fuel pump relay location?

1990 FORD F-350

120,000 MILES • V8 • 2WD • AUTOMATIC

BAREFOOTBOB88

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60 POSTS
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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.

Jan 31, 2008 at 8:00 PM

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.

Jan 31, 2008 at 10:26 PM

BAREFOOTBOB88

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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

Feb 1, 2008 at 3:47 PM

MHARD2BE

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1 POST

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?

Sep 11, 2020 at 11:28 AM (Merged)

MERLIN2021

CERTIFIED EXPERT
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...

Sep 11, 2020 at 11:28 AM (Merged)

WANNABEWRENCH

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2 POSTS

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?

Sep 11, 2020 at 11:28 AM (Merged)

RASMATAZ

CERTIFIED EXPERT
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.

Image (Click to enlarge)

Sep 11, 2020 at 11:28 AM (Merged)

EAEDWARDS

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1 POST

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.

Sep 11, 2020 at 11:28 AM (Merged)

RASMATAZ

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75,992 POSTS

Test the fuel pressure and also see below

Sep 11, 2020 at 11:28 AM (Merged)

SETH1583

MEMBER
2 POSTS

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

Sep 11, 2020 at 11:28 AM (Merged)

MHPAUTOS

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31,937 POSTS

Check for a fuel pump relay that is stuck in the on position, start here.

Sep 11, 2020 at 11:28 AM (Merged)

SETH1583

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2 POSTS

Ok thank u, I'll do that. Where is the relay located?

Sep 11, 2020 at 11:28 AM (Merged)

MHPAUTOS

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31,937 POSTS

It should be under the shield at the air cleaner support bracket, this info is from Mitchell 1 Data base.

Sep 11, 2020 at 11:28 AM (Merged)

BHERBIN

MEMBER
3 POSTS

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

Sep 11, 2020 at 11:28 AM (Merged)

HMAC300

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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

Images (Click to enlarge)

Sep 11, 2020 at 11:28 AM (Merged)

BHERBIN

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3 POSTS

There is only a red and a black wire coming out of the inertia switch

Sep 11, 2020 at 11:28 AM (Merged)

HMAC300

CERTIFIED EXPERT
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

Images (Click to enlarge)

Sep 11, 2020 at 11:28 AM (Merged)

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.

Sep 11, 2020 at 11:28 AM (Merged)

HMAC300

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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

Sep 11, 2020 at 11:29 AM (Merged)

LLYON

MEMBER
3 POSTS

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

Sep 11, 2020 at 11:29 AM (Merged)

BLUELIGHTNIN6

CERTIFIED EXPERT
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?

Sep 11, 2020 at 11:29 AM (Merged)

LLYON

MEMBER
3 POSTS

Thanks, I will give it a try. Regards, Loren

Sep 11, 2020 at 11:29 AM (Merged)

FORDMAN

MEMBER
3 POSTS

1989 ford f350 with 460 engine. something has shut the power off to fuel pumps and injectors. I put a jumper wire from battery to relay plug and fuel pumps are sending gas to rail but won't crank. I can spray starter fluid in air intake and it will run. My book says computer turns power on and off based on rpm and vaccum but does not say where these sensors are. mileage is around 120,000. I bought it not running and have tried everything I know. Any help would be appreciated. Thanks

Sep 11, 2020 at 11:29 AM (Merged)

2CARPRO JACK

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11,533 POSTS

First thing of course is to check all the fuses and fusible links in the underhood power center. If all are ok, then test for power to the EEC relay.It is the main power supply for the ECM.Check those and get back to me

Sep 11, 2020 at 11:29 AM (Merged)

FORDMAN

MEMBER
3 POSTS

I checked all fuse links. I did a voltage test on the battery-12.77, eec relay coil side-12.45, side to be switched-3.46, fuel pump relay coil side-3.02, side to be switched 3.43. There is not enough voltage at the fuel pump relay to activate coil. If I put jumper in relay plug to fuel pumps the 3.43 voltage is not enough to run fuel pumps. I can run jumper from battery to same plug and fuel pumps will run but won't crank because no power to injectors.

Sep 11, 2020 at 11:29 AM (Merged)

BRUCE HUNT

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3,754 POSTS

Just a thought but isn't there a safety cutoff switch? This gets tripped sometimes when jarred or tipped a bit. Have you looked to see if it needs to be reset?

Sep 11, 2020 at 11:29 AM (Merged)

FORDMAN

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3 POSTS

[quote:b7327fe2e6="Bruce Hunt"]Just a thought but isn't there a safety cutoff switch? This gets tripped sometimes when jarred or tipped a bit. Have you looked to see if it needs to be reset?[/quote:b7327fe2e6]Yes the inertia switch is working.

Sep 11, 2020 at 11:29 AM (Merged)