Fuel pressure drops when I turn off the motor

[Blackjeep]

My 90 Cherokee (4.0) has been hard to start since I got it a few years back. Usually, it takes 5 or 6 seconds to fire (turns over fine) and runs ok once running. A buddy of mine checked the fuel pressure and it went up to 35psi when running and dropped like a rock when we shut off the motor. A parts guy at the Jeep dealership told me it was leaking hoses in the gas tank allowing the pressure to bleed off.

Do any of you guys have any input to offer? Pulling the tank sounds like a pain, there's no Jeep dealership to get parts from within 150 miles.

Let me know what you think and thanks for the help!!

[capt. apathy]

mine has always dropped back off when the ignition (and the fuel pump) is turned off.

as far as the long cranking time to start, I also had that. try this, when you turn the key to start the jeep, turn it to the run position, if you listen you can hear the fuel pump come on, let it bring up the pressure for a couple seconds then turn the key to the 'start' possition. this cuts the cranking time in half for me.

[Blackjeep]

Originally Posted by capt. apathy

mine has always dropped back off when the ignition (and the fuel pump) is turned off.

as far as the long cranking time to start, I also had that. try this, when you turn the key to start the jeep, turn it to the run position, if you listen you can hear the fuel pump come on, let it bring up the pressure for a couple seconds then turn the key to the 'start' possition. this cuts the cranking time in half for me.

That's what I've been doing, too. Even doing this, the crank times are too long, IMO. I'm told that the pressure should hold at 35 psi "overnight", so the lack of pressure at initial crank seems to be the culprit. The question is, where does it go? This problem seems worse in the hot summer months, I guess the vapor lock added to the pressure problem is a double whammy. Starters are expensive and go out at "the wrong time" so I'd love to get to the bottom of this.

[kg4bet]

Originally Posted by Blackjeep

My 90 Cherokee (4.0) has been hard to start since I got it a few years back. Usually, it takes 5 or 6 seconds to fire (turns over fine) and runs ok once running. A buddy of mine checked the fuel pressure and it went up to 35psi when running and dropped like a rock when we shut off the motor. A parts guy at the Jeep dealership told me it was leaking hoses in the gas tank allowing the pressure to bleed off.

Do any of you guys have any input to offer? Pulling the tank sounds like a pain, there's no Jeep dealership to get parts from within 150 miles.

Let me know what you think and thanks for the help!!

Check your fuel pressure regulator and your fuel pump.
Your fuel pressure should not fall off after shutdown.
If you rise the back of your Jeep you can get to the sending unit with little hassle 20 mins and five &*(# words later it's out and back in you do not need to remove the tank.
The fuel pressure regulator is on your fuel rail near the front of the engine.

Hope this helps
73's KG4BET