Original owner of well maintained '99 Suburban K1500 5.7L. 140K mi now. It's developed a very strong fuel smell odor from the engine bay and into the cabin. After shutoff, odor builds up in cabin so badly its probably flammable. No CEL's. I'm a 30 yr shade tree mechanic. Truck runs perfect. Good idle, great power, no smoke. Whole tuneup only 1 yr ago. Passed smog 4 mos ago.

EVAP system seems sound. No leaks in hoses or lines. No smell at rear near tank. EVAP relief valve is functional and not leaking. With engine running, fuel vapor makes eyes water and appears strongest at rear of intake. EVAP purge valve on intake is a point of contention. Power to both EVAP valves is good. Replaced purge valve. No change. EVAP canister seems sound; it holds vacuum.

AIR pump functional and not leaking.

Ran dye in the fuel tank and checked for leak at intake manifold or hard lines on EVAP with black light. Nothing. You'd think the motor is dumping fuel all over the bellhousing and its getting sucked into cabin. But no liquid leaks.

 

You might not able to see leak/s but surely there is. Hose and pumps should be checked.