[Gstoneburner]

99 7.3, cclb 6 speed. Truck is hissing from the area around the fuel bowl just after I turn the key to run before I crank the engine. Fuel bowl has no leaks. Any ideas? Air being purged through the fpr?

 

[79jasper]

I've heard this before too.
Can't remember what the answer was.
Maybe the vacuum pump?

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[klhansen]

99 7.3, cclb 6 speed. Truck is hissing from the area around the fuel bowl just after I turn the key to run before I crank the engine. Fuel bowl has no leaks. Any ideas? Air being purged through the fpr?

It's the excess fuel passing thru the fuel pressure regulator. If you've just changed out the filter and are refilling the bowl with fuel, you can really tell the difference as the air is purged thru the regulator, and then the sound changes as the bowl fills and fuel starts hissing thru the regulator.