1986 Ford F-250 Fuelpumps don't energizw

Tiny
NICKR1932
  • MEMBER
  • 1986 FORD F-250
Electrical problem
1986 Ford F250 V8 Two Wheel Drive 125K miles

The fuelpums are OK, but do not run unless I manually close the fuelpump relay coil. I replaced the fuelpump relay, but have the same p[roblem. There is 12Volts and a ground present to 2 of the 4 terminals. However, the points in the relay won't close and allow the pumps to run. Can you tell me how to fix the problem?
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Tuesday, August 19th, 2008 AT 3:28 AM

16 Replies

Tiny
JDISSELKAMP
  • MEMBER
I'm having the exact trouble on a 89 250. Changed the EEC relay and fuel pump relay to no avail. Would like to see the solution to this.
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Tuesday, August 19th, 2008 AT 8:35 AM
Tiny
VENTUREDEERE
  • MEMBER
There is an "inertia" switch under the dash that may have opened. It has a manual reset button. Look on the passenger side of the trans hump. It's a safety item in case of a crash it cuts power to the fuel pump. Hope this helps.
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-1
Thursday, August 21st, 2008 AT 11:30 AM
Tiny
JDISSELKAMP
  • MEMBER
I have checked the inertia switch and its okay. I have twelve volts leaving the EEC when I turn on the ignition, but the Fuel relay does not switch. This can only happen if the relay is bad, (it checked good), if there is a broken wire between the EEC and the Fuel Relay, or the return from the Fuel relay to the Electronic Control Module is not allowing the circuit to complete. How do I check this? When I check the voltage going in to the Fuel relay it appeared I had voltage on both sides of it. 12V from the EEC and 12V from the ECM, thats where I get a little lost.
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Thursday, August 21st, 2008 AT 3:57 PM
Tiny
VENTUREDEERE
  • MEMBER
Unfortunately I'm away from home for a couple weeks and don't have access to my shop manual to take a look at the electrical schematic and offer suggestions (I'm also not a pro). My '86 4x2 has 75K miles and have not experienced this problem.
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Friday, August 22nd, 2008 AT 2:40 PM
Tiny
JACK42
  • MEMBER
If the pumps run with relay manually operated the ineretia switch isnt the problem. There should be 2 powers and 1 ground, the other wire (pink/black goes out to pump. Check the yellow wire at the relay socket for power, comes from starter relay and powers the relay up to work it when engine is cranked/running. The tan/light green should be the ground from the ecm to work the relay, red is hot from eec relay
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Monday, August 25th, 2008 AT 12:44 PM
Tiny
NICKR1932
  • MEMBER
Thank you for your reply. I apologize for not getting back sooner. I was called away on business. The wires on the fulepump relay are not the same color as the ones you mentioned. There is a larger black with a white stripe wire, which is live. There is a smaller red comming from the inertia switch, there is 12 volts between them. The remaining two wires are a red and an orange. I figure that one of them gets voltage from the starter relay, right? I checked and there is no voltage going to the red or orange wires while cranking or otherwise. I assume the starter relay may be the problem. Also, I found that there is no spark to the ignition. Could this be related to the problem? Note: I replaced the ignition modual about a week befor this all happened. Please tell me where the starter relay is and how to check it out? Many thanks!
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Wednesday, September 17th, 2008 AT 4:11 AM
Tiny
JACK42
  • MEMBER
The starter relay makes the starter work. This might be a bad EEC relay. What is the exact production date off the sticker on the inside of the drivers door?
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Wednesday, September 17th, 2008 AT 7:52 AM
Tiny
NICKR1932
  • MEMBER
In reply to your question. The exact production date on the driver side doorjam is 08/14/86
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Thursday, September 18th, 2008 AT 3:52 PM
Tiny
JACK42
  • MEMBER
None of those colors match the wiring diagrams I have. Do you have a ground at one of those wires at the fuel pump relay?. The inertia switch is after the fuel relay, before the pump. It is the last thing to stop power to the pump
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Thursday, September 18th, 2008 AT 6:59 PM
Tiny
NICKR1932
  • MEMBER
There definatly is a ground at the fuelpump relay. It goes through the inertia switch to a red wire that goes to a terminal on the fuelpump relay and as I stated befor, if I put one end of the voltage tester on that red wire and the other end of the voltage tester on the black wire with a white stripe I get 12 volts.
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Friday, September 19th, 2008 AT 1:02 PM
Tiny
JACK42
  • MEMBER
The wire through the inertia switch should be power to the pump, not a ground
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Friday, September 19th, 2008 AT 1:22 PM
Tiny
NICKR1932
  • MEMBER
I have continuity between the battery negative terminal and the inerita switch wire going to the fuelpump relay! You say that power goes through the inertia switch to the fuelpump relay, but it isn't. The power to the fuelpump relay as best as I can tell is coming from an other relay right next to the fuelpump relay, that seem to energize when the ignition switch is turned on. You mentioned that the colors I told you that were on the fulepump were not the same as the ones on your schematic. Is it at all possable you may not have the correct schematic? I"M not doubting your ability in any way, just making a suggestion.
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Friday, September 19th, 2008 AT 7:46 PM
Tiny
JACK42
  • MEMBER
Im not insulted in any way.... I honestly have had this problem before on many Fords.I said was the power goes from the fuel pump relay to the inertia switch then to the pump.I realize you have already donated, but this might be easier if you signed up for an online manual, that way you could look at differnet years and the such to see if you come up with something that looks similar to the wiring in your truck.

http://www.2carpros.com/articles/mitchell1eautorepair-car-repair-manuals

the wiring diagrams are printable and you can save them for future reference
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Saturday, September 20th, 2008 AT 7:35 AM
Tiny
MYGYVER
  • MEMBER
I HAVE AN 86 F250, AND I HAD THE ILLUSION OF THE IN TANK FUEL PUMPS GOING OUT IN MY REAR TANK. THE MIDSHIP TANK HAS BEEN OUT FOR AWHILE. WHAT IT ALL CAME DOWN TO WAS THAT THERE IS AN OIL PRESSURE SENDING UNIT WITH (2) WIRES GOING TO IT LOCATED ON THE BACK OF THE INTAKE MANIFOLD. THERE IS ALSO THE SINGLE WIRE OIL PRESSURE SENDING UNIT THAT GOES DIRECTLY TO THE GAUGES. THE ONE WITH THE 2 WIRES WILL TELL THE INTANK PUMP TO KEEP PUMPING GAS WHEN THE ENGINE DEVELOPS 2-3 LBS OF PRESSURE. THIS CONNECTION RUNS DIRECTLY TO THE FUEL PUMP RELAY THAT IS LOCATED UNDER A PLASTIC HOOD MOUNTED NEAR THE BRAKE BOOSTER. MINE HAS 6 WIRES. A SEVEN DOLLAR PIECE, BUT IT TOOK ALL DAY TO TRACK IT DOWNPRICELESS. HOPE IT HELPS.
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Saturday, October 18th, 2008 AT 10:22 PM
Tiny
NICKR1932
  • MEMBER
Thank you for your input. Where on the intake manafold are these 2 wires? Also, I removed the cover of the fuelpump relay and grounded the frame around the coil, the pumps work, problem solved. My conclusion is that the ground comes from the computer and that the computer is most likely fried. There is a site www. Autodirect. Com 1 800 611 6730, they will repair any auto computer for $75.00. Anyone with a computer problem should check it out!
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Friday, October 24th, 2008 AT 12:43 AM
Tiny
MYGYVER
  • MEMBER
CHECK THE OIL PRESSURE SENDING UNIT ON THE INTAKE MANIFOLD. IT WILL BE THE ONE WITH 2 WIRES. MINE WAS BAD AND AFTER REPLACEMENT, MY PUMP STARTED PUMPING. HOPE IT HELPS
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Monday, October 27th, 2008 AT 9:43 PM

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