Electrical Unknown Relay behind glovebox

[granchico]

Unknown Relay behind glovebox (passenger side)

Hello everybody

Suddendly after starting the engine, this relay is flipping active clunking, someone know their function /name /circuit ?
have some electric Diagram involving it?
1997 Mustang 4.6L

Thanks for reading and advices.

 

[Felony_Cobra_SVT]

Also looking for this answer. Mine is actually warm to the touch, after i hooked the battery up, after v8 swap, no fuel fuel pump power either.

 

[wmburns]

Are the wire colors R, DG/Y, DG/Y, W/R?

If so, the relay is the low/high speed fuel pump relay. It's job is to put a ballast resister in series with the fuel pump in order to slow it down.

 

[granchico]

You are right!, thank you.
Red/Red, Green/Yellow, Green/Yellow, White/Red
This Relay begins to flip each half second endless after 5 or 10 seconds of engine start.
the engine seems to run normally, but the clicking do not stops.
With your info I can locate it in the diagrams, but, where is that fuel pump resistor installed? (I will follow the wires too..)

 

[wmburns]

Also looking for this answer. Mine is actually warm to the touch, after i hooked the battery up, after v8 swap, no fuel fuel pump power either.

Test for initial key on power at the fuel pump speed relay DG/Y. Test both wires. This will let you know if power is making it in and out of the relay.

Test for initial key on power at the trunk mounted IFS cut off switch.

Recommend using a test light that will "load" the circuit. Use a known good ground.

Where there is and isn't power will tell you where to look next.

It would also be handy to test across the control side of the relay to determine IF the PCM is controlling the relay or the relay is clicking on it's own.

Or even better, use an advanced ODB2 scanner to monitor the fuel pump speed PID.

 

[granchico]

Test for initial key on power at the fuel pump speed relay DG/Y. Test both wires. This will let you know if power is making it in and out of the relay.

Test for initial key on power at the trunk mounted IFS cut off switch.

Recommend using a test light that will "load" the circuit. Use a known good ground.

Where there is and isn't power will tell you where to look next.

It would also be handy to test across the control side of the relay to determine IF the PCM is controlling the relay or the relay is clicking on it's own.

Or even better, use an advanced ODB2 scanner to monitor the fuel pump speed PID.

This is usefeull also for me, but further, what may happen if run the engine without this relay?, just for check the pcm signal side to se if is cicling.

 

[wmburns]

This is usefeull also for me, but further, what may happen if run the engine without this relay?, just for check the pcm signal side to se if is cicling.

Take a look at wiring diagram. IF the rely is removed then the effect would be to have the ballast resister in series all the time. This would be the same as forcing the fuel pump into low speed mode. The motor will run fine until the motor's load goes above what the fuel pump is able to deliver. Expect that the fuel pressure would drop.

If it turns out that the ballast resister is part of the relay assembly then removing the relay would cause a break in the power feed to the fuel pump. The results should be predictable (crank with no start because no power to the fuel pump).

There's also a real possibility that the PCM will detect the open circuit voltage from the relay coil ground start control.

*EDIT*: And no. I don't know where the ballast resister is physically located. I don't own (or have worked on) a Mustang with a two speed fuel pump.

Also, if you have access to an advanced ODB2 scanner with two way communication then trouble shooting this issue would be much easier with the ability to command the PCM to control the relay at will.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

 

[granchico]

Thank you for explain, I was looking the circuit and figure out similar effects,
but not realize that the resistor may be inside the same pack, it is inside or not?
going to check signal static and running.