'94 Ranger W/4.0. Starts & runs great for less than 2 minutes, then like flipping a switch it goes so rich the engine dies. I must turn the ignition switch all the way off to get it to restart and then repeats symptom within just a few seconds. When I turn the key to the run position w/o starting, I hear the fuel pump run continuously and does not stop running as does once it builds pressure. The vacuum hose to the fuel pressure regulator is dry inside and does not smell of gas. The engine oil does now smell of gas. I have replaced the relay since I already had a spare, no change. I cannot read the check engine light to read codes because it flashes more rapidly than normal, sometimes flashing again before it even goes out. I cannot drive it anywhere to get it scanned it is so bad. What is left to control the fuel pump's operation? ECM/ECU? Any help is GREATLY appreciated. -Alan-

 

Yeah thats about 99% that the ecm is shot. You might want to give the folks at A1 cardone tech assist department a call.

The ECM is a simple timer & should shut the pump off after 2 seconds.

 

I put a new ECM on my truck about a year ago and it has done great ever since ,,, I saw the Cardone ECM'S then almost fainted when I saw the price!!!! I found a rebuilt unit at Flagship One Inc. 21 Ryder PL East Rockaway NY 11518,,, they said it would ship in either 3 or 5 days I can not remember now but it failed there test they run before shipping it,,, so they rebuilt me another one and expressed shipped it for free to make up for the delay,,, it is still working fine with no troubles,,, I did have to give them a little info to make sure I got the right one,,, there were 8 different ones for my year and model,,, anyway good product with lifetime warrenty at a lot cheaper price than anyone else,,, if you on a budget like me this might be a good option for you

 

Thanks a million guys! I'd really love to make this my daily driver again. I'm the second owner, my dad being the first. My current daily driver is a '93 F150 about to turn over 450,000 miles and getting tired. The '94 Ranger..... Not even 70,000 yet. I did promise my dad I'd take care of it before he passed.

 

These guys have a good rep from what I read:
http://circuitboardmedics.com/

If the injector drivers are shorted, they may supply ground to the injectors, and keep them open continuously. That would flood the engine with fuel.
I would check resistance from the 'computer' side of the injector connector to ground. The other side should have 12v when the ignition is turned to ON. The computer provides ground to complete the circuit, and should NOT provide ground 100% of the time. If you can figure out which is the hot wire, the other has to be the ground from the computer, grounded when desired, and not grounded otherwise.
Running for 2 minutes, things start to heat up. It is possible one of the engine sensors is getting warm, sending some sort of bogus signal. It might be worthwhile to get it to the dealer as they have readers that can absorb the whole 'signal stream' that is put out first, followed by the human-readable slow beeps.
You can buy a plug in reader thing that runs on a 9-volt battery, and will beep and blink for the codes. The EEC-IV system puts out a quick 'blurt' of the codes(readable as above) and then a slow-walked set of blinks/beeps (depending on reader) that should be recordable. I use a pencil and paper, making marks as I hear/see the code, and leaving 'blanks' between, sort of moving my hand slowly, making a mark for a beep, and not making a mark when quiet, but keeping my hand moving. The result can generally be related to the beep codes that should appear. To decode, you need to know the signal sequence, the delays, and the 'confirms', as it will repeat the codes at least once.
If you don't have a book & reader, borrow one, as most shops don't use the EEC-IV stuff much any more, instead using the OBD-II interface on all stuff 96-newer.
You might call the circuit board medics and ask them if they can give you a 'quick test' to confirm your board is bad. It may be bad, or have bad injector drivers, or be something else, as it DOES work for a while, so should communicate 'what it is doing'.
tom