I had main relay failures immediately after installing a Walbro 450. A new replacement relay was also killed immediately. Solved with stand alone relay and wiring to battery.

 

Vegas, our new car will be built with one of the Racepak Smartwire units we have here. Decided to ditch the entire relay system.

 

Awesome. I was kinda curious if you were going to do that. I've watched your smartwire video for the old car, pretty amazing the things you can do wit hit.

 

I sorta forgot we had it here. It's the ideal solution for an enduro car. Andrew (TSE) is evaluating whether the DW300 on a street car necessitates separate/alternate relays. The few data points we have seem to indicate that it might work initially but service life is greatly reduced. Unfortunately, the demand for a alternate solution is both limited and low ROI to develop and produce. It might be one of those ideas that requires the community to make a recipe then publish so others can DIY it.

 

I personally did a rewire because I didn't like the size of the oem bulkhead connector pins, with the possible amperage that could be going through them. They are like 18ga pins, and a 450 can pull 20amps at peak flow and pressure.

Fuel tank is the last place on the car I want a fire.

 

What? No sense of adventure?

 

The cause for the master relay failure is a combination of two main issues. First, with time and mileage, combined with exposure to heat and elements under the hood, the main relay contacts become dirty causing a voltage drop and therefore higher current. Over time this becomes a self-energizing effect, overheating the connections and eventually damaging the contacts with relay failure.

However, the main culpert is the current demands of the fuel pump. As the various connectors and contacts in the harness corrode with time, the resulting cumulative voltage drops steadily drive the current draw up. In a normal low current circuit, this would not lead to a relay failure. But, since the electronic fuel pump has a high current demand, which increases as the the device gets older, the stress on the relay becomes too much and failure is imminent. So replacing a dead relay is not the cure.

The best solution is to remove the high current draw from the main relay circuit, the fuel pump. This is pretty easy to do. You will need a standard universal 30A or 40A 4 prong relay, 12 ga wire, 25A inline fuse, some crimp connectors and some zip ties.

Disconnect the battery. Remove the bulkhead cover behind the seats to access the fuel pump wire (red-blue). Remove the right trunk panel to expose the battery. Cut the fuel pump power wire (red-blue) several inches below the tank and, with butt connectors, crimp enough 12 ga wire to the two separate wires to run back to the battery. Connect the wire wire from harness to the 86 pin of the universal relay and the wire to the pump to the 87 pin. Next, connect the 85 pin with a crimped eyelet/stud connetor under the factory ground at the inner fender pinch seam. Finally, connect the 30 pin to the positive battery cable clamp bolt (use an eyelet/stud crimp connector) using the inline fuse. Zip tie the wires securely, as well as the relay.

If everything is wired correctly, you should be able to reconnct the battery, reinstall the panels and drive it like you stole it.