So I recently installed a Bosch 044 inline pump along with my supra pump in tank. My problem is not with the pumps or wiring but with the relays. I have separate relay for each pump, where both are hard wired to the battery. I used the stock fuel pump power to trigger both relays.
My issue is, I can hear the relay for the in tank pump clicking in and out as I drive. The car doesn't stall because the Bosch pump is still drawing fuel through the in tank pump. I thought that maybe the relay was bad so I replaced it, but I still have the same issue. I just find it weird that it's only happening to the relay for the in tank pump and not both considering that they are both wired identically to the same power and trigger source.

Any thoughts?

 

Sounds like a loose conection...

 

That was my first thought, i just checked all of the connections at both relays, battery and pumps and they are all good.

 

is the trigger y'ed between the two relays, as well as the power feed?

Try switching the two power wires leading to the pumps only, leaving everything else the same and see if your bosch kicks in and out. Otherwise, try running a jumper cable to the in-tank trigger from the battery and see if that makes the difference.

 

The triggers are y'd from the stock fuel pump power wire, the powers are run separately from the battery terminal.

 

You can try swapping which relay powers which pump, i.e. swap the supra pump relay over to the 044 pump and do the same for the 044 relay. Just swap the output (power wires). This way you can tell if the wiring, relay, or pump is the culprit if the 044 doesn't act up with the presumed faulty supra pump relay.