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GiggityGiggity 03-29-2012 10:19 AM

02 Grand 4.7 wont start
Guys, any help or guidance you can provide for trouble shooting would really help, here is my story:

02 Grand 4.7 V8

Started the truck Monday morning, it was idling fine for a few minutes warming up. Jumped in to go to work, as I was pulling out of my drive way it died out on me. Felt like it ran out gas. My gas light was on, thought this was the problem. Managed to get the truck started again, stalled, got it started again but it wouldn't hold an idle. I had to keep one foot on the gas and the other on the brake to get it back up the drive way. Parked it till I came home from work Monday night.

Monday night I get some fresh gas, about $10 worth and put it in the tank. Go start it, the battery is dead. Boost it, truck starts, wont hold an idle. Call it day, decide to tackle the project Tuesday.

Tuesday morning, after recharging the battery, I try to start the truck. Turns over quickly, wont start. With the Key in the on position I see the battery voltage meter is only at 9amps. I've been on borrowed time with the battery so I went out and got a new one on Wednesday.

Wednesday I put the new battery in the truck, it turns over but wont start. Voltage meter on the dash says 9 volts :mad: Put this battery on the charger and tried again this morning.

Today, same thing, turns over quick, wont catch.Voltage meter on the dash still says 9 volts. I pulled the fuel pump and fuel injector fuses, they seem to be ok. I swapped the fuel pump fuse with one of the wiper fuses (same fuse) to be sure and the truck still wouldn't start. I pulled the gas cap off the truck, turned the key to the on position, tried to listen for the fuel pump priming, not sure I could hear it, HVAC system (electronic) is doing its thing with the blend doors and its all I can hear. Tried the dash from the drivers seat to the fuel tank to see I could hear the pump, not sure I'm quick enough to catch it prime.

My questions:

1. With the key in the on position, should the battery voltage meter read 12-14 amps on the dash? Did I buy a dud battery?
2. Whats the easiest/best method to test for fuel and spark? I want to find out if I got fuel and spark to the cylinders.
3. Is there something else I should be looking at/considering as a culprit?

I was getting the truck ready for nice complete detail and wax, was ready to put her up for sale and now I cant get her going. This really sucks. I cant sell the truck at its market value with out it running and I have to much invested to just have someone come and tow it away. Any help is appreciated. :thumbsup:

Heelsparky0501 03-29-2012 11:45 AM

Re: 02 Grand 4.7 wont start
Well a battery should read around 12v if its charged, it will only read higher then 12v when the vehicle is running and and alternator is charging it.

To test for spark you can remove a spark plug out and leave it connected to the coil and hold the plug against a known ground (engine block) to see if you see spark.

For fuel you can get a fuel pressure gauge from an auto parts store and hook it up to see if you have fuel pressure.

Does the sentry light on your dashboard illuminate when you try starting it?

Good luck, sorry i couldnt be of more help.

GiggityGiggity 03-29-2012 12:18 PM

Re: 02 Grand 4.7 wont start
thanks for the reply, what is a sentry light?

GiggityGiggity 03-29-2012 12:41 PM

Re: 02 Grand 4.7 wont start
k, googled it, the sentry light is the key light on the dash correct? When turn the key to the on position, the sentry light stays on with the seat belt light. It has a key with circle and slash going across it. Does that mean its not detecting my key?

Antonio186 03-29-2012 01:05 PM

Re: 02 Grand 4.7 wont start
ok so first things first if you want to check for spark you can pull one of the spark plugs out of the engine, then plug the coil back in and plug the spark plug back in to the coil when you crank the motor over you should see spark coming from this spark plug. but if the crank shaft position sensor is bad or not working then no spark will be delivered to the coils. also to check for fuel there is usually a check valve on the fuel rail somewhere. if not you can unhook the incoming fuel line from the fuel rail it self turn the key to the on position and you should see fuel squirt out a steady stream. if it is sort of just dripping out that means its a possible bad pump or clogged fuel filter. the other thing it could be is a broken timing chain. also the reason it may not have been holding an idle is Idle air control valve or the throttle position sensor maybe faulty most likely the IAC. i hope this helps point you in the right direction.

Heelsparky0501 03-29-2012 01:12 PM

Re: 02 Grand 4.7 wont start
Yes thats the sentry light. From my understanding if it doesnt detect your key upon trying to start it it cuts the ignition or fuel so it doesnt stay running. Ive heard it starts for a few seconds then dies. Do you have a spare key you can try?

Heres some more info on it

Im not entireley sure on it so dont hold me to it. :)

01grand 03-29-2012 03:20 PM

Re: 02 Grand 4.7 wont start
I had a key copy made (no chip) that I keep separate from my regular keys in case I lock them in the Jeep (again....). Just for fun I tried this key in the ignition, the jeep fired up for about 1-2 seconds, the key light came on and then it died.

You haven't mentioned one so I'm guessing no check engine light? The battery should be 10-12 volts when the eingine is off, it only goes up to 14v when the alternator is charging it like others have said. Not sure if my fuel pump is just loud but I can definitely hear it if I get in and turn the key to run, especially if I leave the door open. I would take a close look at the fuel pump and filter/regulator. Good luck!

Frango100 03-29-2012 10:14 PM

Re: 02 Grand 4.7 wont start
1 Attachment(s)
A fully charged battery should read 12.6 V, with the engine off. When the voltage goes below 12.2 V, the battery is already halfway discharged.
Start with the keydance (Ignition switch off/on/off/on/off/on.) The odometer will show "DONE" when all ok, or any fault code.
If no faults shown, you can indeed check for fuel pressure on the fuel rail. When i´m not wrong, at the RH bank side you will find a plastic blanking cap( see attached picture). When you unscrew that one, you will see a shräder valve. Push it gently with a screwdriver or so and if fuel comes out under reasonable pressure, the pump should be ok. When no fuel or just some drips, you have to troubleshoot the fuel supply further.
But lets first see if you have a code and pressure (do the pressure check just after you have switched the ignition to on, to be sure that there should be pressure.)
Very strange that the battery voltage is 9 V, that is not normal. Did you check it with a separate volt meter? There could be maybe something wrong with the alternator, which is draining the battery and causing it to run that bad or not at all.

GiggityGiggity 03-30-2012 10:11 AM

Re: 02 Grand 4.7 wont start
guys, thanks a mill for all the suggestions!

I tried the key dance....a hundred times. I cant get it to work for some reason. Would it possibly be related to the sentry light? I will be checking for fuel in a little while and will provide another update. thanks.

Antonio186 03-30-2012 10:20 AM

Re: 02 Grand 4.7 wont start
even if the key was just a regular key no transponder the engine will still fire up and run for a s few seconds before shutting off and when it shuts off the sentry light will be flashing. so i wouldnt worry about that for now.

GiggityGiggity 03-30-2012 10:32 AM

Re: 02 Grand 4.7 wont start
I have a feeling the truck stoped recognizing the key. Sentry light is on with the slash going through the key, I cant get the diagnostic to display on the odometer, would any of this have to do with the BCM possibly? I dont hear the fuel pump but if its a security issue, the pump would be disabled anyway wouldnt it? I have a spare key I tried and the same thing. Havent checked the fuel yet, shortly. But now concerned that if it is fuel, it may not be the pump but the BCM. is that possible?

Antonio186 03-30-2012 10:35 AM

Re: 02 Grand 4.7 wont start
i dont think it would be the BCM but i could be incorrect on that part. maybe someone else can chime on that subject.

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