Fuel System Question??? Thought I was out of gas

[84convertablegt]

This ones kinda dumb, but maybe u guys have had similar experiences.. i am in the process of replacing my gas tank... i thought it was empty, the car kept stumbling and would stall out under a part to full throttle, so i figured, its finally out of gas (good time to replace fuel tank right).. ok, and by the way the fuel sendor is bad, new one with new tank, etc. anyway, i unscrew the drain plug and whoosh, instantly fill up a 5 gallon container, and i believe theres at least another 5 to6 gallons in the tank. why would my car run like its out of gas. it will idle all day long, just when on the road and you get on it, it stumbles out like it ran out of gas, and then you have to pump the pedal a bunch to get it to restart. the fuel pump is newer, i cant imagine it would be the problem, then old tank has a lot of crud in it, could the fuel filter be clogged or something. i have one of the old school 65 canister filters and a inline unit near the carb, u think replacing them will fix it? what else should i look for? i just dont want another problem right now, ive been working hard to get this new motor and tranny just right!

 

[LMan]

carb accelerator pump, or fuel bowl issues.

 

[84convertablegt]

do you think i should check the level in the fuel bowel through the site plugs, could this cause my problem. the carb is a holley 4160 4bbl, brand new. it is suposedly calibrated from the factory, but im sure it wouldnt hurt to check, especially since its a universal ford carb. anything else guys?

 

[Edbert]

Could easily be clogging in the lines. Not necessarily a particle in the fuel filter either, but a general buildup in the hard lines like heart disease. When I changed out my fuel tank I cut it open out of curiosity and there was an inch of sludge/gum/gunk in there. I was suprised the thing even ran! I replaced all the lines while I was at it.

 

[390Fe]

One more culprit could be the fuel pump. My car would idle - run around town ok, but when I was on it at an 'exuberant' speed or under hard accelleration it would just die. It would restart and drive fine. I replaced the pump and the symptoms went away. I know you said it is of newer vintage, but I've put on "new" distributor caps that had cracks in them.

 

[84convertablegt]

One more culprit could be the fuel pump. My car would idle - run around town ok, but when I was on it at an 'exuberant' speed or under hard accelleration it would just die. It would restart and drive fine. I replaced the pump and the symptoms went away. I know you said it is of newer vintage, but I've put on "new" distributor caps that had cracks in them.

Im gonna try blowing out the lines first and all, but the fuel pump is my number one sneaking suspicion. I suppose i could hook up a pressure gauge but that wont really tell me how much im flowing. maybe a holley mechanical pump would be a better choice than the crappy stocker, especially since im running a bigger carb and more powerful combo than stock.

 

[steel1212]

I swithced from a stock type to a holley mechanical and it fixed my problem.

 

[red65]

Used to have the same problem in my '65, which had sat for years without running at some point in its history. It'd run fine until the gauge dropped below about 1/3 tank, after which it would stumble, misfire and carry on. When I replaced the fuel tank some time later, the 3" or so of brown sludge in the bottom of the tank explained the problem. New tank solved the problem completely. Blowing out your fuel lines (or replacing them) is also an excellent suggestion, as that accumulation of sludge gets pulled up into the fuel lines and can cause many of the same symptoms.

- Hope that helps

 

[Edbert]

I think the original subject has been resolved so it is okay to hijack slightly

I have heard that the stock hard-lines are not up to the tasksof 400 or more fwhp, and that I should upgrade to a 7/16 or 1/2 inch fuel line throughout. I already have the high capacity mechanical fuel pump (mine is a Holley, probably the same one you bought), but some are of the opinion that my fuel lines will hold me back. Anyone else share this viewpoint? If so I have a stock hard line that has never seen fuel and still has the palstic caps on both ends that I wont need. I priced a 20 foot lenght of 1/2" braided fuel line....YIKES!

 

[84convertablegt]

I think the original subject has been resolved so it is okay to hijack slightly

Yes, feel free to hijack, this was only a semi informative request anyway, i have a good basis that it could be many things. I was told by previous owner that the fuel pump was newer, but who knows. and about the fuel tank, i was carrying my old one over to the hose to flush it out and i noticed alot of gunk sloshing around in there. i can only imagine that the pickup must have been clogged some, it is made out of a fiberous material. i think im gonna replace my canister type filter fuel pump with a 66 v8 kind, a carter model. its cheap and says its rated higher for 4bbl applications and accepts all the stock lines without any modifications. also, i have an inline filter that i will replace as well. hopefully this solves the problem. i think a stock type pump should give me enough fuel, im nowhere near that above mentioned 400 hp mark. id say im somewhere around 270 fwhp if im lucky, so yeah. anyway, about the size of fuel lines. they can limit the hp. thats a big problem with people who convert from I6 to V8 motors, you almost have to replace the smaller fuel line. as far as a v8 fuel line goes, its not too large either. anyone running a supercharger or producing a need for much more fuel will probably need to replace the stock fuel line. that goes for all cars. a newer fox body car can only handle about 4 to 500 hp on the stock fuel rails well, its the same principal. hopefully replacing the pump and filter will solve my problems, along with the new pickup and tank.thanks again folks for the replies!