J_C
Explorer Addict
- Joined
- July 30, 2009
- Messages
- 6,074
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- City, State
- Florence, KY
- Year, Model & Trim Level
- 1998 XLT 4WD 4.0L SOHC
If you don't have any data, then you'd put the meter into voltage 20VDC (or nearest higher range) mode, put negative meter lead on any ground (chassis or battery negative terminal) and probe positive lead in the relay sockets to find which one is 12V (or 14.4V, etc, at the battery/charge system voltage) live. When the relay is energized, that will switch that 12V to another contact going out to the fuel pump. The other two used contacts are power to energize the relay and the ground to complete that electromagnet coil inside that trips the relay.
I looked at a wiring diagram for a 2000 but can only assume the wire colors are correct as follows. The relay itself may also have its contacts marked on the side as to their function and/or numbered on the bottom:
Relay pin 1: Red wire, half of coil
Relay pin 2: Light Blue/Orange, other half of coil
Relay pin 3: Light Blue/Orange, power input
Relay pin 4: Not used, there may not even be a contact for it in the relay socket
Relay pin 5: Dark Green/Yellow, power output
I don't know how they have the coil wired. Either one of the two is always live voltage, or one of the two is always grounded, but without the key turned to turn the pump on, you won't have both live voltage and live ground on the coil, but when the fuel pump should be running, first couple seconds with key in aux position or while cranking engine, you should have both live voltage and ground on the coil, then 12V+ on the power output, and at the pump connector plug.
While you can use the multimeter to probe for the power input on the socket contact that corresponds to relay pin 3, but you'd have the relay unplugged and obviously it won't complete the circuit unplugged so there isn't going to be output on the socket contact for pin 5 without the relay plugged in.
If there's power input and coil power and ground, you can presume there will be power output on pin 5 when using a known good relay, and it then follows that you "should" have power on the wire going all the way to the pump connector once the relay is plugged back in, if the circuit is good so far, and then if pump gets power and ground but doesn't spin, it's bad.
Now suppose you had no coil circuit completion, either no power or ground to that part of the relay, then using a jumper wire between the relay socket pin 3 and 5 should turn the pump on if it's good. I mean, odds are only one thing has failed... unless you're cursed.
I looked at a wiring diagram for a 2000 but can only assume the wire colors are correct as follows. The relay itself may also have its contacts marked on the side as to their function and/or numbered on the bottom:
Relay pin 1: Red wire, half of coil
Relay pin 2: Light Blue/Orange, other half of coil
Relay pin 3: Light Blue/Orange, power input
Relay pin 4: Not used, there may not even be a contact for it in the relay socket
Relay pin 5: Dark Green/Yellow, power output
I don't know how they have the coil wired. Either one of the two is always live voltage, or one of the two is always grounded, but without the key turned to turn the pump on, you won't have both live voltage and live ground on the coil, but when the fuel pump should be running, first couple seconds with key in aux position or while cranking engine, you should have both live voltage and ground on the coil, then 12V+ on the power output, and at the pump connector plug.
While you can use the multimeter to probe for the power input on the socket contact that corresponds to relay pin 3, but you'd have the relay unplugged and obviously it won't complete the circuit unplugged so there isn't going to be output on the socket contact for pin 5 without the relay plugged in.
If there's power input and coil power and ground, you can presume there will be power output on pin 5 when using a known good relay, and it then follows that you "should" have power on the wire going all the way to the pump connector once the relay is plugged back in, if the circuit is good so far, and then if pump gets power and ground but doesn't spin, it's bad.
Now suppose you had no coil circuit completion, either no power or ground to that part of the relay, then using a jumper wire between the relay socket pin 3 and 5 should turn the pump on if it's good. I mean, odds are only one thing has failed... unless you're cursed.