94 s10 fuel pump relay clicking no start
The clicking noise at the relay indicates that the relay is bad, or that the wires to the relay and/or connector is bad.
A relay is an electronically activated switch. Inside is a coil. When 12v+ is applied to one end of the coil, and a ground is applied to the other end, the coil gets charged, creating a magnetic field. This magnetic field literally moves a metal lever from position A to position B. One end of the lever is attached to constant battery power. When coil not energized, the lever rests in postion A (which in the case of the fuel pump relay is feeding the battery power to an unused terminal). When the coil is activated, the lever moves to position B (which in this case is a terminal connected to your fuel pump wire). Thus, when the relay is activated, 12v+ is being directed from the battery to the fuel pump.
This fast clicking indicates that the relay coil is not getting a constant voltage or ground supplied to it, thus the lever is moving back and forth between position A and position B, either there is a wiring issue, a connector issue, or an internal issue with the relay.
The relay has 4 wires, black, grey, orange, green with white stripe.
black = ground
orange = battery = 12v+ always
grey = wire out to fuel pump (on some cars this wire is tan with white stripe)
green/white = signal wire from ECM
When key is turned ON, the ECM sends 12v+ out on the green/white wire to the relay for about 2 seconds - this activates the relay coil for 2 seconds, thus running the pump for 2 seconds (priming). When the vehicle is started, the ECM sees a constant ignition signal from the ignition module, and sends a constant 12v+ out on the green/white wire, thus activating the relay coil constantly, and thus running the pump constantly.
When car shut off, no more constant ignition signal, thus ECM stops sending the 12v+ out on the green/white wire.
So, you can kind of test your connector ...
1) remove connector from relay
2) jumper a wire from the slot for the orange wire to the slot for the grey wire - fuel pump should run - wiggle wires to verify at connector
3) probe black wire slot with ohm meter - make sure black wire has constant ground - wiggle wires at connector
test relay ...
1) remove relay from connector
2) rig a ground wire to the tab that had the black wire when in connector
3) apply 12v+ to the tab that had the green/white wire - relay should click once and do this every time you apply the 12v+
That should help you track it down to either a connector problem, a wiring problem, or a relay problem.
Nov 28, 2015 |
Cars & Trucks