Fuel pickup problem?

[kudu]

I went to go start my truck up after a few weeks of sitting waiting on a part and it wouldn't start. I saw that there was no fuel in the filter so I assumed it wasn't getting fuel for some reason. I went through the system checks starting with running an external tank of fuel between all of the points going back from the carb and could get it to run from all of them. I assumed it was either a rust line/hose somewhere under the truck since I could run the truck externally with a line before it went into the filter. For shits and giggles I hooked everything up as it would normally go and the truck would start and idle like normal with no issues. When trying to go up my driveway that's on a hill it had very little power going up it with the front facing the up hill, but when I turned the truck around and tried backing up it it seemed to have more power.

 

I'll be grabbing a fuel pressure gauge from my work tomorrow where I can just T into it and watch it while the truck is running, but while I wait for tomorrow to come does anyone have anything different it may be that I can consider to check tomorrow? I'm leaning towards the pickup being the problem, be it rusted and broken or something else with it. I have yet to fully examine the lines underneath the body which I'll be doing tomorrow as well just to start eliminating stuff that it isn't.

 

Also I assume the tank needs to be dropped on these trucks right to get to the pickup and what not? ('78 if that matters)

Edited December 13, 2021 by kudu

[datzenmike]

You may have a loose clamp or crack in the hose on the tank side of the fuel pump. Air is getting in as the fuel siphons back into the tank. But still, there should be enough gas stored in the float chamber to start and drive a block or more. Once started this crack or loose hose may let air in rather that building good suction to draw fuel from the tank.

 

When cold and before starting, take a look at the round glass sight on the front of the carburetor. Fuel level should be in the middle or near the white dot. If you see gas it should start. 

[kudu]

On 12/12/2021 at 8:51 PM, datzenmike said:

You may have a loose clamp or crack in the hose on the tank side of the fuel pump. Air is getting in as the fuel siphons back into the tank. But still, there should be enough gas stored in the float chamber to start and drive a block or more. Once started this crack or loose hose may let air in rather that building good suction to draw fuel from the tank.

 

When cold and before starting, take a look at the round glass sight on the front of the carburetor. Fuel level should be in the middle or near the white dot. If you see gas it should start. 

All of the hard lines seem good going to the tank. I mean they’re not perfect but there doesn’t look to be any cracks or holes in them that could be letting in air. I tried starting it up the other day to try and diagnose it and now it wouldn’t even idle where as before it would idle fine just not drive good but it has a known good carb on it so I would assume it may be tank related. Do I seem to be thinking correctly?

[Crashtd420]

2 hours ago, kudu said:

All of the hard lines seem good going to the tank. I mean they’re not perfect but there doesn’t look to be any cracks or holes in them that could be letting in air. I tried starting it up the other day to try and diagnose it and now it wouldn’t even idle where as before it would idle fine just not drive good but it has a known good carb on it so I would assume it may be tank related. Do I seem to be thinking correctly?

Try doing a remote tank up front and bypass the stock tank... that should tell you if the problem is up front or at the tank....

[Crashtd420]

Also try the reverse.... 

Make sure the carburetor has fuel in it enough to run and disconnect the fuel line after the pump and see if its pumping fuel....

[datzenmike]

Geezus be careful. Even at cranking speed if pumping it's like a fire hose!!! And you have an ignition source. I always pull the coil wire off so it won''t start.