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I'm hoping someone has some insight to what I am experiencing right now. I have a '57 with a 223 6 cyl / 3 speed. Ive added Clifford Perf. intake and weber carb as well as their headers. Other than that it is stock. The tank looks to be a new tank (I dont know the trucks history) and is still behind the seat. The gas guage and sending unit seem to work too.
The issue: Once the guage gets to 3/4 full the truck acts like it runs out of gas. I fill it back up and it takes 3-4 gallons of gas. It starts up, runs a little rough for a bit but then smooths back out.
What I have done: I've pulled the sending unit and looked into the tank. The pickup tube looks perfect and runs to the bottom. The tank looks clean. See picture below.
What I plan to do: Today I am buying cork gasket material (1/8" thick) to make a new gasket for the sending unit. Currently there is a not so great looking rubber gasket there and I get gasoline on top of the tank when I fill it. I also plan to buy a new gas cap as the rubber gasket on the inside of mine is old and cracked. I also will replace the rubber line underneath the truck (about a 8" section right where it exits the cab) and the section from the hardline to the fuel pump in the engine bay. I also plan to install a fuel filter at that line, currently there is not one.
Anyone have any thoughts as to why it acts this way? Anything is appreciated.
gas cap has to be vented. Bad gasket won't cause a problem. See if vent hole is open. You can rig up a pressure gauge and see what pump is doing It siphons gas out of tank so I would replace any rubber hoses. There is only the short hose under cab and hose to fuel pump and pump to carburetor. One filter inline would be enough.
Did you run it before and after the modifications? I was curious if it made a noticeable difference in power. I ran mine so many years with a worn out engine when I overhauled it I thought I might need a headrest to prevent whiplash accelerating.
Did you run it before and after the modifications? I was curious if it made a noticeable difference in power. I ran mine so many years with a worn out engine when I overhauled it I thought I might need a headrest to prevent whiplash accelerating.
I did but only for a short time. I put about 200 miles on it before doing the mods. A noticeable difference with the mods but the Clifford Performance stuff is pretty expensive. Its 100% worth it if you plan to stick with the 223 but not if youre going to do a swap at some point.
If you do the above and come up short, you could have a blockage in the line or a weak pump. When I was working on my fuel lines, a bug had made a nest inside my hardline near the fuel pump end. I know because it was restricting my breath blowing on the tank end under the cab toward the open end at the fuel pump. I rodded the line with a welding rod and blew it out with shop air... presto it went “phoot” and I shot that nest across the shop! Let everyone know what fixes yours, it appears to be a semi-regular issue.
If you do the above and come up short, you could have a blockage in the line or a weak pump. When I was working on my fuel lines, a bug had made a nest inside my hardline near the fuel pump end. I know because it was restricting my breath blowing on the tank end under the cab toward the open end at the fuel pump. I rodded the line with a welding rod and blew it out with shop air... presto it went “phoot” and I shot that nest across the shop! Let everyone know what fixes yours, it appears to be a semi-regular issue.
Since most of these "project trucks" are found parked for many years, not surprising to have plugged fuel lines. I would bet his problem is fuel cap not venting.
Another possibility is a cracked suction line inside of the fuel tank. As long as the crack is submerged in fuel, no problems, but as soon as the fuel level is low enough for the crack to suck air, then you are no longer sucking fuel. Have had a couple trucks with this problem when I used to wrench on them for a living.
Since most of these "project trucks" are found parked for many years, not surprising to have plugged fuel lines. I would bet his problem is fuel cap not venting.
Originally Posted by wyomingford
Another possibility is a cracked suction line inside of the fuel tank. As long as the crack is submerged in fuel, no problems, but as soon as the fuel level is low enough for the crack to suck air, then you are no longer sucking fuel. Have had a couple trucks with this problem when I used to wrench on them for a living.
Easy to test cap issue, run it with a rag taped over the filler tube leaving the cap off.
Unfortunately there are lots of ways to have fuel issues! I have run engines from 5 gallon gas cans with fuel hose run out from under the car to verify if its the pump or lines. The pump should be able to pull it easily from an external can. Then you at least can start narrowing it down. (Assuming you already ruled out venting above)
I've put a new vented cap on and put a inline fuel filter between the hardline and the pump. I plan on driving it to work on Friday (35 miles each way) and will see how it does. I will be carrying a 5 gal jerry can just in case!! Wish me luck!
I'm not one to say I told you so, but someone should direct you to the part where I said I bet it is the cap. How much did we gave bet?
Actually it was your post that got me heading in that direction! How much do I owe you?
Another update - I let the truck run down to just below a 1/4 of a tank ON THE GAS GUAGE before filling. You folks that are smarter than me probably see where this is going! It took 8 gallons to fill it up. Any thoughts on this one??
I don't know the tank capacity. On mine I add gas with five gallon can. Nearly empty and add five gauge reads about half a tank. There were several posts not too long ago about calibrating floats to gauges and resistors and connections. Don't remember who but maybe red60.
