Crank, But no start with Misfire Codes

lrb6805

lrb6805

Die Living
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Jun 19, 2017
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129
Location
Grapevine, TX, United States
Hello,
So a few weeks ago i was getting misfire codes (the multiple code and cyl 3). It went away after some highway driving and would randomly come back and disappear after highway driving every once in a while. I figured it was due to cold starts or something.

Last night the engine light flashed back on and I figured it was the same thing.

This morning I went out to my jeep and it cranks, but does not start. I read the codes and I am getting P0300, P0301.

I have a 2006 LJ with 99,500 miles. Could it be the ignition rail?


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When did plugs get replaced last and how many miles are on them now? It could be a problem of wiring to the rail itself (or even the computer). If it were the rail I would think you'd get at least two misfire codes since there's three packs (one pack for every two cylinders). Then again you're getting P0300 which is multiple misfire.

For anyone else's edification:

Chris said:
P0300(M) Multiple Cylinder Misfire, Misfire detected in multiple cylinders.
P0301(M) CYLINDER #1 MISFIRE Misfire detected in cylinder #1.
Click to expand...

Do you know anyone else with a 2000+ 4.0 TJ that you could possibly swap rails with just to diagnose? If it works then and doesn't when you switch back then you know it's the rail. Good thing they're inexpensive and easy to remove/reinstall.

At the very least I would disconnect, blow out, and reconnect the wiring to the rail. Sometimes issues like this can be solved just by that.

Good luck!
 
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Try this:

That way you can eliminate the coil packs from the equation.
 
I replaced my spark plugs about 20K miles ago with the recommended autolite iridium tipped. Also replaced the Crankshaft Position sensor about 1.5 years ago. Could a bad Camshaft Position Sensor have symptoms similar to above?

Also, my codes I was getting back in November were P0300, P0301, P0304. They randomly went away, but they started to come back last night, but still drove fine. As of this morning, only P0300 and P0301 were showing. When I get home ill see if more pop up.


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Ok, I replaced the Camshaft position sensor and the Cranckshaft position sensor again, but no luck. I listened to the ignition process again and realized that when I turned the key to the first click, I did not hear the fuel pump run like I normally do. So I did the Starter Fluid test in the throttle body and they jeep cranked a few times then started/ran for a few seconds before dying off. Does this mean its time to replace the fuel pump or should I do any more diagnostic tests?

I rented a fuel pressure gauge from autozone, so I'll probably check that as well.
 
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