90, bronco ll hard start in morning, good fuel pressure , fuel pump runs for at least 5 min in the morning and it won't start untill pump quits running, as the truck warms it will start quicker. Don't know what to do next.

Clogged catalytic converter. Clogged fuel filter. Filters will give the pressure, just not the volume needed.

Sounds like a bad fuel pump to me.Or dirty fuel lines/injectors/regulator.

replace fuel pump relay then test fuel pressure it should not drop no more then 10psi below factory specs

The Bronco has TWO fuel pumps, a low pressure and a high pressure. Low pressure is located in the fuel tank, the high pressure is located....Attached to the LH frame rail ahead of the fuel reservoir.
my guest would be the high pressure pump is getting hot and shutting off, cooled down and starts back up again ??

I'd have fuel pressure tested. I had a 95' did same thing. Cold winter day, worked fine, as soon as it got warmer, or hot out, it would quit, and re-start 20 minutes later and go for a distance then die again. If I parked in the shade on a hot day, I'd get further before it quit for the first time. I started carrying a fuel pressure gauge with me. Cool in the morning my fuel pressure was up to spec @ 49-50psi. Once it got warm/hot out and it died, Hooked up gauge and it was at 2-5psi. Let it sit and cool off 20-30 minutes, pressure would jump back up and run good until fuel pump got hot again and then pressure dropped off and car quit. It sure sounds like the fuel pump, but the hard part will be getting the car to the shop at the right time, or they will need to let it run on the lot until it quits to confirm the pressure drop. One thing you can try is when car quits, have a can of WD-40 or quick start with you and a screwdriver. Loosen the clamp on the air intake hose where it connects to the front of the throttle body and pull it off. With vehicle off, turn throttle linkage so the plate opens up enough to spray WD-40 a second or 2 in the throttle body. Then try to start it. If it starts and runs momentarily, then you can be pretty sure it's fuel related and my guess is the pump needs replacement.

Hi!!
Check the fuel pump pressure. It sounds like you are getting fuel but not enough. Borrow a Fuel Pump Pressure Tester from AutoZone, Checkers or similar auto parts store. Ask the attendant for the right pressure for your pump. Here is how to hook up the Tester.


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Have you checked it for spark when it dies? It sounds like a bad ignition module.

have you checked your mafs that sounds like it the problem clean it witha mafs cleaner

need to check fuel filter in tank

The thing you need to do is run a leak down test on the fuel pump overnight, hook up a fuel pump test guage to the fuel injector gas rail test port, run the engine, note the fuel pressure when you shut the engine off, it should not drop more than 5 PSI overnight, if it does you need a new fuel pump. Your car doesn't use a cold start valve, that was used on very early Bosch K-Jetronic fuel injection systems, they where last used in the 80's