When I'm at about a half tank of fuel my fuel tank lines or Raptor lift pump hoots at me. I hear it more when running uphill or slosh the tank on rough grades. When this sound occurs I can watch my fuel pressure drop suddenly too.I think it is the DS sloshing around and loosing its seal and suck air. Not sure about this but it stops when the tank is full.I was thinking about a billet tank sump so the L/P is somewhat gravity fed. However, DOT has a rule that a tank sump is illegal incase of a fires in a wreck.Anyone know about this? I understand my insurance could decline coverage if they found out.

DOT seems to prohibit direct gravity feed to carberator or FI... not sure it's prohibited to fuel pump, below the level of the IP. Now, that said... is your draw straw & fuel returns both either in or out of the basket on the fuel gauge. This can cause the dredded part tank empty syndrome because the basket itself can not flow as high as the aftermarket pumps allowing the fuel in the basket to be sucked down. Also, if the measurment for the draw straw was done with the tank sitting on the floor, a false measure can happen as the tank bottom flexes up. Ae there any other air leaks like defective lines? I see a lot of complaints with the quick connect fittings between the DS & lines.

Thanks I appreciate the request for info. My fuel return dumps down the filler neck and my drawstraw is in the fuel module with the screens cut out. Been that way 5-6 years without a problem. Even while pulling long grades with a heavy load, it's never been a problem until recent.The 'hoot' sound is like a strange lift pump squeak or maybe in some way an air leak. Actually sort of like a regulator that can't find proper adjustment. All guess work at this point. I think I need to get under the LP when the tank is low and listen for the sound. I pulled the regulator and spring and found no dirt due to the pre-filter.If I get on it hard it will do it and when making sharp turns but very sporadically. At first I thought it was the power steering pump going out. (sounds kinda like that), but, then watching the FP gauge I saw the pressures drop radically when the sound occurs. I probably need to pressurize the tank and look for leaks, but an air leak woudn't sound like this whoot sound. It weird:shrug:

Kinda sounds like a crappy lift pump to me. . .

When you put in the drawstraw, did you have the tank on the floor or on some sawhorses. If on the floor, you probably have about and inch or two of fuel(4-6 gallons/1/4 tank issues) that you cannot use. When you are going up or down a grade, turning a corner, etc. the straw is pulling in air. Depending on the sump that you are going to use, you can mount the sump under the drawstraw and use a longer DS to go all the way to the bottom of the sump. This willl keep the end of the drawstraw covered, not allowing your lift pump to suck air, also eliminating the chance that you will have any insurance coverage problems or D.O.T. problems. I looked at the Hellman Sump, and saw that this attaches to the bottom of the tank and has a outlet for fuel at the side. This would only give the lift pump added benefit if the tank is full, as the liquids would go to the same level. They also state that this can be used on all vehicles. HTH

Any true offroad user should not use any sump. All it would take is one stump, log, or rock to swipe the sump off the bottom of the tank and leave you stuck. Drawstraw is legal to use on the streets where it might be a thin legal line for a sump on the streets.

When you put in the drawstraw, did you have the tank on the floor or on some sawhorses. If on the floor, you probably have about and inch or two of fuel(4-6 gallons/1/4 tank issues) that you cannot use. When you are going up or down a grade, turning a corner, etc. the straw is pulling in air. Depending on the sump that you are going to use, you can mount the sump under the drawstraw and use a longer DS to go all the way to the bottom of the sump. This willl keep the end of the drawstraw covered, not allowing your lift pump to suck air, also eliminating the chance that you will have any insurance coverage problems or D.O.T. problems. I looked at the Hellman Sump, and saw that this attaches to the bottom of the tank and has a outlet for fuel at the side. This would only give the lift pump added benefit if the tank is full, as the liquids would go to the same level. They also state that this can be used on all vehicles. HTH

This is a great idea... the sump with a draw straw:). Thank you. Maybe figure out a way to shield the small sump somehow