pi516

I have a 93 grand Cherokee with the 5.2 v8 in it. it has been a long and costly project the I thought was almost done. but now when I try to start it I have to pour gas down the intake to get it started then it will run fine. but when I shut it off if I let it sit for more then 10-15 mins it wont start again inless I pour gas down the intake again. not sure what the problem is I got under the jeep today and had a friend try to start it and I couldn't hear the fuel pump kick in but my thought was the fuel pump is brand new and if it wasn't working then it shouldn't run fine when it is running. any ideas anyone?

Creature85

Check the connections on the fuel pump and make sure your getting power to it. It definitely sounds like you have a fuel pressure issue.

dave1123

When you turn the key on, the fuel pump only runs for about 5 seconds to bring up pressure, then it shuts off. After the engine starts, then it will run constantly. It may be you have a leaky injector or, if you have an external fuel filter, the pressure valve in the filter isn't holding pressure after you shut it off. You can try hot-wiring the pump and then try starting it.

I just looked at my Haynes manual. Your 5.2 has a throttle-body injection system. The pressure regulator is on the body with a vacuum hose attached to it. It should be easy to replace. If the regulator isn't holding pressure, there won't be fuel there for starting.

I had this problem with a Chevy truck. It had sat for 6 months and was doing the same thing. The pressure regulator had dried out and wasn't sealing. After keeping the truck running for about 5 minutes with a squirt bottle, it started to run on it's own. The guy that bought it told me he didn't have any trouble with it after that. I told him "Good, 'cause it's your problem now." He didn't like that, but he suckered me into reducing the price because we had problems getting it running.

pi516

ok so a update on what I have found. the fuel pump will run if I jump the relay but not if I turn the key on. is there a way to test the fuel pressure regulator?

Bustedback

It's not the regulator causing the pump not to come on.

dave1123

Swap the relay with a headlight relay and see what happens. The relays are all the same if they have the same number.

pi516

I tried swaping out relays there are 3 that are the same and I tried each one and same thing happened just to bad that same thing happened to be nothing lol. I don't know if relays go bad over time or not but the jeep has sat for about 4 years only running a few times here and there. any other ideas? someone told me the tumbler may be bad so idk if that would do it or not.

dave1123

I suspect the problem is with initial fuel pressure for starting. Obviously, once it starts, the fuel is there. Put a guage on the fuel rail, turn the key on and wait. You should get pressure immediately and it should hold. If it dies, the regulator is leaking and it's leaking back to tank.

pi516

the problem isn't pressure. cause when the pump will kick on it will shoot upto 40psi right away. the problem is when I am turning on the key the pump is not turning on. I had someone told me the tumbler may be bad and it was pretty loose so I changed it thinking if it wasn't bad it would be befor to long. and its still doing the same thing sometimes it will kick in sometimes it wont. I also changed the ignition switch well I had the tumbler out. how ever with the key turned on if I use the prong from my test light I can stick it in one of the holes on the ignition switch and if I get it in there just right then the fuel pump will kick in. so I am thinking it is something to do with the wiring

dave1123

Okay, look at the contacts inside the ignition switch connector. You may have a burnt or loose connection.

pi516

ok so when I turn the key on 99% of the time the check engine light wont come on. it is that 1% of the time it will turn on that the fuel pump will run. and as I found out today if I try to turn the engine over and the check engine light did not come on not only do I not have fuel but I also have no spark. I had the jeep running today and was driving it from my house to a friends shop to finsh the frontend work and it was running just fine then it just died and back to the same problem

dave1123

Try wiggling the wire harness and see if it makes contact. I still think it's in the ignition switch wiring.

pi516

tried wiggling the wiring harness to the ignition switch and got nothing. however I was playing with the wiring harness to the PCM and wiggling it around and then the pump kicked on it started right up and ran for about 10 mins then died and was doing the same thing yet again. I tried wiggling the PCM harness again and still didn't get anything.

Creature85

Sounds like possible cracked solder joints on the PCM. If you know your way around a soldering iron you can reflow the connections easy enough.

dave1123

Jeep has had some problems with cracked solder joints and bad capacitors in their electronics. I believe most of the solder problems are due to lead free solder. It tends to be brittle.