Henrietta the '38 Ford pickup has been making a fool out of me with a fuel system issue, but I think I'm on the track of solving it--tell me if my theory makes sense. Henrietta has been running well until recently with 307 Chevy, Edelbrock manifold, and 600 Holley with electric choke. Was running stock mechanical fuel pump, gas tank is an apparently very solid original tank sealed with POR 15, no leaks, tank has been on the truck +/- 7 years with no issues. Started having problems with the truck acting like it was running out of gas (I never let it get below 1/4 tank) when I tried to go up a hill or accelerate. I figured out that it wasn't getting adequate fuel volume and pressure going into the carb. Thinking it was a fuel pump issue (and wanting to change to an electric pump anyway due to the very tight clearance between the mechanical pump and the Ford crossmember), I got an Airtex brand (model E8016S) electric pump, mounted it on the rear crossmember directly in front of the tank, blew out all the lines with compressed air before I hooked up the lines. I also took some stiff wire and rodded out the pickup tube going into the tank in case some trash in the tank had gotten into it and obstructed it. When I hooked everything up, it idled fine, but I made it maybe 5-6 miles down the road before it started the same thing, bogging down when I tried to accelerate and acting like it was running out of gas if I tried to give it enough gas to get up a hill. It would bog down if I tried to race the engine just idling in the garage. I have a transparent gl*** fuel filter between the tank and the pump. With the engine idling in the garage, I can see what should be an adequate volume of gas going through the filter--BUT--and here comes my theory--I notice that there are lots of bubbles in the gas. Bubbles tell me that air is getting ****ed into the line between the bottom end of the pickup tube inside the tank and the filter. All connections are tight with no sign of leakage. Plenty of gas in it, end of the pickup tube is completely submerged in the gas, so the only way I can see for it to be ****ing in air is if there is a hole that has rusted in the pickup tube above the level of gas in the tank. It's got roughly 1/2 tank in it right now. I know gas is a lot heavier than air, so my theory is that when I try to give it more gas, this theoretical hole in the pickup tube inside the tank would cause it to **** more air and less gas when the carb is crying "give me more gas!" To test my theory, I disconnected the line from the tank to the fuel filter and ran a length of 5/16 rubber fuel line from the filter into a can of gas, making sure the line was fully submerged in the gas so no air could get in. Of course I couldn't take it down the road like that, but the truck started easily, no air bubbles visible in the filter, and I was able to race the engine up to 4000-4500 RPM without it bogging down or acting like it was starving for gas. Does my theory--a hole rusted in the pickup tube inside the tank that is causing it to **** air instead of gas--make sense? Anybody else run into the same symptoms and discover this to be the problem? Sorry for such a long post, but I wanted to lay out all the facts in case I'm missing something.
Like I said, Henrietta and I apologize for the lengthy post, but I wanted to lay out all the known facts and not leave out any clues that might point to the solution. This thing has had me stumped, and I am usually pretty good at troubleshooting the old stuff.
Makes sense to me. If you eliminated that section of line and the problem stopped that is where I would be looking too.
95% of fixing is figuring out what the problem is. I think you got this one about licked. Does the pick up tube attach to the fuel gauge sending unit/access plate at the top of the tank? If so pull it out and take a look, you may be able to fix or replace what you have. Or go shopping for a new tank.
Sounds good to me. My '78 F150 did the same thing a long time ago, ended up there were rusted pinholes in the top portion of the sending unit.
It would be an easy fix if the pickup tube was all one piece with the sending unit like it is on newer cars, but unfortunately it's not. The line attaches to the pickup tube on the front side of the tank, while the sending unit is of course up on top. To avoid the expense and work of replacing the tank, I'm thinking about closing off the old pickup tube on the front of the tank with a pipe plug, then drill a hole in the sending unit cover plate and (with the sending unit cover plate removed from the tank, of course) brazing in a new pickup tube that comes off the top of the tank.
Had this same thing happen with a customers' caddy. Not a hard problem to understand, or hell to even fix. The hardest part is getting your mindset right so you don't feel like your a fool, when you finally realize you just had to pull the sending unit.
Thanks, everybody who responded! You've confirmed my theory, arrived at by eliminating just about everything else it could be. I'm going to try my idea of drilling through the sending unit cover plate, running a new pickup tube from there, and closing off the original Ford pickup tube.
You should inspect the whole length from tank to pump-there could be a hairline crack in the steel line, or pinhole. Might save you the effort of digging into the tank. rick
Rick, the pump is only a few inches from the tank, mounted on the crossmember, so there is only a short section of new 5/16" rubber fuel line with good clamps between the pump and where the line attaches to the pickup tube in the tank. So, I'm pretty sure we have in narrowed down to the metal pickup tube inside the tank. Thanks!
Pin holes in line theory could be correct. Have also seen line cracked and also broken clean off just inside the tank. (many years of sloshing fuel). Or The hardest one to find with the same symtoms you describe was caused by a small cardboard disc that came from the cap of a fuel addative bottle. Would **** up to the bottom of the tube and kill the engine. Then it would float away and in a minute or so you could restart the engine and go a few miles. With this one though we realized that the problem never happened on a full tank, but would start when the tank got down to about half. Darn things anyway.
I think we definitely have it narrowed down to the pickup tube in the tank as that is the only place it could possibly be ****ing air into the line. Closing off the old pickup tube and coming off the top through the sending unit cover with a new pickup tube. We'll see how it runs after that.
Have you pulled the line out of tank,take a good look at it maybe push it in tank farther and the br*** fitting slide it in some,and tighen good.
Rockmart Ga ? haha Just a thought can you put a gas can in the front seat with a line going to fuel pump? Then you know its a tank issue, or you might be running out of gas with a dirty sock inside,good luck ..........................YG
Throw that junky gl*** filter away. Check your carb float levels. A engine getting free rev. V/s under a load is like apples to oranges. PS I don't think you have a fuel prob. Every clear fuel filter I have ever seen has air in it. I'll be watching this thread. Hope you get it.
I checked float levels, they are where they are supposed to be. Last night I plugged the original pickup tube and ran a new one through the sending unit cover plate on top of the tank. Haven't taken it down the road yet but it definitely runs better at idle. It was bogging down and stalling when I tried to race the engine sitting in the garage, does not do that now that I have changed the pickup tube, will see what it does when I take it down the road this evening when I get home from work. What do you think it could be if you don't think it's a fuel problem? I've ruled out ignition problems (new points and condensor, points gapped .019, tried another coil off of a running vehicle).
Just an update, thanks for all who responded. I capped off the original pickup tube, drilled through the plate that the sending unit mounts to, and put in a new pickup tube that comes off the top of the tank. Been driving it around close to home with no more problems, drove it to cruise-in at Cedartown (17 miles each way), no problems, ran great. I knew when it didn't die going up Baldwin's Hill, the hill at High Point, Wimberly Hill, or the viaduct over the railroad in Cedartown that we had it fixed. The pickup tube in the tank was the problem all along.
Great,i had one in a 63 Dodge p/u that was closed up and had to drill it out.It was like tar but hard.Glad she,s on the road again....................YG
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