Fuel Cap and Return line

[sk8rdi16]

Ok, quick question. Will not having a vented fuel cap cause diesel to be shoved out of the return line near the IP?

Thanks

[MTTwister]

Well - since no one else has jumped in - I believe the bigger problem is a vacuum build up in the tank - causing the Lift pump and IP to work harder. Down south you could be building up pressure from expansion - don't know, tho'.