Drivetrain riddle for Pelican Tech experts

[CMDR Perry]

Ok I am hoping for some insight via the Pelican brain trust.

I have a Japanese project car that I bought last fall. The engine runs fine, the gearbox and clutch work fine, the car shifts easily and smoothly going down the road. But if I stop and put the transmission in neutral and try and let out the clutch the engine will die even when fully warmed up?

If I shut off the car it will roll forward / backward in neutral. I am thinking the clutch was somehow assembled incorrectly by the previous owner. Maybe the input shaft is binding in the pilot bearing or throw-out fork when the pedal is being released? Or can it just be a crossover misalignment of shafts & gears in the tranny?

This car has a hydraulic slave cylinder to move the clutch fork. The pedal is adjusted for the correct height and range of motion. The clutch pedal switch starter interlock is functioning correctly also.

I know I will have to eventually tear it apart and fix it. Right now I am wondering if anyone else has seen this issue before and can shed some light on the root cause.

Thanks, DP.

[oldE]

When the engine stops while releasing the clutch in neutral, does the car lurch or shudder as if the engine was being overcome by load or is it stopping as if switched off?
Wild guesses:
If it is lurching to a stop, I suspect you might be getting a 'false neutral', however, since you can push the vehicle in neutral, that doesn't seem likely.
If stopping as if it were switched off, I would look closely at the wire related to the circuit which prevents the car from being started without the clutch being depressed. It might be causing something else to short and interrupt either fuel delivery or spark.

Best of luck.
Les

[bell]

I had a Toyota which I forgot to put on the clutch slave heat shield. ... It would randomly boil the fluid and id have no clutch control after stopping..... took me a while to figure it out lol

[wdfifteen]

Wasn't there at one time some kind of interlock on some cars that wouldn't allow you to start the car unless the clutch was depressed? I can see a bad switch causing the engine to shut off on one of these cars.

[GH85Carrera]

Originally Posted by wdfifteen

Wasn't there at one time some kind of interlock on some cars that wouldn't allow you to start the car unless the clutch was depressed? I can see a bad switch causing the engine to shut off on one of these cars.

I would ASSUME that the switch was a starter interlock. It would prevent the starter from working not kill the engine.

On my 74 914 the seat belt interlock was a real pain. If the car was not buckled up it would not crank or run. I always use my seatbelt 100% of the time. The seatbelt interlock computer under the seat would go nuts and shut the car off if I hit a pothole or a RR track. I had it towed to the dealer three times and they replaced the little computer every time. I finally got tired of that and figured out it was looking at the oil pressure switch. If it saw pressure it blocked the ignition. One simple bypass of that switch and the system was bypassed. I still have that useless POS computer in my attic somewhere.

I am guessing the OP problem is something to do with the hydraulic clutch.

[CMDR Perry]

First thanks for the response from the Pelican community.

Well I read through the Haynes manual. No reference to a neutral safety switch, just the clutch pedal switch. So I pulled the console, no switch visible near the shifter. I decided to nose around in the wiring diagrams and look at the bottom of the transmission. I quickly found the back-up light switch on the side of the trans. Correct color wires, etc.

Also in the wiring diagram was a neutral safety switch with a brown and white wire. Did not see anything like that under the car. Searched the internet for the switch, vague descriptions and generic pictures. No mention of location. I went under again and felt around on the very top of the transmission and found some more wires that terminated in a round knob on top. So I pulled them free of a clip and down fell 2 brown and white wires with plug in connectors. I pulled one apart and started the car.

The car still won't run in neutral. Shut car off and made a 3 inch spade jumper, I disconnected the 2nd wire at plug and installed my homemade jumper. Went topside again and started the car.

She runs great and just purrs in neutral with the clutch pedal fully released.

One more item off the project checklist.

Thanks guys. DP

[Hydrocket]

What kind of car?

[CMDR Perry]

Mazda Miata, 1996 track rat.

[wdfifteen]

Originally Posted by GH85Carrera

I would ASSUME that the switch was a starter interlock. It would prevent the starter from working not kill the engine.

On my 74 914 the seat belt interlock was a real pain. If the car was not buckled up it would not crank or run. I always use my seatbelt 100% of the time. The seatbelt interlock computer under the seat would go nuts and shut the car off if I hit a pothole or a RR track. I had it towed to the dealer three times and they replaced the little computer every time. I finally got tired of that and figured out it was looking at the oil pressure switch. If it saw pressure it blocked the ignition. One simple bypass of that switch and the system was bypassed. I still have that useless POS computer in my attic somewhere.

I am guessing the OP problem is something to do with the hydraulic clutch.

If it were working properly it would keep the engine from cranking or running, as the seatbelt interlock on your 914 did. If it's not working properly who knows what kind of havoc it could wreak. Sorta like your 914.