I think I know the answer to my question but I’d like to have A second opinion. I have a 71 442 stock with big block, On hard acceleration it seems to run out of gas, it bogs down, I have rebuilt the carburetor and replaced all gas lines that are rubber, I drop the gas tank to clean it and Replace the nylon sock on the pickup tube. Today I jerryrigged a gas tank inside the engine compartment, bypassing the fuel lines and gas tank and plumbing in a temporary gas line directly to the fuel pump. I went out and flogged it and made several passes without any problems at all. I’m wondering if on hard acceleration the fuel pump is collapsing that nylon sock on the pick up tube restricting fuel flow? I would appreciate any insight others may have or opinions.

 

Maybe the fuel pump can’t overcome the 12 feet of fuel line but has no problem with 2 feet?
Just guessing.
-peter

 

Or it has a leak in the hard line from the tank.

 

If it had a hole in the metal line wouldn’t you see a puddle or something after it sat ?

 

Fuel pump giving up.

 

^^^ If this symptom is new. Fuel filter restricted? Smell the oil dipstick for gasoline, if present fuel pump is failing.

 

OK, so today I installed a new fuel pump and double checked all the rubber lines in the fuel system, no improvement. As long as I run it on the Jerry gas tank that I installed next to the wheel well it runs just fine no problem. But anytime I attempt to hook it up to the main fuel tank and use the metal lines on the frame it falls on it’s face on acceleration. Does anyone have any ideas? I’m thinking of trying to bypass the metal lines with the temporary fuel line to the gas tank and see if that solves the problem, if so then perhaps there’s a pinhole in the metal line somewhere where I can’t see it and sucking air? Other than that all I can think of is possibly the nylon sock around the pick up tube in the gas tank is been collapsed by the fuel pressure from the pump ?

 

Try it with the gas cap loose in case of a vent blockage.

 

Have you replaced the accelerator fuel pump in your carb? I used to be at a stop and when I would accelerate it would stumble and almost die. Replaced accelerator fuel pump and all good.

 

Yes, I rebuilt the carburetor. And as long as I run the makeshift gas tank under the hood it will run just fine it’s only when I hook it up to the main gas tank that has this problem.

 

You can hook up one of those low pressure click click pumps to the rear hard line if it leaks you will see it.

 

Did you replace the fuel filter with they style that has the check valve? Those are pretty restrictive.

Either the pump isn’t capable of pulling the fuel, or the line isn’t capable of supplying the fuel.

I assume you have check the line for kinks or any other damage?

Cap off the line at the tank, put a vacuum pump on the fuel pump end of the line. It will take a while, but you should be able to put the entire line in a vacuum and have it hold vacuum. If not, there is a pinhole. Check the line under the clamps, the rubber hose behind the pass wheel, the clamps, etc.

I have had good luck with the Airtex 40736 pump. There was a thread on here awhile back discussing the differences. I don’t recall if it was ever verified as a higher volume than others, but there is no denying it has more “storage” capacity with the much larger canister.

There are a few different size needle/seats for the carb. Most rebuild kits include the small size. That’s something else to look into. Even though the car performs well with s fuel can under the hood, maybe you have a few less than ideal symptoms that all add up to s big problem. It’s pretty easy to modify the existing needle/seat for a larger size.

 

Have something like this issue with my 98 , last i started the engine it dies when i should
rew it up fast but runs when i increasing the rpm slowly. Waiting for a new fuelpump and should
try again. Turned the throttle lever and could see 2 thin gas streams but not from the
"bottom range". So maybe check the accelator pump if it not works , but the carb is rebuild
carb from Autoline ( Rockauto) so hope this is ok ( almost new )
Edit , also new fuelfilter Wix metal filter between pump and carb.

 

OK so here’s an update, today I bought approximately 15 feet of three eights rubber fuel line and ran it all the way from the fuel pump to the tank along the same route as the metal line , zip tying it to it and keeping it out-of-the-way Of any pinch points or heat. Took the car for a test drive and problem was solved, so evidently it has something to do with the metal fuel line itself. I’ve taken the line loose and checked it , I can’t find any rust on it, unless it’s on the inside creating blockage. So the next question is how do you change the metal fuel line without taking the body off the frame?

 

What are the chances it's only a varnish turd in the fuel line? You dropped the tank, changed rubber fuel lines, etc. - perhaps a varnish turd made its way into the fuel line and it's clogging up the line, as opposed to rust inside the line. At any rate, you might consider disconnecting the rubber fuel lines you replaced (from the fuel pump back backwards) then using compressed air blow the smithereens out of the metal fuel lines from the front towards the back (obviously disconnect the fuel line from the fuel tank). Put a sock or nylon (sheer pantyhose works great) at the end of the line and see if you catch a turd.

I've heard of people fashioning new fuel line on the outside of the frame rather than tackling the interior frame route. Good Luck.

 

Well you never know, it only takes a minute to blow air through the line and see what comes out

 

On my 88 the filter on the 3/8 pipe inlet in the tank don´t look nice when
i removed the gastank and cleaned it.

 

Yeah, I’ looked into that it’s the first thing I changed out a couple weeks ago before I did anything else, I also cleaned out the tank on the inside while I was at it and the tank looked pristine.

 

Ok think i should check this in my 98 also but the gastank is full at the moment . If nothing gets
better with a new fuelpump i should try a can with gas in the engine compartment like you did.

 

If you don't intend to show the car with mirrors underneath why don't you just keep the rubber line. Or go with nylon braided line.
It's not fun getting a metal line back in while keeping the body on from what I hear.

Glad you solved it at least.
​​​​​​​-peter

 

I installed a new hard line by cutting it where it goes over the frame near the rear axle hump. I removed a section of hardline, and connected a rubber line over the hump to the rear section of hard line that was cut from the main piece. Not factory pretty, but works well.

 

It's possible to replace the hard line (and return) in one piece with the body on the frame. I've done it. With stainless. It requires patience, jacking the car up, removing the passenger side rear wheel and sitting the frame on jack-stands so the rear axle is hanging. Gives just enough room to fish the lines where they need to be. It is not fun and you will contort yourself getting everything in and tight - kind of like getting a dash pad out on your back.
I guess it's an option to Roadkill it with hose and zip ties but that wasn't my thing so I took the hard road. Worth it in the end.

 

If the existing steel line looks excellent, what about filling it with a solvent, letting it sit and they blow it clear with compressed air?

 

My dads 85 El Camino had the rubber fuel line on top of tank collapsing when pump was sucking fuel to the front. It took a day to find the problem. We bypassed tank like you and rev engine and it run fine. Plug tank back in same problem. Replaced fuel, drained tank and cleaned then touched the hose on top of tank and it was mush.