check valve fitting for fuel inlet on cylinder head

[06cumminspower]

ok, so I have been trying to get this 01 back together and got it cranked but only running on passenger side so I unplug oil rail and is shooting out and then crack fuel line running from filter into driverside head and is getting plenty of fuel. however I was curious about the fitting inbetween line and head and removed it and I can not blow through it nor does it look wet underneath it. so should I be able to blow through it with ease with my mouth? ford wants nearly 80 bucks for this and looked at the obs heads I had lying around and they seem to be a straight through fitting with out a check valve so my next question is; is it even neccesarry for this check valve or can I just use a regular fitting? I have took the tiny snap ring out and tried cleaning it up but still near impossible to blow through ( I did get shop air to go through it and then could blow with ease in either direction but now its hard again?)

 

[79jasper]

I've heard differing opinions.
You can get the set of two high flow ones from riffraff for like $40.
Also make sure the UVCH is good on the driver side. It can shut one side down if there's a short.

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[Double-S-Diesel]

it is a check valve
was told it is needed on the superdutys due to the dead head fuel system.
OBSs do not have them.