View single post by Mark Rosenbaum
 Posted: 05-07-2006 02:44 am
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 The fuel pump derives its power from the ignition switch through a rather convoluted path.  If your brake lights work when the ignition is on and you step on the brake pedal, you can assume that this wiring remains in good shape.  Barring PO intervention, there are no fuses involved, so if you have power at the white wire in the trunk, the pump can be expected to operate.  If not, give the pump a few gentle whacks with a mallet and see if that helps.  If there's no power at the white wire, it's probably broken or the pickoff at Fuse #2 may be bad.

In some cases a PO may have incorrectly used the wiring for the factory hardtop's rear window heater to power the fuel pump.  This wiring normally has an inline fuse in the trunk, and if the fuse should blow, the pump obviously would quit.

For early cars, the START position of the ignition switch activates a relay that in turn activates the starter solenoid, thus powering up the starter motor.  Here, the ignition switch, relay, solenoid, or associated wiring may be bad.

For later cars (basically, those made for North America 1974-up) the START position of the ignition switch runs to the Infamous Seat Belt Warning Module (ISBWM), which determines whether or not to activate the relay that operates the starter solenoid.  The ISBWM is also connected to the under-seat paddle switches and seat belts, and the hand brake.  Unless the seat belt for each occupied seat is fastened, and the parking brake is engaged, the ISBWM prevents activation of the relay that in turn activates the starter solenoid.  A failure anywhere in the system will prevent anyone from starting the car -- something to be reflected upon every time one drives through a railroad crossing.

Try fastening the driver's seat belt when sitting in the driver's seat; that may allow the engine to be cranked.  Or, you can disable the system by jumpering pins 11 and 12 on the round connector that plugs into the ISBWM.  One of these pins normally has a white-red wire, the other a lightgreen-red wire, but this may differ for your car.  There should be tiny numbers on the plug itself.

If problems persist, you'll have to do some troubleshooting.  If you desire originality, spare ISBWMs appear cheaply on eBay from time to time, or you can discard the entire system, losing two functions: (a) the seatbelt warning light and (b) the buzzer that sounds when the key is in the ignition and the driver's door is opened.  With a bit of rewiring and a buzzer available from Delta Motorsports, you can regain function (b).