[whitehorse123]

I have a 1992 Mustang GT I bought it a couple of weeks ago and is in Immaculate condition. The owner had it sitting up in a garage since 2002. Here's the problem. I am getting power to the injectors, spark, and jumpered the eec test to see if the fuel pump relay is working its clicking and has power to it. I ran into a problem though. I have no power going to or from the fuel inertia switch. The button is pushed in. I don't hear the fuel pump kicking in at all. When I went to look at the car, I siphoned the old rotten gas out of the tank and filled with new gas. It ran kinda rough though. After I got it home, It won't run. I shot it with ether and will run for a second or two. Getting good spark. Do you guys have any idea whats going on. I've read and followed through with the fuel pump diagnosis post. I just want to know for sure its the pump before I buy a new one. Thank you.

 

[5.0Mustang1989]

If you don't have power to or from the inertia switch, then you're not getting power to the pump, which means don't go replacing the pump. Check to see if you are getting power to the fuel pump side of the relay. If it clicks, you have power and ground to the control side, but not necessarily the pump side.
Get a wiring diagram and just work your way from the pump back upstream. Start at the pump, then the inertia switch, then relay, then fuse, until you find power. Then replace whatever component you're dropping voltage over.

 

[whitehorse123]

I was just looking at that, whats the other relay right next to the fuel pump relay?

 

[whitehorse123]

Okay, my fuel pressure relay is under my mass sensor, but theres an identical relay right next to it. Obviously its a different circuit, but whats it for?

 

[5.0Mustang1989]

your fuel pump relay should be under you drivers seat. You have your EEC relay and something else in the passenger fender.

 

[whitehorse123]

1992 was the first year ford moved it to the inner fender under the mass airflow meter. I thought it was under my seat, it was on older models. I don't have but one wire under my seat and its for the seatbelt. So I have an EEC relay and a Fuel Pump relay under the mass meter.

 

[5.0Mustang1989]

Lets focus on the fuel pump relay. Make sure you are getting power to the input on the Fuel Pump side of it. Then turn the key on to prime it and make sure you are getting power on the wire that goes back to the fuel pump. If you're getting power in but not out, it's either the relay, the computer, or the control circuit.

 

[5.0Mustang1989]

and that other relay is probably the EEC relay. (sends power to the computer)

 

[whitehorse123]

Not getting power to green/yellow. I removed the relay and checked connector where it plugs in, no power.

 

[5.0Mustang1989]

I'll pull up a wiring diagram in class tomorrow. Then I'll be able to be a lot more helpful. If that's the wire that provides power for the pump to the relay, then check the fuse it gets its power through.

 

[whitehorse123]

Wheres the ECM relay? I am sorry I am new to gas EFI I want to learn, but sometimes get confused

 

[5.0Mustang1989]

I'm not sure about where they are specifically, but there will be an EEC relay, a fuel pump relay, and a WOT cutout relay. On mine (1989) the WOT cutout and EEC relay are on the fender by the MAF.

 

[whitehorse123]

Heres whats got me confused. I had it running the day I had it towed to my house I siphoned out the offending fuel and replaced with new, fresh gas. I've replaced the coil, plugs, wires, thermoustat, cap and rotor, I've went through everything I could think of. I'm beginning to think my ECM is toast. I checked the wire going to my battery, no corrosion/ new battery and terminals. I guess I'm going to pull the ecm tomorrow and check the plug and capacitors.

 

[5.0Mustang1989]

Alright, I got a diagram.

Check all of the wires at your fuel pump relay. Should be a
Pink/Black wire that provides power on the pump side of the relay. This should have power all the time. If it does not, I would suspect Fusible Link D is the issue.

If this has power, check for power on Dark Green/yellow (with the relay connected) wire when you turn the key on to prime the pump. If this has power, the issue is between the relay and pump, or is the pump. If this does not get power, but the relay clicks, replace the relay. If this does not get power and the relay does not click, check the control curcuit for the relay.

The red wire I believe should always have power (maybe only with the key on). If it does not then your problem is between that pin on the relay, and wherever that wire gets power from.

If the red wire has power, check for a ground at the Lt Blue/Org wire when you turn the key on to prime the pump. If the computer never grounds this wire, then the problem is most likely the computer.

Easy way to check the control side is a test light. Put the test light on the red wire an Lt Blue/Org wire. When you turn the key on, it should light up. If it does, then your computer is not the problem.
If the control circuit is good but the relay does not click, replace the relay.

When you need check for power or ground on a complete circuit, never modify and wires. Get a T-pin or use a paper clip. Gently insert it into the connector right beside the wire.

 

[89coupe]

Most likely the fuse link or relay if the relay is clicking. At this point dont even worry about the inertia switch. All it does on this year vehicle is cut off power directly to the pump. You have to get power there first.

quick and easy. If the pink/black wire has power. Then just remove the relay and jump power directly to the dark green wire. pump should run. If it does. The relay is your problem if its clicking.

 

[whitehorse123]

When I jumper the Green/Yellow wire on the fuel pump relay using my test light, I hear it click. I'm going to jumper it again using a wire and check my fuel pump and inertia switch see if I'm getting power. Thank you.

 

[5.0Mustang1989]

what did you jump the green wire to? if you jump it to the pink and black wire with the relay disconnnected, the pump should run.

 

[whitehorse123]

Okay, heres what I did. I jumpered the green/yellow wire with a spare piece of wire I had lying around to ground. With the key on I went to the Inertia switch and got power on both wires, one going to it and one going out if it. I also get power to all wires on the fuel pump relay. Without the jumper going to the green/yellow wire jumpered I get no power to the inertia switch. I also get power to 3 wires on the relay minus the green/yellow wire. I switched the relays with the EEC plug because both relays are the same model# I still get the same result.

 

[89coupe]

The dark green yellow wire to a ground?????? That should do nothing at all. Unless some one has messed with the wiring to the relay. Dark green should go directly to the pump.

What color wires are on the inertia switch?

 

[whitehorse123]

Acording to the diagram Dark Green/Yellow goes to the Inertia Switch.