I have been having an issue that started about 6 months ago, where over time moisture I assume is building up in either my fuel directly or in the in line fuel filter.

At first I thought it was bad gas, but it doesn't seem to matter where I get gas from. Over time my afr gets leaner and leaner in general.

But the odd thing is, as soon as I change out the in line fuel filter on the frame rail all afr go back to normal and all is fine again. But it steadily comes back again, and after about a month it's difficult to drive again.

Any ideas on some things to look into that could be allowing moisture into the fuel that has never been there before about 6 months ago?

Truck is 6.0 swapped regular cab 1999 gmc sierra

 

What's your fuel pressure when you have high AFR? Arbitrarily calling it water in the fuel is misdiagnosing the problem.

FYI, in BR, fuel filters do not block water since the ethanol content in the fuel is at least 10% already. The "water block" filters can ONLY work when ethanol is not present.

 

I'll have to get a fuel pressure gauge and check on that.

Any recommendations on electric vs mechanical gauge?

And best brand?

 

Most basic Autozone gauges are good for getting a read. I'd only invest in an expensive/electronic one if I was doing spot checks on the go or in a professional environment.