How does the fuel pump relay work in a PCM?
When the ignition switch is turned to the “START” position, the PCM closes the ground circuit to the fuel pump relay, resuming operation of the fuel pump. After the ignition switch is returned to the “ON” position, power to the fuel pump is supplied through the fuel pump relay.
Why does the fuel pump relay not stay on?
The relay is weak and is not staying on when it is energized by the PCM. When the engine is running, the extra charging voltage may be enough to hold the relay on. The relay is located in the power distribution box under the hood. Here’s a description of the fuel pump relay circuit from the Ford SZservice literature.
What to do if your fuel pump won’t start?
Ugh…..I hate chasing down electrical problems. If jumping the fuel pump relay makes the pump run, and if the relay tests good. Then you need to determine why the ECM is not telling the relay to close. Start by testing continuity back to the ECM.
What is the second half of a fuel pump relay?
The second half of the relay is the “switch” that controls power to a particular accessory; like a fuel pump. Terminals 86 and 85 are the primary side of the relay. It utilizes an electromagnet to close (connect) the secondary electrical circuit inside the relay.
Is the fuel pump relay controlled by the PCM?
Consequently, the fuel pump relay is usually controlled by, the ignition or powertrain control module (PCM). As a result, when switched on, the fuel pump relay; will provide current to the fuel pump, so that it may function. Therefore, any faults with it, can cause fuel pump issues.
When is the fuel pump relay turned on?
The fuel pump relay is activated whenever the ignition is turned on. A fuel pump relay functions primarily to maintain a consistent voltage supply to the fuel pump. The ignition or powertrain control module (PCM) usually controls the fuel pump relay.
Why is my fuel pump not turning on?
Thanx. Try swapping the fuel pump relay with another one, that will truly rule out it being the relay. fuel pump gets ignition, nothing to do with ecm as far as power is considered, sounds like a fault contact on the relay, possibly fuse box, check grounds aand for corrosion
Where is the Red ECM plug on a fuel pump?
I traced the Pin 85 bl/gr wire to Pin 9 on the Red ECM plug and confirmed that there is continuity, which is no surprise since it works half the time.