1999 Ranger fuel pump circuit problem

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Jan 15, 2005 | 04:40 PM

RichAdame

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1999 Ranger fuel pump circuit problem

My 1999 Ranger conked out on me while driving last week. After not hearing the fuel pump working when I turned the key to RUN, and hearing the fuel pump relay kick in, I determined the fuel pump was bad. Removed the bed and accessed the pump and replaced. Guess what? Still didn't work...no power to the pump.
In the power distribution box, checked all fuses....good. Checked the relay...I get 12V to the coil, which closes the contacts. I have 12V on the "lt.blu/org" wire going to the contacts, but on the other side of the contacts "dk. grn/yel", I am getting 6.75V. This wire (according to Haynes schematics) goes to the inertia switch and also the PCM. At the inertia switch, I am still getting 6.75V on the "dk. grn/yel" wire.
Do I have a failed PCM? How do I check? 12V straight to the pump makes it work, so I suspect the PCM. Agree?

Thanks!
Rich

Jan 15, 2005 | 05:30 PM

Dave257

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You should have 12 on the black/yellow wire on the relay that gets switched to the fuel pump when the relay closes. Be sure to check it before you replace the PCM.
Dave

Jan 15, 2005 | 05:46 PM

RichAdame

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Dave...Blk/Yellow wire?

Dave, I am looking at my Haynes schematics....where is the "Blk/Yel" wire coming/going to? I see a "lt.blu/org" wire from 20A fuse to the fuel pump contact common, a "red" wire feeding the relay coil, a "lt.blu/org" to PCM #80 from other side of relay coil, and the "lt grn/yel" wire from the relay contact to the PCM/inertia switch.
BTW, I have a 3.0L, VIN "V", flex fuel engine, 2WD.

Jan 15, 2005 | 06:24 PM

Dave257

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I was looking at the Hanes manual number 36071 for 93-2000 ranger. However looking at the ford manual for the 98 ranger it shows the wire as LB/orange from the 20 amp feed. Guess the hanes manual is wrong, good catch by you. If the relay is closed there should be 12 volts, I would look at the voltage going to the PCM close to the connecton at the pcm to make sure there isn't anything wrong between the pcm and the fuel cutoff, but 6.75 volts won't get it done.
Dave

Last edited by Dave257; Jan 15, 2005 at 06:27 PM.

Jan 15, 2005 | 07:04 PM

Rockledge

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How did you rule out the relay?

Jan 15, 2005 | 07:11 PM

RichAdame

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Relay

I ruled the fuel pump relay out by swapping the same type relays around it in the Power Distribution Box. All 4 of them had the same type of relay.

Jan 15, 2005 | 07:37 PM

Rockledge

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OK. Well, looking at the schematic myself and based on what you've done already, I think that pretty much leaves the PCM. I don't see anywhere else in the circuit where you could further test it out, in any case.

Good luck, let us know what happens.

P.S. Welcome to FTE!