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86 fuel pump relay grounding circuit

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Justfixit

86 fuel pump relay grounding circuit

Life long Ford lover and custom builder. Millwright by trade but have worn many mechanics hats over the years.

I don’t normally ask for help but after reading for hours and hours on different forums I am at my wits end. Restoring my late father‘s 1986 Ford F150 4x4, 5.0, manual transmission, with dual tanks.
The issue I am having is no fuel pumps with key in on position.
I have 12 V constant power to relay and I’m getting signal to relay when ignition key is on but the tan and green wire going to pin number 22 is not receiving ground signal from ECM. If I hook up ground to test connector pumps will run and engine starts as long it it is connected. image269.jpg
I drove it to the paint and body shop 18 months ago and now having this problem so it could be something as simple as a plug that I am missing that they fail to hook up when they removed fenders. Also on a side note the alternate appears to be draining battery so I know I need to replace that also but not sure if it’s related to this problem.

86 F150,4x4, standard transmission, duel tank, 5.0

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

Welcome to the Bullnose Forum! Glad you joined.

But before we dive into problem solving we need to discuss our guidelines. You probably missed the email you were sent asking you to go to the New Members Start Here folder, read the guidelines, and then introduce yourself by starting a new thread in that folder. Don't worry, about 50% of the people miss that email/step.

However, at least the "read the guidelines" portion of that step is important as we hold everyone to those guidelines. So we want to make sure you've had a chance to read them. Given that, please assure me that you've read them and then we can get on with the problem solving.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Justfixit

Re: 86 fuel pump relay grounding circuit

Sorry. Yes I have read the guidelines, I didn’t receive that email until after I had started this thread. I did go back and post about myself.

86 F150,4x4, standard transmission, duel tank, 5.0

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

In reply to this post by Justfixit

Yep, that happens. But all is well.

On Page 107 of the '86 EVTM there's a troubleshooting section for the fuel pump. Since you know you are getting power, the only applicable suggestion is to check that G701 is clean and tight. It is the ground behind the instrument panel, pretty much right behind the radio.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

Oh yes, I wanted to add your picture. It is too large of a file, meaning it is larger than 1Mb, so I used the Resize option and put it to Big. You can read about that on the page at Bullnose Forum/Forum FAQ's.

But now that I have, I'm confused. That looks to be an '87 or later and you said it is an '86.

Gary, AKA "Gary fellow": Profile

Justfixit

Re: 86 fuel pump relay grounding circuit

You are correct on the year and I was wrong😕 Date Of Manufacture is 03/87. So I guess I’m in the wrong page. Sorry all this time I’ve been calling it an 86😣

86 F150,4x4, standard transmission, duel tank, 5.0

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

It isn't a problem at all. We even have a moderator with an '87 and no Bullnose. So let's continue to work the issue.

But the only issue this might cause is that there might be some wiring changes between '86 and '87, so we will have to be careful. I think I have an '87 EVTM, so tomorrow I'll compare it to the '86 version and see if there are differences I can spot.

Gary, AKA "Gary fellow": Profile

Justfixit

Re: 86 fuel pump relay grounding circuit

This post was updated on .

Thank you Mr Lewis. I have gone as far as I know how to on this. My son works for the local Ford dealer as a tech and has been unable to find information that is helpful, probably because I was wrong on the year.....

86 F150,4x4, standard transmission, duel tank, 5.0

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

Welcome. Don't forget to check that ground and all grounds. You said that it might be a plug that hasn't been connected, but if they painted the truck and didn't get the grounds back solidly then that may be the problem.

In fact, IIRC, Bill/85Lebaront2 has said several times that there is a ground on some of the trucks near the battery and it has frequently caused problems.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 86 fuel pump relay grounding circuit

Administrator

The main ECM ground attaches directly to a pigtail on battery negative.
This is what's used to ground the injectors, so if this connection goes flakey the injectors won't open.

You're right, Gary, in that the TFI modules are known to overheat.
The vehicle will stall when called on to accelerate.
Sometimes they come back when it cools down.
There were even lawsuits about this.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Justfixit

Re: 86 fuel pump relay grounding circuit

Problem found. There are two identical plugs that are long enough to go to the ground at the battery and they had the wrong one plugged in still trying to figure out where the other one goes to. Thank you for the help

86 F150,4x4, standard transmission, duel tank, 5.0

ArdWrknTrk

Re: 86 fuel pump relay grounding circuit

Administrator

That's great, it was an easy fix!

Often you can identify a circuit by the wire colour.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

In reply to this post by Justfixit

Excellent! And Jim is right, what wire colors are in the other plug?

Gary, AKA "Gary fellow": Profile

Justfixit

Re: 86 fuel pump relay grounding circuit

In reply to this post by ArdWrknTrk

One is black one is black with white tracer. They are both ground wires but one of the plug halves was missing so I had to go to the scrap truck and steal one off of it , runs like a champ now

86 F150,4x4, standard transmission, duel tank, 5.0

Gary Lewis

Re: 86 fuel pump relay grounding circuit

Administrator

Black/White is used here:

Power in Ckt 526 from Fuse Link P to trailer lamps

Power from Fuse 12 in Ckt 171 to power door locks and mirrors

Ckt 359 which connects the TPS, EJP, MAP, ECT, Air Charge Temp Sensor, & Knock Sensor to pin 46 on the ECU

Power to the windshield washer pump via Ckt 941 from the wiper switch

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 86 fuel pump relay grounding circuit

Administrator

IDK the details, but for many of these trucks a single black/white wire is stator power to the choke coil on the carburetor.

Glad you've got it figured out.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.