Installed mustang ecm/harness, but no power to fuel pump now

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Installed mustang ecm/harness, but no power to fuel pump now

July 02, 2006, 10:00:21 PM

I've looked for this issue at coolcats.net and haven't found the answer. I really wish I would have bought an '86 tbird 5.0, instead of an '85 because I think it would have been a HELL of alot easier to swap the HO into. With all these pesky little issues, an '86 would have been a weekend swap, while the '85 is now six months, and growing. Well, enough of my bitching and unto the issue: I installed the H.O. motor, along with the mustang ecm and computer, but i've got no power to the fuel pump. I have just realized that the green connector on the harness, right next to the ecm, has a real important purpose...according to some other websites, it powers up the pump. I saw no mention of this at coolcats and now I'm stuck with a car ready to drive, except no power at the fuel pump. Any ideas on how to address this. Thanks again for all your input in advance.

Installed mustang ecm/harness, but no power to fuel pump now

Reply #1 – July 03, 2006, 01:15:59 PM

this should clear up all your questions........pages 57-60,,, of course your computer will be expecting the harness to match as well but the wiring you have will be 90% on the money.

Installed mustang ecm/harness, but no power to fuel pump now

Reply #2 – July 03, 2006, 01:20:24 PM

and this one

Installed mustang ecm/harness, but no power to fuel pump now

Reply #3 – July 06, 2006, 01:38:40 PM

I made the same mistake when i swapped the HO into my 85 bird. I don't know what car you got the wiring harness from. I used an 87 cougar so I took the fuel pump connector from the cougar and cut my old one off going back to the pump and soldered on the connector from the cougar and then plugged it in. If you used the mustang harness go to a salvage yard and snag the other half of the connector from a mustang. I was having a lot of trouble with the wiring at first as well. I spent a lot of time starring at the stupid thing and tracking down wires before I got the idea of hacking all wires at the firewall and putting in the whole cougar harness. That was easier for me to do since 90% of the colors either matched or were very similar at the firewall. That did force me to cut and solder the headlamp connectors though. I got a lot of help from people on this board but I think just about everyone that has done it did it a little different. The evtm pages jcassity is showing you are extremely helpful. I had a evtm for the donor car 87 cougar and one for my 85 t-bird so I could compare wire colors.

Installed mustang ecm/harness, but no power to fuel pump now

Reply #4 – July 10, 2006, 11:25:48 PM

Thanks fellas. I've been starring at those pages that Jcassity posted and I'm not sure where I am...I also went back to my local salvage yard and picked up the other half of the mustang connector (as suggested by Jasontbird), and I also picked up from a Tbird what I believe to be the fuel pump power wires/connector. As you can see in the picture, I''ve got a yellow, red, and tan-lightgreen spots inside of my Tbird, and now I've got to connect one or some of them TO one or some of the many wires on the mustang connector. THE TRICK IS FIGURING OUT WHICH ONE GOES WITH WHICH!!!:o

By looking at the gauges of the wire, the yellow (Tbird) is the thickest; on the mustang connector, the only wires that could correspond is the gray/yellow and pink/black---although the gray/yellow is a bit thicker than the pink/black.

Any ideas???

Installed mustang ecm/harness, but no power to fuel pump now

Reply #5 – July 11, 2006, 12:45:04 AM

ok,, so you do have a mustang harness,, get the EEC wiring diagram from that year and compare my pages to your mustange schematics.

They will be close from what ive heard. Matter of fact, my factory shop manuals lay out Marks/mustangs/Cougs/Continental as the same so keep that in mind. The harness for each are very similar.

I dont have mustang connections.

from the pic it looks like you would need to extract and relocate the two outer wires on the three pin harness.

What is the third harness for?

there wouldnt happen to be a connector number on the three wire harness? (ie- C123 ect ect)

Installed mustang ecm/harness, but no power to fuel pump now

Reply #6 – July 11, 2006, 02:18:24 AM

I'm sorry that my picture confused more than helped the issue...the two upper pieces go together--I hadn't noticed that in the picture I layed them down wrong, but they do snap together correctly. However, that piece is what I cut from a Tbird at the salvage yard...one side of that is what is left in my car--I just don't remember which side:screwy: The lower (bigger) connector is the mustang piece that matches up with mustang harness now attached to my engine and to the ECM. So, I've got to JOIN the lower mustang connector with one of the upper Tbird pieces. My problem is I don't know which wire to join with which.

I hope that helps.

Installed mustang ecm/harness, but no power to fuel pump now

Reply #7 – July 11, 2006, 10:06:55 AM

what area in the mustang JY vehicle did you get the lower connector?

Installed mustang ecm/harness, but no power to fuel pump now

Reply #8 – July 11, 2006, 11:25:01 AM

I have an 86 5.0 tbird harness in my garage. It has the same connector for the fuel pump as that. Don't know what they might be like at the firewall though.