Also, yesterday, the same pump stayed on/"buzzing" long after I stopped cranking it and pulled the keys out. Don't gotta be mechanically inclined to know that's not right, right?
No it's not, but Ford had that problem in their early EFI truck models. Fuel pump relay was not internally diode protected, and bi-directional current spikes served to weld the relay contacts shut. In brevity, pumps stayed running with key off.
Simple fix is replace the fuel pump relay. Get a Motorcraft unit, and you might as well do the EEC Power Relay (aka Main Relay) while you're at it. The live together.
Here's Ford's TSB text on this issue:
90ford25
^ NO START - 1.9L, 2.3L, 3.0L, 3.8L, 4.9L, 5.0L, 5.8L, 7.5L - LOW STATE OF BATTERY CHARGE
^ BATTERY - DISCHARGED - 1.9L, 2.3L, 3.0L, 3.8L, 4.9L, 5.0L, 5.8L, 7.5L
^ FUEL PUMP - NOISY - 1.9L, 2.3L, 3.0L, 3.8L, 4.9L, 5.0L, 5.8L, 7.5L
^ NOISE - "BUZZING" OR "HUMMING" FROM FUEL PUMP AFTER ENGINE IS TURNED OFFArticle No. 90-18-3
FORD: 1983-90 CROWN VICTORIA, ******, EXP, MUSTANG, TEMPO, THUNDERBIRD 1986 LTD 1986-90 TAURUS
LINCOLN-MERCURY: 1983-87 LYNX
1983-90 CONTINENTAL, COUGAR, GRAND MARQUIS, MARK VII, TOPAZ, TOWN CAR 1985-86 CAPRI, MARQUIS 1986-90 SABLE
LIGHT TRUCK: 1983-90 BRONCO II, BRONCO, ECONOLINE, F-150, F-250, F-350, RANGER 1988-90 F SUPER DUTY
ISSUE:
A "buzzing" or "humming" noise from the fuel pump may occur after the engine has been shut off. There may also be a no start condition or a discharged battery. These conditions are caused by a sticking fuel pump relay.
ACTION: Install a new fuel pump relay. Refer to the following procedure for service details.
1. Check the fuel pump relay circuit for proper operation. Refer to the appropriate EVTM for troubleshooting details.
2. Install a new fuel pump relay, if the old one is defective.
3. Check the vehicle for proper operation.
PART NUMBER PART NAME
F19Z-9345-A Fuel Pump Relay Assy.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: Eligible Under Basic Warranty Coverage
OPERATION DESCRIPTION TIME
901803A 1985-86 LTD/Marquis 0.6 Hr.
(includes pinpoint test)
901803A 1990 Town Car (includes 0.4 Hr.
pinpoint test)
901803A All Other Cars (includes 0.5 Hr.
pinpoint test)
901803A All Trucks (includes pinpoint0.5 Hr.
test)
These early fuel tank switches nd valves on dual tank setups also had problems The switches would short internally to power and effectively run both pumps. This could compound the other problems they had with the switching valves failing and pumping contents of one tank into the other while your engine runs, sometimes to the point of overflow out your filler neck!
Only on factory dual-tank setups though.
Also heard FI motors don't get vapor locked, so I'm confused.
You are right again; can't happen with EFI in traditional manner, as others here have already alluded.
(I've seen rare cases of fuel boiling in the rail--basically vapor lock--here in our warm climate when Costco dropped the ball and sold Midwest winter blends, but only a couple specific Honda models would actually "lock" and not start, and even that was not consistent. What was consistent is lean running symptoms and codes)
There is a different kind of lock these same early EFI Ford trucks suffered, and that was Hydro Lock. Ruptured fuel pressure regulator diaphragms would leak fuel into the control side, where manifold vacuum is applied. It could (and did!) got bad enough that fuel would flood into the intake and get drawn into a LH rear cylinder(s) nearest the FPR vacuum port. Cylinders would fill with fuel and cause real serious, fatal engine damage when fired back up.
Here is a cutout of the FPR, located front driver side mounted onto injector rail with a red vacuum hose attached to top ******.
This failure came on gradually, starting out with random, rich running conditions that would progress and include raw fuel ofors under hood and out tailpipe.
If you suspect this, the first whiff of raw fuel, shut it down, pull the FPR vacuum hose and inspect for raw fuel in hose and FPR vacuum port. If present, DO NOT DRIVE IT! Replace that regulator right away.
Most common cause of your reported symptoms are not fuel though. Well, not directly anyway. They are, in my experience:
- Green fuzz resistance in the PCM ground ground connector that pigtails off the battery negative. You can actually wiggle and tweak the connector while idling, and if bad, you'll hear your engine sputter, or even run nicer (round barrel connector below)

- Faulty Profile Ignition Pickup, or PIP sensor. That's the ignition trigger inside the distributor (this can be verified if you disconnect the SPOUT connector--the ignition timing bypass plug comes off your distributor--and the engine runs better)
- Squishy vacuum hose to Manifold Absolute Pressure Sensor (MAP) They get old, **** shut and wreak havoc with your fuel delivery when the computer calculates your driving at 19,000' altitude and delivers just enough fuel to cause your engine to buck, pop, fart and die.
This is your MAP sensor. Make sure vacuum pipe and rubber hoses are in goof shape, not squishy or pourous/cracked or otherwise leaking vacuum.
Good luck brah, and welcome to the playground!