Idling versus Shutting Off the Car

[diamondlarry]

I don't think all cars have the fuel pump issue that was mentioned. I know someone else with a Saturn that spliced a switch into his injectors to shut off the engine so he wouldn't lose any mileage from waiting for the engine to die. I would like to try this sometime but haven't gotten around to it. As for the alternator problems, I haven't noticed any ill effects from coasting with the engine off.
EDIT: Interesting. Two for one posting. :-)

[JanGeo]

The fuel pump is kept alive with ignition pulses from the distributor - was that way in the Geo. The alternator if it has an external regulator would be driving the rotor field with power form the ignition switch trying to produce output voltage to keep the battery charged. Newer alternators with built in regulators work off the excitor voltage they generate and operate independantly of the ignition. Because the field is driven hard and not spinning you probably overheated the regulator or rotor windings.

[krousdb]

Originally Posted by MetroMPG

how did you wire it? did you simply tie it in to the existing key-ignition circuit?

Pretty simple. Found a piece of speaker wire, 6ft long. To both leads on one end I connected a normally closed momentary pushbutton rated at 15A. Ran the other end through the firewall to the distributor. Found the power wire which powered the coil inside of the distributor. Cut the wire and connected the two leads of the speaker wire to the two cut ends of the ignition power wire. Basically I hacked into the ignition circuit at the distributor and put a pushbutton in between. Kills the engine without having to turn off everything that the ignition switch turns off.

[diamondlarry]

Pretty simple. Found a piece of speaker wire, 6ft long. To both leads on one end I connected a normally closed momentary pushbutton rated at 15A. Ran the other end through the firewall to the distributor. Found the power wire which powered the coil inside of the distributor. Cut the wire and connected the two leads of the speaker wire to the two cut ends of the ignition power wire. Basically I hacked into the ignition circuit at the distributor and put a pushbutton in between. Kills the engine without having to turn off everything that the ignition switch turns off.

Does anybody have any ideas on how to do this on a distributorless ignition like the one on my Saturn. I like the simplicity of the pushbutton idea.

[krousdb]

Originally Posted by diamondlarry

Does anybody have any ideas on how to do this on a distributorless ignition like the one on my Saturn. I like the simplicity of the pushbutton idea.

Didnt know a distibutorless ignition existed. But you still need power to get to the spark plugs somehow. Find the power source and splice your pushbutton into it. Do you have a schematic that you could post?

Just look for how power is supplied for ignition. Cut into that wire.

[MetroMPG]

i was trying to think of a way of testing this concept without having to actually wire it up first. ie. test the car & ScanGauge's response to an "engine-off" condition that was not initiated through the ignition key switch.

would this be valid: point the car down a hill at a walking pace and then intentionally stall it out with a high gear.

then coast down the hill and watch what happens to the SG - and also whether i can re-start with the clutch at the bottom of the hill.

[krousdb]

Originally Posted by MetroMPG

i was trying to think of a way of testing this concept without having to actually wire it up first. ie. test the car & ScanGauge's response to an "engine-off" condition that was not initiated through the ignition key switch.

would this be valid: point the car down a hill at a walking pace and then intentionally stall it out with a high gear.

then coast down the hill and watch what happens to the SG - and also whether i can re-start with the clutch at the bottom of the hill.

Yes, that would be similar to a kill switch. Give it a try.

[JanGeo]

distributorless may be tricky to kill, each coil is driven by the computer and may not have a common power lead.

Definately could stall the motor on a hill and try the bump start at the bottom - you may have to turn the motor over a few seconds to activate the fuel pump.

I was wondering if I could turn on my odometer in my xB so I could log my miles without keeping the motor running.

[diamondlarry]

Originally Posted by JanGeo

distributorless may be tricky to kill, each coil is driven by the computer and may not have a common power lead.

Definately could stall the motor on a hill and try the bump start at the bottom - you may have to turn the motor over a few seconds to activate the fuel pump.

I was wondering if I could turn on my odometer in my xB so I could log my miles without keeping the motor running.

Most likely, all you'll have to do is turn the key to the run position to get the odometer to register. My uncle told me that an odometer is basicaly a voltage meter. The ignition provides the power to energize the mechanism much the way an alternator is energized. I don't know whether or not the voltage to the odometer is ac or dc but I think it starts out as ac like the alternator. I beleive my uncle's explanation is probably true because my speedometer/odometer registers speed and mileage in reverse.
My Saturn doesn't seem to have any problems with the fuel pump being active when coasting. I have gotten to where I can start the car in 4th gear and you can't even feel the car jerk when I do it os it seems as though the fuel pump is always ready to work as long as the ignition switch is on.

[JanGeo]

The idea is not to have the ignition on to see the odometer - having the ignition on turns on all the bells beeping and idiot lights on the dash and fuel pump and everything else running - draining the charge off the battery.

Bump starting the motor in 4th or 5th should be easy if it is warmed up - should fire on the first compression of a single cylinder.