Starting a gas vs diesel

Is it harmful to start a gas engine the same way a diesel engine is started? My husband says it doesn’t make any difference. After fueling our gas vehicle, he will turn the key to the “on” position for about a minute (like he does with our diesel vehicle) while he resets all the mileage settings. I thought this was hard on the electrical/ignition/battery. Please help to settle the “discussion”. Thanks. ElleJ


If your battery can’t take a minute in the on position before starting, it’s not in good shape

No harm at all.

If you kill the motor and for some reason forget to take the key out and leave it in the “on” position when you park it for the night - then you can have a dead battery in the morning.

In the early '80’s some Ford electronic ignitions would burn out if you left the car “on” without the motor running. That meant a pretty hefty repair bill.

People use the on position all the time to listen to the radio while waiting for someone then start the vehicle. So the answer is no it will not cause harm to do so.

It’s a habit that is unneccessary but should do no harm.

Thanks for all the feedback. Very much appreciated.

With many vehicles the maintenance reminder is reset with the ignition on and engine off, this is acceptable.

No problem. :smiley:

For the record, the only difference between the way a gas engine starts and a warm diesel engine starts is that the gas engine uses sparkplugs to ignite the fuel, whereas a diesel uses heat generated by combustion pressure to ignite the fuel.

A gas engine sprays the fuel in first, compresses it, and then ignites it with a spark.
A diesel compresses the air to where it gets hot enough to ignite fuel, then sprays the fuel into it and it ignites itself.

Other than that detail, there’s no difference as regards starting.

No big deal. After driving a diesel for many years, it took at least a year before I stopped turning the key and waiting on the gas fueled car. Unnecessary but no harm no fowl. The reason you wait on a diesel is to let the glow plugs warm the cylinders so the diesel will be ignited.

Back (before the mid '70s) when gas engines had ignition points they could be damaged by leaving the ignition on without the engine running.

I’ve never owned a diesel. In fact I don’t think I’ve ever driven one. I wonder, why does OP’s hubby wait a minute after turning on the diesel to start it? Is that so the glow plugs can have some time to warm up before cranking begins? Or do they even use glow plugs these days?

Hubby probably got in the habit of doing this on the diesel for exactly the reason you said, to allow the glow plugs to add some heat to the cylinders before trying to start the engine when the engine is cold.

For the OP’s reference, a glow plug is a little heating element, and when a diesel engine is too cold for the compression alone to create enough heat to cause combustion when the fuel is sprayed in, these little heating units (glow plugs) assist the process.

Doing so on a gas engine does nothing but drain a wee bit of power from the battery, well within what a healthy battery will tolerate.

Yes, glow plugs are still used these days . . .

However . . . they are far different than back in the day

For instance, on some applications, the glow plugs remain on, even when the engine is already running

The glow plug system on modern diesel vehicles is quite advanced

Yep. On the Olds you turned the key to on and the wait light would come on while the glow plugs came on. About 20 seconds later the wait light would go off and you’d turn the key to start. Once you do it for a few hundred thousand miles, it just becomes habit no matter what car you drive.

Thank you! At least now I know where I learned about damaging an engine by leaving the ignition on with out the engine running (mid '70s). Tells you how old my knowledge is :smile: I own a 1993 Full Size Chevy Blazer (2-door) with the throttle body (pretend fuel-injection as I call it). I have 265k miles on it with original engine/transmission and it is in excellent condition. I used to change the oil every 3000 miles, but I did update my frequency of oil changes to every 5000 miles and I do drive it in extreme hot and cold temps in Colorado. I frequently get asked if I want to sell it. :wink:

GeorgeSanJose wrote:
Or do they even use glow plugs these days?

My wife has a diesel BMW X5. It has glow plugs, but since there’s a pushbutton start, everything is automatic. In cold weather, there’s a short delay with a glow plug symbol illuminated on the dashboard before the car actually cranks.

Everything happens automatically in all the newer diesels. Aren’t computers a wonder?