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Rev-limiter latching up


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1978 Targa with about 90,000 miles.

The engine quits and the key must be cycled off for a count of 5 and than can be restarted w/key. Also will not push/coast start until key is cycled off and then back on. Previous conclusion was that rev limiter, "triggered" by too many sparks from the (faulty..?) CDI, was latching up due to battery being over-charged.

Last fall, Nov., the drive from Seattle to McCall Id , last 100 miles, was only completed via installing a new battery and disconnecting the external regulator. Car was not driven much over the winter months but on the first warmish day, May 17th, and problem repeated.

New alternator w/internal regulator was installed at that time, mid-may, and problem could then NOT be repeated.

Until yesterday....

I have advised the new owner that the rev-limiter should be disconnected as Zimmerman recommended.

Analysis of the removed alternator indicated internal overheating to the point insulation was burned off of the wires between the stator and diodes and bare wire was probably contacting metal alternator frame intermittently. Car would intermittently begin mis-firing and back-firing after driving over bumps.

I'm bothered, bugged, by the possibility that since the battery is mounted all the way forward of the car with the alternator at the rear is there a poor connection somewhere in between that is resulting in the alternator output spiking (PWM regulation) to a too high voltage for the CDI and/or rev-limiter on each cycle of the regulator.

When I was there in May I checked a few of the possible poor connection points, at the alternator itself, alternator/engine, at the starter, the battery posts and the battery ground strap, and I called myself checking the engine/chasis grounding strap but don't now have good memory of that.

Any suggestions...??

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When this first started happening we verified that the fuel pump relay was being energized and that was what was shutting the engine down. There are only three circuit connections that can energize this relay, a factory alarm, the air intake microswitch, and the rev-limiter. No factory alarm, no alarm at all, so only the rev-limiter has a possibility for latching up and thereby requiring a switch "off" before restarting.

The rev-limiter is now disconnected and the engine still shuts down so I guess the next step is to send the CDI away to loren at Systems Consulting.

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  • 2 weeks later...

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