Why must car start in P or N and not D.
 

Why are cars designed so they can't start in drive? Is it just a safety thing so you don't start moving right away, or is there a more mechanical reason?

What I'd like to implement it an off button for use while at red lights. Something that cuts the engine when pressed, and starts it back up when released. Building such a device would be easy, I just want to make sure it isn't going to do any damage.

So one doesn't accidentally run over someone or some thing. Generally though, you don't want to start the car in drive since your starter will be both turning over the engine, TC and trans. Your starter might have enough grunt to do it for the rest of its life or you could kill it off quick.

For the record I don't think this is a wise mod and you shouldn't do it. But all you'd have to do is ground out the NSS usually. That way the trans computer thinks its always in neutral or park.

I'm guessing it's because in drive there would be an extra load on the starter of trying to move the Torque Converter. In P or N that load isn't there. At least I don't think it is.

That makes sense. The alternative would be to place the button on the shifter, so I can push it into N, hold the button to keep the engine off. When the light changes I let go of the button, and pull it into drive.

well, you'd have to crank the starter over to get moving again though. So the button would be a kill switch, then you'd have to turn the key to start it again

so yeah. this is what I do anyways. drop in N, kill it. Light goes green, fire it up, drop in D and go. Only problems I'm having are the key/brake/shifter links don't like this much, because it won't give me the key back sometimes. I believe its just a solenoid problem, and starting it again, put it in gear, then park, all while holding the brake, key off, release brake, the solenoid kicks off, key removed. Annoying? yes. A deal breaker? no. Worth building a secondary circuit for on-off work? Not even close.

I've bypassed the neutral safety switch in a 1976 Chevy van for over 20 years and not had a starter failure. My ignition switch went bad, so rather than replace it, I just wired in a relay and a push button switch (I was poor at the time) and its worked fine ever since (my dad still owns the van). And I've often started it in gear. It is a little weird to start moving as soon as the engine starts though. At cranking speed there is very little resistance from the torque converter, so it doesn't really add much to the starter's load. The reason manufacturers don't let you start in gear is strictly liability, remember Audi's "unintended acceleration"? That wasn't the same issue, probably a pedal placement problem, but the point is the same. Imagine what the average driver with a cup of coffee and a cell phone would do if the car started moving as soon as the key was turned and you see the problem. If I was going to wire something like this up, I would probably use a three position toggle switch mounted within easy reach with the center position normal, one direction kills the ignition / injectors, and the other direction to the starter. It would also allow easier EOC if you're so inclined, which saves a lot more gas, according to the people who do such things.

In my application, I'd be worried about transmission wear.

Reason being: I would likely be tempted to kill the engine while in gear and just key-on to restart (providing the speeds allow the TC to remain locked). Otherwise, I'm trying to see the advantage...

How would this react without rev-matching from Neutral?

RH77

This is intended for use at stops only, I don't do EOC in my car. As soon as I let up of the break, the vacuum assist is gone.

The two way toggle is a great idea. I'd prolly mount it in the center console near the gear indicator. Now all I have to do is wrap my head around the poor "schematics" in my haynes manual. I may go to the library and look at the Mitchel1 book, since those schematics are properly drawn.

We have an 89 dodge spirit (same as your car but a 2.5 turbo) and someone hardwired the neutral start switch. You can start it in any gear, but if you do it in drive it doesnt really move while cranking, but after it starts it starts rolling forward a bit.

Yea, after I wrote that I thought about restarting while moving, and I'm not sure that would be a good idea either. I've never actually done that, and the torque converter in a 76 doesn't lock so it would be different in any case. Good luck.

In most older carburetted cars, and also in fuel injected cars, but usually to a lesser extent, there is a fast idle immediately after starting a cold engine.

If you could start the car in Drive it would immediately take off through the wall of your garage, or run over your puppy, or something else undesirable.

my younger bro tried to start our family car years ago while it was parked in R in the garage, it skipped and jumped back 10 feet. goo thing the garage door was open.
safey.

this question made me laugh a lil , d would be in gear.

my 1st experience with a manual transmission was at a paper drive.
i was obsessed with starting vehicles ..as my mom walked towards the truck.
my good deed moved the truck 2 or 3 feet while i tried to start it in gear.

The transmission safety switch on my off road race truck is bypassed, I occasionally start it in drive if it stalls while racing etc. It's an auto trans, the starter doesn't make the truck move that much until I punch the gas. There is more load on the starter but I don't think much more. The auto "free wheels" until enough rpms are built up.

The t/c has a stall speed in most passenger cars over 1200 rpms, the starter rotates the engine nowhere near that speed. The t/c is bolted to the ring gear and is always turning with the engine. Its just a safety feature that you have to start it in park, apply the brakes then pull it into gear, with the exception of being able to start it in nuetral. I guess thats why its called a nuetral safety switch and not a turn the key and see what happens switch!
I guess my point is, you cant do any damage internally starting it in a gear.

I was thinking about that for the Clunker. When the clutch went out, I was easily able to start it moving in first gear with the key, and it worked surprisingly well, even on hill starts. I'm thinking about bypassing the switch so I can do the same to get moving at lights. The tradeoff would be more wear on the starter vs. less wear on the clutch (clutch is already all the way out when the car starts moving.) Of course, this would only be on level/slightly downhill streets.

The starter is pretty easy to replace, so I figured I could buy a spare starter and keep it in the trunk for when I finally kill this one.

FWIW: I used to have an old (55) Pontiac 3-speed standard. The clutch fork broke and wouldn't disengage so I drove it for quite a while without using the clutch. Just coasted to a stop in neutral, turned the motor off, put it in first gear and hit the starter when I wanted to go. The motor would start and I would just drive off!!:D

The sensor or whatever is broken in my car so I can start it in whatever gear I want, It makes my check engine light stay on but I like it better being able to turn it on in whatever gear

the clutch cable broke in a Chevy Spectrum I used to own. Thank goodness I knew how to shift without the clutch. I drove it from Colorado Springs to Denver (about 90 miles) without a clutch during a blizzard and had no issues. Driving in town was annoying, but doable.

Not having a safety switch saved me a bit of pushing the car once when my Datsun 210 ran out of gas. I used the starter to move the car about a mile down the road to a parking lot. It was funny finding out how fast I could go on just the starter and in 5th gear!

BTW when the starter engages on an auto, the torque convertor goes for the ride in any gear. In neutral and park, it's the clutches that are in neutral, and like others mentioned, at such a slow speed it's unlikely you'll get much drag from the convertor if in gear.

because remote starters would have comedic value ?

remote starters already have comedic value :) Best thing for efficiency and quick warmup is to start driving.

In my mind, the only use for a remote starter is in really, really cold weather (below 0* F), you could start the car while you're walking to it if it's parked outside. This would give it about 30 - 40 seconds to get the cold fluids flowing by the time you got in and started driving. Otherwise, they're just a waste of gas, especially in something like my Jeep that probably sucks over a gallon an hour at idle (even warmed up).

I think it was used as a safty device, for the people with coffee and cell phones.

In the automatic speedway cars everyone bridges that switch so they can start if they spin and stall (yes it's possible). I started mine in gear many times intentionally and it never had any issues (without any gear selector indicator it was safer to start in gear than select the wrong gear for the race and have to change it on your way to the first corner with 8 other cars).

well I had to kill a neutral kill switch once in an older car but that was because of a bad clutch. IE could not clutch to neutral so could not start the car or shift gear into 1st

so I disabled the switch put it in 1st and started it up. since this also MOVED the car as it was cranking (hence why the switch is their) I was able to get the car going and driving :-) (just had to get it down the street) you can clutchless shift and just turn if off to do it all over again if you have to stop.

a nice emergency way of moving the car if the clutch is hosed.

With newer AT's I have no idea what would happen. When I'm driving with the engine off, and forget, and down shift, it does nothing. It just stays in N. So I freak out a little and turn the key, but it wont start because it's still on 2nd or something. My brakes stop working when I drive with the engine off some times, down shifting is my instinctive other braking option, so I've done this twice... I keep the engine running now. But if it can be in 2nd and decide it should really be in N and then it was started, it could work out fine, or possibly really bad, but the torque converter is a good thing.

to nerys: i've had the neutral switch disabled in an aging Datsun once before, and was indeed able to move an extra mile to a better parking spot when I ran out of gas. I discovered I could get up to 35 mph using the starter and being in 5th gear!

to the Doc: if the engine is off, and you select a gear while rolling, normally nothing will happen because, without the hydraulic pressure coming off the pump which gets its energy from the engine, nothing can be engaged. However, beware of the lock up torque convertor trying to engage in such a situation. Bad things can happen if the spped is high enough and the computer send the signal to the convertor to lock up.

Otherwise, no harm no foul assuming the torque convertor remains unlocked. which is to say being in 2nd is safer than being in D with the engine off during a coast.

This was a result of the early 1980s Audi 5000 unintended acceleration debacle. It forces drivers to properly find the brake pedal before driving.

Autosafety.org

TheTruthAboutCars.com

My car is good about this unless I do a good job of rev matching on the highway, then it engages with a thud. But at least it's never more than 150 RPM difference. I don't bother rev matching any more, and things go smoother.

Safety switches pre-date that by a lot, the first Powerglides had them... My 1957 ford fairlane has one as well.

When 4 wheeling in rocks its very common to stall a vehicle engine and restart in gear because if you hit the clutch you will go backwards down hill very fast. BAD>>>>

The Torque convert as well as the transmission pump and hydraulics are all turning when you crank the starter, its just bypassing until you switch the auto to a gear that engages a planetary and puts power to the road... Much like that AC clutch....

Dave