Can't keep fuel equal in tanks.

[TerryB]

(02-06-2023 )TerryB Wrote:  

(02-05-2023 )Rawze Wrote:  all fuel that returns to the tanks has to go thru a return line splitter y-pipe for it to send it evenly.

It does, it does go thru a splitter. Goes from the pump to the splitter and to the tanks. The suction and return fitting in the tank coming from the engine have a stand pipe on them. The return fittings from the pump do not, the fuel just splashed in from the top. In theory, it's the static pressure in from the fuel in the stand pipes that keep the tanks level. If one tank it 3/4 full and the other 1/4, there would be more fuel returned to the 1/4 full tank because it takes less pressure to overcome the stand pipe that has 1/4 tank of fuel in it, until they come level or close to it. On the suction side it's easier to suck out of the 3/4 full tank, and so on. With the engine shut off, a siphoning effect takes place and will level the tanks(of close to it) with the engine shut off. Does the fact the return fuel from pump does not return thru stand pipe mess with the leveling capabilities? If the OEM pump did have a return line going to each tank and it didn't utilize a stand pipe, then I would say it doesn't matter. If the OEM pump did not have a return to the tank from pump and the return was added with the Fasse system, then maybe this is my problem.

Looking at the OEM parts build for this trucks serial number, I only see 2 fuel lines going to the tanks. Just the suction and return from the engine. Both of them go thru a splitter before that tanks. I don't see a 2nd return line. That leads me to believe there was no return from the pump, the pump return was added with the Fasse system. I'm assuming if there was return fuel from the OEM pump was plumbed in with the return from engine. I could be wrong on that but seems like that's what they should have done with this Fasse system.