quirky fuel issue for opinions

[SteveO_71]

On my 71 mach 1 351c, I recently had an oil filled fuel pressure gauge go from reading normal (5-6lbs) to reading zero even though engine ran fine. This was installed into an NPT T fitting that is between the pump steel line to carb. Thinking it was the gauge, I ordered another oil filled one and installed it.

Started the car and the needle in the gauge was jumping and engine was surging, barely running, to the point where it wouldnt idle. The only thing that was changed at this point was the new gauge in the NPT fitting.
I didnt determine if the engine was flooding or not getting fuel.

Thought it could be some fuel pump issue. but started with the simplest fix. Removed the gauge rubber line and installed a piece of 5/16 line where the gauge was, between the steel line to carb.

Engine starts and run fine!

BUT I was wondering how that could be the reason or what am I overlooking??? Checked the gauge rubber line and T fitting and didnt see any blockage, I dont believe there is a fuel pump issue. Maybe a stuck needle valve or float that was making the engine run flooded?? Could the gauge have been over tightened in the T fitting and somehow restricting fuel?

I dunno..any other opinions?

 

[Sheriff41]

Could there be air getting sucked in at the gauge fitting?

 

[SteveO_71]

Sheriff, Thanks for your thoughts on this issue. I checked the gauge NPT threads that were screwed into the NPT T fitting and there is a section that was not covered by the Permatex paste. That most likely has to be the issue since the 'problem' went away once I removed the gauge.

Although I've used the PTFE paste for connections in the past, I'm wondering if I should have used the teflon tape for this or used the PTFE paste correctly.

thanks!

 

[Hemikiller]

See my answer in your previous post

gauge dies after working initially

On my 71 mach 1, 351c 4v engine, I have a fuel pressure gauge between the mechanical fuel pump and the carb. Initially when new, it reads in the 6 - 8 psi range or thereabouts. BUT, at some later time it stops working for whatever reason. I have fuel flowing, car runs fine but gauge reads 0...

7173mustangs.com

 

[SteveO_71]

See my answer in your previous post

gauge dies after working initially

On my 71 mach 1, 351c 4v engine, I have a fuel pressure gauge between the mechanical fuel pump and the carb. Initially when new, it reads in the 6 - 8 psi range or thereabouts. BUT, at some later time it stops working for whatever reason. I have fuel flowing, car runs fine but gauge reads 0...

7173mustangs.com

Yes, I saw your post and plan on trying the aeromotive gauge, with proper thread sealant. Thanks!!