New issue for me...need help with diagnosis

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

I will try to keep this as short as possible but include all the details. This past Sunday I went on a daytrip with the family (about 1.5 hours away) and was almost stranded. We arrived at our destination around 12pm and left around 4:30, so the car had been sitting for a reasonable amount of time. When leaving, I went to start the Libby and it just continued to crank and would not turn over. Immediately, I checked all of the obvious items: battery, fuses, bled fuel filter...all good plus no engine light. As I mentioned, the battery was good because the car cranked strong and all the lights/gauges were very bright, and I just replaced the red top a few months back. After I called a friend to drive the 1.5 hours to come and get us, I decided to try one more time and it started first time, like nothing had been wrong. Needless to say, very frustrating.

This morning, Tuesday, after the car was sitting overnight, it started to do the same thing. It began to crank just like before, but lukily sputtered to a start this time. I'm getting nervous now because I'm afraid to drive it a long distance for fear of being stuck somewhere. I read on another post that some seemed to think it might be the starter switch. Without any kind of obvious signs, I am up to replacing the switch because it is a cheap part but wanted to ask for any opinions before I start replacing any expensive items. Thanks!

Squeeto · **Posted:** Tue Jul 12, 2011 1:28 pm

Sounds as if you are the hands on kind.
Buy a code reader if you haven't yet. Absolutely invaluable.

Still sounds like a fuel issue.
I had similar issues in the past but no longer since installing a lift pump.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

It is not the starter switch, otherwise it would not allow cranking. If it cranks and does not fire it is most likely air in the fuel. The next time it does this have someone pumping the fuel primer while cranking to see if this helps. Are you still using the stock fuel/water separator head? If so, there is an updated part from Mopar that fixes an air leak path through the fuel heater circuit.

The fuel heater connector is closest to the driver on the fuel head. Unplug this and check for burnt terminals, then press the primer a bunch to see is fuel starts leaking out the connector. If it does this is your issue. Good Luck!

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

Sorry...forgot to mention that I do have the upgraded Mopar filter head.

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

I still think its a fuel related problem. There are known points in the system where air can enter the system and not just limited to the fuel head. A lift pump would greatly help resolve this issue.

Suggestion: Run some clear fuel line from filter head to engine and see if you have bubbles or air in system next time it acts up.

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

Drewd wrote:

I still think its a fuel related problem. There are known points in the system where air can enter the system and not just limited to the fuel head. A lift pump would greatly help resolve this issue.

Suggestion: Run some clear fuel line from filter head to engine and see if you have bubbles or air in system next time it acts up.

So...not to question your suggestion, but I'm just trying to understand...

When I had the first occurrance, I bled the fuel system 2 separate times. If was truly air in the system, why would it have not sarted after I primed the system? Are there other "glitches" that it could be in the fuel system besides air?

Squeeto · **Posted:** Wed Jul 13, 2011 2:37 pm

barnez224 wrote:

If was truly air in the system, why would it have not sarted after I primed the system? Are there other "glitches" that it could be in the fuel system besides air?

Pumping clears the air at the top of the fuel filter (top of the fuel system). It doesn't ensure all the air is out until the truck is running for a few seconds. Like you said "sputtered to a start".

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

Just wanted to post this for other who might have a similar problem. After taking the Libby to the local dealer, they were able to find a stored code. The code was for a failed crankshaft position sensor. After going to the service manual, it all made sense.

Accoring to the manual, "The ECM uses the engine temperature sensor and the crankshaft position sensor (engine speed) inputs to determine fuel injection quantity. If the ECM does not receive a crankshaft position sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system."

The failed sensor caused the no-start condition and continuous cranking because the ECM was not communicating with the sensor causing the fuel injection system to be shut down.

racertracer · **Posted:** Wed Jul 20, 2011 7:29 am

Great,

Thanks for keeping us informed and returning to post the resolution, many do not.

Squeeto · **Posted:** Wed Jul 20, 2011 11:38 am

barnez224 wrote:

After taking the Libby to the local dealer, they were able to find a stored code.

Kind of why I suggested getting a code reader. I always justify the cost of tools against the cost of having someone else do it for me.

dkenny · **Posted:** Wed Jul 20, 2011 9:50 pm

the other thing you didn't mention or I missed..when did you last change the fuel filter?

my wife just had some problems with hers running..no power..dying..
lift pump ran fine..bled the system..but not much help..checked the filter..yep dirty...replaced and rebled..so far so good.

-dkenny

barnez224 · **Joined:** Fri Jan 19, 2007 11:28 am **Posts:** 130

dkenny wrote:

the other thing you didn't mention or I missed..when did you last change the fuel filter?

my wife just had some problems with hers running..no power..dying..
lift pump ran fine..bled the system..but not much help..checked the filter..yep dirty...replaced and rebled..so far so good.

-dkenny

Fuel filter only has about 10k on it. I had the old leaky filter head (now have the upgraded) so I know what that issue was like...and when this issue first started, it did not have the same "feel" of a fuel filter problem.

dkenny · **Posted:** Thu Jul 21, 2011 7:39 am

if you want to be sure its not the filter install a vacuum/pressure gauge between the filter head and the CP3.

the higher the vacuum the dirtier the filter. and the more likely it'll draw in air.

my wife had about 15K on her filter. it only takes a couple of tanks of dirty fuel to plug a filter. also if a chunk of dirt dislodges from the filter it'll allow more fuel to pass until that spot plugs up.

-dkenny

New issue for me...need help with diagnosis

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