Fuel pump or relay ..... or maybe some thing other?

[massacre]

Glad to hear it all worked out

[Mainemantom]

Thanks again Pete for the clarification.

[tbear853]

Glad to hear it all worked out

Thank you. Thinking might have been a case of a chip reader failing to read a clone key's chip. . I'll be very particular from here out, take note of which key I use. .

[tbear853]

Update on situation. I returned the fuel pump and the sock. I have tried all 5 keys several times, always when I go from run to start, I hear the fuel pump. Today, we took it to town, shopping, several stops and shut downs, not a single glitch. I've studied on it, I am increasingly becoming convinced it was a failure to read a chip issue, though I do not yet know why. I've seen where some have added wire to increase reception by the car. One local mechanic said he knows of one that a customer has will sometimes read a cloned key, and other times it will ignore the same key ... but it always seems to read the remaining original key.

It was really nice driving today, still amazes us how many groceries will fit in that trunk. I have to look real close, in bright light, but I can just barely make out the very smallest beginnings of tire side wall cracks, so will be changing those soon enough. As she sits now though, I'd drive her about anywhere east of the Mississippi River avoiding those 75 mph hot west Texas roads. Bought a 5 qt jug of 5w30 MC blend for a change too, got 700 miles on her since last change in '21. I see was about then I did coolant and brake fluid too.

[tbear853]

Grrrrrrr, it did it again today, near 2 years later, but it was in my driveway. I was re-reading this thread, gonna try swapping out some relays tomorrow. PCM & FP. I had just had the car around back, topping off tire pressures, and then pulled it up into the driveway, we loaded up to do some errands, Wife and I seated, put key in, turn to run, no fuel pump purring, and no start. I had only swapped the AC and FP relays last time, missed the PCM suggestion "then". Car has run perfect since last time.

[tbear853]

Well, looks like the PATS is reading the keys after all. I had not looked last time in 2023 that I recall, but now in 2025 when I insert and turn the key from off to run, the PATS light goes solid red for a brief time, then it goes off. It's supposed to go into a fast blink if it doesn't recognize a key that's inserted. I think that it's about gotta be a relay or maybe a fuse, but I'm gonna try thumping the tank with a rubber hammer too. It was running so perfect until I turned it off as we locked the house and were preparing to go out .....

..... then the "no start" event.

Today I checked fuses and relays too, tried rubber hammer too but only out at ends. Monday, I'll jack it up one wheel at a time, so I can block two up and get under there to look at the wires and check for 12 volts back there at the pump I guess, found some links where harness was chaffed, wires broke inside tape. Will try thumping it closer to the pump too.

[tbear853]

Still no joy, but do have a plan for if needs R&R, like siphon gas down, etc. Seen where some remove a top bolt and a bottom bolt over a drain to get the level low enough. I think is OK, but just in case.
Did get it moved to a better spot using long chain to '77 F-150.

[tbear853]

Well, Igot delayed, but I do have car raised some ... just not quite enough to get to change it out if is the pump ... but I'll fix that.

QUESTION .... as best as I can see, looks like. 2001 Mercury Grand Marquis at in tank pump face, 4 wires come out through the white grommet.

1. a pink/black wire will be pump motor pos +
2. a black wire is pump motor neg -
3. a yellow/white wire is fuel level sender pos +
4. a pink/orange is fuel level sender neg -

YES or NO?

I think 99% sure that the Pink / Black (#1) is my test lead for 12 vdc as ign. switch is cycled from run to start .... and while there I'll test the Black (#2) for continuity to ground. I know it reads like easy deal, but I was having a tough time getting in to see the colors and my old CD was not communicating with my much newer PC. I finally found it worked on an old PC, enough to tell me the colors, and I finally got a photo that is clear enough to confirm is what I have coming out. Raining today as I write this edit, but hoping it is the pump motor bad, easy fix. I have thought of having it towed to a shop, but everyone is backed up with work.

I am debating a choice, replace whole fuel pump module as it exist with fuel sender as a unit ... or just drop it out and just swap a new pump motor in place, with new sock, but reuse the sender and hanger portion, I have a NIB Ford gasket.

There are a couple other wires that branch off to go up to top of the tank.

[gadget73]

The other few wires I believe are the evap control solenoid and/or the pressure sensor for that system.

[tbear853]

Thank You Sir, Woops, but I see my mistake. I put a question after mentioning the colors. I knew of the other wires going to the sensor up top, so didn't even mention colors. I was trying to determine which of the ones I detailed I needed to check for 12 volts when the key is turned from run to start, and since then I found the colors are as I posted. Pretty sure that in just run it will not activate the fuel pump if the engine is not actually running. Pink / Black should do it for testing for 12vdc, but will also check the Black for continuity to ground.

[gadget73]

I think even the newer stuff runs the pump for a second or two when the key is first turned on, but no it won't keep running the pump unless the engine is spinning. If you have a fancy OBD2 tool that can force things on and off, that would get it done.

[tbear853]

I think even the newer stuff runs the pump for a second or two when the key is first turned on, but no it won't keep running the pump unless the engine is spinning. If you have a fancy OBD2 tool that can force things on and off, that would get it done.

If the pump is bad, it would explain it not doing that 2 second prime ... but you're right, the pump shouldn't continue to run unless the engine runs. PCM would see to that ... I could supply 12 vdc via long jumper, but it might would back feed the PCM and do some evil there so I would not do that .... unless I disconnect the inertia switch & did it from there, just to see if the pump started. Will check there first too.

Car will "try to start ... even fire" on a shot of starter fluid.

[sly]

Things to check - Fuel pump relay, inertia switch, chassis ground on fuel pump harness, pump.

[tbear853]

I pulled the trunk liner loose, opened up the piece of harness running to the inertia switch, skinned the pink / black wire that is the wire that powers the pump, clipped a test light lead to it and the ground lead to ground. Sat in car, inserted key, turned switch from off to run, and just like the pump should do, the light came on for about 2 seconds.

I retaped the skinned wire and rewrapped the two wire harness. I now just need to order a pump after deciding whether to replace the whole thing, or just a pump motor with sock. I have the gasket.

Still hard to imagine a pump going out so many years ago, then work ... then stop in 2023 and start 2 days later, but no doubt in my mind, is a dead pump here in 2025.

[sly]

just make sure the actual ground from the fuel pump to the chassis under the car is securely bolted first. If that's come loose, your test will light the light, but a new pump will still not work. A continuity check from the pump harness to chassis should confirm this. Also, good to make sure the fuel pump harness is still connected and the wires aren't rat chewed.