What's up with my minivan?

an associate of mine and myself recently put a new fuel tank with a used fuel pump in my voyager. the problem is that now it starts weird. when i come out in the morning regardless of how cold it is it will start right up just like it always did. if i shut it down very briefly say to get gas or something again it seems to start right up. but if i let it sit for say ten or twenty minutes it will crank over for sometimes as long as ten or so seconds before it will start. i’ve tried a few different fuel additive products thinking that it might be being caused by some type of byproduct of the manufacturing process of the tank or something to no avail. what do you think it might be?

Next time this happens, go out and loosen the gas cap, then try again. If it starts right up, then your tank isn’t venting properly. It’s possible that your associate pinched a vent line when installing the new tank. It’s pretty easy to do.

Your post suggests to me like you have a faulty fuel pressure regulator.

Perhaps the used fuel pump is the problem. Not priming properly.

If that were the issue, it would take a long time to start the first time in the morning too.

There may be a leaky injector causing the fuel to be too rich. When the problem happens again try holding the accelerator pedal to the floor to see if that helps get the engine running.

That could also be caused by a faulty temperature sensor or MAF sensor which forces the computer to allow the wrong fuel to air ratio. Just a maybe.