Fuel cap pressure 300 tdi

[John Z]

I'm trying to figure out if it's. Normal to have pressure (not sure if it's positive or negative) when I remove the cap.

I recently swapped the cap(new land Rover tdi cap) my old one had been leaking fuel out of the lock cylinder for some time and it didn't do well when we had the extreme cold around Christmas.

I had been doing Google searches, and I'm getting mixed results some say normal some say it's a possible tear in the fuel pump diaphragm. I know I need to get a definite answer in positive/negative pressure. Just not sure how to really check without having a smoker or something to make it visible

 

[expanse]

is the truck running or stalling out? are the only symptoms you have is hissing when cracking the fuel cap and the leakage around the fuel lock on the cap?

 

[John Z]

Truck runs fine.

Only symptom was leaking from the old cap, and now hissing when removing the new cap. Other than that everything is normal. Just trying to keep it that way.

 

[jymmiejamz]

What fuel tank and filler neck setup do you have

 

[John Z]

Side tank, stock filler neck located between rear wheel and passenger door
This was the post I saw https://forums.lr4x4.com/topic/82540-1995-110-defender-vented-filler-cap/

 

[Mirrajumper]

Do you have a sedimenter installed and what does the fuel filter look like? Are you still using factory plastic lines? Check the return line to the tank or replace with rubber line.

 

[John Z]

Factory everything, changed the fuel filter maybe 15k km ago. Have another one on hand so just gotta get it done.

 

[erover82]

Caps have pressure relief valves, so up to that preset point you'll still have a pressure differential in the tank. I bet your cap is just not sealing properly - same with OP of linked post.

https://www.defendersource.com/threads/fuel-leak-92-110.167949/