Fuel pump wiring - FFCars.com : Factory Five Racing Discussion Forum
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post #1 of 14 (permalink) Old 07-04-2019, 02:08 PM Thread Starter
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Fuel pump wiring

Ok installing new AAW harrness. It does not have fuel pump circuit in it. I have the ECU relay working but need to get the fuel pump relay to work. Dose the ECU ground the relay? Can I remove the inneracia switch? The wires for it where removed before I got the new harrness I am not sure were to run the red wire to I see it should be to the tan lt.green wire but I am not sure I have the correct one. Becuace when I try wiring it in the pump still doesn't run.
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post #2 of 14 (permalink) Old 07-04-2019, 04:11 PM
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Usually, Ford grounds the fuel pump through their ECU. It picks up continued run (after statup) by seeing the RPM signal.

I like the inertia switch, but I don't run pump power through it to the pump. I like to interrupt the signal to it, whether ground or hot, so it controls the relay itself. This way, you run a complete relay powered wire directly to the pump. You can wire the inertia switch anyway you want because it's just a on/off switch.

Using the Ford ECU the pump should run for about 5-10 secs once the key is turned on then shut off until RPM signal is found. My Holley ECU does the same thing.


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post #3 of 14 (permalink) Old 07-04-2019, 09:06 PM Thread Starter
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Thanks for the information I believe that is the way I have it set up. My issue is that I am not getting the ground through the ECU. I am trying to find out where and or what wire to tap into.

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post #4 of 14 (permalink) Old 07-06-2019, 11:36 PM
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Fuel pump wiring

Not knowing what engine configuration you are running makes this answer questionable at best.

For early engines (SBF's) the EEC does not ground the pump but rather the pump relay - pump draws too much current to have the EEC ground it, but the relay only draws about 200 Ma.

EEC triggers (grounds) the relay to latch for approx. 2-3 seconds during initial "key to on" function. This is to pressurize the fuel rails only.
Once the engine is [actually] running the PIP / TFI module send triggers to the EEC to constantly re-trigger the relay - keeping the pump running.

The inertia switch is an in-line (series) on-off switch used to cut power to the pump, wired into the power feed line, it will not drop out the relay.

Clear as mud, right??

I can't speak for the later engines (Coyote), but more-than-likely, the same process.

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post #5 of 14 (permalink) Old 07-07-2019, 02:44 PM Thread Starter
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Thanks Doc.
I have a stock 90 5.0 set up. Yes I was talking about grounding the relay. I am not sure what wire to tap into. I could just ground the relay then the pump would not do the prime thing it would run the anytime it the ignition is turned on. I would rather wire it so the ECU had control. Gregg
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post #6 of 14 (permalink) Old 07-07-2019, 05:05 PM
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Early EEC

If you are using the early EEC computer (88-91 A9L), the fuel pump relay grounds thru pin 22 - Tan w/ Light green.

If you are using the original FORD harness for your EFI, these connections should be pretty simple. Just supply + power from the EEC (Pin 37/57) to the relay coil, ground the relay coil thru the EEC (Pin 22). When you wire the pump, run fused power to the inertia switch, then inertia switch to the pump, ground the pump.

Now, whenever you turn on the key, the pump should run for a few seconds and then stop . . . if you start the engine, the pump will continue to run, getting that signal from the EEC.

Here's the wiring diagram for 88-91. Lower right hand corner should be helpfull . . .



HTH

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Last edited by Big Blocker; 07-07-2019 at 05:24 PM.
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post #7 of 14 (permalink) Old 07-07-2019, 05:11 PM
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Looks like pin 22 tan/light green sends a ground to the fuel pump relay to activate it. That sends +12v both to the fuel pump (put your inertia switch in line there) and back to the ecu via a splice to pin 19 to apparently let the ecu know that the pump has received +12v.


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post #8 of 14 (permalink) Old 07-07-2019, 06:23 PM
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Ha, Doc, looks like we had the same idea at the same time
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post #9 of 14 (permalink) Old 07-07-2019, 07:26 PM
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same-same

Beeman,

Always good to know that there are reliable sources on this forum . . .

Just because someone says it, doesn't validate it . . . until some one else posts the same thing. Then you can pretty much feel good about it.

Great minds think alike, right?

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post #10 of 14 (permalink) Old 07-07-2019, 09:56 PM Thread Starter
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Ok for some reason I am not getting ground through the T/LTGR wire when I IG on. If I ground the control side of the relay and IG on the pump runs. I am going to have to check all the grounds for the ECU.

Thanks for help.

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post #11 of 14 (permalink) Old 07-08-2019, 03:51 PM
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Fuel Pump Wiring

So, just to get this straight in my mind, does the pump run for a second or two when you first turn on the key? or not at all?

How are you powering the pump? Power for the pump should come directly from the battery.

Power for the relay [coil] should come from Pin 37/57 (VPWR) on the EEC.

PIN 22 only gives a momentary ground at initial ignition turn on, controlled by a timer circuit in the EEC.

After this initial ground, that "timer" has to be constantly reset to continue to provide ground for the pump relay - this is controlled by the engine running and the signal from the PIP/TFI module in/on the distributor. Pin 19 (FPM) sees power when the relay is energized to reset the timer . . . it doesn't guarantee that the pump is [actually] running, only that the relay is activated.

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Last edited by Big Blocker; 07-08-2019 at 03:58 PM.
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post #12 of 14 (permalink) Old 07-08-2019, 04:22 PM
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The battery doesn't supply direct 12v to the pump, it goes via a relay. If it did, the fuel pump (when grounded) would run constantly regardless if the engine is running or not. It gets it's power from the pump relay which is triggered by the ECU relay when the key goes on (provided all ECU and wiring is correct).

If you can ground your tan/grn wire as you say and the pump runs, you know the circuit is good with the key on. I would put the inertia switch in this circuit to protect from at least a hard hit "accident" to stop the pump. Most ECU's that control the pump are done in the means to cutoff the power supply to fuel and ignition if the engine stops spinning, i.e. ignition loss. So, unless you have something wired incorrectly or the ECU itself isn't properly working, you don't have many options.

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post #13 of 14 (permalink) Old 07-13-2019, 01:57 AM Thread Starter
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Doc. No the pump doesn't run at all when I IG on. When I wore the T/LG wire from the relay to ground and IG on the pump runs as it should. I haven't had a chance to recheck all the ECU grounds yet. I did have to replace the ECU a few years ago because it did the pump running all the time no start thing. That is why I don't think it is the ECU but it could be.
Thank you all for the help I will let you know what I find out about the grounds when I get a chance to check them have family stuff all weekend but get some time Sunday
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post #14 of 14 (permalink) Old 07-20-2019, 08:31 PM Thread Starter
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Ok found the issue pin 40 and 60 at the ECU were not grounded. I repaired the the ground issue and now the fuel pump runs when I IG on. Now to wire the fuel.pump sending unit clean up and loom the the tial light wiring re install the tank and see if she will run again.
Thanks for the help
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