Adding Fuel Pump Relay and Cut-Off Switch

-
Divenut

Divenut

Well-Known Member
Joined
Sep 22, 2011
Messages
3,522
Reaction score
1,794
Location
Naperville Illinois
Hey Folks,

Did some research online but answers vary. Looks like the PO of my Duster installed the electric fuel pump directly off the ignition/fuse box?). Pump runs when key is turned to accessory and run positions. I'd like to be able to disable the fuel pump to allow me to do electrical testing without the fuel pump running. Traced the wires and there does not appear to be a relay? That said, I'd like to add a relay (30 amp?) and cut-off toggle switch. Question, should the switch go before of after the relay, i.e. between fuse box and relay or between relay and fuel pump. Bare with me as wiring in not my forte! :)

Thanks all,
Pat
 
If you want to use a toggle switch, that switch will turn your relay on, which will allow power to go to your pump.

If the battery is in the trunk, run a power lead right off the battery with an appropriate sized fuse to the 30 terminal on your relay.

Basic relay wiring
30 is power from battery for your pump
87 is power out to your pump
85 ground
86 on/off toggle switch
You can flip flop 85-86 terminals in most cases unless there is a diode in the switching circuit. Most relays don't have a diode here. This diagram has them flipped.

35092434.wiringwithrelay.jpg
 
In addition to above, check the coil for a diode, using your multimeter. check low resistance across 85, 86 and then reverse the probes. If resistance is different, you have a diode, and need to pay 'tention to polarity.

You can put a toggle, security switch, and crash switch all in series with either sided of the 85/ 86 coil terminals

This shows one with a diode. A couple of members on here claim some of these relays have reversed diodes. It would be good to check this, as applying wrong polarity power will act as a short. In the diagram below, power + is applied to 86

IMG_7451b.jpg
 
You must log in or register to reply here.
-

Back
Top