Unintended Acceleration...

Since the fuel injection system is pressurized, it might _not_ "shut the engine down in short order".

For an emergency shutdown I'd try to somehow shut off the ignition. ...Jim Thompson

Not a bad idea. Also serves as a anti-theft device if hidden somewhere.

tm

Ditto. If the engine management computer is an obvious module, just cut power to that.

If not, cut the signal from the spark timing sensor (probably the crank sensor) to the engine management computer.

If it's a diesel, well, you may have to get creative.

Accidental engine shutdown -> no power brakes and no power steering.

VLV

But it is a pressurized liquid. There is no stored potential energy like a compressed air system.

Stopping the pump will kill the engine in seconds.

Manual transmission. ;-)

The rationale was that power to the ECU might be supplied by several circuits plus any possible parasitic power sources that may keep it energized. Too much possible interaction that will vary from one vehicle's implementation to another. Working here on the KISS principle. Interrupting the fuel source seems reasonable.

Many cars are electric assist steering. Engine loss will not affect steering in that case. With hydraulic assist, yes, it does get more difficult - but not impossible to steer. Particularly true when you are still moving.

Most brakes are still vacuum assist. On all cars I've tried it on, if you keep pressure on the brake and not take your foot off, there is adequate safety margin to bring the car to a stop. Worst case, pumping the brake (foot totally off and then on again) I usually see at least 5 cycles before boost is lost. After this, you put two feet on the brake pedal and push HARD.

Oppie

Regarding parasitic power sources- think of the engine run-on condition that was a problem in the late 60s and into the 70s.

A parasitic power source supplied limited power to the ignition coil when the engine was running and the ignition switch was turned off. Supplied from the battery through the closed alternator field coil relay, through the alternator idiot light and into the ignition coil. In that case the fix was to add a diode in the idiot light circuit (oriented so the light would come on when the key was in run and engine not started). Fixed quite a few run-ons that way.

I don't if that will work either. Been awhile since I did automotive, but my designs would drop to a default timing regimen if the sensor was lost.

Yep. If it has mechanical injector pumping... who knows how you stop it :-(

Reminds me of a late '70's event with a Chrysler product rented from AVIS while on a family Disneyland trip. Driving down from LAX, the accelerator pedal kept sticking.

When we got to our hotel, I called AVIS and told them of the problem. They allowed as how they could get me a replacement vehicle by late the next afternoon.

I allowed as how that was OK... if the car tried to run away on me again, I'd just take it out of gear and blow the f***ing engine.

Had a replacement car in 20 minutes >:-} ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

There ARE some systems that use a fuel pressure accumulator akin to the expansion tank on a hydronic heating system or pressure tank on a well-pump water system. In this case, it would take some time to deplete the stored volume. At WOT (wide-open-throttle) this interval is likely to be minimal.

Oppie

That depends on how many flexible hoses there are in the system, and whether there's an accumulator somewhere. I doubt the accumulator -- but hoses, and even steel pipes, will flex a bit, as will the liquid itself.

Barring an accumulator (which I doubt is there), at full throttle there's probably not enough spring in there to cause problems.

It's probably gentler on the engine to cut the ignition -- cutting the fuel means it stops lean, hot, and without lubrication to valves and injectors.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Love the diesel rental story! I worked on diesels long ago though mostly industrial stationary units. Those had all mechanical pumps and injectors. The only electric item was a fuel shut-off solenoid. Of course, if you had a leak in your turbocharger seals and lube oil got sucked into the intake, the engine would run away. Often thought about putting in a backup butterfly in the intake to choke off air induction or a compression release.

For the crank sensor. Again, it goes through the ECU and like you said, it may go to limp home parameters. Most engines use the crank sensor to enable the fuel pump. No signal and the pump stops... if the ECU is in it's right mind.

All the better. Toyota will replace everything then, maybe even a new car.

Also, at wide open throttle, cutting the ignition may not stop it from dieseling. Cutting the fuel will. And at w-o-t, it won't run for long.

On a sunny day (Thu, 31 Oct 2013 13:34:33 -0400) it happened "Oppie" wrote in :

Yes, the funny thing about that lawsuit was that NASA experts had looked a the thing and concluded it was OK.... No wonder they need Russian taxies.

I coined the "limp home" phrase while working with GM in the late '60's - early '70's.

They were so panicked by Californica smog standards that they wanted the ignition to simply die if the sensor was lost.

I refused to be a party to such a fiasco, arguing someone could die if the engine quit at just the wrong moment, and suggested the "limp home" method. When they realized I'd simply bow out and rat ("whistle blow" in modern lingo :-) on the whole scheme they agreed with me. ...Jim Thompson

Hopefully >:-} ...Jim Thompson

I'd rather be alive and wrong than dead and right.

For Philco-Ford, early '70's, I designed RPM limiters that worked on the basis of skipping every other firing. ...Jim Thompson

True. Went over a bump one day in a VW Rabbit, croaked, in a very direct, noticeable, no long delay manner. Had wrong fuse in fuel pump, the bump had been the last straw for it. Pulled the fuse from the fan, put it in the fuel pump, got home, bought spare fuses. Not sure who the guilty party was on the wrong fuse, though I'd bet the dealer.