15 gal poly tank - ran out of gas at half mark

Since my refurb is "done", I've been cruising and tweaking my jeep. Luckily today, I pulled into a gas station to fill my tank up right when Ole Blue started stuttering. The gauge was sitting at half full. I filled it up and only took 7 gal, so the gauge is close to correct. It started right back up and ran good as soon as the pump was primed back. Sound like a fuel pickup issue? Anyone else experienced this? It's an MTS tank and their pickup/sending unit they sell. Thanks.

 

I am guessing that
A: either the fuel pickup is too short, or
B: you have a hole in the pickup line in the tank. Right at the half mark.

 

X2 . Or the sock filter could be messing with you. I'm thinking the pick up tube is to short Or the tank is not venting and collapsing .

 

The sock filter has me wondering. It is just a slide-on fit. I can see it could fall off the end of the pickup tube. But, I don't remember the metal pickup tube that the sock slid over only going half way down the tank. It would be great if someone could measure the tube length for me so I can compare to the height of my tank. I believe the MTS sending unit is like others off the shelf.

I believe my tank is venting properly. I have the vent set up going to a rollover check valve and then to a charcoal canister.

 

If you have a 73 as your sig notes, the filter isn't really a sock, but slides over the pickup tube which should almost reach the bottom of the tank. Similar to this:

 

Yes that is the one I put in my 73. I called it a sock since it just slides over the end with nothing really to hold it on; sock is probably not the correct term. Does the tube need to be bent down to set it at the proper level? I haven't read that anywhere though.

This makes me wish I had a trap door cut in my floor to access the unit without dropping the tank to check it. Oh well, dropping the tank may give me a good excuse to order and install one of those good looking Cross Enterprise bumpers when I can access behind the cross member. 8)

 

I cut my tube off to install an intank fuel pump. It was bent just like the picture.. I doubt the sock is the problem.. You probly are gonna hafta drop the tank [not my fav job] to see whats up. If there is a hole in the tube when the fuel drops below the hole it will suck air.. It happened to me on a Blazer..

FWIW I absolutely hate dropping my tank. But I learned to remove the rear wheels and place the Jeep on jack stands.. A simple siphon helps too as well as a floor jack.

 

Before I drop my tank, I'm going to let it happen again, remove my gas cap, and make sure it's venting. I'll do that to check for air locking.