If the diaphragm were to stiffen with age, that could result in higher pump pressures. Never seen that actually happen, but theoretically it's possible.
Howsomeever, as I recall you initially started with the ZS. That carburetor does not seem as sensitive to over pressure as the SU's are. Not that the ZS is immune, it's just not as apparent a problem. Personally, I suspect a whole lot of ZS problems come from excessive fuel delivery pressure. The Paul Harvey "rest of the story" is that many of the replacement mechanical fuel pumps produce too much fuel pressure for these carburetors. They produces pressures of 4-7 psi, which is fine for a Japanese or American carburetor, but way too much for an LBC. Using an inline pressure regulator has solved the running problems of many an LBC, including my own. >>> "Ken" <[EMAIL PROTECTED]> 10/07/03 07:09PM >>> Anyone ever had a mechanical fuel pump suddenly develop higher than normal pressure ? I can understand the diaphragm rupturing and the pressure dropping to zero, but is there a failure mode causing higher pressure ? The reason for the question, I'm having difficulty getting the new engine to idle properly. Went ahead and pulled the dual HS4's and replaced them with dual HS2's and the problem remains. Both carburetor sets worked perfectly on the old engine. Been through all the normal troubleshooting procedures to no avail. The problem could be fuel getting past the needle and high fuel pump pressure could be the cause. ----------------------------------------------------- The information contained in this communication may be confidential, is intended only for the use of the recipient named above, and may be legally privileged. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication, or any of its contents, is strictly prohibited. If you have received this communication in error, please re-send this communication to the sender and delete the original message and any copy of it from your computer system. Thank you. ----------------------------------------------------- <<<<GWIASIG 0.07>>>> *** http://www.team.net/the-local *** *** unsubscribe/change address requests to [EMAIL PROTECTED] or try *** http://www.team.net/cgi-bin/majorcool *** http://www.team.net/mailman/listinfo *** Archives at http://www.team.net/archive *** Edit your replies!
