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Date: Sun, 11 May 2003 13:05:10 GMT
From: ma_twain <>
Subject: Re: wiring problem on a 85 900

someguy wrote: > "dave silva" <> wrote in > > >>Greetings, >> >>I'm looking at a 1985 Saab 900 4d, fair condition all the way around. >>Wife loves it. The good 'ole boy who owns it says it has a wiring >>problem to the fuel pump. One day it stopped running. HE had someone >>look at it, that person connected something to the fuel pump leads in >>the trunk and the car started right up. I've never owned a Saab but >>I'm guessing there is a relay and/or a fuse that controls power to the >>pump. >> >>DOes the fuel pump run constantly like some chevy's or is it on demand >>via a pressure sensor? >> >>I'm an aircraft electrician so these things don't intimidate me much, >>(unlike mechanical problems) But I need a general direction or a >>list of things to look for before I buy this car on spec. >> >>If the fuel pump is constantly on then i can just bypass the relays >>and power it up (ok, not entirely safe) but if it runs on demand then >>the system has to be right. >> >>His opening price was $700 as is, Does that seem high? It has 140,000 >>miles, interior is decent, manual sunroof, 5-speed, etc, (car was not >>for sale, i approached him about it) >> >>THanx >> >>Dave Silva >> > > The fuel pump runs constantly as long as the ignition is on and the engine is > running (there is a fuel return system which feeds the unused fuel back to the > tank). The pump is powered from the battery via a fuse and a relay. You can > bypass the relay if you for instance want to empty the tank or want to check out > the pump when it is still in the rear, have done that a few times using a switch > soldered to two long wires that are crimped to the standard flat pin connections > that plug into the relay box when the relay is removed. > > Some people used to go in and install a hidden switch in series with the fuel > pump, making a very simple car theft system (the 900 classic is a great car but > easy to steal, at least for the Swedish thieves that have learned the trick). > > However none of those methods are recommended since they impair the function of > the car, for instance having the pump running when the engine has stopped could > be very dangerous if you end up in an accident! Having the pump turned off due > to a bad contact when driving could also make you end up in undesired > situations. > > Thus my advice is to check the relay/fuse and the contacts in the relay/fuse box > for any bad contact force or oxide and not do anything "special". Normally the > cables running through the car should be fine and the problem should be either > in the relay or fuse connections (maybe there is one more cable junction, I > don't have the circuit diagrams any longer but you can find them in good repair > manual). > > I have the Saab factory Service manuals for that year 900. If you buy the car I can send you the electrical diagrams you want.

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