I'll touch on this exact subject today as yesterday I had a very successful use of Sniff/Crack in a Can...Either...yer name I don't care it was very successful.
As the vehicle was plugged in and the folks could not get it to go...93 E350 they came to me and asked if I could help.
OK..
I looked over the truck, clicked fuel shutoff with jumper..OK
Now they've tried for a few days to get it to go fully charged battery, my Red top
plugged in..no go.
The intake has a air shutoff that is utilized in oilpatch for safety. it checked out as passing air not closed off.
So I said start cranking it...I sprayed about 1/3 second puff (about a parrot farts worth) on air filter while cranking...wait two seconds of cranking...2nd puff same....wait two seconds of cranking 3rd puff ***** she lights off and runs like a hot damn...I spray ONLY onto the air filter NOT DOWN INTO the intake..I did not dissable GP (THIS TIME) no explosion no nothing...just fired and ran fine.
After a few minutes of running. Turned off truck, restarted instantly...thus GP's are the issue.
These two spent days working on this with gelled fuel and so forth....
Done right...sniff is safe...