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Fuel pump relay location?

Tiny
BAREFOOTBOB88
  • MEMBER
  • 1990 FORD F-350
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Ok. I just bought this truck. I have dual tanks. After I got it home I was playing around with it a little and I decided to switch the tanks to see how much fuel was in the rear tank. I flipped the switch and the truck stalled 2 seconds after. The rear tank was empty. So, I flipped the switch back to the front tank after I had shut the key off again. (The front tank had a half tank) Then I tried starting is again and it would not start. I'm figureing that the selector valve is now vapor locked or stuck somehow, the relay for the front tank had coencidentally went bad at that moment, or the fuel tank switch may have also coencidentally went bad at that point. I am not sure if there is two pump relays for this truck though. My 88' f-150 had dual tanks and had two relays; one for each tank. I couldn't get a chilton manual that could help me with this dilema. I am assuming that there is only one relay for the fuel pumps though. I think it is the green one. My 88' had a green relay and a brown relay. I would for sure like to know if there is more than one relay so that I can eleiminate that. I would also like to know where the selector valve is for the tanks. I pry should also add that when I use the rear tank I can hear the pump kick on for the second that it should to prime the line. When I try to use the front tank the pump doesent kick on but I can hear something click. Which is pry the relay. Thank you.
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Thursday, January 31st, 2008 AT 8:00 PM

26 Replies

Tiny
BAREFOOTBOB88
  • MEMBER
  • 60 POSTS
Well now, to answer my own question. 1.) I have figured out that there is only one fuel pump relay for both pumps/tanks ( it is the green on on the driver side fender wall ), 2.) There is no external selector valve that switches the tanks. 3.) The fuel pumps themselves have a check valve on the outlet side of the pump that delivers fuel to the engine. When the pump is energized by selecting the tank the pressure in the pump builds up behind the check valve and forces it to open allowing fuel to be pumped to the engine.
THERFORE. I have one of two problems. The lesser of the two evils is that my selector switch is pry bad and needs replaced. Or the greater evil, my fuel pump needs replaced because the outlet check valve is stuck shut. Which means I have to figure out where I'm going to stick 9 gallons of gas in order to drop the tank. Since I don't hear the fuel pump kick on when I try to use my front tank I am hopeing its the tank selector switch. I will post my findings.
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Thursday, January 31st, 2008 AT 10:26 PM
Tiny
BAREFOOTBOB88
  • MEMBER
  • 60 POSTS
It was the tank selector switch after all. I pulled the one out of my 88' f-150 and used it in my f-350. I flipped the switch to the front tank and turned the key on. Sure enough I heard the pump knick on and the truck started right up. The switch leg for the pumps power was not closing and the switch leg for the fuel gage was closing. Thats why the pump wouldn't work but the fuel gage still worked for the front tank. :D
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Friday, February 1st, 2008 AT 3:47 PM
Tiny
MHARD2BE
  • MEMBER
  • 1 POST
  • 1990 FORD F-350
  • V8
  • 2WD
  • AUTOMATIC
  • 189,000 MILES
I am receiving an error code 542 Fuel pump secondary circuit failure: PCM to ground. My truck is a 1990 ford super duty rollback wrecker. I have replaced the in tank fuel pump, checked the fuel pump relay (i switched this one with the one in my 1991- the one out of the super duty works fine in the 1991 f250). The error reads "Fuel pump secondary circuit failure: PCM to ground" what else should I try?
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
I don't know the exact location, but look for a black with lt green stripe wire, usually near a headlight, remove it, clean the ground and remount it. That waire is your EEC ground.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
WANNABEWRENCH
  • MEMBER
  • 2 POSTS
  • 1989 FORD F-350
  • V8
  • 4WD
  • MANUAL
  • 13,000 MILES
Dorve 2 miles shut off, key to assy, 10 minutes later it won't restart. It will turn over like out of fuel (theres fuel)dual tanks. No power to inertia switch, pump, tank switch.
It will fire using some gas on air filter though. Replaced fuel relay, same problem. Power to both eec & fuel relays is good. Has had similar starting problem after running in past, but usually fires within 15 seconds and cracking foot throttle 1/2". Your thoughts?
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the computer if its properly grounded- The computer energizes the fuel pump relay then power goes to the inertia switch thru the brown wire then fuel pump. Here is the location of the fuel pump relay in the diagrams below.

LH Side Of Engine Compartment, On Relay Bracket. Fuel pump relay is next to the EEC Relay.

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
EAEDWARDS
  • MEMBER
  • 1 POST
  • 1989 FORD F-350
  • V8
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
I have replaced both internal and external fuel pumps and fuel relay and now I am not getting gas to the fuel filter. My truck started right after I changed out the pumps and ran for a few minutes, then died.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Test the fuel pressure and also see below


https://www.2carpros.com/forum/automotive_pictures/12900_fp1_2.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_fp2_2.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_fp3_1.jpg

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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
SETH1583
  • MEMBER
  • 2 POSTS
  • 1989 FORD F-350
  • 7.5L
  • V8
  • 2WD
  • MANUAL
  • 116,000 MILES
The fuel pump on my truck stays running when I turn the ignition off. It won't stop unless I disconnect the battery. Is this the relay failing? If so where is the relay located
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Check for a fuel pump relay that is stuck in the on position, start here.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
SETH1583
  • MEMBER
  • 2 POSTS
Ok thank u, I'll do that. Where is the relay located?
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
It should be under the shield at the air cleaner support bracket, this info is from Mitchell 1 Data base.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
BHERBIN
  • MEMBER
  • 3 POSTS
  • 1989 FORD F-350
  • 7.5L
  • 4WD
  • AUTOMATIC
I have no power going to my fuel pump. A couple weeks ago my truck kept dieing I thought it was the fuel pump so I replaced both the high and low pressure fuel pump but now have no power going to pump. I have checked the eec and fuel pump relay have a constant 12v at yellow wire and 4.5v on red wire. I have checked the inertia switch and its not popped. All my fuses are good. I am about ready to just blow it up. So to begin with my truck ran out of gas I put gas in it and then it started acting funny, it would die then start right back up so I thought it might be a clogged filter so that was the first thing I replaced. That had no affect so I thought the fuel pump might be going out so I changed the high pressure one first. The truck ran fine for a day then when I went to start it the next day nothing so I again changed the high pressure pump thinking I just got a faulty one, but no same problem. OK so I have just swapped out the inertia switch still no results. The truck is m7.5 L 460 motor. The back tank is not hooked up. There is no power to the inertia switch and no power to the pump. Please help
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check the brown wire that goes to the inertia switch then see if inertia switch has power on both sides it could be just a bad switch. It could also be a bad relay as well. If no power coming out of brown wire at relay try replacing it with a like relay and see if it works. It can also be a bad ground on fuel pump. I am assuming this has dual tanks so it could also be the tanks switch I am sending that along on how to check for that.

LH Side Of Engine Compartment, On Relay Bracket. Fuel pump relay is next to the EEC Relay.

Applicable to: 7.5L/V8-460

Check out the diagrams (Below). Please let us know what you find.

Cheers
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
BHERBIN
  • MEMBER
  • 3 POSTS
There is only a red and a black wire coming out of the inertia switch
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Unless someone has changed the wiring or it may be old as well. it should be brown on one side and pink on other. regardless check for power on both sides if power on one but not the other then the inertia is bad or the switch has popped.or you can use an ohm meter and see if you get 0 through both. Here are the engine and fuel pump wiring diagrams with the guide to help you do some testing.

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (Below). Please run this test and get back to us.

Cheers
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
BHERBIN
  • MEMBER
  • 3 POSTS
Thanks for the guide I found the problem was a connection at the relay all corroded the truck is running great! Thanks for you help I love this site.
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Friday, September 11th, 2020 AT 11:28 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers
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Friday, September 11th, 2020 AT 11:29 AM (Merged)
Tiny
LLYON
  • MEMBER
  • 3 POSTS
  • 1986 FORD F-350
  • V8
  • 2WD
  • MANUAL
  • 150,000 MILES
For several months the truck would run out of fuel even though there was fuel in the tank. Switching to the other tank immediately got it going again and after a few moments, switching back to the original tank worked fine.
Now, the truck won't start. I fed some gasoline into the carb and it ran fine.
I would suspect fuel pump if the earlier symptoms hadn't been exhibited.
What steps should I take to troubleshoot this problem?
Do you suspect the switch, relay or fuel pump?
Thanks,
Loren
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Friday, September 11th, 2020 AT 11:29 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Test for power going to switch and relay. If power is to both, check power at pump. If power is at all components, check relay or have it tested at a local auto part store such as AutoZone. If it checks out, test switch for power being supplied when key is turned. If this checks out as well and there is power going to the fuel pump, it is probably faulty.

Can you hear the pump kick in for a few seconds when you first turn key?
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Friday, September 11th, 2020 AT 11:29 AM (Merged)

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