Question about Ford F-150
Hi, your circuitry is shown below. The relay coil is powered by the PCM relay but get's it's ground turn-on from the PCM separately. There is an intertia switch in the power circuit, and If you have dual tanks, there is also the tank switch to worry about. What I would do is interrogate the pump relay socket to see what's going on. Pull the relay out and use a 12 volt test light as follows:
Connect the test light clip to chassis ground, and probe the relay socket. You should get one hot terminal from the 20 amp fuse O. Next, turn the key on and probe the socket again. You should have 2 hot terminals, the additional one coming from the PCM relay.
Next, move your test light clip to battery positive and probe the socket again. With the key still on, you should get a light from the PCM ground signal. This is the one that is usually a problem. If you don't get this light, the PCM is not turning the pump on (perhaps due to a security system) or you have a bad wire from the PCM (pin 22) to the relay.
There is also usually a dim light on the last terminal (that goes to the pump). If you don't get that dim light, your inertia switch or tank switch may have failed open.
Please let me know if you have questions and thanks for using FixYa.
Posted on Mar 24, 2011
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Posted on Jan 02, 2017
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