quick fuel pump question

I have a 94 xj with no fuel pressure coming out of the tank(I checked it right before the fuel filter)

-there is fuel
-the pump makes noise when I turn the key forward, but no pressure
-car turns over fine(still no pressure), tries to start when I spray carb spray in the TB
-pickup is attached(I dropped the tank)

I tried physically blowing through the pump and it is not going easy, but that might be normal. all the other steel lines are good. There is one of the grounds inside the tank that has a little fraying of the rubber around the wire, but its still connected and seems like it wouldn't cause that to happen

I've been hearing a lot about the CPS and how you wont get spark or fuel pressure if it's bad. however seems like this could not be the problem since the pump "turns on" when I prime the key.

Is my pump just bad, or could it be something else?

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If you are SURE you have fuel and you are SURE the pump makes noise but still have no squirt at the disconnected fuel line then you do have a bad pump assembly, even tho you can hear it running.

PS: CPS has nothing to do with the fuel, just the spark output.

not entirely true. "This sensor is used to indicate to the powertrain control module (PCM) that a spark and or fuel injection event is to be required. The output from this sensor, in conjunction with the camshaft position sensor signal, is used to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders."
if the pcm does not see the cps signal within something like 3-5(?) secs. it will shut off the fuel pump.

also, have you checked to see if you have lost spark as well?

I left my brand new spark checker in my chicks car like a moron. Maybe there is a redneck way to do it. othewise tomorrow or hitchhike to get it tonite.

Ten High said:

not entirely true. "This sensor is used to indicate to the powertrain control module (PCM) that a spark and or fuel injection event is to be required. The output from this sensor, in conjunction with the camshaft position sensor signal, is used to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders."
if the pcm does not see the cps signal within something like 3-5(?) secs. it will shut off the fuel pump.

Click to expand...

I did a little test today because this CPS/fuel thing was confusing me. when I had the CPS completely unplugged I would still pressurize the rail, even when the car would not start. I guess that's where the "3-5 secs" comes in. I'll try it when it is starting.

Also for everyone to know. I took the tank off, took out the pump, hooked it up to the electrical and stuck it in a yogurt container with fuel in it, the turned the key forward. it would BARELY push a little fuel, and not even enough to squirt out the steel line. Gotta be the pump.

yeah, cps signal or otherwise, it will still "power-up" when you turn the key. after that though, while cranking, if the pcm doesn't see a cps signal it will shut off the pump. although that new info sounds like a weak pump.