What The Heck Is My Fuel Pump Doing? (video)

[Jason 302]

It's an Aeromotive 340 in-tank, only about a year old. I have it wired with one of their wiring kits which allows me to run it full-time so I can emtpy my tank, which is what I was doing. Seems like it pumps, then slacks off, then starts pumping like it should again. It ran fine for the first few minutes, but after the tank got down to about 1/3 or 1/4 tank, it started doing this. Any ideas? Should I just go ahead and put a new pump in?

You will probably have to turn up the volume.....


View: https://www.youtube.com/watch?v=2t3xWsHt0yQ

 

[5.0ttops87]

It's an Aeromotive 340 in-tank, only about a year old. I have it wired with one of their wiring kits which allows me to run it full-time so I can emtpy my tank, which is what I was doing. Seems like it pumps, then slacks off, then starts pumping like it should again. It ran fine for the first few minutes, but after the tank got down to about 1/3 or 1/4 tank, it started doing this. Any ideas? Should I just go ahead and put a new pump in?

You will probably have to turn up the volume.....


View: https://www.youtube.com/watch?v=2t3xWsHt0yQ

Doesn't have enough back pressure to stay primed when that low has less head pressure? if you filled it up or had it full would it do the same thing? I mean most pumps i would think run better when they have a fpr for some back pressure to keep primed? But then again they're submerged in gas already? weird.

 

[jrichker]

Have you checked the voltage at the pump to make sure that it is constant?
Is the fuel pump getting hot and the slowing down as the fuel level drops?

Fuel is what keeps the pump cool, and the return typically drops fuel right on top of the pump. With no return fuel dumped on the pump to cool it, the pump may run hot and slow down. As heat in a DC motor increases, the motor's internal resistance increases, which causes it to develop less power and slow down.

 

[Jason 302]

All thoughts that have crossed mind, I have not checked the voltage at the pump though. I will add that to my check list. I dropped the tank and pulled the pump and I overlooked something when I installed it.
There is a "vapor purge port" located at the bottom of the pump that may have been blocked or restricted by the rubber insulator that goes in between the pump and the hanger. According to Aeromotive, this could cause "slow or no priming and may damage your pump due to dry run".

http://aeromotiveinc.com/wp-content/uploads/2014/09/111-4002-0revE.pdf