When I let my bronco sit over night the fuel pump doesn't want to build pressure but if you drive it all day its fine I have changed the pressure regulator and all the relays associated with the fuel system.Any Ideas?
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1990 Ford Bronco Question: fuel system
Answer #1patrick mannion from Greg Solow's Engine Room, September 08, 2009, 19:31Master
I have seen the fuel pressure regulator leak on these, (twice in several years on the same truck).
Things to verify and check are fuel pressure and delivery, if these are low verify voltage at the fuel pump prior to condemning the pump. Voltage drops can significantly reduce pressure/delivery.
Fuel volume should be about a pint of fuel in 10 seconds and fuel pressure should be 35 to 45 psi key on engine off and 30 to 40 psi with the engine running. Do you get power to the fuel pump when the engine is being cranked over? These have an inertia switch but if it failed the truck would not start at all but check the voltage at the red wire at the inertia switch to see it is getting full battery voltage on cranking and running conditions. If the voltage is low check the voltage on the brown wire at the inertia switch which gets its power from the fuel pump relay (brown wire). It in turn gets its power from the blue 20 Gauge fuse link (link W).