no fuel pressure, help?!

i have a '90 xj. it will crank and crank and crank, but no start. checked the pressure at the fuel rail, and only a trickle or none. i just changed the fuel filter, but no luck. the fuel pump is running. i don't know what to check next?
any help would be great!
thanks
amber

If the pump just keeps running there are two things that can be causing it. Either the impeller in the fuel pump is destroyed, allowing the pump to run but not build pressure, or the fuel pressure regulator is wide open (the most likely)

The tip off is the pump keeps running. It should run for a few seconds and shut off after the pressure builds up. A restriction in the fuel line that would keep you from getting fuel pressure at the rail would also let the pump get to pressure and shut off.

thanks for the the info. i'll check that out tomorrow.

i was wondering if you could tell me exactly where the fuel regulator is? i'm still learning what is under the hood and where!

There is a silver pipe that runs from the front of the engine to the rear on the drivers side right next to the valve cover. It has 6 short sections that jut down and connect to the injectors. It is referred to as the fuel rail. The gas comes in the rear next to the firewall. The fuel pressure regulator is at the front of the rail and is about the size of a handball. It has a hose with a quick connect exiting it that bleeds gas back to the tank. It also has a small vaccum hose on a push on connector. The vacuum is used to vary the fuel pressure as the vacuum in the intake changes with rpms.

Its been a while since I've taken one off, but I think there is one bolt that holds the unti down to the intake manifold. Once that bolt has been removed, the regulator can be gently twisted and removed. It is sealed with an O-ring. Maybe someone else can fill in the gaps on this, its been a couple of years since I pulled one. The last time I saw one fail, I tested it by taking a pair of vice grips and clamping the relief hose. That allowed the pressure to build and the engine started and ran. You should be careful not to damage the hose, but it will tell you for sure if it is the regulator or not.

i can hear the fuel pump run. it runs for a couple of seconds then stops. there is still no pressure at the rail. i'm going to swap out the regulator this afternoon. if that doesn't work, is there anything else i should check before dropping the tank?

Yeah, disconnect the fuel line going from the pump to the fuel filter at the filter end, hold a clean container underneath, and ask a buddy to crank the engine over for about 20secs. During that time, you should collect about 1/2 a liter of fuel in the container. If you collect only a few drops, the fuel pump needs to be replaced.
When you do this procedure, make sure neither you nor anybody else nearby is smoking a cigarette, otherwise the consequences will be quite scorching.

I recently had a simular problem on my '89. Turned out to be the hose between the pump and the tank bracket in the tank. I replaced the short piece of hose and it started right up. The old hose was shot and all the fuel was pumping back into the tank instead of up to the fuel rail. HTH

Jerry

Same here. It's a small piece of fuel line that connects the top of the pump to the hard line on the pump assembly. Mine was like swiss cheese Hope your problem is as simple as that.
Good luck!
Jeff

is it possible to remove the pump assembly w/o dropping the tank, or is it just easier to drop it? i'm asking, because i have a full tank of gas!

Kreutz said:

is it possible to remove the pump assembly w/o dropping the tank

Click to expand...

Ya, You just want to be sure that the fuel level is below the pump mount,and be sure to use a brass punch. If you jack the back up and put some jack stands under the frame then let the rear suspension droop there is a lot of room. If you have a FULL tank of gas you are going to have to get some of that out.

Jerry

Turns Out To Be The Fuel Pump After All. Thanks For All The Help.