Electrical problems with 86
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
Electrical problems with 86
I'm having some trouble with my 86. I got it used not running, so I'm starting with no background info.
Apparent Problems
Crank no start,
the dash seems to be dead as well.
What I've found
-EEC and Fuel Pump relays are tripping, but fuel pumps aren't running.
-Inertia switch has been bypassed
-fuses seem to be good, but I haven't found a good fuse box diagram.
-fuel tank appears to be new
Any input is appreciated. Getting the fuel pumps going is main objective
Apparent Problems
Crank no start,
the dash seems to be dead as well.
What I've found
-EEC and Fuel Pump relays are tripping, but fuel pumps aren't running.
-Inertia switch has been bypassed
-fuses seem to be good, but I haven't found a good fuse box diagram.
-fuel tank appears to be new
Any input is appreciated. Getting the fuel pumps going is main objective
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Lead Driver
Joined: Jul 2011
Posts: 8,678
Likes: 191
From: On the Edge of the Desert
Found an alarm system. Way too many wires....
I'll work on taking it out. They always cause more problems than they solve in my experience. And I don't want it anyway
I'll work on taking it out. They always cause more problems than they solve in my experience. And I don't want it anyway
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
That would be a start LOL
Do you know if it is a fuel issue or spark issue?
Pour a little gas down carb or spray starting fluid and see if it will light off and run a little.
This will tell you how to go but you may know as the pumps may not be running.
Dave ----
Do you know if it is a fuel issue or spark issue?
Pour a little gas down carb or spray starting fluid and see if it will light off and run a little.
This will tell you how to go but you may know as the pumps may not be running.
Dave ----
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Lead Driver
Joined: Jul 2011
Posts: 8,678
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From: On the Edge of the Desert
Yes it's a EFI 302.
I found this plug under the dash, right by the ECM.
Wires are Red. Tan/ green stripe. Black/ green stripe.
I can't find it on my chilton book wiring diagram.
Red is hot with key
I think tan/green goes out to the FPR under the hood, and I think black/green is ground.
Does a 3 pin relay go there?
There's not a plug for it under the dash that I can see.
I found this plug under the dash, right by the ECM.
Wires are Red. Tan/ green stripe. Black/ green stripe.
I can't find it on my chilton book wiring diagram.
Red is hot with key
I think tan/green goes out to the FPR under the hood, and I think black/green is ground.
Does a 3 pin relay go there?
There's not a plug for it under the dash that I can see.
Lead Driver
Joined: Jun 2013
Posts: 5,641
Likes: 1,152
From: Tolland, CT
1986 EVTM - Gary's Garagemahal (the Bullnose bible)
That may help too. You can find different years on that site.
That may help too. You can find different years on that site.
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
I unplugged the ECM and cleaned the plug. Plugged it back in tightly. Now I had power TO the fuel pump relay but not coming out of it. (What is the tan/green wire that goes from the relay to the ECM? It's not marked in my book)
The relay and connector were questionable at best, So I wired in a new relay and plug.
Now my fuel pumps are running. And I have a major fuel leak underneath
The relay and connector were questionable at best, So I wired in a new relay and plug.
Now my fuel pumps are running. And I have a major fuel leak underneath
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
Originally Posted by Franklin2
Here is your fuel pump relay. You can see the red, tan/lightgreen and the other wiring. The ECM grounds the tan/lightgreen to turn the relay on.
So this is what I did to wire up the new relay.
Yellow is power in
Pink/black is power out to the pump.
Red is trip power from the ECM/switch.
I grounded the relay to the fender, since I wasn't sure what the tan/green wire did, and didn't want to risk damaging the ECM.
So, I can ground the relay to the tan/green and it will work properly?
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Joined: Jan 2001
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From: Virginia
If you look in the diagram above, there is a fusible link that feeds the yellow wire. Fusible link "S". I would not fuse it and have nuisance fuse blowing leaving you stranded.
The red wire is powered from the ECM power which turns on and off with the keyswitch. So the relay coil has power anytime the key is on. Yes, the tan/lightgreen is the ground for the relay coil. When the ECM grounds the tan/green wire, it turns the relay on and the relay then sends power to the pump. It's the ECM which powers the pumps for a few seconds when you first turn the key. The ECM will also turn the pumps off if the ECM does not see any signals from the distributor. When this happens it assumes the engine has stopped and it turns the pumps off.
The red wire is powered from the ECM power which turns on and off with the keyswitch. So the relay coil has power anytime the key is on. Yes, the tan/lightgreen is the ground for the relay coil. When the ECM grounds the tan/green wire, it turns the relay on and the relay then sends power to the pump. It's the ECM which powers the pumps for a few seconds when you first turn the key. The ECM will also turn the pumps off if the ECM does not see any signals from the distributor. When this happens it assumes the engine has stopped and it turns the pumps off.
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
Ok, thank you for explaining that. Makes perfect sense but this is my first time really getting into a bullnose so their systems are new to me.
I'll ground the relay back to the ECM so that everything is doing what it should when it should.
I'll ground the relay back to the ECM so that everything is doing what it should when it should.
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olred85
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Apr 25, 2012 08:22 PM