Electrical 93 LX Fuel Pump Issues w Relay & Fuse Link

Mustang5L5

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Mod Dude
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1. The wires coming into the pigtail (see pic 32) should be the same color on both sides of it -- or did Ford change wire colors coming in/out of a pigtail/connector?


Yes. I know of a few examples of where Ford changed wire colors on each side of the connector.

The EVTMs are great at showing this in the diagrams. Give me a few mins and I’ll see if I can find that wire and tell you of it should match or not.

That’s the grey 12-pin right?
 
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Mustang5L5

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Mod Dude
Feb 18, 2001
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I have my hands on a year 93 EVTM. In the EVTM...
-- where does the EVTM tell the pin size (or # of pins) of e.g., connector C103 (the fuel pump relay).
-- what is the reference e.g., 151- 5- B10 used for (there is a 151- reference beside each part in the EVTM diagrams)? Does it identify the wires going into or out of a certain connector?

Go to the back of the book. It lists all the connectors, grounds splices, etc towards the rear. If you look up C103, it will show you the color, the relative location on the vehicle and any applicable page nunbers.

The reference 151-5-etc is a page number. Turn to page 151-5 and look at diagram b10 fpr example.
 
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Mustang5L5

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Mod Dude
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Edit: disregard. You mean the blue/orange wire in the black 12-pin. The below is the wrong connector but I’ll leave it for now



So page 24-2 has one of your wires in that connector

C207 is the gray 12-pin.

Dark Green/Yellow (wire 238) feeds the inertia switch


Do you see this and is there a wire on both sides?


Page 90-1 has two more wires to the taillights. Light green/orange and orange/light blue


Basically I’m just skimming through some of the diagrams looking for C207.

I also have the 1991 EVTM so I can compare to that as well. If you can get your hands on one it would make things easier for you as well.
 
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Mustang5L5

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Mod Dude
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I loooed at that same connector on my ‘88 and every wire has a matching wire on the opposite side. However I do know all the wire colors did change from my head to 91/93.

I’ll have to check the wiring diagrams later when I have time to sit down and study, but it does appear the gray 12-pin does have the wiring to the fuel pump going through it. You might want to confirm that wire is there
 

Mustang5L5

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Mod Dude
Feb 18, 2001
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Is your fuel pump relay integrated into the harness like this?

If so, can you trace that up to the drivers kick panel? Does that plug into the gray or black connector?


Can you unplug the relay and the 12-pin connector and confirm your wire colors by testing continuity to the relay socket to the harness here? I’m assuming they all go to the same.

Unfortunately I can’t dig through my evtms right now.


572EB676-E978-4A9D-96E1-941AFC15CF8A.png
 

diesel farmer

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I loooed at that same connector on my ‘88 and every wire has a matching wire on the opposite side. However I do know all the wire colors did change from my head to 91/93.

I’ll have to check the wiring diagrams later when I have time to sit down and study, but it does appear the gray 12-pin does have the wiring to the fuel pump going through it. You might want to confirm that wire is there
The grey 207 connector does have the dark green-yellow wire to the fuel pump relay. The dark-green yellow wire on the engine side of the connector is a different shade of green.

The black connector (probably C203) has the blue-orange wire (see pic 24) that goes to the fuel pump relay -- but the engine side of the connector (as seen in pic 25) doesn't have a wire in that slot -- I suspect this is one of the main wiring issues.
 

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diesel farmer

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Is your fuel pump relay integrated into the harness like this?

If so, can you trace that up to the drivers kick panel? Does that plug into the gray or black connector?


Can you unplug the relay and the 12-pin connector and confirm your wire colors by testing continuity to the relay socket to the harness here? I’m assuming they all go to the same.

Unfortunately I can’t dig through my evtms right now.


572EB676-E978-4A9D-96E1-941AFC15CF8A.png

Yes my fuel pump relay appears to be integrated very similar to this picture. I will pull the wiring apart tomorrow and trace it to the connectors and report back - thanks!
 

Mustang5L5

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Mod Dude
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So I had some free time. I dig out my 1991 EVTM.

C203 is the black 12-pin.

For fuel pump wiring, you have a red wire, and a light blue/orange wire. They match up color for color with a wire on each side.

The main power feed for the pump also passes through C203 on the pink/black wire. Should be matching wire on both sides

This is for 1991. Compare it to 24-2 in the 1993 EVTM and you’ll see that the feed to the pump through C207 (Gray 12-pin) is a little different too.
26DCA73A-B03B-4052-A437-49B628B318CE.jpeg


Check c207 gray 12-pin for the dark green/yellow wire and see if there is a wire on both sides
 

Mustang5L5

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Mod Dude
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The grey 207 connector does have the dark green-yellow wire to the fuel pump relay. The dark-green yellow wire on the engine side of the connector is a different shade of green.

The black connector (probably C203) has the blue-orange wire (see pic 24) that goes to the fuel pump relay -- but the engine side of the connector (as seen in pic 25) doesn't have a wire in that slot -- I suspect this is one of the main wiring issues.


Ok. Starting to make sense.

It looks like since your dash harness is from a 1993, you are missing the two wires that feed the fuel pump relay in the 91&older cars.

The blue/orange wire and red power wire in the dash harness is supposed to run across the dash over to pin 22 on the ECU in the 91&earlier cars.

Im suspecting that the body harness that runs rearward from the kick panel is also from an earlier car. It was swapped in but since the dash harness is from a 1993 it is missing the blue/orange wire and red that should be there.

You need to get a wire from that orphan blue/orange eother over to pin 22 on the ECU connector, or to wherever the orphan wire from the 91 engine harness is. I think I know where that might be.
 
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Mustang5L5

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Mod Dude
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Ok. I would check here.

AFBE555F-14BA-428B-BF2D-E38F5D5D544A.jpeg

C216 on the 1991 EVTM. This is where the engine harness connects to the dash harness. Gray 8-pin round connector.

This is also on the 1993 harness, but I am betting the ECU side of this plug has an orphan blue/orange wire on it with nothing on the dash side.

If you look back at the diagram in post #108, the red power feed for the relay also passes through c216 and c203. It also might be missing the wire across the dash.

If they are missing, I would bet running a wire (or two) from c216, across the dash over to C203 and connecting the two blue/orange wires (and maybe red) might get your pump relay working.

Does that make sense to you?
 
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diesel farmer

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Ok. I would check here.

AFBE555F-14BA-428B-BF2D-E38F5D5D544A.jpeg

C216 on the 1991 EVTM. This is where the engine harness connects to the dash harness. Gray 8-pin round connector.

This is also on the 1993 harness, but I am betting the ECU side of this plug has an orphan blue/orange wire on it with nothing on the dash side.

If you look back at the diagram in post #108, the red power feed for the relay also passes through c216 and c203. It also might be missing the wire across the dash.

If they are missing, I would bet running a wire (or two) from c216, across the dash over to C203 and connecting the two blue/orange wires (and maybe red) might get your pump relay working.

Does that make sense to you?
Yes that makes good sense. I will check it tomorrow AM.
 

diesel farmer

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Yes, we have found the problem! See the pics (33 and 34). The 6 pin connector with 6 wires going to the engine and it is a different color and has some black speckles on it so we know it isn't likely original to the car. The car interior or computer side of the connector (in pic 34) has 6 pins (and 6 wires) w/ the blue-orange wire and red wire that are needed for the fuel pump relay. The connector on the engine side only has 4 wires with no wires that match up to the blue-orange wire or red wire on the car side. Looks like I have these options to wire it in:

1. Get a different connector for the engine side that has at least 6 pins and wire up a blue-orange and red wires to it and run it separate from the harness under the dash to the left kick panel side.
2. Cut the blue-orange and red wires from the connector on the car side and splice separate wires to them and run them to the left kick panel.
3. Get the proper year 93 engine harness. This would be the most time consuming.

I am guessing that the red wire is (or should be) running to pin 57 on the ECU and then to the fuel pump relay, correct?

I like option #2 the best.
 

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Mustang5L5

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Mod Dude
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You can add pins to those connectors. You just need a donor harness to steal the pins and short wires from. If you dig around you might be able to find the terminals new as well, but having just tried this myself it’s time consuming.

I like option 2. I’m assuming the red wire is the power first for the pump that goes to pin 57.

You should have 12v on key on on that wire.

Looks like you have two wires to run and then you’ll have power to the relay. After you run the blue/orange, you should have continuity to the fuel pump test wire on the eec test connector and be able to run the pump in test mode.


From what I can gather, your engine harness is 1991, the dash and doors are 1993, but the harness that has the fuel pump is from an earlier car. 90 or 91.
 

diesel farmer

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Do you see in the 91 engine harness diagram if the pink-black wire goes to a fuse link? It does on the 93 diagram. I am missing that wire too in the connector. I think I will hook it to a hot fuse on the fuse panel.
 

Mustang5L5

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Mod Dude
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Fuse link D off the big yellow wire on the 1991 engine harness. Brown one

Supposed to run directly down to C203. This is 1991 EVTM
4A072C73-6404-4243-8843-B9631E07396C.jpeg
 

diesel farmer

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I ran new wires from the harness by the ECU to the left kick panel and now the fuel pump runs at start up like it should! Finally we have figured it out. :)

I am still tracking down wires. I pulled the center console and whatever knuckle-head installed new carpet left the mirror switch and cigarette lighter unhooked. Do you know what this bulb is for? It comes out of the harness that has the fuel pump relay wiring.
 

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diesel farmer

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The mirror switch was defective. I was able to wire in a mirror switch from an 86 T-Bird that I had in the box. The connectors don't match, but the wires match up perfectly. The green connector in the pic is from the T-Bird. It's surprising that Ford used the same wiring on these cars for the mirrors.
 

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