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Date: Mon, 14 Mar 2005 00:33:30 +0000 (UTC)
From: Craig's C900 Site <c900nospam.apana.org.au>
Subject: Re: Troubleshooting the Bosch CIS cold start system


Paul Halliday <pjghnospamyonder.co.uk> writes: >in article d0fe0c$sgi$1nospamn.btinternet.com, Tomnospamtech at >saabtechnospamnnect.com wrote on 06/03/2005 17:18: >> It sounds like you may have a problem with the warm up regulator, [fixed to >> the side of the cylinder head by the thermostat housing], it should have a >> 12 volt supply all the time the engine is running. The 12 volt supply and >> heat transfer from the the cylinder head works on a bi-mettalic strip which >> controls the fuel pressure to the fuel disributor and thus the injectors, >> when the engine is cold the pressure is higher and as the engine warms the >> pressure lowers [control pressure], If said device is fault then it makes it >> immpossible to correctly set idle speed for both cold and warm. You really >> need a fuel pressure gauge to diagnose properly, but a good indication is if >> you have access to a co meter, disconnect the vacuum/pressure hose that is >> fitted to the regulator, plug the manifold and apply about 10 psi to the >> regulator and this should increase the co to about 7%. If no difference or >> a small increase is noted then the diagphram inside the regulator is >> knackered. >Hi Tom ... Just to recap on this one. When the engine warms, how does the >system lower fuel pressure? Does the bi-metallic strip open or close current >to the fuel distributor? AFAIK, the warm-up regulator is the primary device that controls master pressure in the fuel distributor. The other devices used during the cold-start and warm-up phase (thermo-time switch, cold-start injector, auxilliary air valve) do their job and are no longer taking part in the fuel pressure regulation after the engine has come up to normal temperatue. The airflow sensor plate linked to the bottom of the fuel distributor controls how much of the master pressure fed to the fuel distributor is delivered to the fuel injectors. That's probably a very simplistic overview. Cars with turbo's have additional features which interact with the devices in the fuel system, but my C900's are all non-turbo cars so I'm not able to relate anything about cars with turbo's from a technical point of view. Regards, Craig. -- Craig's Saab C900 Page --> http://nospam/~c900 Sydney, NSW Australia Craig's Saab C900 Workshop -- For all Saab C900 Enthusiasts world-wide! http://www.nospam.net http://www.nospam c900nospam.apana.org.au Come and explore our site, and check out our web-forums, mailing list, etc.

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