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Old 06-22-2009, 11:25 PM   #1
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Unhappy 1999 Grand Cherokee Wont Start - Fuel Pump Won't Run/Stay Running

I'm hoping someone here can help me, I've been scratching my head trying to figure out whats wrong and am literally running out of options.

I have a 1999 Jeep Grand Cherokee that died on me last winter ( Feb 09' ), At the time I believed it to be the timing b/c I could hear noise and loud clicking/knocking when I tried to restart and it has 175k miles.

I figured that I'm keeping this thing for a while so I redid the engine. I got the thing back together and it still wouldn't run. Turns out I am not getting fuel from the pump to the rails/engine. I then checked the fuses and replaced the pump and still nothing, no fuel to the rails.

I then checked the pump and electrical connector for voltage, of which I know I am getting ( which justifys that the relays are energizing and passing voltage and the fuses are good ). I also hot-wired the pump with a 12V pack of AA batteries and I can hear it run and I pumped fuel to the rails so I know the pump is good.

Also to verify that my crankshaft and camshaft position sensors were working properly I hit the intake with some starting fluid, when I do that the engine fires up and runs good for about 3seconds until the starting fluid runs out - so I know my timing and spark is good.

After all this I don't know where to go...I know when I turn the key on I get a voltage spike to the pump for about 1, maybe 2 seconds ( should it prime longer that that with the key in the "on" position? ), and I also know that I have power at the relay terminals at the Power Distribution Center, but when I try to "Jump" the relay the voltage cuts out to 0.

Could this be a PCM ( Engine Computer ) issue? I have a feeling something electronic is cutting off the voltage to my fuel system, but am literally running out of ideas and things to replace. I'm running out of options here for what I thought was a simple fuel delivery system...can anyone help me? I've provided what I know, obviously I've had some time to do some science experiments to try and narrow down the problem...

Any Help Would be GREATLY appreciated...
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Old 06-22-2009, 11:51 PM   #2
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For reference the following links are from here.http://www.wjjeeps.com/jmenu.htm
The PCM doesn't control the fuel pump. http://www.wjjeeps.com/modules.htm
Check in the PDC, http://www.wjjeeps.com/misc/power_dist_ctr_02.jpg
there is a 20 Amp fuel pump fuse, a 30 Amp Auto Shut Down fuse, a fuel pump relay, and an ASD relay.
Any one of those failing can cause the loss of power to the fuel pump.
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Old 06-22-2009, 11:53 PM   #3
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yes,the computer could be the culprit. Is it throwing any codes? have you replaced the filter/regulator and checked all these http://www.wjjeeps.com/misc/fuel_filter_wj.jpg fittings and lines for rot?

nevermind..ol'blue beat me to it
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Old 06-23-2009, 12:05 PM   #4
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I will go to the dealer and get new replacement relays, I checked the 30 and 20A fuses and they are both good. As far as the PCM goes the fuel circuit is completly independent of it? Does the ASD relay shut down the fuel pump too? I thought it just killed spark? It seems like when I have a completed circuit there is a voltage interruption for some reason at the pump, but if the circuit is open and I probe it with my voltmeter I get voltage at whatever terminals Or connector check...

I will replace those relays and post an update...but let me know any thoughts on the above comments...
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Old 06-23-2009, 12:42 PM   #5
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I will go to the dealer and get new replacement relays, I checked the 30 and 20A fuses and they are both good. As far as the PCM goes the fuel circuit is completly independent of it? Does the ASD relay shut down the fuel pump too? I thought it just killed spark? It seems like when I have a completed circuit there is a voltage interruption for some reason at the pump, but if the circuit is open and I probe it with my voltmeter I get voltage at whatever terminals Or connector check...

I will replace those relays and post an update...but let me know any thoughts on the above comments...
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Old 06-23-2009, 01:38 PM   #6
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I know the ASD shuts off the fuel pump on other Mopars but I'm not positive about yours. According to the link above regarding modules, the PCM doesn't control the fuel pump. If it did there would be no need for the ASD relays. JMO
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Old 06-24-2009, 06:26 PM   #7
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Quote:
Originally Posted by RHStorm11 View Post
I'm hoping someone here can help me, I've been scratching my head trying to figure out whats wrong and am literally running out of options.

I have a 1999 Jeep Grand Cherokee that died on me last winter ( Feb 09' ), At the time I believed it to be the timing b/c I could hear noise and loud clicking/knocking when I tried to restart and it has 175k miles.

I figured that I'm keeping this thing for a while so I redid the engine. I got the thing back together and it still wouldn't run. Turns out I am not getting fuel from the pump to the rails/engine. I then checked the fuses and replaced the pump and still nothing, no fuel to the rails.

I then checked the pump and electrical connector for voltage, of which I know I am getting ( which justifys that the relays are energizing and passing voltage and the fuses are good ). I also hot-wired the pump with a 12V pack of AA batteries and I can hear it run and I pumped fuel to the rails so I know the pump is good.

Also to verify that my crankshaft and camshaft position sensors were working properly I hit the intake with some starting fluid, when I do that the engine fires up and runs good for about 3seconds until the starting fluid runs out - so I know my timing and spark is good.

After all this I don't know where to go...I know when I turn the key on I get a voltage spike to the pump for about 1, maybe 2 seconds ( should it prime longer that that with the key in the "on" position? ), and I also know that I have power at the relay terminals at the Power Distribution Center, but when I try to "Jump" the relay the voltage cuts out to 0.

Could this be a PCM ( Engine Computer ) issue? I have a feeling something electronic is cutting off the voltage to my fuel system, but am literally running out of ideas and things to replace. I'm running out of options here for what I thought was a simple fuel delivery system...can anyone help me? I've provided what I know, obviously I've had some time to do some science experiments to try and narrow down the problem...

Any Help Would be GREATLY appreciated...
When PCM does not receive a crankshaft position signal within 3 seconds of cranking the engine, it will shut the injection system including the fuel pump through its relay. To check the CPS first unplug its connector then you need a Volt Meter set to the lowest ohm, then measure across the CPS leads, the resistance should be between 125 - 275 ohms if its out of this range replace it. Another way to test it you need other guy to help you crancking the engine doing the same method by the Volt meter now you should measure the VAC by switching the Volt meter to the lowest AC range. Keep you eyes on the screen and ask your friend to crank the engine, the reading should show 0.5 - 1.0 if less thats a bad one.

Cheers mate
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Old 06-26-2009, 01:18 AM   #8
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Thanks for all the input, but I had a breakthrough last night and I got the darn thing running this evening. Turns out there is a power interuption / break in the circuit on the (+) side of the power supply. Here's what I did to figure that out.

1. Hotwired the pump to the battery, Pump (-) to Battery (-), Pump (+) to Battery (+). Result PUMP WORKED

2. Left the positive side alone, jumped the positive terminals at the pump connector and ran a wire from the (-) pump terminal to the (-) battery terminal. Result PUMP DID NOT WORK

3. Left the Negative side alone and jumped the negative terminals at the pump connector, then hooked up a wire from the battery (+) terminal to the (+) pump terminal. Result PUMP WORKED

This led me to know that the problem was in the (+) side wiring/supply circuit to the fuel pump. I then started hotwiring my extra fuel pump ( b/c I replaced it already and the old one still worked - even though it was old ). I hooked it up to the (-) battery cable because I knew that side of the circuit was good and then tested the (+) side at each major junction - PDC connetion, fuse supply, relay supply... all of which caused the pump to run. I then went to the down stream side of the fuel pump relay ( I opened up the wire harness about 8" outside the PDC under that little plastic cover. I stripped the wire coating back on the fuel pump (+) wire ( it was a green wire with a black stripe/tracer ) and spliced a bananna clip to the exposed wire which I then ran directly to my test fuel pump...result, it ran the fuel pump ( Note, I also had to manually jump the relay w/ a piece of wire too to get power downstream ). Knowing that there was power there, I then ran that supply directly to the fuel pump in the tank, had the negative termainals jumped ( at the pump connector ), put all the relays back and then tested the vehicle.
With the fuel line disconnected at the rails and a small container on the end to hold any fuel that was pumped, I turned the key to "on" and saw a small amount flow into the bottle ( SUCCESS! It was Priming )...I then cranked the engine and watched the bottle start to fill with fuel. Knowing that all circuits were functioning properly I hooked up the fuel line and within 3 seconds of cranking BAM! The engine fired up and ran.

Really all this tells me is that my circuit interupption is somewhere between fuel pump relay and the fuel pump connector...I'm gonna try to narrow it down so I don't have to run too long of a wire, but I think I got this problem by the ***** now. '

I hope this was descriptive enough of what I did...all I can really do is try to put out enough information on my problem so that I can save someone else weeks of headache and money in the future...

Thanks to everyone for the input and for saving me a costly mistake of potentially having my PCM sent out to be R&R'd. I now know more about electrical circuits and fuel supply than ever before...and of course keep on Jeepin.
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Old 06-26-2009, 01:21 AM   #9
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Also, let me know if anyone wants me to post the wiring schematic for the fuel system...I have them in my repair manual and they were the initial driver for determining my electrical problem.
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Old 07-03-2009, 08:45 PM   #10
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Quote:
Originally Posted by RHStorm11 View Post
Also, let me know if anyone wants me to post the wiring schematic for the fuel system...I have them in my repair manual and they were the initial driver for determining my electrical problem.
Forum rules prohibit posting copyrighted material. You can send the info via a Private Message if needed.
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"I NEED MORE TRACTION, NOT MORE BOOST"


Last edited by ol"blue; 07-03-2009 at 08:50 PM.
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Old 07-08-2009, 09:22 PM   #11
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I have a 99 grand cherokee limited i was driving the car and it shut off at the light i and the gas gauge went off and a light with a key with a circle around it crossed out came on and a check gauge light came on left the switch on and after a few min. the gas gauge came back up and the car started. the next day i was driving home and the car did the same thing so i thought that the fuel pump was going out " so" ireplaced the pump but now im not getting power to the pump i checked all the relays and fuses the all look good and i changed them with each other but i still dont get power to pump.

"""PLEASE HELP"""

open for thoughts
thanks
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Old 07-08-2009, 09:57 PM   #12
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Are you still getting the "crossed out key" lighting up? That is your SKIS indicator light,you may have a problem with your SKIS system,which will prevent your jeep from running.
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Old 09-07-2010, 10:03 AM   #13
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RHSTORM11, what was end result of your problem, i am experiencing same problems, also inotice gas gauge shows empty, has full tank, also key with circle is lit, cant get engine to fire by using starting fluid????
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Old 09-08-2010, 12:59 PM   #14
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My problem actually ended up being the fuel pump connector itself ( the 4-wire one underneath the vehilce right before the fuel pump ). Even though it was plugged together the (+) feed ( Green/Black Wire) wasn't passing the voltage to the fuel pump. I ended up soldering in a new 2wire connector for the power circuit and it worked fine. Later on one of the wires in the other circuit ( which is the float/sender circuit ) broke and I lost my gas gauge, so I had to wire in another 2-wire connector for that guy as well...

In regards to your problem. As far as the gas gauge goes, I would check the connector to make sure nothing funny happenned to the wires. You can also unplug it and (with the key in the "on" position ) use a voltmeter to see if you have a voltage signal at the connector too for the pump level sender wires ( they are the 2 smaller ones ). If you think you're not getting fuel, when you first key on the vehicle you should hear a "whirring" sound in the tank for like 1-2 seconds, thats the pump priming the fuel injection system.

When you see a Key with a circle on it, thats the security system on the car I believe, those cars use a SKIM key as part of their antitheft device. Mine gets funny too sometimes. I can only disarm imine with the main keyfab, if I arm it with the main one and disarm it with another and then start the car the alarm goes off and makes a god awefull racket until I disarm it with the main one. Also I have a remote start, that messes with the security system and will shut the vehicle down and display that "no key" light so I don't use it.

If it won't start with starting fluid it means something is telling it not to fire ( which means you have no spark ). The computer energises the ASD ( auto shutdown relay ) which allows the car to run when it senses a crank and cam sensor input I believe ( the 3.7/4.7L engines ran on crank and cam sensor inputs ). These could be something to check but I''d focus more on the security/SKIM side of things right now, because the computer is probably thinking your car is getting stolen right now.

The first thing I'd do is pull the diagnostic codes on your vehicle, put the key in the ignition and turn ito on, off, on, off, on. On the third "on" leave it there and you should get the diagnostic code readouts on the electronic odometer. Once you get those P-Codes, if any...look them up and see what the computer is trying to tell you. if you get any go to this website and see what they mean, and you can go after the problem from there.

http://www.wjjeeps.com/faultcodes.htm

that would be a good first step, I hope this helps...let me know what you find out and we can take it from there...
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Old 09-08-2010, 06:37 PM   #15
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RHSTORM11
tried the codes prior to posting for help. I cant get it to read any codes. before I could. Now that we are talking about the codes, i did have the check engine light on for awhile the code was for low voltage to do with the fuel system, however i cant remember that code, i will look and see if any of these look familiar. Jeep ran fine, shut it off, 4 hours later tried to start it and it just cranked. I tested all fuses and relays as you did and have power every where. i have no power on the "hot" wire coming out of the second big plug that bolts into the bottom rack and then runs wires down the drivers side. jeep only has 66661 miles on it,
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