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Re: C900 won't start Posted by The Saabster [Email] (#945) [Profile/Gallery] (more from The Saabster) on Sun, 8 Apr 2018 12:48:39 In Reply to: Re: C900 won't start, StoicBlue87 [Profile/Gallery] , Fri, 6 Apr 2018 14:02:55 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If it runs by jumpering the fuel pump, it will tell you that your fuel pump is good and not the problem. However, the jumper won't tell you what the problem is; perhaps just what it's not.
If your fuel pump runs and car starts with the jumper, but not otherwise, I would suggest checking the FP relay next. It's on the passenger side behind the the lower "kick panel" piece of trim below dash on inside wall, and just barely under the knee bolster. Your ECU is behind that kick panel too. When you turn the key on the ECU supplies a "ground" to the fuel pump relay which causes it to run. A frequent problem on your 91 Saab is ECU fails to send the ground to the FP relay. Believe me, I have a 91 convertible and it's on its third ECU for the same problem.
The Bentley manual tells you how to diagnose the problem. It's been so long since I've done it, I can't tell you all the steps, but jumpering the relay as Stoic suggested is one of them. Bentley's will eventually lead you to supply an external ground to the relay without the jumper in place. If it runs with the supplied external ground but not without it, then that's a pretty good indication that your ECU is bad. About $125 last time I bought one from online salvage yard.
Good Luck,
Steve
Wildwood, Mo.
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