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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 10-06-2011, 09:26 AM   #1
Sleeper90
 
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Vehicle: 1990 Mustang LX 5.0
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Default Fuel pump not turning on

My fuel pump won't turn on when I turn the key to the on position. I have researched the fp relay and replaced, replaced the fp and the solenoid and fixed the gr/yl wire which changes to or/bl before getting to the solenoid. The previous owner rigged the pk/bk wire coming out of the fp relay to have constant power through the fuse panel, this caused my fp to run constantly and to prime constantly. I put the pk/bk wire back where it was suppose to go but now I don't know where the pk/bk wire goes. I think it goes to the ignition switch but not 100% sure. I have pics of what I'm talking about. Any help would be appreciated


http://i264.photobucket.com/albums/ii186/dllundgren/photobucket-4149-1317905953514.jpg




http://i264.photobucket.com/albums/ii186/dllundgren/photobucket-4091-


http://i264.photobucket.com/albums/ii186/dllundgren/photobucket-4449-1317905916528.jpg1317905930780.jpg
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Old 10-06-2011, 08:32 PM   #2
Bubba 95SN
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Veryuseful.com will show wiring
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Old 10-08-2011, 09:20 PM   #3
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It would be on a circuit that has battery power when the key is in the on position.
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Old 10-08-2011, 10:39 PM   #4
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The pink/black wire is a 12v constant source that has a fusible link. That is the wire that powers the pump when the key on 12v power engages the relay. I don't remember which connector it goes to....

The fuel pump is supposed to prime until the PIP signal is received by the ECU and then it kicks off. The previous owner obvious bypassed a deeper issue.
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Old 10-08-2011, 11:26 PM   #5
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Thanks for the responses. I have actually taken the dash off at this point. Not only because of this issue but I have to do a heater core replacement, alarm system removal, just seeing what the h3ll others have done, etc. The most recent discovery is the lack on connectivity between the pin 19 wire (pk/bk) at the EEC and the wire at the fuel pump relay also pk/bk. Is there a fuse, fuse link, connector etc between the EEC and the quick connect that is behind the fuse panel on the drivers side?
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Old 10-09-2011, 06:56 PM   #6
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On 10-6 11 I gave you what you needed. Very useful.com has color wiring diagrams. If you had taken the time here is the correct answer...pk/blk goes to inertia switch then on to power the fuel pump.
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Old 10-10-2011, 03:57 AM   #7
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Bubba 95SN, I already looked at those diagrams, and multiple others, none show what I wanted to know, hence the second question. Either way, I've test multiple options and now am at a lose. The only two things not replaced at this point are the grounds for the vehicle and the EEC. These are the only two options left. My EEC is giving 6 volts when the key is in the ON position. It has 7 volts when the engine is on. I have tested the grounds at the solenoid, under the EEC, block to frame, and a couple of others, all are tight, any appearances that looked shady to me, such as a junk splice have been redone so I've all but ruled out ground issues. If the EEC is bad I would think pin 19 would get no volts and other things would be wrong with the vehicle. Any suggestions, rumors, outbursts, etc???
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Old 10-10-2011, 09:13 AM   #8
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If you cant find what you need from those wiring diagrams, you should bring the car to someone who understands schematics... because this is clearly over your head
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Old 10-10-2011, 07:42 PM   #9
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Well, thanks for the opinion, AdderMk2. My question is clearly too complicated, I'll try another site.
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Old 10-10-2011, 08:51 PM   #10
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I'll take a peek at my diagrams tonight when I get back.
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Old 10-10-2011, 08:51 PM
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1990, 199050mustangfuelpump, 50, eec, fuel, fuseable, gt, inertia, link, location, mustang, priming, pump, relay, switch, turning

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