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Only Bentley (damn big and heavy) isn't drilled.
Saab manual doesn't say anything about 'pre-pump' function. But I've got another Fuel Systems manual (obviously it's a translated version of some US or EU manual) - maybe you know it, Ray. It contains a huge table of cars and injection system used in each of them on last pages.
According to this manual each fuel injection system has a list of built-in functions (like AIC valve handling, overrev built-in function, MAF wire-burnoff, limp-mode implemented, codes display via CEL, etc) and each version (i.e. for Alfa-Romeo and BMW) differs only in fuel maps and other similar settings. List of functions remains the same within all ECUs that are of the same version (LH 2.2, 2.4, 2.4.1, 2.4.2, Fenix 5, etc). This means that if LH 2.4 for BMW 320 MY1994 has a 'pre-pump' function then all LH 2.4 cars (from Audi to Volvo including Saab as well) also have it. Just check your manual on LH 2.2 (or 2.4?) - it has a 'coding' function about cold start valve install. If one pin is grounded then ECU assumes that car has a cold-start injector built-on. Have you ever see LH-based C900 with cold-start injector, uh?
As for your indubitable useful advise on tuning fuel pump relay, Ray - I take it that it's probably of inlet manifold design (pls have it as a assumption only). Maybe that guy put the switch not into fuel pump loom but into ignition amplifier wiring. And once he turns the switch on the amplifier sends a single pulse/signal to fuel ECU which thinks that there just was a half of rev of crankshaft and from its side bounces injectors for with a single pulse. This enriches the intake and can really help with long cranking issue.
Nice theory? :)
Zig
P.S.
Justin, I assume you'll read this post as well so as for your explanation then CIS systems had this function (pre-pump) implemented in the fuel relay. Once the relay is powered up it bounces the fuel pump for half a second. In ECU-based systems this function is moved from relay to the computer that turns the relay on to pressurize the system before cranking.
posted by 85.140.108...
, Tue, 13 Nov 2007 09:46:05, Tue, 13 Nov 2007 11:35:29, Tue, 13 Nov 2007 16:34:42
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