Thread: Nonstarting 930
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boostfix boostfix is offline
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Join Date: Nov 2006
Location: Vancouver, BC Canada
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Trouble Shooting List - No Start

Probably time to start at the beginning of the trouble shooting process.....In the porsche manual page 28-6 outlines an ignition trouble shooting process.

underlined and italic is text from the manual, other text is my $0.02. If yes to each step then proceed to the next step if NO then follow to step (No.) or(direction)

1. connect a spark plug to the coil wire, set gap to 12mm and check for spark. Make sure you ground out the spark plug properly when checking for spark. (8)
2. check distributor cap, distributor rotor, ignition lines and spark plugs. Resistance of ignintion line including plug: 4 kohms. resistance of distributor rotor: 5 kohms. Spark from spark plug? (repair high voltage end)
3. check ignition timing. Timing correct? (adjust timing)
4. check fuel system. Engine receiving sufficient fuel? (repair fuel system)
5. Check ignition transformer (coil). Disconnect plug and high voltage wire at coil. Between coil primary (terminal A and B): 0.1 to 0.165 ohms. Between coil secondary (terminal 4 and A): 390 to 630 ohms. Resistance correct? (replace coil)
6. check wires and plugs or ignition system (CDI control unit, ignition/starter switch, distributor, ignition transformer, tachometer) for tightness and oxidation. Everything correct? (eliminate defects)
7. For ignition failure: disconnect tachometer. If ignition failure is gone, the tachometer has a defect. If not, the tachometer is good. Ignition failure eliminated? (replace control unit) control unit is the CDI box. Someone in an earlier post mentioned something about a diode in the tachometer....step 7 proves that there is something in the tach that could fail
8. disconnect wire plugs at air flow sensor contact or bridge terminals 30 and 87 on the base of the relay for fuel pump II. Check voltage at disconnected control unit plug between terminals 6 and 8 with the ignition on. The voltage must be equal to the battery voltage. (eliminate break in supply line) This is where my manual must be missing some update sheets. The picture of the CDI plug shows 8 pins and my 88 930 only has 6 pins on the CDI plug. So I'm not sure between which pins I should be finding 12V.
9. Check sensor resistance including sensor line at disconnected control unit plug between terminals 3 and 7. resitance: 490 to 700 ohms. Resistance correct? (repeat test at two-pole plug in sensor line)
10. check ground of sensor coil including sensor line at disconnected control unit plug between terminal 3 and car's ground and terminal 7 and car's ground. Test value correct: repair or replace wires between plug and CDI control unit. Test values incorrect: replace distributor. Resistance infinite? (repeat test at 2-pole plug in sensor line)
11. check sensor system for mechanical damage. Visual inspection: is there clearance between the rotor and stator? Sensor system good? (replace distributor)
12. Disconnect tachometer. If there's an ignition spark now, the tachometer is defective. Tachometer good? (replace tachometer)
13. continue at point 5

Good luck!
88 930 blk/gry
Old 10-18-2008, 10:53 PM
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