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why do cars have trouble starting if not used in a week?

C

CasioTech

Diamond Member
I go to start my 70k truck that I havne't used in a week and something sounded like it snapped when I tried to start it and then it just died so I try to start it the second time holding it and it was reving until it finally turned on. I turned it off and back on again but with a hot engine, of course it would turn on easily.
 
One of the many things that happens is the engine oil slowly creeps back down into the oil pan, if it's a carb'd vehicle then the float bowl needs to fill up with fuel before it will start, requiring more cranking. Also with a worn fuel pump the fuel will slowly creep back down the lines requiring more yet more cranking.
 
My 93 ford takes a little longer to start when it has been sitting for awhile but not bad. Your car just doesn't like you 😉
 
Quite possibly something is drawing down the battery while it sits.

You can use an ammeter (which would be a PIA as you would have to disconnect a terminal.)

Or you can take the specific gravity of the electrolyte. Most motorcars have a 12v system so that's 6 cells - average this sg and record it.

After a week on non use, take another reading and compare. If they are nearly the same indicating the charge is still good, your problem exists elsewhere.
 
no I think it's the battery because when it's fired up it's at 15v, when it's off it's at 12v after a week it's down to 8-9v. It's an old battery in a humid environment.
 
Originally posted by: Eli
Fuel system not holding pressure.
Click to expand...

Doesn't an electric fuel pump build operating pressure on the rail within a second of the ignition switch being turned on?

(Sorry I'm not a car person)
 
Originally posted by: MS Dawn
Originally posted by: Eli
Fuel system not holding pressure.
Click to expand...

Doesn't an electric fuel pump build operating pressure on the rail within a second of the ignition switch being turned on?

(Sorry I'm not a car person)
Click to expand...




neither am I, i'm like a girl when it comes to cars.

 
Originally posted by: MS Dawn
Originally posted by: Eli
Fuel system not holding pressure.
Click to expand...

Doesn't an electric fuel pump build operating pressure on the rail within a second of the ignition switch being turned on?

(Sorry I'm not a car person)
Click to expand...

It should, but only if the fuel pump is good.
 
Some fuels, especially thiose which have alcohol in them. will draw water out of the air - especially where it's humid,
and when the water reacts with aluminum parts in the injectors, it corodes quickly leaving a whitish powder
which will clog the fuel injector ports.
 
Originally posted by: MS Dawn
Originally posted by: Eli
Fuel system not holding pressure.
Click to expand...

Doesn't an electric fuel pump build operating pressure on the rail within a second of the ignition switch being turned on?

(Sorry I'm not a car person)
Click to expand...
I'd imagine it's pretty quick, but I don't know exactly how quick.. and it probably depends on a few things, too.

People will tend to notice even a half a second longer in cranking time.... anything longer than that is definitely noticable.
 
if it is an FI car then your cold start injectors might be worn out...i've left my 99 FI sitting for weeks at a time and never had a problem starting it, even with over 240k miles...good maintenence FTW 🙂
 
If your battery goes dead in a week of no use, there's either some kind of serious draw on your electrical system, even when the car is shut off, or your battery is toast...Remove the negative terminal and measure the draw with a multimeter between the cable end, and the battery post. Start removing fuses to see where the draw is. You can troubleshoot from there, once you know which fuse has the most current across it.
 
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