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HDGENE
HDGENE, Ford Senior Master/Diesel/Trans
Category: Ford
Satisfied Customers: 4784
Experience:  25 years Auto experience, Ford ,GM, Chrysler, Asian & European
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I have a 1994 F150 4.9 auto. The fuel pumps will not come on

Customer Question

I have a 1994 F150 4.9 auto. The fuel pumps will not come on when I turn the key on. There is no power coming out of the wire from the pump relay. I have replaced the relay, and I still have no power to the inertia switch.
Submitted: 1 year ago.
Category: Ford
Expert:  HDGENE replied 1 year ago.

Hello, does the check engine light come on when the key is turned to on and do you have power at the relay?

Customer: replied 1 year ago.
I have pose to the relay from the ignition and the fuse. There is no power coming out of the relay
Customer: replied 1 year ago.
the check engine light comes on, but then goes of.
Expert:  HDGENE replied 1 year ago.

Ok if you jump across the relay do you have power to the fuel pump? Does it come on then?You should have two power sources to the fuel pump relay. and the pcm grounds the fuel pump relay only for a few seconds to prime the fuel circuit

Customer: replied 1 year ago.
I meant power control module
Expert:  HDGENE replied 1 year ago.

Im sorry, what about the pcm?

Customer: replied 1 year ago.
The pcm is not sending the signal to ground the relay. Could this be caused by a bad ground at the fuel pump?
Expert:  HDGENE replied 1 year ago.

No, the pcm sends the signal when it sees a key on demand to prime the pump.long as the eec power relay is working and you have communication with the pcm it should ground the pump but only for a few seconds not all the time.

Customer: replied 1 year ago.
Right, but when I cut the key on the pumps do not prime. Is there anything that would cause the pcm to not give the signal to prime. Such as a bad ground at the pumps or a faulty ignition switch. I found out this morning that I have a faulty manual lever position sensor.
Expert:  HDGENE replied 1 year ago.

Here is a schemtaic of the fuel pump circuit if you didnt have it.Do you have communication with the pcm and is it storing any codes for the fuel pump circuit?