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Wait a minute... Posted by Justin VanAbrahams [Email]  (#32) [Profile/Gallery]
(more from Justin VanAbrahams) on Wed, 29 May 2002 02:59:53
In Reply to: LHECM Fuel Injection Computer - '90 900, Jamie C., Tue, 28 May 2002 20:42:18 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Hold on!
I just went down and read some of your original posts... You said above that the car won't start - but reading below it sounds like it won't even turn over.
If that's the case, there are far fewer culprits and almost zero chance it's a bad ECU. The starting system on a Saab is exceedingly simple - you have an ignition switch, a solenoid, and a starter. Putting the key into the "start" position provides +12v to the solenoid, which engages the starter and grounds the starter motor causing it to spin. If the car won't even turn over, you likely have one of three problems:
1. No battery voltage at the starter, or low amperage. You can check the former with a multimeter. Check the big red battery cable at the back of the starter.
2. A bad solenoid that either isn't engaging or isn't providing the ground to the starter. That click you hear may be the solenoid, but you wouldn't feel it in the brake pedal. It's possible that the click may just happen to be coincident with the ABS system pumping up.
3. A bad ignition switch. This is a definite possibility.
There are a couple other things which could be the problem. Among them, bad wiring (highly unlikely) or a starter inhibitor, either as part of an alarm or a stand-alone system. Finally, if your car is an automatic, it could be the start inhibitor built into the shifter, which under normal circumstances allows the car to be started only while in Neutral or Park.
Assuming you've got power at the starter (again, test the big red cable), get a test light. Ground one side, connect the other side to Pin 50 on the starter. It should be a yellow wire. Have someone try and crank the engine. If the test light doesn't come on, the problem is before the solenoid. If it does, the problem is likely the solenoid. If you've failed this test, next pull up the center console and repeat the same check at the switch mounted to the shifter (automatics only). Check both sides of the switch, making sure the car is in park. You can jumper a wire across the switch to bypass it for tests. If you get a light on one side but not the other, the switch is bad. If you don't get a light on either side, check Pin 50 on the ignition switch itself. If you don't get a light off Pin 50 while cranking, your ignition switch is bad. Any of these components - the ignition switch, shifter switch, or solenoid - are all possible failure points.
If you are feeling saucy, make SURE the car is in neutral (or park) and the handbrake is on. Connect one side of a wire (at least 14 gauge) to Pin 50 on the solenoid (again, yellow wire) and connect the other side to the positive (+) side of the battery. The car should crank. If it does, the problem is electrical, somewhere in the car as above. If it clicks but nothing else happens, the starter motor itself is probably bad. If nothing happens at all, you've got a bad solenoid and possibly a bad starter as well. My advice, replace them both with rebuilts and call it a day.
None of these have anything to do with any ECUs anywhere, and there isn't a diagnostic computer in the world that could be hooked up to *anything* in the starter circuit much less tell you anything useful.
Bottom line: Find a new mechanic.
-Justin
posted by 64.166.4...
, Wed, 29 May 2002 02:59:53 <-- Viewing This Message, Tue, 28 May 2002 21:53:39, Tue, 28 May 2002 23:09:52
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