bronco II fuel problem

I have a 1986 Bronco II and I am having a fuel problem. I replaced the low pressure pump in the tank and everything was working fine for a while, but now it won't start. If I prime with starter fluid, it starts but will barely idle (really low rpm) although if I slowly give it gas, I can bring the rpms up and it will continue to run as long as I give it gas. Fuel pressure is 40 - 41 psi and holds steady but when I turn the key on and the high pressure pump kicks in, it never shuts off even after the pressure stabilizes at 41 psi. Anybody have any ideas?

I would check the mfg. recommended fuel pressure it acts like it is to low.
Check the pressure regulator if this one uses vacuum if you find gas in the vacuum line to it install a new one. If its the one I think it is it on the fuel rail and uses small metric 4mm allen screws.
If you haven't changed the fuel filter change it also.
Are you sure this is a 1968 Bronco I would think it would have carburetor.

Thanks for the reply...it's a 1986 Bronco II (sorry about the typo).
According to Haynes, the recommended fuel pressure is 40 psi so it is dead on.
I changed the fuel filter when I replaced the fuel pump so I'm good there.

I've been racking my brain over this and I keep going around in circles. It doesn't make sense that the fuel pump would keep pumping once the pressure has stabilized. It only takes a few seconds after turning the key on for the pressure to reach 40 psi so why won't the pump shut off? Do any of you know if the fuel pressure regulator is involved with shutting off the high pressure fuel pump? The pressure doesn't drop over time and when I pull the vacuum line off of the fpr, no gas dribbles out so it acts like it's working fine. I don't see an electrical connection to it so I can't imagine how it would be involved with shutting off the fuel pump but I don't know how the pump would "know" to shut off without sensing the fuel pressure. Could it be "something" with the relay that keeps the pump on? Does anybody know what the feedback mechanisms are for the fuel pumps? Finally, (and this is the real kick in the pants) if the fuel gets all the way to the fuel rails at 40 psi what possible reasons are there for it not to start unless I prime with starter fluid?

The fuel pump runs all the time. The fuel pressure regulator maintains pressure all the time. You have a bypass line that returns fuel back to the tank. This cools the pump and you have a steady stream of fuel to the injectors. Use a vacuum pump and check the pressure with vacuum on the regulator. Its been a while since I tested one I think the pressure is higher and drops when vacuum gets to the regulator.
Are the two injectors working properly can you observe fuel coming out. You could clean the injectors. Is the engine timing correct. Ohm the temperature sensor for the computer maybe the temperature is setting the injectors to lean to start.
Use a flashlight and watch the injectors with a flashlight tell me what you observe.

Thanks for the fuel feedback loop info, but the high pressure fuel pump does cut off (or at least it used to) when you turn the key on (without starting) and it reaches pressure. You can hear the pump run for a couple of seconds and then cut off until you start the engine. Same thing when you turn the engine off and leave the key on...the fuel pump runs for a few seconds and then cuts off. Once the engine is running, the pump runs continuously.

I'm afraid that I don't understand about watching the fuel injectors for fuel. Do you mean pulling the fuel rail, leaving the injectors on and cranking the engine over to see if fuel comes out of the injectors? You mentioned a flashlight...should I be able to see the fuel injectors working in place? Besides, this plays into the part that is really confusing to me...if I start the engine by priming with starting fluid, I can keep it running by opening the throttle manually or depressing the accelerator...and it actually runs very smoothly and responds to throttle which implies that fuel is passing through the injectors after I start it. It just won't start without the primer and barely has enough rpms to idle and I basically have to keep giving it gas for it to run.

It started and ran like a champ one day and the next day I couldn't get it to start so I don't think it's a timing issue but I will try to check but it's gonna be tough if I can't get it to idle properly.

I don't have a vacuum gauge for the fuel pressure regulator so I will try that last.

The temp sensor seems like a good place to start because everything points to fuel being available through the injectors but just not when starting up.

If its like a 1985 Ford T-Bird with a 302 it had a throttle body with two injectors on top of it. With the air cleaner off have somebody try to start the vehicle. Watch the bottom of the injectors as they should spray some fuel.
Just like your doing with starting fluid.
With the gage on the vehicle you could put a short hose on the pressure regulator and suck on it see if this changes the pressure. Put a plug in the open end.Some people used to check vacuum advances on a distributor this way.
I had a loose ground wire next to the computer on my 1985. It tripped the EEC IV relay and shut off fuel. Located in the right kick panel next to the computer.

i have an 87 bronco ll i changed the intake for some reaon i have no power going to my fuel pumps after i put it togather
i can not get fuel to the engini changend the fuel pump in the tanke and bench tested the pump on the frame and it will run but i am not getting any power to the pumps

Check for the fuel pump relay I think it is on the drivers side by the engine. It should be a green color. Put your finger on it and it should pulse when somebody tries to start the vehicle. I have pulled them and used a jumper wire to test. This year has small terminals for the relay and large terminals for the pump.
Check all engine grounds and computer grounds.
Use a 12 volt test light and check for power to the pump.