Off the road.... again! Fuel pump issue

[86 t-tops]

Looks to be a blown fusible link on what looks to be a black wire with a yellow stripe... they tried another fusible link and it started to smoke... looks to be a short somewhere in the harness... I'm pretty sure that it's this black/yellow stripe wire that turns the EEC on...

The brown fusible link that leads to the yellow wire is fine.

Just talked to Mustang Specialteaz and they also stated that it's a one year harness as well... but don't have one in stock, will keep an eye out for one.

I don't have an extra TFI...

[toofast306]

Pretty sure I fried that same wire when it grounded to the chassis! I kept part of it because the fusible link remained intact while the rest of it went up in a cloud of smoke! But I thought my Bk/Y wire was for the alt... different year, different engine, YMMV.

[86 t-tops]

So I have the main wiring harness disconnected inside the engine bay. On the inside I have the computer harness disconnected and one brown plug just above the computer disconnected as well... however, there is a small group of wires the looks to run across the interior dash back over to somewhere on the drivers side. I'm assuming this group of wires runs to the fuel relay under the driver's seat.

Anyone have any tricks to disconnecting and fishing this wire out without removing my dash, driver's seat, and carpet? I would like to avoid cutting any wires....


If not I'm very tempted to cut these wires and then splice them back to together with a replacement harness or my harness if I can repair it.
Thanks

[Slope]

Pretty sure the initial prime is a function of the TFI

Initial prime is a function of the ECM.

Subsequent pump activity is triggered via the PIP.

[86 t-tops]

So my journy continues... I know very little about electrical (can install a car stereo but that's about it) but I've looked at several electrical diagrams for 86 mustangs and the wire I'm dealing with is 100% the EEC power on lead from the starter solenoid (Black with an Orange stripe).

I had replaced a section of this wire last summer as it had become brittle and broke... thus not telling the computer to turn on. In hindsight it may have been a fusible link that I replaced with just a regular wire. The burnt wire that Joe, from DaSilva, found was the wire I had added last summer. I'm surprized it lasted this long...

To try and find the fault/short I unpluged and unraveled the main wiring harness back to the firewall in the engine bay. I pulled the black and orange wire from all others and found no damage or burn marks... my hope for an easy fix is now gone.

My understanding is that this wire goes to pin #1 on the EEC. However, I was wondering if it first gose to EEC relay located next to the EEC behind the passanger side kickpanel and then to the EEC. When starting the car the key is turned and the ignition switch tells the EEC rely to close and power is then fed to the EEC from the black and orange wire from the solenoid... or am I way off the mark?

The reason I'm asking is that I think Joe noted some smoke coming from the dash when they tried another fusible link on the black and orange wire that attaches to the starter solenoid (sent an email to Joe to confirm). Could this be from a another fusible link blowing that runs from the ignition switch to the EEC rely? I swear I saw such a wire when looking at the 86 wiring diagrams.

[Slope]

The Black/Orange feeds the Keep Alive memory of the ECM, the ECM relay and the Fuel Pump relay.

[Tailites]

slope could re wire the space shuttle...seen it wit me own 2 peeperz

[86 t-tops]

Ok... that helps and make sense based on what I did tonight...

1. connected a fuse holder to the black and orange wire and hooked it back up to the starter solenoid (this was the burnt wire Joe found while the car was at DaSilva racing). I figured if it is bad the fuse will blow... it didn't (15 amp fuse used).

2. Unplugged the EEC Relay and checked if I'm getting 12 volts at the plug from the black and orange wire, I am.

3. Unplugged the main computer harness, left the EEC Relay unplugged, and checked if I was getting 12 volts at pin 1, I am. This makes sense as I believe this is the Keep Alive power to the EEC feed. So the keep alive power looks to be good at the EEC harness.

4. Checked the Red/Light Green wire at the EEC relay plug for 12 volts when the keys are in start position, I am. This means that the ignition feed to the EEC relay is being provided power.

5. Plugged the EEC relay in and checked if I'm getting any power at pin 37 on the main computer harness, fed by a red wire from the EEC relay plug, as this should occur when the key is in the start position based on the wiring diagrams I've reviewed. Nothing! No power at this pin... this red wire also splits off and feeds the inertia switch, then the fuel pump.

So... based on this I would say that my EEC relay has gone bad as it's not closing the circuit to power the fuel pump... thoughts? Comments? This is just based on me testing voltage at the key points based on the wiring diagrams...

Not sure why the EEC relay would go bad or how this caused the fusible link (and my repair wire) to burn up at the point were the black and orange wire connect to the starter solenoid.

I think my next move is to order a new EEC relay... I'm assuming you can as I've never looked for this part...

[toofast306]

Based on this schematic, I'd say you're right on the money.
https://www.google.ca/search?q=86+mu...l%3B1213%3B973
Can you bench test the EEC relay to be sure?
Also note that ignition switches were/are problematic.

[86 t-tops]

Picked up another EEC power relay today... pluged it in and turned the key... inline fuse I installed on the black/orange wire coming from the starter solenoid blew. Installed my old EEC power relay, replaced the blown fuse, and turned the key... fuse did not blow. I believe this is telling me that the replacement EEC power relay works while my old one doesn't... and that I continue to have a short to find... only triggered when the EEC power relay switches over...