Dual tank issue

JZCracker

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Location
Idaho
First Name
John
Truck Year
1973
Truck Model
K20 FLEETSIDE
Engine Size
350
73 K20 4x4 with rebuilt 350. I've spent a lot of time getting the dual tanks, switch valve, etc working. A year ago I had a small leak in the driver side rubber tank hose. I did not want to drop the tank so I spliced in rubber gas hosing but needed to loop it to avoid a kink. This caused the truck to sputter over 40 mph. I removed the kink, fit a 90 with the rubber hose and problem solved. Forward to now... I left town for 3 weeks and now the issue is occuring again. It is even sputtering at low speed on this tank. There are no issues running off the right tank which has a shorter run to the fuel pump. A buddy told me those fuel pumps are very low pressure and that is why the loop caused the issue. I'm just not sure what the issue is now.
Appreciate any help:)
 

REVINKEVIN

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Sugar Land Texas
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Kevin
Truck Year
1986
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Silverado
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406
Hey. It could be that your valve is not moving all the way to the next tank. The gas that we have now starts separate out and it can cause some sticking inside the valve. I don’t drive my truck very much at all, but when I do, it never wants to swap tanks. I got so ticked off with it I just ordered a single tank kit so I can trash the dual tank set up. Kind of drastic, but that’s where I am at with it.
 

JZCracker

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John
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1973
Truck Model
K20 FLEETSIDE
Engine Size
350
Appreciate the input. I actually took the valve out of the loop and still the same issue. Barely any fuel inside the fuel filter compared to the passenger side tank. I'm not sure what is in there now, but I'm thinking of putting in a 40 gph fuel pump. NAPA sells a 28 and 40 gph. Not sure if this will have other ill affects.
 

Snoots

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Georgia
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Roger
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1973
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Jimmy Sierra
Engine Size
350
Pick-up sock in the tank could be clogged.
 

fast 99

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Brian
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81,85
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K20
Engine Size
350
Being as it runs fine on one tank a higher performance pump may just mask the problem or not fix it at all.

On fuel flow issues have used air pressure to locate a restriction. Takes 2 people. Wrap a rag around the air nozzle stick it in the fuel fill opening. Have to be very careful with the air, just a short puff or 2. Doesn't take much to rupture the tank. Disconnect lines until good flow is found. Problem is most likely in, or near the tank, in the changeover valve or lines in between the 2.
 

75gmck25

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Bruce
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1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
You have me confused about your fuel system. A ‘73 should have a mechanical fuel pump on the engine, and the fuel system is designed to run with about 5psi pressure because it’s a carburetor. Switching to a higher pressure pump will really screw up a carburetor. A stock mechanical pump should be good up to 300+ horsepower and should not cause any fuel delivery issues with a relatively stock engine.

My guess is that you have a rubber fuel line with a leak or crack, and the pump is just pulling air instead of fuel from that tank. The rubber lines are old, and ethanol gas makes them deteriorate even faster. It’s time to drop the tank and replace the rubber lines.
 

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