Needing help with 390 pump to carb line routing

[colnago]

Disconnect the line going to the carb. Run a new line from the pump to a bucket. Crank the engine. Are you getting gas dumped into the bucket? If not, there's a problem between the tank and pump. If you do get gas, the problem is between the pump and carb. If you're daring, disconnect the line from the tank to the pump, and blow. If you get gurgling in the tank, at least that line is clear. Or, put the end in your bucket, and the siphon should pull it from the tank, if the line is clear.

Also, do you have a tank selector under the driver seat? Is it turned to the main tank?

On my truck, the rear/upper port on the pump goes to the carb, and the front/lower port goes to the tank.

This is just easy (and free) stuff to check.

Joseph

[Charlie67f100]

Hey thanks for replying I'm gonna try that tomorrow and see what I get its got dark on me outside I don't have a tank selector on mine only got the line from in cab tank and then a rubber section under the truck joining it to the line on the frame to the pump and the inlet and oulet aren't labeled on the new pump.

[1guydude]

I can get some pics for u if needed charlie. Should be a threaded side. This one on mine comes straight up out of the fuel pump. 90s than straight up and loops to the carb intake. Like u said. From the fuel filter its mostly rubber and connection pieces. U change ur fuel filter? Do u have rust in ur tank?
Im new to this but yesterday my truck wasnt getting fuel and i primed it with the small plasctic wine glasses in the carb. 1st time was just 1. It did start to run and turn fuel when it got going and the vaccum was strong enough i think.
U said urs would run for a minute which u would think would be long enough. If u have an air compressor. Id blow the lines and everthing else just to make sure.
D

[Charlie67f100]

Alright fellas went outside and had a look fuel pumps working good it pushes out fuel but it's not reaching the carb it has a rubber fuel line running up to a 3/8 metal line to the carb

[Charlie67f100]

Could the rubber line not be building enough pressure

[colnago]

Rubber line is cheap. Run a new line directly from the pump to the carb. No filter, no stainless, just a direct rubber line. Once you have the engine running, you can start adding in the other stuff.

Also, is 3/8" stock for your truck? My truck uses 5/16". Not a big difference, but different diameter means different pressure, different flow.

Joseph

[Busboy]

Could the rubber line not be building enough pressure

Wow, it might be time to verify that your fuel pump cam is actually in place and rotating.

[Charlie67f100]

I replaced the rubber line along with the new pump the pump draws fuel but doesn't want to push up enough almost like it ain't drawing enough full the I installed the pump like it's supposed to go with the arm below the the cam. Could it still not have enough fuel to draw it to the pump 19.5 gallon has tank brand new absolutely no rust in the tank cap is a vented cap it's brand new too tank has 9 gallons of fresh gas in it.

[Charlie67f100]

Could it be sacking air in some where and vapor locking

[Charlie67f100]

Sucking air and I had it running yesterday for about five minutes after tapping the carb but as soon as I mashed the gas pedal it choked out and back to square one pulled the line of the carb and no fuel going up to it

[colnago]

How does your oil look? I'm wondering if the pump is getting enough lubrication for it to pump, or if it's oil-starved and "sticking."

Joseph

[Charlie67f100]

Oil look good I just put brand new fresh oil in it and new coolant everything on it is about brand new it's got good oil pressure

[colnago]

I just googled mechanical fuel pumps, and someone suggested to have a bucket/can with gas, and run a line from the bucket to the inlet of the pump. That way, you're completely ignoring the truck's gas tank. Their thought was that you could either have a partial blockage between the tank and pump, or you can have a hole somewhere in the line between tank and truck, and are sucking in air.

They also thought the eccentric on the inside could not be turning on their truck. I think the only way this could happen is if it's missing the pin that turns it with the timing gears. I don't suppose you can tell if the front engine cover has ever been taken off, can you?

If you have a pressure gauge, the output of the pump should be around 6PSI.

Joseph

[Charlie67f100]

The engine is new the eccentrics nice and tight watched the pump work with the line going to the bucket I'm gonna check the holley for a blocked fuel filter tomorrow might be an issue also got new steel pick tube for the tank and the one running down the frame under the cab ordered.

[colnago]

You mentioned filter. Do you have an in-line filter after the pump? I have one as well, but I have been told that the mechanical fuel pumps don't like pushing gas through a filter. If there is an in-line filter, or a filter in the Holley (I don't know; I'm not a Holley guy), maybe that's the problem?

Joseph