Lil Roger

I have a 1989 f150 with a 300 6cyl i have changed the inline fuel filter. I just changed the high pressure fuel pump. When the truck gets hot the fuel pressure drops down and it loses power and luggs. The only thing I can think of changing is the fuel pressure regulator or the fuel pump in the tank. Has anyone else had any problems similar to this.

Thanks Roger

Good old Bill

Pull the vaccuum line off the regulator and see if gas is present. If gas comes out the nipple the reg is bad, not sure if this rich condition will cause the bogging down. Fuel pressure was tested with a gauge, right?

Lil Roger

Yes the pressure was reading 46 psi during idle when first cranked. I let it idle for about 5 minutes then drove about 5 miles. During the drive it started jerking in fourth gear you let off the gas and it stops jerking. As long as you take it easy and drive slow it is fine if you get into the gas and pick up speed it starts jerking again. When i got back home bleed pressure off gauge and took another reading it is at 28 psi. If I disconnect the vacuum line to the regulator the reading jumps up to about 56 psi.

Thanks Roger

Good old Bill

I'm still not up to speed on the fuel injected engines. Fuel pressure is supposed to be 30-40. With carburators fuel issue problems were not jerking or missing just plain no gas, no power, like the engine quit and slowly you went to the side of the road. It seems fuel injection can cause bucking and jerking issues, due to the electrically actuated injectors. Better bow out and let the knowlegable take over.

Just call me Sean

iTrader: (1)

I'm going to have to say the regulator is bad. Unplugging it sends the pressure way up, so the in tank pump must be working. If the in tank pump wasn't supplying enough fuel then the frame pump would make a lot of noise, mine does.