99_f150aj

how do i check fuel pressure with my 4.2 v6 f150..

otto457

Connect a fuel pressure guage to the schraeder valve on the fuel rail. Pressure should be about 28 psi at idle and if you bump the throttle - it should rise and then resettle to 28 once it falls back to idle.

99_f150aj

thanks where is the schraeder valve under the intake?

otto457

It shouldn't be. I can't remember which side on the V6 right now (V8 it's on the driver's side) but the fuel rail should be right on top and one side will have a cap sticking up out of it. Under the cap is the valve.

99_f150aj

thanks found it..checking it tomorrow..can you have a weak fuel pump? i been driving like this for month now and has not gone out..issue that i have is bad start up sometime and can not floor it over 3,000 rpms with out it bucking and choking..i replace mass,plugs and wires,also fuel fliter and it was clean..

otto457

The fuel pump can be weak. It's usually not a total failure when it goes. Make sure you check for vacuum leaks too while you're there, they can cause goofy symptoms too.

99_f150aj

deff no vacumm around the intake spent a hour spraying her down with carb cleaner nothing..taking it to a dyno shop friday and they can have fun finding the problem