1999 Ranger 4.0, OHV, AT. I've been trying to diagnose a misfire and in so doing, was checking the fuel pressure. I'm getting a constant 60 psi at the fuel rail at idle and when revving to 2500 rpm. After shutting the engine off the pressure drops quickly to zero. KOEO the fuel pump does pulse for a few seconds. Also, I have noticed a bit of a longer crank time to start. The fuel pump was changed about 2,000 miles ago. So, the pump is new. I have to assume that the pump has a faulty check valve. My question is, how much of a problem is this really. Other than a bit longer to crank, I'm trying to picture in my mind what problems this could cause but I'm no seeing one. If you see this Ron D, I would appreciate your feedback, and anyone else who wants to jump in.

I have watched another video of a fellow diagnosing his fuel pump pressure loss by disconnecting the fuel filter and testing the pressure on the engine side of the filter. I will probably verify my check valve as well using this method. In the meantime, any thoughts on this issue would be appreciated.

Thanks folks.

 

Fuel pressure regulator has gone bad. It part of the fuel pump in the tank.

 

Thanks for your feedback but I'm not sure. Would it NOT hold 60 psi if the regulator was bad?

 

They say when you turn the key, you can hear the fuel pump take 2 seconds to pressurize the system.
Knowing how long it takes might indicate something.
What brand of pump did you get?

 

Sorry, I'm slow getting to emails and replies and I'd have to do a lot of digging to find actually what brand fuel pump that I put in this 4.0 liter. Couldn't get a Motorcraft fuel pump so got what I could find. What I can tell you is I do hear the fuel pump come on for a couple of seconds. I also took an amp clamp reading off of the fuel pump inertia switch. Kept me from having to crawl under the vehicle. Anyway, I got a good wave form of about 0 to 6 amps. So, pump is working and it does hold 60 psi until the engine is shut off. I still have not gotten a pressure reading from behind the fuel filter. I'll probably take readings jus before and just behind the fuel filter. I've got a relay adapter coming that will allow me to run the pump without starting the truck. If the pressure dropx down quickly then check valve is either non existing or not working. Will get to that one day. Might be a few weeks as there are too many other irons in the fire right now.

BTW, I checked the service manual and I find that the fuel pressure spec is as follows: 441 kPa plus or minus 55 kPa or 64 psi plus or minus 8 psi. So the range is 56 to 72 psi. My guage shows 60 psi so is well within range.