Fuel Tank Solenoid Valve

[Ammodog69]

Hello all. I'm having an issue with my 75 C2500 I recently bought on Craigslist and I'm hoping someone on here can help. When I first bought the truck it ran perfectly fine and I still think I got a really good deal for the truck ($1000). It didn't pass emissions right off the bat but Once I threw in some new plugs, Distributor cap and rotor it passed. About a month later while I was cruising it started to act like it wanted to die but would pick back up. It would start doing this after about 10 min of driving at any speed. I was pretty sure it was some sort of fuel issue so I started with the cheapest thing first which was the $1 fuel filter. That wasn't it because it continued doing the same thing and then it started getting worse and would die completely but would start back up after about 5 min and I could drive for another few miles and it would die again. so then I thought it might be the fuel pump going bad so I replaced that. Guess what? That wasn't it either so the next thing in line was the solenoid valve which I ordered online and still haven't replaced yet for two reasons. One reason is I'm not sure that is the problem because it happens no matter which tank I happen to be on meaning the switch and valve seem to be working properly. The gauge registers on both tanks too even though I know it's not quite accurate. The other reason I haven't replaced the valve yet is because the wiring currently connected to it is different than on the new one. I'm pretty sure I bought the correct valve because I shopped around online and every site I checked listed the same model number valve for my truck. The one on the truck now only has one wire connected to it and the new one has a 5 terminal female connector. That makes no sense to me at all because I found a wiring diagram and it shows 1 wire for the gauge, 1 wire for the selector switch on the dash, 1 wire each for the tank sending units and I'm assuming the other wire would be ground. I'm really stumped as to how my engine (454) is even getting any gas with a single wire connected to the valve. There's a birds nest of wires around the valve but I'm kind of reluctant to start cutting them and tracing where they go in order to hook them up to the new valve, especially if that's not even the problem. I guess my question is, what else could be causing this problem?

[Corts60]

You could have garbage in the fuel tanks that is clogging the pick up and then settling back to the bottom when the engine dies, allowing it to start again. Best way to confirm is to hook up a separate fuel tank directly to the fuel pump and run it. Then you'll know if it is tank related issues.

[Ammodog69]

You know, that thought crossed my mind because I had some new cherry bombs and larger exhaust installed and they dump right in front of the tanks. I was thinking the exhaust pulses could be vibrating crud off the inside of the tanks. Seemed a bit silly at the time but who knows.

[hatzie]

You have a new 81-91 Pollack Motorized valve. As you discovered that's not the right part.

The 73-80 valve is a single wire solenoid valve. Standard motor products FV1T three port valve can be used but it only switches the fuel feed lines.
The AC Delco 467513 is the original 6 port single wire valve for feed and returns.

[DBLSPRT68]

You could also have a vapor lock issue. If this happens again, open your gas caps. If you get a pressure release, your exhaust is heating up the fuel in the tanks. You might need to insulate the heat from the tanks. Let us know how this works out. Clogging the pick-up line with trash is also a possiblity. Let us know what the fix turns out to be. David

[Dead Parrot]

Check all of the rubber gas lines around the tanks. My 75 did something similar to yours and it was the rotted rubber line from the valve to the steel line leading to the fuel pump letting air into the gas intake. Don't overlook the possibility that the steel line might have a small rust hole letting air in.

My non-emission 75 valve has one wire and three gas line connections, 2 in , 1 out. Aftermarket Pollack valve.

[Ammodog69]

Thanks for all the advise. I will investigate this weekend and see what I can find out. I didn't think I did but I guess I did buy the wrong valve. I got the one Rock Auto told me was for my truck. Hopefully it's not the valve because the one I would need seems to be hard to come by and is pricey.