Gas tank vent issue?

[64 Plan B]

Hey
I’ve developed an issue on my 67 Belvedere…
For years I ran a stock mechanical fuel pump , original 5/16” hard line and thermoquad
I decided to upgrade to an Eddie torquer
Demon 750 and quick fuel hi volume mechanical pump. While I was at it I put in 3/8” fuel line and tank pick up assembly
It works well enough , however-
Occasionally the carb seems to run dry….
I have an in line fuel pressure gauge that is reading 5 1/2 psi at idle
I’ve thoroughly checked the fuel line to the tank and it seems fine…
Any thoughts?
Thanks!

 

[Durandal25]

Hey
I’ve developed an issue on my 67 Belvedere…
For years I ran a stock mechanical fuel pump , original 5/16” hard line and thermoquad
I decided to upgrade to an Eddie torquer
Demon 750 and quick fuel hi volume mechanical pump. While I was at it I put in 3/8” fuel line and tank pick up assembly
It works well enough , however-
Occasionally the carb seems to run dry….
I have an in line fuel pressure gauge that is reading 5 1/2 psi at idle
I’ve thoroughly checked the fuel line to the tank and it seems fine…
Any thoughts?
Thanks!

Gas cap! Make sure its the vented kind......and if it is, make sure its venting. Easy to test.

 

[Durandal25]

Hey
I’ve developed an issue on my 67 Belvedere…
For years I ran a stock mechanical fuel pump , original 5/16” hard line and thermoquad
I decided to upgrade to an Eddie torquer
Demon 750 and quick fuel hi volume mechanical pump. While I was at it I put in 3/8” fuel line and tank pick up assembly
It works well enough , however-
Occasionally the carb seems to run dry….
I have an in line fuel pressure gauge that is reading 5 1/2 psi at idle
I’ve thoroughly checked the fuel line to the tank and it seems fine…
Any thoughts?
Thanks!

....just a thought also.....5 1/5 psi seems a bit light. What kind of gauge you using? Is it oil filled? Check the reading cold.....then hot. If its oil filled, make sure the rubber nipple is cut and facing up.

 

[64 Plan B]

Gas cap! Make sure its the vented kind......and if it is, make sure its venting. Easy to test.

 

[64 Plan B]

Thanks for that….
I don’t have the original cap
Would you recommend a source for a repop?

 

[Durandal25]

Thanks for that….
I don’t have the original cap
Would you recommend a source for a repop?

There are a few out there......but make darn sure they have a "S" stamped on them. Plenty of pics on line.....re-pops are pure crap. Not just saying that.....they are plastic vented and will fail quickly. Most old school ones can be cleaned and put back into service.

 

[R/T Boy 67]

67 Plymouth B bodies do not use a vented gas cap. They have a small vent line at the top of the filler neck inside the trunk. They also have a large vent line, but it is just for filling the tank. Dodge B bodies use a vented cap.

 

[64 Plan B]

So , is there an easy way to check the vent tube ?
I’m guessing it must partially function or I would have a constant problem…
Also - I suppose a vented cap would solve it as well?
Thanks , again!

 

[R/T Boy 67]

You could hook a small hose to it from the underside and blow through it. I'm guessing here, but a vented cap might stain the paint as the cap is on the outside of the body. Dodges have the caps behind a door.

 

[diesel_lv]

67 Plymouth B bodies do not use a vented gas cap. They have a small vent line at the top of the filler neck inside the trunk. They also have a large vent line, but it is just for filling the tank. Dodge B bodies use a vented cap.

Maybe Plymouth. My '67 "Dodge" Coronet, which I inherited from my Great Grandmother completely original unmolested, has no tank vent other than the gas cap. The smaller of the 2 lines from the gas tank to the filler neck is to equalize so as fuel is added, the air in the tank can escape. But it is not a "tank vent" for purposes of reducing a vacuum from fuel pump once cap is on.

 

[snakeoil24]

Check filter sock and pump push rod also 5.5 psi is fine

 

[diesel_lv]

My '67 did the same thing initially when I went to FI w electric fuel pump. You psi is just fine as your pump pumps volume and the regulator bypass psi n excess fuel. It is the volume that is causing it to create a vacuum. I drilled a hole in an old cap until I ordered a repop. No issues since.