Can a fuel system de-pressurize?

Heres the scenario. Miyuki was relieved of her gas cap by a thoughtless ex-wife some time ago, pre-move. Fast-forward several months, and I've not been driving her daily, as I've not been working. Makes no sense to drive, you know? In any event, go to start her, and she refuses to idle. Runs fine under throttle. Once running for a minute or two, will idle fine. Will start, idle, and run once its been brought out of slumber, as it were. But if i leave her sitting for a few days, we're right back where we started. Battery is strong. I suspect fuel because it smells pig rich when first starting. Am i off base?

What is this car?

If it's been sitting that long with the cap off and a tank full of ethanol gas, I'd be worried about the tank having picked up enough water to cause the fuel to start separating, especially if the tank wasn't full. Try to burn off as much of that gas as you can and get some fresh stuff in the tank, see if it gets better.

Yeah, having the cap off won't cause a fuel pressure problem, but it can cause other problems - fuel separation as rslifkin pointed out, accelerated "varnishing," and emissions error codes.

gearheadmb wrote: What is this car?

Derp, sorry. 1993 corolla wagon.

+1 for fresh gas. Burn off what's left, fill it with fresh gas, then change the fuel filter.

While I agree with the above, yes some can lose pressure. Usually due to a damaged/dirty check valve or pressure regulator.

Since many of the fuel pumps are triggered by the ignition circuit while cranking, it can take a while to build up pressure and get to running well.

Toyota trucks were/are somewhat notorious for this. I still have one that does this. Really old ones had a switch you could push to force the fuel pump on. I think about wiring a normally open pushbutton switch on my truck whenever it does this.

Removing gas cap is how you depressurize an e36 and will idle like crap and eventually start throwing codes.

mndsm wrote:

gearheadmb wrote: What is this car?

Derp, sorry. 1993 corolla wagon.

Leaky injectors can cause long crank times and loss of prime.

I'd start with a cap and a fuel filter. I suppose you could also be losing a temperature sensor or something that is over enriching things on start up.

Kenny_McCormic wrote: I'd start with a cap and a fuel filter. I suppose you could also be losing a temperature sensor or something that is over enriching things on start up.

Caps been replaced. Will look into fuel filter. Has florida gas in it now, fresh tank...2 weeks ago? Idk. Ill burn what's it and replace the filter.

Also, renting a fuel pressure test gauge will tell you a lot regarding the fuel pump, leaky injectors, etc.