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Fuel Pump voltage

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Old 04-06-2009, 06:28 PM
flytwins flytwins is offline
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Fuel Pump voltage

I am helping my neighbor get his 1989 f150 v8 running. It is getting spark, but no fuel pressure. The high pressure pump mounted inside the driver's frame rail was bad, (verified off the truck), I replaced it, but it is only getting 3.6 volts on the connector, and it needs 12 volts. Is there a fuel pump relay that would limit the voltage if bad? If so, how do I find it? If not, what else would reduce the voltage to the pump?
The truck has dual fuel tanks with a switch on the dash. The low pressure in-tank pumps are not pumping from the tanks to the high pressure pump either, perhaps due to low voltage.
Thanks
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Old 04-06-2009, 06:57 PM
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Originally Posted by flytwins View Post
I am helping my neighbor get his 1989 f150 v8 running. It is getting spark, but no fuel pressure. The high pressure pump mounted inside the driver's frame rail was bad, (verified off the truck), I replaced it, but it is only getting 3.6 volts on the connector, and it needs 12 volts. Is there a fuel pump relay that would limit the voltage if bad?
NO there is not.
The voltage you are looking at is zero not 3.6 Volts. You should not be using a volt meter in the fuel circuits. Use a test light and you will find it to be zero volts.
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If not, what else would reduce the voltage to the pump?
The Fuel pump relay is open and you are reading leakage from pin #8 of the EEC Computer.
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Originally Posted by flytwins View Post
The truck has dual fuel tanks with a switch on the dash. The low pressure in-tank pumps are not pumping from the tanks to the high pressure pump either, perhaps due to low voltage.
Thanks
Check your Inertia Switch to see if it is open. If OK ground pin#6 of the self-test connector and turn on the key and see if the fuel pumps run.
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Old 04-06-2009, 08:51 PM
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Bill, thank you. I have GM vehicles so my experience with Fords is minimal. I will check the inertia switch tomorrow. I understand it is on the inside firewall left of the brake pedal. Where is the self test connector located? If the fuel pumps run with the #6 pin grounded, what will that tell me?
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Old 04-06-2009, 09:04 PM
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Bill, thank you. I have GM vehicles so my experience with Fords is minimal. I will check the inertia switch tomorrow. I understand it is on the inside firewall left of the brake pedal. Where is the self test connector located?
The self-test connector is named EEC Test in the photo below, it is under the cover. And is located on the drivers inter fender under the hood.
It is also called the Data Link Conn. or DLC in the second diagram.

http://i54.photobucket.com/albums/g9...ays/89f150.jpg
http://i54.photobucket.com/albums/g9...taLinkConn.jpg

Good Luck.
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Old 04-06-2009, 09:18 PM
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The self-test connector is named EEC Test in the photo below, it is under the cover. And is located on the drivers inter fender under the hood.

It is also called the Data Link Conn. or DLC in the second diagram.
http://i54.photobucket.com/albums/g9...ays/89f150.jpg
http://i54.photobucket.com/albums/g9...taLinkConn.jpg

Good Luck.
Thanks Bill. I believe I saw the EEC Test under the hood the other day on a strip with other connectors. If the pumps run with the #6 pin grounded, what does this mean?
Fred
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Old 04-07-2009, 07:58 AM
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Thanks Bill. I believe I saw the EEC Test under the hood the other day on a strip with other connectors. If the pumps run with the #6 pin grounded, what does this mean?
Fred
It means that the:

1. You are getting Power from the EEC Power Relay to the Fuel Pump Relay Coil.
2. You are getting Power from the Fuse Link at the Starter Solenoid to the Fuel Pump contacts common pin.
3. You are getting Power from the Ignition Switch to the EEC Power relay Coil.
4. Fuel pump & EEC Power relays are OK.
5. Inertia Switch is OK.
6. Fuel Pump Selector Switch is OK.
7. Selected Fuel Pumps are OK.
8. The Wiring & Plugs are OK from the fuel pump relay to the pumps.
9. The Ground for the Pumps is OK.
10. You are getting Power from the Ignition Switch to the EEC Power relay Coil.

And you have just bypassed the EEC Computer so now you may need to look at the EEC Computer, its plug or the small black wire with a green stripe at the NEG (-) Post of the Battery and make sure it has a good ground (connection).
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Old 04-07-2009, 08:52 AM
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Bill, thank you very much. I'm new to this forum, but belong to a Porsche forum and have received, as well as given, help often on that forum. Porsche is a very different animal and these forums are a blessing. You have taught me a lot about Ford's fuel systems in these few postings and I really appreciate you taking your time to help a Ford newbie!
Fred
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Old 04-07-2009, 09:30 AM
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Your welcome and here is a wiring diagram of the 1989 F-series Fuel System:
http://i54.photobucket.com/albums/g9...989FSeries.jpg

And a diagram of the fuel lines:
http://i54.photobucket.com/albums/g9...FuelSystem.jpg

/
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Old 06-11-2017, 06:34 PM
zamusmc zamusmc is offline
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1989 f250 Low Voltage (8 Volts)

I have read this post several time and followed some of the instructions (thanks). I have a 1989 f250 with 5.9 liter engine. My issue is i have tested the voltage all the way back to the fuel pump. It registers at 8 VOlts. I tested the ECC/Fuel Pump Relay and both read 12 volts. I followed the circuit to the fuel tank selector and it also reads 8 volts. I checked the inertia switch and cannot obtain a reading. What else can i do / where else can i check to determine where i am losing voltage?
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Old 06-11-2017, 07:04 PM
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I have read this post several time and followed some of the instructions (thanks). I have a 1989 f250 with 5.9 liter engine. My issue is i have tested the voltage all the way back to the fuel pump. It registers at 8 VOlts. I tested the ECC/Fuel Pump Relay and both read 12 volts. I followed the circuit to the fuel tank selector and it also reads 8 volts. I checked the inertia switch and cannot obtain a reading. What else can i do / where else can i check to determine where i am losing voltage?
When you are testing voltage to your fuel pump, it is very important that you fuel pump relay is energised. This is the purpose of grounding pin 6 as subford originally said. With the ignition on and pin 6 grounded, you should be able to measure full battery voltage at the contacts of the fuel pump relay, the inertia switch and at the selected tank fuel pump as well as the frame mounted fuel pump if so equipped. If the relay is not energized, you may read 5 volts at these points as the computer uses a lower voltage to test integrity of the fuel pump circuit when it is not energized. The computer also supplies a ground to the fuel pump relay to energize it. Same connection as pin 6 of the EEC test connector. Of course, the computer does not supply this ground if the engine is not running or cranking. Thus the purpose of the test pin for the fuel pump on the EEC test connector.
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Old 06-12-2017, 06:42 PM
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Ok, thanks NotEnough...!

i will give it a shot.
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Old 07-23-2017, 07:00 PM
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NO FUEL PRESSURE AT FUEL RAIL

truck won't start and i am getting "no fuel pressure at fuel rail". I recently replaced the fuel tank and pump on the rear tank (side tank is out). I tested the pressure before the inline pump and after and the filter as well it is at 45 PSI. I also replaced the fuel pressure regulator. When i test the fuel rail I get 0 PSI. I previously just took the schrader valve out and it pumped some fuel out (free flowing). I assumed it was ok. What else can I do. Can the fuel rail be clogged? I am testing the fuel pressure with a fuel pressure testing kit.
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1989, 1996, 460, 89, bad, check, f150, f250, ford, fseries, fuel, high, pressure, pump, running, voltage

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