There is a control pressure actuator attached to the side of the fuel distributor. A steel reed inside oscillates up and down, controlled by the computer. Feedback from the oxygen sensor modifies the reed duty cycle. The duty cycle of the oscillation determines the control pressure to the bottom of the fuel distributor because the duty cycle changes the amount of fuel that's allowed to pass through. The control pressure determines the fuel mixture. If this reed fails, as it did in one of my 300E's (twice, both times cracked), strange things happen because the system is no longer stable. It can stick open, stick closed or just not oscillate.
If your fuel pressure is correct then I'd suspect this part. And Mitch is correct, the system does flow a lot of fuel. They do this for 2 reasons. The first reason is that they actually use hydraulic pressure generated by the fuel flow, plus restriction (a pressure regulator), to control the system (mentioned above) and to do this, they have much more fuel flowing through the system than needed to maintain a steady control pressure. The second reason is to keep the fuel cool. The car would not be running if you had a blockage in the tank, etc... Some have one fuel pump, some have 2. Both of my 1986 300E's had one. Earlier CIS systems did not a control pressure regulator. They depended entirely on the balance between the air flow sensor plate and a calibrated internal spring to manage fuel flow. Thanks, Tom Hargrave www.kegkits.com 256-656-1924 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hendrik Riessen Sent: Wednesday, July 18, 2007 8:05 PM To: Mercedes Discussion List Subject: Re: [MBZ] 300e fuel issues. . ?? Cold enrichment is more for idling than when the car is in motion. I am not 100% up to speed on the last versions of the CIS/E system but the basis of all CIS/E systems is that even without any electric input they continue to work. That is why MB was so reluctant to let go of the sytem, even when just about everyone else went to full electric fuel injection (which MB did in 93/94). However every CIS system needs fuel pressure to work, if your fuel pressure is wrong then it may give the impression of fuel stavation. http://www.humanspeakers.com/audi/timing2.htm at the bottom of this page is a basic layout of the KE (CIS/E) system http://covintechnical.pwp.blueyonder.co.uk/tech_2.htm http://ffp-motorsport.com/tuning/kejetronic.php http://web.archive.org/web/20060104183213/mb.braingears.com/ have a dig around in here for tech stuff How long since you checked your O2 sensor, maybe when it gets to operating temp it starts to send out bad vibes to the computer. It may be possible to diconnect it to see if there is any change. Blocked fuel tank? I would say no because the symptons would not be so regular and would repeat themselves during the course of driving. It has to be remebered that the CIS system pumps a lot of fuel with something like 90% being returned to the tank. This is the same reason I am not thinking blocked fuel strainer and/or fuel filters. "My theory is there is enough fuel in the pump and line to get us the 1.5 mile. But at that point the pump must take over, and for whatever reason it is struggling. Either the filter is occluded, or their is air getting into the system. I understand from my mechanic that this car has two fuel pumps, and they are known for causing issues." Sounds good on paper but when you realise the amount of fuel that is pumped through the system............ If air gets into the sytem you would have a fuel leak. If you have fuel pump issues then the problem would not be so regular but more intermitten. Anyhow we need some more info before we can start to track down a likely culprit, such as engine operating temp when the problem occurs, is the car fine once it gets past the 1.5 mile mark and any other odd things that are happening. Has your mechanic checked the trouble codes? From about 88 on the CIS/E system has self diagnostic abilities. ----- Original Message ----- From: "Mitch Haley" <[EMAIL PROTECTED]> To: "Mercedes Discussion List" <mercedes@okiebenz.com> Sent: Thursday, July 19, 2007 1:36 AM Subject: Re: [MBZ] 300e fuel issues. . ?? > > > Troy Kocher wrote: >> >> Listers, >> >> Recently my 'new' 300e seems to be having a fuel supply issue. . >> >> Each morning about 1.5 miles from home it begins to starve for fuel. > > Sounds like a cold enrichment system is shutting off too suddenly > or too soon. > > Mitch. _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
