1996 SL2 questions

[froggydogg]

Greetings everyone, I had a couple questions specific to the 1996 SL2, and this seemed like the perfect place to ask them.

Back in 2004, a young woman went missing from the scene of a minor accident she'd had, and she was driving this particular make/model at the time. I'm just trying to clarify a couple of technical points concerning the vehicl, and hope someone might be able to provide me with a definitive answer or two.

Did the 1996 SL2 have any sort of fuel cut-off in the event of an accident? I know it did NOT have an inertia switch, and I also know that it did have a fuel cut-off tied to security system, but I believe that is only part of the anti-theft system, and would NOT cut the fuel in an accident.

Did the 1996 SL2 have any sort of emergency fuel cut-off?

[fdryer]

All Saturns have a pseudo fuel cut off; the fuel pump stops whenever the engine stops running. When ignition is turned on, the fuel pump is commanded on for two seconds if the engine isn't started, then shuts off. When starting or running, the fuel pump/ignition system/injectors are alive; the crank position sensor only outputs during engine rotation. Crank sensor outputs precise timing signals to allow the PCM/EFI system to operate. No engine running, no fuel pump/no spark/no injector pulses. If a car crashes and the engine stops running, the fuel pump stops immediately. If the engine continues to run after a crash, the entire EFI system still runs; crank sensor outputs timing signals to the PCM, the pcm operates fuel pump, ignition and injectors.

[froggydogg]

Thank you very much for your response.

Just to make sure I'm understanding this correctly: the only way the fuel would be cut-off, in this circumstance, is if the engine stopped running? If the engine was still running the fuel would not cut-off?

The car had no "impact sensing" fuel cut-off of any sort?

Thanks again for the help!

[fdryer]

Safety design in EFI systems dictates a way to ensure high fuel pressures with the pump running won't contribute to a crash by fueling a fire. GM, and most likely all vehicle manufacturers with EFI/high pressure fuel injection found a simple and elegant method to ensure pump operation ceases if the engine doesn't run. The heart of GM's EFI system is the crank sensor. The ecm/pcm cannot run without it and only run when the sensor detects engine rotation. Read the previous descriptions again to understand basic EFI system operation.

Ask yourself a simple question. If an engine runs, do you want the fuel pump running or not? EFI requires higher than older carburetor fuel system (7 psi) fuel pumps. EFI systems runs between 30-60 psi of fuel pressure for injector operation. If a fuel pump stops, how will an engine continue to run? If you don't fully understand fuel pump operation, start your car and locate the fuel pump fuse or fuel pump relay. With the engine idling remove either the fuel pump fuse or pump relay. Observe how long the engine runs. As fuel injectors continues to operate, the loss of pump operation means loss of fuel pressure until the engine dies from lack of fuel pump operation. The crank sensor still outputs but this experiment is to see how long the engine runs without power to the fuel pump. Technically, if you are able to disconnect one of two wires to the crank sensor or able to disconnect it altogether, this effectively duplicates an engine stopping, if an engine stops in a crash, to kill EFI system operation (no pump operation). In a horrific crash where a fuel line is ruptured, the sudden loss of fuel pressure will result in lower pressures to injectors. Lower pressures with a leaking fuel line usually means the injectors cannot spray enough fuel per injection cycle so the engine starves, stumbles and eventually stops. The leaking fuel line will pump out fuel but only when the engine remains running. No one can predict how long a leaking fuel line/engine running will continue but if enough pressure is lost, the engine will starve itself of fuel (loss of pressure to injectors) until it stops. This might be a worse case scenario with possibly a fuel fire. If you were to examine the crash history of vehicles with EFI systems, you might find that the majority of horrendous crashes never results in a fire unless the fuel tank ruptured and an ignition source ignited spilled fuel.

Any impact sensor to disable fuel pump operation isn't needed or necessary. Impact sensors are used in another area, airbags.

[froggydogg]

Originally Posted by fdryer

Any impact sensor to disable fuel pump operation isn't needed or necessary. Impact sensors are used in another area, airbags.

I am not a mechanic by any stretch, which is probably painfully obvious by now, but this is the main reason that brought me here.

The airbags inside her car had been deployed, and a few people were speculating that as soon as the airbags go off there is a safety fuel cut-off, in which the car can't be restarted, but I've never found mention of this in my research on Saturns, and know that some other makes/models could be started regardless of airbag deployment. I know for a fact that the '96 SL2 did not have an inertia switch, so I'm just trying to rule out the "airbag fuel cut-off" as well as any "impact-sensitive" fuel cut-off.

[billr]

I gotta ask, and I don't mean to be cruel:

Did the entire car and driver go missing after this accident; neither has been found?

[froggydogg]

Originally Posted by billr

I gotta ask, and I don't mean to be cruel:

Did the entire car and driver go missing after this accident; neither has been found?

The car was found abandoned, but locked, at the scene. She hasn't been seen or heard from in over 13 years.

The car was also alleged to have started right up in the garage it was towed to when her father looked it over.

[Jonasan308]

I was in an accident in a 1999 sl1 and the airbags deployed. As far as i remember, the car cut off when the accident happened, but was able to be restarted.
And out of curiosity, why do you need to ask about this?

[froggydogg]

Originally Posted by Jonasan308

I was in an accident in a 1999 sl1 and the airbags deployed. As far as i remember, the car cut off when the accident happened, but was able to be restarted.
And out of curiosity, why do you need to ask about this?

Did you have to reset anything to start the car back up? Did the engine stop running during the accident, triggering the crank sensor cut-off?

I ask because I don't have access to a 1996 SL2 myself, and am trying to get as many specific details about the car, and it's behavior in an accident specifically, to try to answer some questions about what might have happened, and this seems like the place to go for Saturn-specific answers.

[fdryer]

A '96 Saturn does not have an airbag/fuel cutoff', 'impact fuel cutoff sensor' or inertia cutoff', period. More imagination is occurring than facts provided here about EFI systems and how Saturn engines operate. If the car electrical and electronics are intact, the engine starting up is normal. '96 Saturns did not have a theft deterrent system to prevent starter or engine operation.

If you are at all interested in how any accident investigation is conducted with better than average conclusions, try reading any small airplane accident investigated by the NHTSA. The 'party' concept is used where professionals from every area of expertise is asked to participate in an airplane crash; medical examiner, engine manufacturer, pilot records, airframe manufacturer, metallurgists, electrical and electronics specialists familiar with avionics, weather specialists with NOAA, local airport management, tower operators (if the accident occurred as a towered airport), local police and fire personnel, family, friends of the pilot and any passengers, etc.. Many variables are considered in an airplane accident to determine the cause of a crash. With many people contributing expertise with on one gaining any advantage, answers are found to explain why planes crash. Car accidents are less clear with less participants involved in an investigation while most are explained to the satisfaction of insurance companies since they're not interested in doling out any more money for medical and reimbursement expenses than necessary.

[Jonasan308]

No, it was just turn key and it started back up. Though, it was leaking fluid, and probably would have overheated if kept running. Yes, the engine did stop after the impact. The car was totalled afterwards.

So, from what i have read, a woman crashed her car into something, and then disappeared and has not been seen or heard from since. Right?

[billr]

Did the car in question have a manual or auto transmission? With a manual trans, coming to an abrupt stop (collision) almost always results in the engine being stopped, and that would interrupt the crank-sensor signal. The only thing that affects that signal is rotation of the engine (crankshaft); if the crank is turning, then the signal is present.

I'm assuming you are trying to "re-enact" the scene to help resolve this tragedy. Keep asking questions and I will try to help as best I can.

[froggydogg]

Originally Posted by Jonasan308

So, from what i have read, a woman crashed her car into something, and then disappeared and has not been seen or heard from since. Right?

She did. There are a bunch of other odd circumstances, but some questions come back to the Saturn itself, and I'm just trying to get get definitive answers to those.

[froggydogg]

Originally Posted by billr

Did the car in question have a manual or auto transmission? With a manual trans, coming to an abrupt stop (collision) almost always results in the engine being stopped, and that would interrupt the crank-sensor signal. The only thing that affects that signal is rotation of the engine (crankshaft); if the crank is turning, then the signal is present.

I'm assuming you are trying to "re-enact" the scene to help resolve this tragedy. Keep asking questions and I will try to help as best I can.

The car in question was an automatic. I'm just trying to get as much of the pertinent info relating to the Saturn itself.

There was "spiderweb" crack high in the windshield too (right at the tinted strip), that many speculate was a result of her head hitting the windshield, but the airbag had deployed, and she was only 5' 7" so I personally believe the windshield was cracked solely from the deployment of the airbag. I've seen many videos of airbags cracking when the airbag goes off, and have even seen photos of the exact same car with the exact same crack in the same place that also had the airbags deploy.

Anyone know if the airbags in the '96 SL2s were prone to breaking the windshields?

[OldNuc]

As has ben stated above there is NO automatic item, sensor, or circuit in any module that cuts off power to the fuel pump in the event of any impact of any magnitude. Direct damage to vehicle could render the car no longer able to run and/or be drivable but that is a different question.

[toggenburg]

Private eye guy?

Crime scene reenactment for criminal justice?

Missing person: Insurance company investigation with regard to inheritance payment?

Or?

[fdryer]

Originally Posted by Jonasan308

.....So, from what i have read, a woman crashed her car into something, and then disappeared and has not been seen or heard from since. Right?

You're the only one here supplying info. Have any news posted about it? With so little info given, anyone can speculate; drugs, medical issues, drunk, texting, weather, etc..

Airbags deploy towards driver and passengers so its pure speculation that any airbag contributes to window damage. Its more likely for windows to crack from stress, flexing of frames during a crash than from airbag induced damage. The whole point of airbags are to cushion the head from going thru the front or side windows. Watch some youtube videos.

[froggydogg]

Originally Posted by toggenburg

Private eye guy?

Crime scene reenactment for criminal justice?

Missing person: Insurance company investigation with regard to inheritance payment?

Or?

Concerned citizen that lives close to where it happened and has been trying to help find answers. The case has quite the following online; blogs, podcasts, etc. Google 'the disappearance of Maura Murray'.

[froggydogg]

Originally Posted by fdryer

... its pure speculation that any airbag contributes to window damage.

youtube dot com/watch?v=lV6jkag4aM4

Being a newbie, I can't post links, but replace the " dot " in the above link with a normal.

The airbag alone breaks that windshield in the video, though it is not a Saturn. It's just my own belief on that particular point, especially after seeing the other SL2 with an identical crack in the identical location.

[fdryer]

Link doesn't work............