Fuel tank hose setup

[jwendell413]

I feel more stupid every day. Just finished the Painless #10206 set and the truck won’t start. It’s cranking and turning over but no matter now much I slam the gas pedal it’s not starting.

I removed the fuel tank and replaced the sending unit, etc. in the process.

Process of elimination - is it hooked back up correctly? What’s the unused outlet for at the top, an air vent?
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[HO455]

A couple of things. Are you sure you have the hose hooked to the correct tube on the sender body? The unused tube would be for a return line from the fuel pump depending on the year of your truck. No return line then cap the unused tube.

Are you using a mechanical fuel pump? If so it is unlikely it will pull a prime through the filter you have installed by the tank. It should be on the pressure side of the pump.

Do you have the fuel lines on the pump hooked the correct ports?

How much fuel is in the tank? The fuller the tank is the easier it is to get the pump to prime itself especially when all the lines have been drained.

And most importantly for safety reasons you should never have more than 12 inches total of fuel hose in the fuel supply system.

[jwendell413]

Thank you for all the feedback. I did replace some fuel line and the filter but didn’t change the placement (guess it was wrong initially and my ignorance replicated it?). Not sure where the pressure side would be to place the filter differently. Or I can remove it from the line altogether if that’s needed.

Tank is just under 1/2 full. I could put more in if it’d help.

No, I’m not sure I have the hoses hooked up to the correct port. I thought I did but neglected to take good before pictures of it when I unhooked it all a few weeks ago.
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[sick472]

The larger of the sending unit's lines is the line that goes to the fuel pump. YOU can test this by blowing through that line and listen for gas bubbling. The supply line is the only one that goes down far enough to cause bubbling since all the other lines are very near or at the top of the tank. The unused line in your photo, as HO said, is the return line and can be capped off if your pump does not use this function. One reason for a return line is to help avoid vapor lock since unused fuel is returned to the tank and not allowed to heat up so much in the engine bay before it gets used. This is a nice function for higher HP engines, big blocks, and soup'd up engines, but not typically necessary for mild small block builds. I do not have a return line on my 350 HP 400 build. The plastic filter should be located between the pump and the carburetor, but I have had them between the tank and a mechanical pump before without issue.

Your tank vent is shown in the second photo and travels up into the upper cab corner and back out and down. If I recall, it then travels back across the floor and down and out of the cab through the floor. Some of these trucks, if not all, terminated that vent line at a charcoal canister under the hood. Make sure that vent line is not pitched or clogged. If so, your pump would be pulling against a vacuum in the tank...given you have capped the return line. A pinched vent line would not be your current problem if the return line is open...it would act as a vent .

If it were me, verify the lines are clear by blowing 10-20 psi air through them (unhooked of course), take the filter out at least temporarily, hook it all back up with the exception of the supply line at the pump and I'd use my mutivac to draw the fuel to the pump, then reattach the supply line to the pump. Put the clear plastic filter between the pump and carb and try to start it. The lines have been proven clear, primed at this point, and you can see if the pump is pushing fuel through the filter to the carb.

I second HO's advise on running as little rubber hose as possible. Hose is functional and will work for your troubleshooting, but steel line is much more reliable in the long run. I have only a few short pieces of hose at the tank and on either side of the plastic filter.

[72SB]

OP, if you have not, check under the truck the condition of the soft fuel line hose that bridge the hard lines from tank to hard lines on frame. I just got my 72 a few days ago and while it "looks good" and has had the tank replaced by PO....it still has the original soft line hose under the car that has basically fossilized. Also I see a hack someone did by installing a filter on one of those lines which as mentioned is a big no but the truck otherwise runs. I have the 6 cyl so have 5/16" hard lines & fuel pump. I assume V* with 4 brl models came with 3/8" line

If you don't cap off the open nipple on your tank you will have gas fumes in cab. My truck is a 72 so has the return line and charcoal canister. All those lines were cracked which I just replaced yesterday. My point is go through the entire line system and replace the soft line sections. I got "fuel injection" hose clamps. IMHO better than the worm drive type for soft fuel line

So today I will replace the old rubber lines under truck.....I suspect with gas in tank it will come pouring out so will have to use a nipple on the supply line as a temp stop and be quick when I do connect it to the forward hard line.

[Accelo]

Using an air gun blow into the feed line, at the fuel pump, with the tank cap off.
That will clear the line and keep them from siphoning fuel after you disconnect the lines.

[HO455]

Once again the old adage rings true.
80 percent of all carburetor problems are electrical.