Clutch Pedal Starter interlock Poll

[Charles421]

I have to depress the clutch, otherwise no starty.

[bk7794]

my 91 civic has a clutch interlock.

[Maggiolone]

My '84 VW Jetta doesn't have this; I've habituated myself to starting the car without a foot on any pedal

[ClutchFork]

Seems my 1977 F100 did not have the interlock because the clutch linkage broke once and I drove home without the clutch and at one point was forced to stop. To get going I shut off the engine, put it in first gear, and turned the key.

But with my 2001 Ranger when the slave cylinder blew apart on me, I had to get towed because I drove no clutch trying to make it to the repair shop a mile away but it was rush hour and I was forced to stop. I did not know how to defeat the interlock, much less whether I could get up under dash to do so if I did know. So, the interlock may be a safety feature, but can also be a roadblock.

[Rope-Pusher]

I had a friend one time (Can you believe it?) that was driving ....was it an '86 Dodge Shadow?....and her clutch release cable failed while driving home from work. Well, the Clutch Pedal Interlock switch was....incorporated into the clutch pedal assembly....and she could drive it as if it had no CPI because depressing the pedal (Alas,....so sad!)...to restart the car. That was while another friend of mine (Yes, two (2) friends that year!) was releasing the new and improved clutch cable with stainless steel wire and a higher wire count, too. It was more flexible and not subject to stress corrosion like the original cable design (that had somehow worked fine since the days of the '78 Dodge Omni, but as cars got bigger, heavier, came with more gear ranges and had engines with more totrque, life had gotten more difficult for your average clutch release cable). Anyway, the friend with the prototype version of the new, improved clutch cable got togethe with the friend with the failed cable and he gained a failure data point and she gained a replacement cable that wasn't likely to fail.

Just a few years later,....OK, it was maybe 10 years later,...I took on the responsibility of the clutch release system and I found that testing (now to 1M cycles) and warranty data revealed there could be mid-to-high mileage failures of the diecast zinc fitting on the end of the clutch release cable corewire. If the cut wire end isn't preformed (Birdcaged) properly and inserted properly in the diecast mold, the zinc did not penetrate the space between the wires and/or the wires were too close to the suraface of the zinc and the zinc fitting fractured and came off the end of the wire. I found that when this problem was first noted in warranty return cables, the cable manufacturer's response was to double their end-of-line Proof Test load. Well, it was found that all that did was unknowingly prematurely fracture some of the zinc fittings, leaving them to fail at a low mileage.

I toured the manufacturing facility of a brake cable supplier and saw them using something known as an extruded button fitting on parking brake cables. It was an almost fool-proof manufacturing process -a machine holds a steel "Button", a steel cylinder maybe 8mm diam and 8 mm long, with a through-hole running along the axis of the cylinder. As the brake wire is inserted through the hole in the button, it contacts a switch and the button is extruded through a die, necking it down firmly around the wires. The position of the fitting is very repeatable and the button doesn't come out the other side of the extrusion die without a tight grip on the corewire. I released an extruded button fitting on the clutch cables and I never heard a peep out of them in warranty again.

Sometimes you have to kill a problem over and over until you kill it dead...with FIRE!

...and then in a few more years everything is using a hydraulic clutch release system and you have to find and solve all the issues with that.

Nobody ever had to learn how to properly bleed a clutch release cable at a vehicle assembly plant or in service!

....and a hydraulic clutch release system costed ~ $27 more per vehicle than a cable clutch release system.

[Rope-Pusher]

Yanno, the clutch pedal starter interlock is just that - the starter won't function until the clutch pedal is depressed (So Sad!).

It's not guaranteeing that the clutch is disengaged and torque can't pass from the flywheel to the transmission input shaft, it's just saying that the driver is aware it's an Amish vehicle and has depressed the clutch pedal. It is much simpler to sense the clutch pedal actuation state than it is to sense that the release bearing has pressed (or pulled, in rare cases) on the fingers of the clutch diaphragm spring in the clutch cover a sufficient amount to unclamp the clutch disk from between the pressure plate and the flywheel.

It's kinda like that for Slushbox interlocks, also. They use the signal from a switch on the brake pedal to show that the brake pedal has been depressed prior to allowing the silverbox to be shifted out of Park position. It's not inferring that there is sufficient pressure in the brake lines to hold the vehicle from rolling, but rather that the driver's foot is on the brake pedal and not the accelerator pedal.

[ClutchFork]

The CPI apparently foils car-jackers who take a running manual and manage to stall it and cannot restart it because they don't think to push the clutch pedal.