Jeep won't start, please HELP! - JeepForum.com

 
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post #1 of 11 Old 12-05-2016, 08:52 AM Thread Starter
resavage
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Jeep won't start, please HELP!

My 2004 Jeep Wrangler LJ won't start. I was driving down a washboard dirt road and didn't see a small washout. I hit the washout going about 25 and the Jeep quit. After some fairly thorough searching on this forum, I attempted the following:

Checked the fuel pump relay and fuel fuse under the hood (by swapping with relay/fuse known to be good).
Removed the crankshaft positioning sensor and tested with multimeter (results showed good, based on a forum post I found). I then reinstalled.
Checked for spark at each plug by pulling the rail and jumping with a screw. No issue with spark on the first three cylinders from the front of the Jeep, so I stopped.
Attempted to check fuel pressure, but the '04 does not have a port on the fuel rail. As I didn't want to cut into the rail or get too involved, I went with the starting fluid route.
If I spray starting fluid into the throttle body, the jeep will start, sputter and fail.
As I did not hear the fuel pump whirring noise when I turned the key to on (in addition to previous information), I assumed the fuel pump or regulator was bad.
So, I replaced the entire fuel pump assembly yesterday. The Jeep still won't start.

What am I missing?

The Jeep acts fine in every other way. The check engine light has not come on, so I don't think it's stored any codes. It will crank but won't start. I still do not hear the fuel pump whir when I turn to on position. When I test the wiring for the fuel pump, the multimeter shows resistance, so I assumed it was good. I am no expert with wiring, so I could be reading that wrong. I'd consider myself fairly mechanically inclined, and I can follow directions. I managed to install a Mopar fuel injection kit on a Jeep CJ years ago, so this type of work isn't completely foreign to me. I'm being as thorough as possible to provide any necessary details for proper diagnosis.

If we cannot find a solution, does anyone have a recommendation for a repair shop in Tucson?

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post #2 of 11 Old 12-05-2016, 09:55 AM
Jerry Bransford
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Did you check that the impact of the landing didn't just knock the wiring loose leading to the fuel pump's electrical connector on the driver's side of the fuel tank skid plate? Use a voltmeter to see if you're getting 12 volts on the connector pin with the green wire with white stripe when the key is first turned on. That 12 volts is only there for a second or two then shuts off if the engine doesn't start. Someone needs to read the volt meter with someone else turning the ignition switch on. Once the engine starts that 12 volts is always there. The black wire going to that connector is connected to ground which is the other required connection to the fuel pump.

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post #3 of 11 Old 12-05-2016, 11:09 AM
fromme
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Try jumping the fuel pump relay to see if it will turn on the pump and start.

"The Wicked Flee When No Man Pursueth, But The Righteous Are Bold As A Lion."
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post #4 of 11 Old 12-05-2016, 02:46 PM Thread Starter
resavage
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Thank you gentlemen. I will give those a try as soon as possible and report back. One additional question: does my Jeep have an emergency fuel cutoff? I'm thinking the bump may have been big enough to trigger this, and I didn't think about it until now.
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post #5 of 11 Old 12-05-2016, 03:04 PM
Jerry Bransford
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There are two rollover valves on top of the gas tank but their job is to prevent fuel from draining into the fuel tank vent in the event of a rollover. They would not prevent fuel flow to the engine once the vehicle is righted.

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post #6 of 11 Old 03-02-2017, 09:31 PM Thread Starter
resavage
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SOLVED, mostly...

My apologies gentlemen for taking three months to reply; life gets in the way! I finally worked over the Jeep today with some help, and it is now running fine. However, I never found a conclusive answer to the problem.

I started with Jerry's suggestion and found no 12 volt power. I then pulled power directly from the battery to the harness, and the fuel pump whirred instantly. I cut into the insulation on the green/white wire just before (toward the front of the Jeep) the plug to the fuel pump/tank assembly. So, I did not have a bad ground and power wasn't getting back to the pump. I let the pump build pressure by running for a few seconds and then cut the power to it. The Jeep started right up after sitting for three months. It ran for about 10 seconds and sputtered out.

I began rechecking all the relays, fuses and under hood wiring and found nothing. Before hunting down a wiring diagram, I decided to try running the Jeep with 12 volt battery power applied directly to the pump again.

It started right up and ran fine. I drove it around the block without issue. I pulled the 12 volt wire and the Jeep stayed running, and has run fine since. I cycled the engine on and off a couple times with no issue. I tried putting the transmission and transfer case in Neutral, and alternating the two, thinking maybe something was off there after flat towing the Jeep home. The Jeep still started without issue. The transmission interlock still works fine, as it won't fire up while in Drive.

So, I'm not certain what solved the problem, but it's working fine after 50 miles. Some speculation:

The new pump needed this manual override to get going due to air in the fuel line.

The PCM needed this manual override to "reset" the system after the bump.

Some sensor or relay is worn, but not completely broken and the problem will reoccur soon. (If it does, I will certainly report back).

The worn ignition cylinder is causing an issue I haven't isolated.

Does anyone have any thoughts or commentary on this?
I hope this helps anyone that has a similar problem. It may be worth a shot to manually jump the fuel pump and see if that solves anything.
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post #7 of 11 Old 03-02-2017, 09:32 PM Thread Starter
resavage
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Also, thanks so much for your comments and assistance.
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post #8 of 11 Old 03-20-2017, 10:39 PM Thread Starter
resavage
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Problem is back, thinking ignition

Not sure if I should make a new thread here...My starting issue returned this evening.

The Jeep has worked perfectly since my last post, driven 8 - 10 times. Yesterday, my wife drove it on some dirt two tracks without issue; easy road, no 4WD necessary, just a little bumpy. She parked it in the garage, where it sat for 24 hours. When I went to use the Jeep, it wouldn't start; same symptoms as described in my original post. I pulled a jumper wire directly to the fuel pump from the battery again, and the Jeep fired right up. It remained running after I disconnected the jumper wire and drove fine. I turned it on and off without issue.

So, I'm thinking this may be the ignition. To start, the ignition is worn physically. The key will fall out while driving and Accessory & Off are sometimes hard to distinguish.

That being said, I'm thinking the ignition may play a role in telling the fuel pump to start. And, the bumps are just enough to throw it off. Thoughts?

Thanks in advance.
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post #9 of 11 Old 03-21-2017, 04:06 PM
Wildgood
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Thanks for sharing us your experience.
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post #10 of 11 Old 03-21-2017, 06:39 PM
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My guess is you have an intermittent wiring issue that can be influenced by bumping around on rough roads. It certainly seems that was the original cause based on all your posts. When you spliced into the fuel pump to provide 12 volts you knocked something about which temporarily fixed the issue. Your explanation of air in the fuel line doesn't really ring true. Air at the pump may cause failure to move fluid, but not in the line. Since the pump is submerged this just doesn't happen.

Check for 12 volts at the pump again. If its not starting it's likely that 12 volts is missing again. Find out why.

JSt.Marie
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post #11 of 11 Old 03-21-2017, 09:36 PM Thread Starter
resavage
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UPDATE: Jeep still has intermittent issue...and an old alarm

So, I decided to remove and inspect the under dash portion of the ignition system. Since my key cylinder was badly worn, I figured I'd at least accomplish something. Per some other posts I've read in my research, I inspected the ignition actuator pin assembly, thinking it may have broken, but it's fine. The ignition module appeared fine under a cursory inspection as well. I did not test any of the wires.

However, while I was under the dash, I found the remnants of a Viper alarm system; involving many splice connectors and a 4" square box . How worried should I be about this as a possible cause to my symptom? While I get an old alarm can open a whole Pandora's box of electrical issues, would any of these splices specifically involve the fuel pump?

Thanks again,
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