The FSM has a drawing, below. 

It's not clear how you're using this vapor detector device.  I think that the most common source of gasoline smell, that's hidden, is the bottom of the charcoal canister.  The carbon/charcoal gets clogged over time and does not absorb all fo the vapor.  The bottom of the canister is open to the atmosphere.  That's where I'd be looking, after I tightened all fo the clamps.

 

21 minutes ago, Zed Head said:

The FSM has a drawing, below. 

It's not clear how you're using this vapor detector device.  I think that the most common source of gasoline smell, that's hidden, is the bottom of the charcoal canister.  The carbon/charcoal gets clogged over time and does not absorb all fo the vapor.  The bottom of the canister is open to the atmosphere.  That's where I'd be looking, after I tightened all fo the clamps.

 

Gotcha - thanks for the picture, I will keep the clamps at the top.  A friend is bringing over the socket I don't have to tighten these and then we should be good to go - I'll check the carbon canister after that for sure.

Regarding the sniffer, I pull the oil pressure switch plug and set the key to 'on' to pressurize the system.  I then turn on the sniffer and move its bendable head to each spot with a rubber hose and clamp.  It beeps and shows the concentration on the screen when it notices fuel vapors.  The device is pretty impressive.

Update: Cranking down the final injector clamp (ended up using a 1/4 inch socket with a u-joint, and an extension.  The car doesn't smell anymore and the sniffer isn't picking anything up.  I tested the device just to be sure by opening the fuel door and it smelled fumes by the gas cap (I didn't remove the locking gas cap). 

Looks like case closed 🙂 - thanks all!

On 2/11/2025 at 11:44 PM, cgsheen1 said:

To actually answer your original question: I've seen many technicians successfully use hydrocarbon sniffers to detect leaks on HVAC installs and on natural gas systems (even automotive A/C). (As a journeyman plumber, I just used "soap" type leak detector on pressurized piping)  Most don't use them for gasoline specifically but it should work just as well - a hydrocarbon is a hydrocarbon.

Let us know what you find - mine drove me crazy for months.

Using hydrocarbon sniffers can really improve leak detection and repair, and at Royal Vallejo Plumbers, we’ve found them reliable for spotting even small leaks efficiently.

Hydrocarbon sniffers can be surprisingly effective across different systems, and sometimes combining them with a simple soap test helps confirm the source faster. Hope you track it down soon.