Rubber fuel line.

[blue69runner]

I got 3/8 rubber line to tie my 5/16 steel line together at fuel tank and fuel pump. When driving the car, I notice that small air bubbles are coming into my clear fuel filter at the fuel pump. This don't seem right to me. Makes me think I have an air leak somewhere. I know ethanol fuel boils at a much lower temp than regular fuel. Is this what is going on. Car ran fine for a 60-mile trip to a car show. Stopped at a 7 Eleven and topped off the tank. With 93 octanes. Which the car has been running fine on from other filling stations. Started the ride home and car would stall like it ran out of fuel. Put fuel in the carb. and car would fire up and run a little longer down the road and do the same thing. It seems like vapor lock like we had back in the day. But these air bubbles is what has me concerned that I might have an air leak somewhere. Any thoughts would be appreciated.

 

[oldbee]

Your fillup might have had water in it? Small bubbles shouldn’t be a problem.

 

[Fran Blacker]

Sucking air at 3/8/ 5/16 connection? Can you get a 5/16 line on 3/8 line?

 

[69Bee]

Yep, your first sentence explains your problem...

 

[SlinktRR]

The 3/8 lines hose clamp needs to be tight, could draw air. However it is more likely that your fuel filter or fuel tank sock is plugged by a rusty tank, causing the pump to cavitate with air bubbles on the discharge. This happens when you put fresh fuel in because it stirs up the crap on the bottom of the tank. If it starts and idles fine, the rust has settled but will plug again. I would take the sending unit float assembly out and check.

 

[blue69runner]

New tank and sending unit. Thanks for all the comment's this is food for thought. I know I won't be buying any more fuel from the 7 eleven stores. Had been buying my fuel from Racetrack and no prob's. Now have 7/16 rubber fuel line coming from Summit. Going to change all the 3/8 lines out. Wish me luck.

 

[69a100]

I got 3/8 rubber line to tie my 5/16 steel line together at fuel tank and fuel pump.

Why are you using 2 different size lines? Sounds like your creating a problem when there doesn't need to be one!!! Good Luck

 

[69Bee]

New tank and sending unit. Thanks for all the comment's this is food for thought. I know I won't be buying any more fuel from the 7 eleven stores. Had been buying my fuel from Racetrack and no prob's. Now have 7/16 rubber fuel line coming from Summit. Going to change all the 3/8 lines out. Wish me luck.

Now I am really confused. So, you started out with 3/8" rubber hose to connect to 5/16" steel line which was causing air leaks due to the size difference, but now you want to replace the 5/16" steel line with 3/8" line, but also INCREASE the hose to 7/16"??? You do understand that 5/16" steel line is used with 5/16" hose, 3/8" steel line uses 3/8" hose, 7/16" steel line would use 7/16" hose, and so on...

 

[SlinktRR]

I hope you're right. New doesn't mean good though, especially these days with reproduction parts. could be shiny on the outside and full of free floating metal (not necessarily rust but grit from poor manufacturing) on the inside. Don't take anything for granted.

 

[blue69runner]

Now I am really confused. So, you started out with 3/8" rubber hose to connect to 5/16" steel line which was causing air leaks due to the size difference, but now you want to replace the 5/16" steel line with 3/8" line, but also INCREASE the hose to 7/16"??? You do understand that 5/16" steel line is used with 5/16" hose, 3/8" steel line uses 3/8" hose, 7/16" steel line would use 7/16" hose, and so on...

Sorry no I have 5/16 fuel line's and now going to use 7/16 rubber line to connect the two lines together 5/16 to 5/16. Hope I cleared that up for you. Blue.

 

[69Bee]

Sorry no I have 5/16 fuel line's and now going to use 7/16 rubber line to connect the two lines together 5/16 to 5/16. Hope I cleared that up for you. Blue.

5/16" OD steel line will measure around 0.3125" and 7/16" ID fuel line will measure 0.4375". That is a difference of 0.125", or 1/8" which is a GAP and a hose clamp is NOT going to seal it. That means that there is a continuous 0.0325" (or 1/16") gap between the tube and rubber hose. I could put it another way; imagine a 16yo kid trying to have sex with an 85yo prostitute, nuff said...

 

[1STMP]

I got 3/8 rubber line to tie my 5/16 steel line together at fuel tank and fuel pump. When driving the car, I notice that small air bubbles are coming into my clear fuel filter at the fuel pump. This don't seem right to me. Makes me think I have an air leak somewhere. I know ethanol fuel boils at a much lower temp than regular fuel. Is this what is going on. Car ran fine for a 60-mile trip to a car show. Stopped at a 7 Eleven and topped off the tank. With 93 octanes. Which the car has been running fine on from other filling stations. Started the ride home and car would stall like it ran out of fuel. Put fuel in the carb. and car would fire up and run a little longer down the road and do the same thing. It seems like vapor lock like we had back in the day. But these air bubbles is what has me concerned that I might have an air leak somewhere. Any thoughts would be appreciated.

 

[1STMP]

I'm running 5/16 steel to 3/8 rubber and not
a single problem. I would check all clamping
connections, tank vent, and pick-up screen
in the tank, or your gas cap. Your system is
creating a vacuum somewhere and is sucking
in air. The size of the lines has little effect
on fuel delivery at most fuel pumps delivery
pressures. 7 psi is 7 psi regardless of inside
hose diameter. Volume is the deciding factor
for inside hose diameter and I doubt you
need any more than most.