Need help troubleshooting starter and P0301 issue

TeflonTrout

TeflonTrout

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Joined
Apr 18, 2019
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7
Location
Pennsylvania
Hey y'all, I'm at my wits end trying to solve this issue plaguing my TJ for a while now. Here's a basic run down of what's going on:

1) A while back I was having some starter issues. I would turn the ignition and nothing would happen, the jeep had power but no cranking. If I jiggled the brown wire going to the starter it would start fine. So I replaced the terminal on that wire.

2) Everything was working for a while until recently. Now I turn the ignition and it cranks but it won't start untill 2-4 times turning the key. I've heard people say that could be a fuel regulation valve issue (forget the exact name). So I just dismissed it since it's not a "must fix" issue. Until THIS HAPPENED

3) I went to start my jeep last night and it took 2-4 cranks but when it finally started I felt the engine miss and sure enough the CEL decided to celebrate Christmas and lit up lol.

I drove home and didn't feel any misses, only just after it started. Checked my OBD sensor and it read P0301 (cylinder 1 miss)


I've read some people saying it could be the Camshaft Position Sensor but I'm just not sure how to tackle a cylinder miss.

ANY HELP IS GREATLY APPRECIATED!!!
 
It could be a lot of things. Fuel pump could be going out, so check fuel pressure at the rail. But before that I’d check my battery terminals by detaching, cleaning, and reattaching.
 
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A question, does the slow start only occur after it has been sitting several hours or does it happen within minutes, like if you shut the engine off long enough to get gas?

Assuming it only happens after it has been sitting several hours, try this the next cold start after it has sat for some time. Before trying to start it, do this... turn the ignition switch on-off-on (not to Start) a dozen times while leaving it in the On position 2 seconds each time. That gives the fuel pump a total of 24 seconds of run time since it automatically shuts off each time after 2 seconds. THEN try starting it. If it starts right up you have a bad/leaky check valve inside the fuel pump. That check valve prevents the gasoline from leaking down out of the engine and back into the gas tank. The length of time yours is taking to start is how long it takes for the fuel pump to get the gasoline back up to the engine when its check valve has failed and started leaking.

If the fuel pump proves bad per the above test, go strictly for a good quality fuel pump, avoid all store brands as they usually either fail or start leaking at the check valve prematurely. Are you mechanically adept enough to get inside the fuel pump assembly to replace just the fuel pump? Whether you feel up to that or need to have someone else take care of the fuel pump issue decides on what recommendation to give you fuel pump vs. fuel pump assembly.
 
Reviving this thread - as I'm having a corollary to this same problem with my 2006 LJ Rubicon. In my case I have to crank the engine a solid six to eight seconds before the Jeep starts. If it's cold or if the engine is warm, doesn't matter. Only time it starts right up is if I kill the ignition and restart the Jeep, then no problem. But first thing in the morning, and if the Jeep has been driven but left to sit for more than a few minutes, takes forever to start. Additional info: In the morning it'll almost always run a bit rough for a few minutes and then light up with a P0300, or a random P0301 or 304 or 305, misfire on the other cylinders. 8 times out of 10 I'll get P0300 though. Then after it's warm, as in drive it down the street, the engine will miraculously clear up and it runs smooth as silk the rest of the day. I have a Scan Gauge and can clear the codes, after it's warm it almost never gives a P0300 or 0301 or any codes, just runs perfect. It's been a weird problem, annoying but after it's warmed up it runs great. Over the past year I've taken it to a couple shops for diagnosis, nobody's been able to figure it out.

A couple weeks ago I replaced the fuel pump in the tank, was putting on a skid plate and while the tank was dropped tried a new pump. That did not change the problem, but at 137K miles a new fuel pump can't hurt. A couple nights ago I was on the toll road - speed limit is 75 - and with my gears that means I'm at 3,300 in 6th. Wham! Something forced the engine into rough mode, I coasted to a stop and dropped the engine to idle for a few minutes. CEL came on and showed a P0016, indicating a OPDM or cam position sensor? After idling, I pulled back onto the highway and it ran perfect below 2,500 RPM. This morning, (after the usual hard start and 0300 drill) it ran fine just like normal, but I kept it below 2,500. I'm thinking of adjusting counterclockwise or replacing the OPDM just to see if that changes anything and try to reproduce the problem on the toll road again.

I'm also going to try the Jerry Test above, until this thread I hadn't thought of that possibility.
 
Powelligator said:
A couple weeks ago I replaced the fuel pump in the tank, was putting on a skid plate and while the tank was dropped tried a new pump. That did not change the problem, but at 137K miles a new fuel pump can't hurt.
Click to expand...

So did you dismantle the assembly and just swap the pump? If so did you replace the regulator? Or did you purchase a whole new assembly? What brand?

Have you checked fuel pressure? And check the pressure after it sits for a bit?

-Mac
 
TeflonTrout said:
Hey y'all, I'm at my wits end trying to solve this issue plaguing my TJ for a while now. Here's a basic run down of what's going on:

1) A while back I was having some starter issues. I would turn the ignition and nothing would happen, the jeep had power but no cranking. If I jiggled the brown wire going to the starter it would start fine. So I replaced the terminal on that wire.

2) Everything was working for a while until recently. Now I turn the ignition and it cranks but it won't start untill 2-4 times turning the key. I've heard people say that could be a fuel regulation valve issue (forget the exact name). So I just dismissed it since it's not a "must fix" issue. Until THIS HAPPENED

3) I went to start my jeep last night and it took 2-4 cranks but when it finally started I felt the engine miss and sure enough the CEL decided to celebrate Christmas and lit up lol.

I drove home and didn't feel any misses, only just after it started. Checked my OBD sensor and it read P0301 (cylinder 1 miss)


I've read some people saying it could be the Camshaft Position Sensor but I'm just not sure how to tackle a cylinder miss.

ANY HELP IS GREATLY APPRECIATED!!!
Click to expand...

I'd clear the code and run it more to see what codes re-present. If it's always P0301, then you know it's related to a single cylinder (#1), which rules a lot out (fuel pressure, cam sensor, crank sensor, as examples), and indicates some things to investigate (cylinder compression, spark plug, coil, fuel injector, as examples).
 
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Entire unit was replaced with a Delphi brand fuel pump. I'll be honest, I never checked pressure before or after, my thought at the time was since I was dropping the tank anyway I might as well replace something that has been in there for 15 years and 137K miles. With me, it would be just my luck that a week later if I didn't I'd wish I had. I will measure the fuel pressure, I might need to dig up some test equipment for that. Thanks!
 
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have you changed your spark plugs ? I ask because my brothers 06 had a bad skip when he got it, plug gap was .100 with 93k miles on it. bought my 05 with 95k and (always 1st thing I do when I get a used vehicle is change the plugs) gap was over .080 . when you have a engine miss 1st thing and easiest thing to do if you dont know how old they are is change them or atleast pull em and inspect !
 
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