I'm on a bit of a time crunch and am installing a axuillary tank in my truck, and trying to figure out a good way to do it. So... I was gong to use a pump or gravity feed. My truck is a 2002 F350 7.3 so here is my question:

When you fill the truck, and it stays running, does the trucks stock fuel guage move up at that time, or do you have to turn the truck off and back on to get it to register the needle movement?

Thanks in advance. I was gonna order a kit but I don't have time to ship it since I leave this Friday (4 days) so I'm fabbing one up real quick... hopefully.

-Ryan

 

The fuel gauge will go up with the truck running and the low fuel light will go off. The overhead computer on the other hand won't reset correctly but they are often wrong anyways. There is a issue if you go over a specified number of miles without shutting the truck off where you will set a code. I think the number was around 600 or 800 miles.

 

If I fuel either one of mine while running, the needle stays where it was. Over time, it will gradually come up, but I find the fastest way is to shut it off and then restart. Maybe my trucks have something wrong though...

 

Initial fuel reading is taken on first energization. The needle will jump to the correct level when you turn the key on.
If the engine is running, the slosh module in the dash will not allow a rapid gauge change (hence the "slosh module" name). Filling with the engine running will cause a slow rise in the stock gauge.

So yes the stock gauge moves up. How fast depends on the factors above.

If you are using an auxiliary tank to fill the main tank, shut off the transfer pump at about 3/4 full and allow the gauge to catch up.
If you are using a valve to switch supply tanks, the gauge should jump to the correct level when you switch (if properly wired).

 

Not necessarily true. My vegi tank uses the dash gauge to read between the two. If my diesel tank is low and the vegi tank is full it can take up to 15 minutes for it to read the correct volume of fuel in the vegi tank. And just the opposite, when switching back to diesel it can tank the same amount of time to go back down to the lower reading.

I have searched and search for a solution to this issue with none to be found. I'm using a 30amp automotive relay to switch the signal wire from each sending unit.

The only way to really get a instant tank reading on either is turn ignition on, pull the realy out of the socket until the low fuel light comes on, turn truck off, then switch to which tank reading you want and turn ignition back on.

I really wanted to see how the OBS's with twin tanks were wired because the reading on those tanks were instant upon switching between tanks.

That is unless you have a secret to wiring this up?

 

You could put a very short delay onto the system when you switch the tank. I'm talking 1/3 second delay (time off) before the gauge begins to read the tank you switched to.

Other than that, I have only seen the quick reading on dual tank trucks. I think they had a different slosh circuit on the stock gauge.