On the latest cars (late 75 & 76 2.0L) the Brain/harness came with an additional logic circuit plugged in to a connector near the MPS.
What was this for?
Would the car run w/o it?

any pix and do you know if it's as supplied by the factory? Only component I can think of that might be id'd as a logic circuit is the L-Jet relay mounted to the battery tray support. Decel valve on the same mount as the MPS is not connected electrically.

sorry I should have been more clear, yes this is a OE feature.

Ive been driving a late djet car for many years. Ive never seen what you are talking about. We need a pic please.

Me 3. The only connection's in that area are the map & CHT, unless the CA model was different.

That's a CA-only speed limiter circuit...details on my harness webpage at the link in my signature block below.

Yes...it will run without it, just unplug it.

thanks Jeff
Speed limiter? what, how does it limit speed?
Would cars not delivered for the CA market also have that same harness just no limiter?

Speed control module limits rpm by shutting down injectors at a pre specified rpm. Car will run just fine without it, but you will not have over rev safety. My 76 California model has one. The cars with the additional cat and egr dash lights have the speed module.

That's exactly correct. There is a CA version (with the branch/connection) and a 49-state version of that harness (without the branch/connection).

I think he meant might you find that CA only harness on non CA cars, just w/o the limiter module?

So I have a question why was this necessary, and only in CA, since the cars already had a limiter..the rotor in the Distributor.

Possibly: 49 state cars used rev limiting rotors which cut ignition but not fuel. And in CA they used the speed limiter to cut the fuel so they were not dumping Raw fuel into the cat.

Jim

I believe that to be the case. ECU on these cars had overrun fuel cut-off and and over-rev fuel cut-off (module) to prevent cat from overheating hence the thermocouple (cat temp module in rear trunk) and warning light on dash which flashes when a overheated cat is detected.

I have a California 76 car and it had the silver box your extra connection probably plugged into. I removed it with the rest of the pollution control and never missed it.

This circuit was actually a 1975 & 1976 'feature'. See this from the 1975 S&T manual, no similar manual was published for the 1976 cars.

S&T manual ?

maybe this is a good opportunity, we should add pics of all the concerned elements, and move this thread to the CW & originality forum?

What is the engine speed limit?
How does this work?

Rich

I dunno how it works...its a circuit. I do know that its wiring is connected to the triggter points so it senses engine speed, I think there is circuit diagram somewhere, I'l post it if I can find it.

Service and Training Manuals. Really good stuff, you should see all the info on the 914/6 and 73 2.0L. Here is a summary I wrote up a while ago...keep an eye out for them, they show up on ebay only rarely.

USA 914 Service and Training Manual Highlights

S&T manuals were supplied to dealerships presumably for tech and sales training purposes. They describe new model year features and upgrades and detailed information some of which is not found in other factory documentation. The manuals were published in several languages including English, German, Italian and French. In addition to subtle cosmetic and functional changes they describe:

1971 914/4 and 914/6
• 104 pages
• Manual describes both the 1970 ad 1971 model years
• General description of the 914s basic features
• Selected 914 prototype features
• Detailed engine specifications
• Detailed D-Jetronic fuel injection description
• Detailed Sportomatic transmission description
• Transaxle driveshaft adjustment specifications
• Limited slip differential
• Detailed suspension specifications, maintenance and adjustment requirements
• Detailed steering system specifications and maintenance and adjustment requirements
• Detailed brake system specifications, maintenance and adjustment requirements including brake force limiter
• A significant number of part numbers
• Detailed section drawings of manual and Sportomatic transaxles, rear brake caliper and brake force limiter.
• Cabin extractor duct system
• Electrical system specifications and wiring diagrams for 914/4 and 914/6
• Detailed engine tune-up procedures

1972 1.7L only
• 24 pages
• 6-digit model numbers
• Engine CO adjustment procedure with new adjustable ECU
• Positive crankcase ventilation (PCV) system
• Cabin heating and ventilation system
• Overrun air supply system (decel valve) and evaluation
• Engine intake air preheating system and evaluation
• Crankcase oil baffle plate and installation
• Revised engine intake vacuum hose routing
• Revised lubrication and maintenance schedule
• TPS evaluation and adjustment procedure

1973 1.7L and 2.0L
• 49 pages
• 6-digit model numbers
• Dimensional specifications of major new engine parts – Crankshaft, connecting rods, pistons, valves, valve seats, heads, intake manifold
• CO adjustment value for 2.0L engine
• Fuel injector pulse width graph
• 2.0L decel valve and auxiliary air valve function and hose drawing
• 2.0L PCV system function and hose drawing
• 2.0L engine distributor vacuum and centrifugal advance/retard curves
• Sideshift transmission improvements
• Sideshift transmission shift linkage adjustment procedure
• 2.0L clutch pressure plate specification
• Minor brake and suspension revision
• Wheel centering specifications
• Door window operator mechanism revision

1974 2.0L only
• 15 pages
• 6-digit model numbers
• Standard and Appearance Group specifications
• Seat belt warning system

1974 1.8L only
• 26 pages
• 6-digit model numbers
• AFC (L-Jetronic) fuel injection system and evaluation

1975 1.8L and 2.0L
• 21 pages
• 6-digit model numbers
• Modified exhaust system
• Catalytic converter (CA vehicles only)
• Exhaust gas recirculation (EGR) system (CA vehicles only)
• Air injection system (2.0L engines only)
• Fuel feed cutout system (2.0L engines only)
• Fuel pump revisions
• EGR/Catalytic converter service interval warning light system
• 5 mph bumper system
• Exhaust gas measuring procedure and values

(the short & sweet of it!!)

AFAIK, this is exactly the reason.

I think that the box shorts out the trigger points signals (to ground), so you get no injection events.

--DD

If I had to guess it shunts trigger point signal to the ECU momentarily to control speed. It does not interrupt the signal because it runs fine without it. Just my theory.

Here is the circuit. It senses the trigger points (circuits 12, 12, 22) and TPS (circuit 17-off idle?). Circuit 16 and 24 are power to the ECU.