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86 fuel pump relay grounding circuit


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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.thumb.jpg.73735db52610f84351536bbe11f7c79a.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.

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Welcome to the Bullnose Forum! Glad you joined. :nabble_anim_handshake:

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.

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Welcome to the Bullnose Forum! Glad you joined. :nabble_anim_handshake:

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.

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.

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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.

 

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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.

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. :nabble_anim_confused:

image269.jpg.fb05389c4f00fa05a5665880995a94de.jpg

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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. :nabble_anim_confused:

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😣

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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😣

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.

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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.

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.....

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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.....

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.

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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.

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.

 

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