you think?
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-27-2009, 07:59 PM
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Wouldn't that simply point to your control pressure being too low for normal driving (cruise). have you tried raising the control pressure for this, then leaning the idle out via the CO screw?
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Old 11-28-2009, 02:00 AM
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Control/system pressure should be ~85psi stock all of the time. Warm pressure at cruise as measured after the WUR is half that.
Internet diagnosis is difficult at best. Have you checked for exhuast system occlusion?
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-28-2009, 06:18 AM
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Brain, I've checked the exhaust and even changed out turbos. That was one of my original thoughts. I have my euro exhaust on there that works like a champ on my 80 turbo
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 06:57 AM
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You said: When I rev it up to say 3-4k rpm it instantly goes rich (10-11 AFR or more) with NO BOOST

So, do you do this with the CIS gauges hooked up? If so, what is happening with your control pressure during this 3-4k rev?

Your control pressure should remain constant until boost is sensed... If it's dropping suddenly durning the "rev" then my guess is that there is something wrong with the WUR/settings... If the pressure isn't changing during the "rev" but you still see AFR's dropping suddenly, then my 2-cents is that the plunger is being pulled down too far allowing too much fuel for too little air???
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Old 11-28-2009, 07:32 AM
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Thanks Mooney, I'll be looking at this probably later today or tomorrow ( tough to do it alone).
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 08:06 AM
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Quote:
When I rev it up to say 3-4k rpm it instantly goes rich (10-11 AFR or more) with NO BOOST
So this happens with no load on the engine? Like sitting in the garage and blipping the throttle?

Stupid question but have you verified that this reading is correct and there is no issue with your detection equipment and O2 sensor placement?
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-28-2009, 09:49 AM
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Well I am pretty sure I"ve got a good O2 location ( middle of the muffler, downstream from the turbo) and even if I didn't 5-8 mpg on the highway and a HUGE rich smell.
So yes just sitting in the garage.. I'm going to have my cute blonde friend over and help me blip the throttle so I can watch the control pressure.
I think it keeps pointing towards the fuel head..
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 10:35 AM
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Update,, went out and using the pictured set up.. Engine cold 6 degC I get the following
System pressure 6.5 bar
Control pressure 1.9 bar

On another note I also did a pressure check and after 20 min still had 1.6 bar so I have a good fuel accumulator too!

I am waiting for my friend to come over so I can see what the control pressure is running and what happens when she bleeps the throttle
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 01:03 PM
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Do you have a rebuilt or modified fuel head by chance?
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-28-2009, 01:04 PM
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Brand spankin STOCK
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 01:06 PM
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What happens when you keep the revs at 4000rpm sustained? Do the AFRs eventally go up?
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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
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-28-2009, 01:10 PM
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Nope,,drove that puppy from LA to Tahoe a few weeks ago with my laptop in the copilot seat and watched the control pressure hang out at 4.8 and the WUR was commanding 5.0 ( the max that UTCIS allows) all the while the AFRs were in the 12 range. And theoretically it should have been so lean it wouldn't run
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 01:13 PM
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Brian, just tried to call the CIS Helpline,, but you didn't answer LOL
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 01:16 PM
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Ok cute blonde just came over,, started it up control pressure slowly climbed into the 2's had her bleep it to 3000 rpm control pressure didn't blink but the AFR's went to 10 and change..

Mooney, does this point to the plunger in the fuel head ??
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"Todd"
98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
91 Spec Miata (yeah I race a chick car)
"life"ll kill ya" Warren Zevon
Old 11-28-2009, 02:01 PM
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Isn't the plunger travel mechanically limited by the sensor plate linkage (I'm thinking of my SC, which is opposite the 930 head, but principally the same)? If you go way rich and your control pressure doesn't change when your helper revs it from idle, then there is a differential pressure problem within the head. Maybe something is gummed up in the fuel path to the injector ports?
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Old 11-28-2009, 02:39 PM
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