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914fan's Avatar
Join Date: Jan 2004
Location: FV CA
Posts: 66
trigger points

How do you test trigger points in the car?????
Can I put on ohm meeter on the conector? there are 3 connections witch two do I use????? help
Old 01-29-2004, 12:35 PM
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bowlsby's Avatar
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The center contact is common, the outer two alternatingly should close continuity as the engine cranks and the dizzy spins. Use an analog ohmmeter and watch the needle bounce.
Old 01-29-2004, 12:38 PM
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Dave at Pelican Parts's Avatar
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Better yet, use an oscilliscope and make sure they make some approximation of a square wave. If you see a "bounce" on the scope (open...close-open-close) they are bad.

Randy had some pics of the 'scope readout when his were doing this. You might be able to find them if you surf through for a while.

Pelican Parts 914 Tech Support

A few pics of my car:
Old 01-29-2004, 01:37 PM
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Here is a quick in car test, although not exact, will help trouble shooting efforts. Trigger points fire alternating pairs of injectors. 1/4 and 2/3. With the ignition in the run position go to the engine bay. Operate the throttle from closed to wide open ( note: the engine is NOT running) the TPS, throttle position switch will send a signal to rapidly open close the injectors 1/4 or 2/3 according to the trigger point position. ( this is sort of an electronic accelerator pump function) With one hand operating the throttle, place the other on an injector. you can feel the "BRRRRRP"sound made by the injector when operating the throttle. You should be able to feel/ hear the BRRRP from two injectors on opposite sides of the engine. 1/4 or 2/3 Now, Turn the engine over 180 degrees. You should now be able to repeat the process with the other pair ( opposite sides of the engine). This will tell you that the trigger points are making contact and completing the require circuit. However, you may still have some sort of trigger point mechanical failure, although rare that could still be a problem during operation. I have used this trick to trace bad injectors, poor grounds, a bad wiring harness ... This test does require a good TPS ( throtle position switch) and should be tested before jumping to Trigger point conclusions...

Hope this helps...

1982 911 SC
1962 sunroof bug
1991 WE Vanagon CARAT WRX conversion
Old 01-30-2004, 05:36 AM
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Like DD says, the real test is if they bounce. Simple on/off functionality does not assure they are working correctly. I would suggest that if your trigger points are of indeterminate age or are nearing 100K miles of use, replace them.
Old 01-30-2004, 11:18 AM
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