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The one on the right is the relay that came with the harness. The one on the left is the replacement from the Canadian equivalent to Harbour Freight ( Princess Auto ). Both appear to be cheap chinesium.
Last edited by F350towing; Dec 27, 2025 at 10:16 AM.
I’m of no help, but I do recall SSJ has described how he wired up dual fuel pumps in the past. IIRC he used one as the primary and then the other was based on demand. You might search up his posts and find it if interested.
I’m not understanding the need for relays on both pumps. Why would you not use the factory harness to feed one and then wire in a relay for the secondary? School me sir.
FWIW, my in-tank Bosch 044 is powered by a dedicated, fused power line straight from the DS battery running through a relay triggered by the factory fuel pump power supply.
I’m not understanding the need for relays on both pumps. Why would you not use the factory harness to feed one and then wire in a relay for the secondary? School me sir.
This is something I hadn’t even considered as an option. I was too focused on using the factory + as the trigger wire like noob has done. The school of thought was…this way each pump would be getting a dedicated 12v battery power while still retaining the 20sec KOEO feature.
As for the relays I have ordered the Amazon fuse/relay box I linked.
Will have to get some quality relays as replacements.
I’m not understanding the need for relays on both pumps. Why would you not use the factory harness to feed one and then wire in a relay for the secondary? School me sir.
It’s a precaution in case the aftermarket pumps draw significantly more current than the factory pump.
