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Discussion Starter #1
I have been slaving away the last two weeks to resurrect my '90 Bird. The new fuel sending unit arrived yesterday to replace the crusty one that was in the tank. Here's where I'm at.

  • Turning the key to run will not trigger the fuel pump.
  • I can manually run the pump by applying 12V and ground to the tank harness via a battery charger. That works.
  • I physically removed the inertia switch and verified it with a multimeter. It works and is reset.
  • All fuses in the car have been inspected and are good.
  • With the trunk lid open, I can hear the fuel pump relay click back there. Seems to be working.
  • Per the shop manual, grounding the FP terminal in the EEC test connector and turning the key to run yields no results.
Any suggestions as to why I'm not getting the fuel pump to run? I am obviously missing something. :confused:
 

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Relay clicking means the turn on signal is functioning, but it only relays power if its present or the relay is capable of making a good connection - you have checked for power ( battery voltage ) at the relay with a multimeter ??
 

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Discussion Starter #3 (Edited)
Your question brings up another. The relay is inside a plastic cage with some funky fasteners holding it to the inside of the trunk. How do you gain access to the stuff under there?

I'll probably wait until Saturday to resume diagnosis. I'll make sure the ground terminal in the fuel pump connector has continuity to ground and start at the 30 amp fuse in the power distribution box and verify it's supplying power back to the relay.
 

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in addition to the relay, ford installed a fuel pump cutoff switch that would kill the fuel pump in the event of a rear end collision. i have had one of those fail on my old 84 tbird, and had one pop on my moms 97 sable. once they were replaced or reset things worked normally.
 

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Discussion Starter #5
Update. This morning I verified 12V in the power distribution box by the battery at the FP fusible link. I also fished the fuel pump relay from behind that blasted cage (how the hell does that come off?) and verified that the Black/Yellow power feed to the relay does have 12V. So either the relay is not relaying or I have a continuity issue of the Pink/Black wire from the relay to the tank.

I'll probably just go get a relay today since the original has 171,000 miles.
 

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Discussion Starter #6
1990 fuel pump relay interchange?

Does anybody know if the 1990 fuel pump relay interchanges with anything more common? Two out of four major parts chains don't list it and those that do must order it. Even the Ford dealer said it's a special order. Must be made out of hens' teeth. :rolleyes:
 

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Discussion Starter #8
Yeah, I'll go that route if I just have to have one as I've already dropped about $300 with them on this Bird in the last week and a half. I was just hoping to find something in stock locally, Thanks.
 

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Fuel Pump Relay

That's a pretty common relay actually..If you're looking for a used one in the junkyard..

All MN12's 89-91 share the same Fuel Pump Relay in the trunk on the driver side..

As far as the Ford Dealer special ordering it..My guess is because it says Ford on it..An aftermarket relay works just fine.. ;)


Here's one from O'Reilly's-->> Fuel Pump Relay (Part #2DR1039)



Rayo..
 

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Discussion Starter #10 (Edited)
Well, I'll be...

The biggest difference I'm seeing is the shape of the connector portion. Mine looks like this:



The other, more common one's look like this:



Will the bottom style plug into my harness? I guess so since it's being sold for my car. Thanks.
 

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Discussion Starter #11
Ok. I picked up the Cougar relay and it plugs in fine. (Why the electrical engineers have to make so many variations of a simple thing....)

Anyway, apparently, I have something else amiss. I did verify that the vehicle harness at the tank has continuity to ground on the black wire. Then I put a multimeter probe into the pink wire terminal and the other side to a good ground. When I turn the key, I see 12 volts for one second and then I get a steady 6.4 volts at that terminal. I believe that the system is designed to prime for a second and then wait for engine start. Problem seems to be that I'm not getting any pump output while cranking.

With the pump plugged in, if I cycle the key on/off a couple times, the engine will start for a split second until it runs out of gas again. (Oh, and I poured five gallons in last night.) any more suggestions?
 

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Discussion Starter #12
:facepalm: Doh!

It runs! I crawled back under there and grabbed the vehicle side of the harness again and looked into it and realized that when I had poked the damn multimeter probes in there I distorted the rectangular terminals into round ones. They were no longer contacting the mating terminal on the tank harness. Once I straightened them out...vroom. :D
 

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Even though the relay "clicks" it does not mean it is working. Swap your relay with a known good one (horn, headlights, power windows) and see what that does. Also verify your ignition switch is sending correct voltage.
 

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Discussion Starter #14
Thanks but it's up and running. See my post just above yours. It is definitely a lesson learned.
 
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