Fuel pump getting no power.

Tiny
SHANEPAYE
  • MEMBER
Inertia switch was not tripped, what controls the fuel pumps running for 3-4 seconds when the key is turned on? What would make them stay running?
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DIXON1
  • MEMBER
Ok truck is now down to 1 tank I bypassed the dfr thinking it may have been recycling gas to the front tank. Original issue still there with the pumps running and the key off. I final took a chance while it was running and I cut the brown wire at the the fuel pump relay the motor never missed a beat so I then turn off the key and my pumps stopped. I then tried restarting 1st turning the ignition switch to the on position and paused to listen for the pumps rear tank and high pressure pump both worked and the truck restarted. I drove it 5 miles and evrything is still workin off the key, so this seems to have fixed the problem for now but I would like to find out what caused this if there is a direct ground short or what
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
JAMES W.
  • MEMBER
Check terminal 22 at the eec module and see if the eec grounds the term when you turn the key to "on" and then to "start. Let me know. If this term doesn't turn on the ground, the eec is bad. Let me know.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
JUST THROWING IN SOME JUNK TO THINK ABOUT

DOES THIS THING HAVE A RETURN LINE BACK TO THE TANK FROM THE PRESSURE REGULATOR?

IF SO, IS IT RETURNING BACK TO THE CORRECT TANKNOT EVENTUALLY FILLING THE OTHER ONE UP, AS YOU DRIVE IT. LEAVING YOUR "PRIMARY FUEL SOURCE" EMPTY PRETTY DARN FAST?

ZAT MAKE SENSE. IF NOT, MAYBE I'LL SHUT UP AND SAY NO MORE!

THE MEDIC
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
SHANEPAYE
  • MEMBER
K pin 22 when harness is disconnected has good continuity to test port and to fuel pump relay. When I test for ground when plugged in to the eec when the key is on I get 8.5 volts. When the key is off I get 0 volts. I just bought an eec from pick n pull today with same numbers from a 1988 bronco. Same readings as stock eec. Is it possible to have two bad eec's or is there something i'm missing here?
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DIXON1
  • MEMBER
Was possible but as of earlier I bypassed the dual function reservoir. The rear tank is the only one hooked up at the moment. But even this way the pumps were still running, thats why I cut what I believe was the ground "brown wire"at the fuel relay it seems to have corrected the pumps running with the key off which is the main issue
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
JAMES W.
  • MEMBER
If, with key on, you ground harness pin # 22 at the eec connector end of the harness (tan/lt grn), does the fuel pump relay close. With "key on" pin #22 on the eec module should go to ground not 8.5 volts.
Also, with the harness connected to the eec module and key on, do you get the same 8.5 volts at the relaysocket (tan/lt grn)? AND at the diagnostic connector (tan/lt grn)?
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DIXON1
  • MEMBER
But to answer your thought which was mine yes but now return line goes directly to the the rear tank which is the only 1 plumbed in
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
SHANEPAYE
  • MEMBER
With key on and connector plugged in to the eec I have 8.5 volts at fuel pump relay tan w/lt grn and at the eec iv test port. When I ground it out at from the test port tan w/lt grn. The pumps come on and continue to run. When I turn the key off the tan w/lt grn wire has zero volts anywhere I test it. I guess the big question is can the computer cause that or do you think the tan w/lt grn wire is making partial contact with a power wire somewhere in the harness when the key is turned on. But when I ground it out I don't get any kind of spark or anything out of the tan w/ lt grn wire. It seems to me that is the only logical explanation, that the grnd wire is picking up power from somewhere in the harness.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DIXON1
  • MEMBER
Ok here is my update truck is now single tank with no dual function reservoir. Still have the electrical issue with the pumps if I connect brown wire that I cut which turned out to be the ground wire for all the pumps, high pressure and pickup pumps. Only know this because I pulled a new wire all the way thru. But other then the wire being cut im driving it dailey again!
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
JAMES W.
  • MEMBER
OK. Picture this; When the power relay closes it sends 12 volts to the fuel pump relay, fuel injectors, EGR solenoid and a bunch of other stuff. If you are reading 8.5 volts at the test connector rather than 12 volts, thats voltage drop due to the resistance in the FP relay coil. Also, if you're getting the same 8.5 volts at the wire at ECM term 22, it's for the same reason. BOTTOM LINE; If you have 8.5 volts at the wire on pin 22 at the ECM "key on" and you ground this wire "with key on" and the fuel pump runs, the ECM is bad.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
GLAD YOU ARE BACK ON THE ROAD

ARE YOU DONE, OR ARE YOU GONNA CONTINUE TO GET IT BACK RIGHT?

THE MEDIC
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
SHANEPAYE
  • MEMBER
Ok well the reason it only had 8.5 volts is because thats all my battery had in it. I've done every test three flippin times and every time its the same. Its definitely not grounding. Now the ecm. Is there only one for that truck or can I interchange it with a different one? I'm having a really hard time finding one with the same numbers on it. My numbers on the computer are
e8tf-12a650-e2a 8qc
6ec2830f09 9927 - 165 8c30.

Do all those numbers have to match. And I really do appreciate the help and I will definitely be donating more your way when my wife gets here with my wallet.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
PARTSPAUL6
  • MEMBER
To answer your original question, the fuel pump relays are probably stuck in the on position. They will only shut off when you unplug them or cut the PCM ground wire to them. Because of where they are mounted, they get lots of water splash on them making them a target for corrosion. Replace the two relays with new Ford pieces and repair the wiring that you cut into. Should work like brand new.
I have seen many of these 87 to 91 trucks sitting in a parking lot buzzing away. A good thump on the left fender usually shut them off. If it didn't, I would leave a business card to my dealer on the door.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Replace or charge the battery. ECM needs a minimum of 9 volts to operate correctly, power level too low!
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
PARTSPAUL6
  • MEMBER
Reading some of the other posts, the tank selection switch turns the fuel pumps on. The resevoir you have opened only to find springs in is a 'check valve' as it were to stop backflow from one tank to another. The electrical selection valves stopped in 1986.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
JAMES W.
  • MEMBER
We have a lot of information at our fingertips, but unfortunately, interchange is not part of it. I would recommend checking with a salvage yard and ask them what will interchange with your unit.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DIXON1
  • MEMBER
Thank you CJ MEDEVAC. I will most likely run it this way now, theres no hot wires "temp wise" or dead battery after sitting a couple days, so I think I will run it this way.
And also Thanks to partspaul6. I have replaced all the relays with new ford parts and fixed the wire 2x now and have the same problem so the wire stays cut for now. And I hope this post from you helps clarify things for some others.
Replied on May 15, 2012

Reading some of the other posts, the tank selection switch turns the fuel pumps on. The resevoir you have opened only to find springs in is a 'check valve' as it were to stop backflow from one tank to another. The electrical selection valves stopped in 1986.

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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)
Tiny
DARTH_TED_82
  • MEMBER
I know I'm reviving an ancient thread, but I need to know if this guy resolved his problem. I have the exact situation his last posts explained. Pumps don't run unless I jump the FP test port on DLC. Both EEC and FP relays are new so should be good. I will do the voltage tests mentioned in the last page. Please, any help is appreciated. '88 Bronco 5.0/AOD.
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Tuesday, December 19th, 2017 AT 6:39 PM (Merged)

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