90nSSMD

Hey Guys/Gals,

I recently acquired a 1990 GT, and it's been great. I recently came across a pretty mind numbing issue.

As I drove the car home the other night, I completely lost power. It drove fine for a good 15 miles, and then all of a sudden.. complete cut off.

I pulled to the side of the road, and kept trying to turn her over, but nothing. Originally I thought it was the Alternator or something else, but I also noticed the fuel pump was NOT engaging each attempt to re-fire. Stumped, I called for a flatbed, and got towed home (I wasn't very far, just didn't feel comfortable on the highway stranded).

The moment I got home, I turned the key to the on position (right after I got it off the bed), and the pump turned over, and the car started right up without issues. Put it in my driveway, and went to the research.

I've seen Distributor, MAF, IAC, etc as the culprit, however I have another one for top contender. One of the previous owners installed a bypass of the Fuel Pump Relay switch, and the harness which is located in the trunk, is shorting. I'm absolutely horrible with anything electrical, so this is not a job I feel that I can do myself. Not to mention the area it was put around.

How much do you think this would cost to get fixed, and how/where can I find the parts needed for a setup like this?

Location: Trunk (Underneath frame, but cut up to allow in-frame positioning/grounds


Pics below: (They are a bit too big for me to load into post, sorry)

http://imageshack.us/photo/my-images/834/imag0474a.jpg/
http://imageshack.us/photo/my-images/23/imag0475o.jpg/
http://imageshack.us/photo/my-images/268/imag0476z.jpg/
http://imageshack.us/photo/my-images/688/imag0479f.jpg/
http://imageshack.us/photo/my-images/203/imag0480e.jpg/
http://imageshack.us/photo/my-images/35/imag0477x.jpg/

mattdel

Good lord that's retarded. Do Darwin a favor and shoot the previous owner. The phrase "playing with fire" becomes literal here.

That's gonna need to be all redone, for safety reasons alone, but also to ensure proper functionality. You seem rather coherent so I could walk you through the process of rewiring it, step by step. Otherwise any shop should be able to redo it all. Probably take a few hours.

90nSSMD

The person I bought the car from did not do the mod. He was a great guy, and knew his stuff. The owner previous to him did it, and the guy I bought it from literally only put 229 miles on the car itself.

I'd love to hear/see a step-by-step process, so I can get an idea what I would be getting myself into if I were to tackle the task myself. I could possibly ask a few friends to help, but I'm not sure how far some of them would be able to carry, considering only a select few of them have any mechanical knowledge, let alone performance mechanical knowledge.

If I feel the process would be too daunting, or even too risky for myself, I'll talk to a few local shops and see what I can come up with. I'm assuming a few hours of labor to re-wire would run me with a bill around the $500 range? (parts + labor cost). If that's the case, then the car is going to sit for at least a month while I put together some money.

I'm all ears for a guideline on what to do to fix this, however. If I don't understand something right away please forgive me, this is my first Mustang, and I'm just your average DIY guy.

dawson1112

I think I would start by first dropping the tank out of the car completly and getting it away from the car. Then pull the whole harness out of the trunk to get it out of the way. Next I would repair that retarded flap that someone cut out of the trunk (for what ever reason) by welding it back in place and then grinding it smooth . That round plastic plug is there to keep the wires from rubbing on bare metal where the harness goes into the trunk.

mattdel

Alright this is how you want your FP and relay wired up proper like:

Inside the relay next to the terminals, they should be labeled 1-2-3-4-5.

Pin 1 should be a Tan/light green wire, follow it out and it should splice out in 2 directions, one to Pin 22 of the computer, and one to the self test connector under the hood.

Pin 2 should be a Red/black wire, this leads to one end of the inertia switch in the trunk. The other end of the inertia switch should be a single Red wire, this splices out eventually as the main power source for most engine sensors. It should originate from Pin 57 of the computer.

Pin 3 should be a permanently hot(12v) Orange/light blue wire. This one leads out to the starter solenoid on the fender, and has a fuseable link somewhere near there.

Pin 4 should be a Pink/Black wire, that almost immediately splices out to Pin 19 of the computer and to the fuel pump.

Pin 5 should be empty.

What you wanna do is remove all the wire looming and trace them. Get rid of anything else seemingly spliced in ***** nilly.

90nSSMD

Great info thanks! A friend came by this morning and looked at everything with me. He knows someone who can do the entire fix under the table for 50-100.

Do you think I will just need a new fuel tank wiring harness for the fix? Also are there any specialty tools that I need to loan out from a local parts store?

We plan to do the job in my driveway on Saturday, I just wanna get everything together that I'll need before then so the job doesn't take all day.

90nSSMD

Update:

Re-wired everything Friday. My god.. the person who did all of this was an idiot. No soldering done on any of the cabling, and the ground wire from the wiring harness connector was used with SPEAKER WIRE. LOL.

We took a new harness, cut off the red connector, and used black ground wire from the old harness as our ground to the chassis. The fuel tank sending connector + sending unit were fine when we checked them.

So we got past the veggies (yeah.. that stuff was just the appetizer). Let's move on to the roast beef and mashed potatoes..

Fuel pump and fuel pump assembly... Holy... We dropped the tank, and pulled the assembly and pump out. The guy put in a Walbro 255, so it seemed like he looked online to do the hotwire mod to bypass the relay. There was NO STRAINER, the pump had electrical tape holding it to the assembly, the assembly was bent and twisted up (which explains the electrical tape really), and the assembly wiring/grounds were absolutely shot. Let's not forget his half assed attempt at the hotwire mod. This damn thing shoulda never been dropped into the tank like this. Who the hell does this? No wonder the damn thing wasn't kicking on.

Bought a new assembly and fuel pump (just an Airtex 50gph pump -- couldn't afford anything better for the time being, and I'm not really running any serious power to warrant a bigger pump), cleaned the female ends of the wiring harness connector, threw her on, voltage read a clean 11.7-12v, replaced some fuses, and she fired up the first turn-over with zero issues or hiccups.

She had a mild surge on the start, but after she got to normal operating temp we reset the idle to 850, started her up, and she's been singing like Aretha Franklin since.

Thank you again Mattdel and Dawson, I was going to revert back to the OEM Relay setup, but figured when I looked more in-depth into this, it didn't seem like a bad setup.. It was just done very very half assed. If you're gonna do something, do it right the first time. Unfortunately I didn't take pictures during the job, as we were trying to beat a storm that swept through, and we were semi-covered in gas . If you guys are interested in what it looks like now, just let me know and I'll try to get some quality shots of the wiring.


Edit -- We opted to not go to a mechanic and did it ourselves. Couldn't trust the guy who was gonna do the job under the table, seemed shady. The old saying goes.. "you get what you pay for." Pretty great feeling to do something like this for the first time with lots of research put in, to have it come out really good.

mattdel

Excellent