Several weeks ago I posted a problem about my truck running poorly on start up.

I changed out the overflow valve upon suggestion of the list. To make it short, it did not work. It was a nice try and a good suggestion, but no cigar.

I couldn't figure it out, so I finally broke down and took it into the shop. It took several tries, but the shop found the problem. It was the fuel/water separator valve on the bottom of the filter. It had a small leak and was sucking air back into the fuel system while sitting.

So, for others that might have a problem, here is something I never considered.

HTH

 

Actually the valve leaking is quite common. Most times it just has some crud in it and a simple flush fixes it.

Fuel system leaks can be hard to find. Often they will suck air but not leak fuel. Easy way I've found to track the tricky ones down is to pressurize the fuel tank to no more than 10 psi with compressed air. You can either hear the leak or find the dip quite easily. I have a fuel cap that is drilled and tapped with tire chuck (schrader valve) in it just for this.
This is also a great way to fill and bleed a just changed fuel filter.