Fuel Pump wiring issue? - help - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 11 Old 03-03-2011, 03:51 PM Thread Starter
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Fuel Pump wiring issue? - help

OK, so I have an 86 LX, I have put ALL wiring from an 86 5.0 SEFI into it (mine was a 2.3). I am trying to make sure my fuel system works before I bolt the tank up. I currently don't have an inertia switch, as the 86 2.3 cars didn't have them, and I have those two wires jumpered together FOR NOW, I will get a switch. I put power directly to the fuel pump and it kicks on, so that is good (new pump, it better be). When I turn the key ON, I hear the ECU relay clicking, but can't really hear the FP relay, but when I turn the key off, I hear the FP relay click. Maybe it works that way? Anyways, the fuel pump WON'T kick on to prime or anything. Dunno if the FP relay is getting proper voltages, or what else my problem could be. I have tried two fuel tank wiring harnesses also. At the FP relay wiring under the seat, with the key off, I am getting :

Yellow - 12v
1st Pink / Black - nothing
2nd Pink / Black - .3v
Green / Yellow - nothing

With the key in RUN :

Yellow - 12v
1st Pink / Black - nothing
2nd Pink / Black - 12v
Green / Yellow - .3v

So the 2nd Pink/Black and the Green/Yellow change with the key.. Any of this look right or have any ideas? Would like to get this 418 fired up.


Thanks


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post #2 of 11 Old 03-03-2011, 04:24 PM
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Going by this, I don't know what wires you have. I would assume the yellow is still the 12v in which is good, and one of those pnk/blk wires is your output to the pump.

Can you pull the relay out and post what pin numbers go to what wire colors on the harness? They should be labeled right on the relay itself where the male connectors stick out of it. 85 and 86 are going to be your triggers, so one will come from the inertia switch and should be hot with the key on (or constant 12v, not sure which), and the other should be coming from the EEC and will be a negative trigger. Pin 30 will be your output to the pump and 87 should be your yellow input.

Edit: going back and looking, the wire coming from the inertia switch should be hot with key on.


Last edited by fogged306; 03-03-2011 at 04:27 PM.
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post #3 of 11 Old 03-03-2011, 04:30 PM
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If I were to guess, I would say that green yellow would be coming from the EEC and be your negative trigger. Check that wire and see if it goes to ground when you turn the key on and the pump should be priming.

If it does, I'll bet the wire for the inertia switch doesn't have the 12v with the ign on that it's supposed to.
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post #4 of 11 Old 03-03-2011, 04:59 PM Thread Starter
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Thanks for the effort. My relay isn't labeled in the 80s, it's labeled 1-5.. (or is it 10-50)

Color | Ign. Off | Ign. On (Relay out) | Ign. On (Relay in) Relay Post #

Yellow | 12v | 12v | 12v | 4
Tan / Green | 0v | 0.3v | 5.5v | 1
Red (pk)/ Blk |0v | 0.3v | 12v | 2
Pink / Blk | 0v | 0v | 0v | 3

One I had listed as Pink/Black might actually be red, hard to tell. But the one that is MORE pink, is always 0v, position #3 on the relay. Ideas?

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post #5 of 11 Old 03-03-2011, 05:49 PM
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Do you have a test light or just a multi meter?
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post #6 of 11 Old 03-03-2011, 06:25 PM Thread Starter
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Using a multimeter now. Might have a light out in the tool box, if not I can run get one, ideas?

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post #7 of 11 Old 03-03-2011, 06:36 PM
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Either put the red lead of your multi-meter on a 12v source and use the ground lead to test the pnk/blk to see if it's the input from the EEC, or use a test light the same way to check.

Those readings you have tells me something isn't right, but I can't tell which is the trigger wires are which are the input/output wires. I was assuming the yellow was the input wire, but maybe it's not the way you were getting 12v on the red wire with the relay in and ign on. A relay will backfeed through the trigger wires if it has 12v on one side but no ground on the other, it will feed 12v through the coil and over to the other trigger wire. You having 12v on the red wire when the relay plugged in but not there when it isn't tells me that either the relay is working, properly and the red wire is the output, or that it isn't and it's one of the feed wires that should have either a ground or a 12v signal on it.. if the relay doesn't click when it is plugged in then it's not working. Have you tried a different relay just to eliminate the possibility of a bad relay?
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post #8 of 11 Old 03-03-2011, 09:49 PM Thread Starter
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Well.. You got it.. I know parts store parts are junk alot of times, but a brand new relay was junk apparently. I had two new ones, one for the FP and one for the A/C WOT. I pulled the A/C and put it where the FP one was, and it tried to prime up. Thanks a bunch, now I can strap this tank up. Do you know if I NEED the A/C WOT cut out relay, if I'm not running A/C? I had converted a 3.8 CFI car over to 5.0 SEFI once before, and it seems it wouldn't start without it.. Could be wrong.. Thanks again.

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post #9 of 11 Old 03-03-2011, 11:56 PM
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Sweet, glad it was something easy. You shouldn't need the A/C relay if you're not going to use the A/C. I can't say for sure on an 86 because I've never worked on a 4 eye, but on my 89, I've eliminated the A/C wiring right down to the EEC and haven't had an issue.
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post #10 of 11 Old 03-04-2011, 03:04 PM Thread Starter
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Still have a few issues. I swapped out both switches on the column, the wipers come on when I turn either turn signal on. Otherwise they work fine, except no delay wipers work, low and high do work.. Ideas?

ALSO, back to my original issue, I got all the fuel system hooked up, fuel in the tank, turned the key on, and the pump comes on and primes the line to 40 psi at the regulator, but it DOESN'T go off.. Fuel pump stays on... Ideas on that?


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post #11 of 11 Old 03-05-2011, 02:54 AM Thread Starter
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Any point me in the right direction?

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