Jeep dies while idling - NOT air in fuel

jimmyjames · **Posted:** Fri Nov 20, 2020 12:55 am

First off, this is a great forum with so much useful knowledge. I don't post much, but I have read the NOOB guide several times and found it helpful as well.

I replaced the fuel filter head preemptively about a month ago. Ever since I’ve been getting the following issues. (the jeep never died on me with the old fuel filter head)

Symptom: Jeep dies while idling or sometimes decelerating to a stop and will not restart unless the filter is bled profusely. (I realize that this might also just be time consuming as the engine is allowed to cool while I bleed the fuel, or even possibly that I run enough cool fuel through the filter to cool off the fuel temp sensor, if it’s a fuel temperature related problem. Either way I bleed it for 5-15 minutes and get between a cup and a quart of fuel out.)
Once or twice it wouldn’t start after sitting for 30-60 minutes. Never had this problem when the Jeep was cold, or sat overnight or for multiple days, then it would always fire right up.

Actions taken:
1.) I installed a in-tank lift pump to try and make sure there was no air in the fuel, but it didn’t change the frequency with which the jeep would die. Its stalled several times with the new lift pump. There are no visible fuel leaks, and no drips of fuel on the ground under the jeep.
2.) I unplugged the fuel temperature sensor and fuel heater plugs– this seems to be the fix, temporarily.

Today I reconnected the fuel temperature sensor, and withing an hour of running errands in town, it stalled while decelerating to a red light. I unplugged it and it started right up. I haven’t plugged it back in to double check that it wasn’t a coincidence, but I plan to next time I go for a more leisurely drive.

Has anyone else experienced this? Running with it unplugged doesn’t seem ideal, as it throws a CEL. I have a new filter head coming, and Amazon was willing to warranty the old one even though it’s passed the return window, so it’s not a total loss.

I’ve started to record the resistance of the sensor at various temperatures, and so far it all seems linear enough.

Are there other things I should be looking at?

WWDiesel · **Posted:** Fri Nov 20, 2020 1:36 am

Have you had it scanned?
Does it set any DTC codes when it acts up?

jimmyjames · **Posted:** Fri Nov 20, 2020 2:21 am

Doesn't throw any codes, besides the 0183 for the fuel temp sensor fault now.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

I don’t know why you’d experience that since you have a pump in tank. Have you verified that it’s pumping? Im going to try gooping my sensor and heater plugs with dialectic grease in hopes that it seals them up real well without disabling them like silicone glue would.

Billybob · **Posted:** Fri Nov 20, 2020 3:14 am

When you replaced the Fuel Filter Head recently did you not perhaps disturb the nearby wire harness slightly?

The 2006 CRD has a known problem that the Main Harness goes behind the Fuel Filter Mounting Bracket which can damage the harness by forcing it against the firewall.

No harm in removing the Bracket and inspecting the wire harness carefully in that area! :wink:

jimmyjames · **Posted:** Fri Nov 20, 2020 6:30 am

@Jett- The pump is definitely pumping. Found that out when I went to open the bleeder within 20 seconds of turning the key on, and got quite a strong stream.

@billybob- I will definitely check the wiring harness behind the filter housing, that’s a good call! Maybe a wire intermittently shorted to ground is killing it?

jimmyjames · **Posted:** Tue Nov 24, 2020 4:12 am

Checked the wiring harness behind the filter and it all looked original and undisturbed. took a multimeter to the wiring between the fuel temp sensor plug and the giant plug that goes into the ECM. ground and voltage pins both have good continuity.

I did notice that the heater always has continuity between the two terminals. I thought that the wires going to the heater always had voltage and that there was an internal circuit that was supposed to break the circuit and stop heating the fuel. Seems like mine is always calling for heat. I'm in Hawaii and the filter rarely gets below 80*F.

The new filter head arrives wednesday, so we'll see if that changes anything.

Thanks again for the ideas.

WWDiesel · **Posted:** Tue Nov 24, 2020 12:06 pm

jimmyjames wrote:

Checked the wiring harness behind the filter and it all looked original and undisturbed. took a multimeter to the wiring between the fuel temp sensor plug and the giant plug that goes into the ECM. ground and voltage pins both have good continuity.
I did notice that the heater always has continuity between the two terminals. I thought that the wires going to the heater always had voltage and that there was an internal circuit that was supposed to break the circuit and stop heating the fuel. Seems like mine is always calling for heat. I'm in Hawaii and the filter rarely gets below 80*F.
The new filter head arrives wednesday, so we'll see if that changes anything.
Thanks again for the ideas.

After looking at the wiring diagrams in the FSM, it shows that the fuel heater relay is energized at all times anytime the ignition switch is in the "RUN" position.
So, it heats all the time regardless of fuel or ambient temperature.
I put together the WD all on one diagram so that shows the entire fuel heater circuit/system. :wink:

jimmyjames · **Posted:** Tue Nov 24, 2020 5:10 pm

Here's the new development that has me scratching my head today. I plugged the fuel temp sensor back in to double check that it was causing issues, and sure enough, within about an hour of driving it died while pulling into a parking spot (coasting decelerating). I unplugged it and it restarted just fine.

Here's the weird part: about 5 minutes after I left the supermarket, it died on the road again while decelerating and coasting to a stop (at about 20 mph). The sensor was already unplugged and this time I had to sit for about 25 minutes before it would restart. I bled the fuel filter once (I have an in-tank pump, so really just did this for good luck) but I didn't get any air out, nor would it restart. After sitting it fired up immediately like nothing had ever happened.

It has only ever died while decelerating or idling and never while reving or driving more than about 20-30 mph.

Are there other sensors I should be thinking about? doesn't really sound like a crank position, but maybe something between the transmission and PCM, like its keeping the cluthes engaged as I slow to a stop and its stalling? but why only sometimes and why does that prevent the engine from restarting right away?

I'm confused.

WWDiesel:
did some reading about the fuel heater. you were right.

From the FSM,
"The element inside the heater assembly is made of a Positive Temperature Coefficient (PTC) material, and has power applied to it by the fuel heater relay anytime the ignition key is in the “on” position. PTC material has a high resistance to current flow when its temperature is high, which means that it will not generate heat when the temperature is above a certain value. When the temperature is below 7°C (45° F), the resistance of the PTC element is lowered, and allows current to flow through the fuel heater element warming the fuel. When the temperature is above 29°C (85° F), the PTC element’s resistance rises, and current flow through the heater element stops . Voltage to operate the fuel heater is supplied from the glow plug module, through the fuel heater relay, when the
ECM senses the ignition (key) switch."

TKB4 · **Posted:** Thu Nov 26, 2020 12:02 pm

May not be important but when I turn my key on with lift pump I get fuel from bleeder on fuel head in just a few seconds . Way less than 20 seconds. This makes me think there still could be air getting in the line and a some point creating something akin to a vapor lock (not from heat) that is overcome by CP3 pump except when it is "stalling":. Not sure even a fuel pressure guage would identify this. It might be helpful, to make sure there isn't a raised loop of fuel line that might allow fuel past but still hold air. Granted this is a small possibility.

WWDiesel · **Posted:** Thu Nov 26, 2020 4:22 pm

TKB4 wrote:

May not be important but when I turn my key on with lift pump I get fuel from bleeder on fuel head in just a few seconds . Way less than 20 seconds. This makes me think there still could be air getting in the line and a some point creating something akin to a vapor lock (not from heat) that is overcome by CP3 pump except when it is "stalling":. Not sure even a fuel pressure guage would identify this. It might be helpful, to make sure there isn't a raised loop of fuel line that might allow fuel past but still hold air. Granted this is a small possibility.

Keep in mind, there is always fuel being returned back to the fuel tank from the CP3 via the Cascade/Overflow Valve.
When you turn the key to the "ON" position, the fuel pump relay is energized instantly and starts pumping fuel to the CP3.
The pump will run for approximately 15-20 seconds and shut off if your don't start the engine.
When you start the engine, the fuel pump relay "locks" in and runs the intank fuel pump continuously the whole time while the engine is running.
So any air that could get trapped in a line would be pushed back to the fuel tank via the Cascade/Overflow Valve.
But if you had a place where air was getting into the fuel line, when the fuel pump pressurized all the fuel lines, you would see fuel leaking out very quickly.

I have a fuel gauge on mine and have observed how the intank fuel pump operates on power up and engine start.
Fuel pressure is instantaneous.

Video of power up and engine start:> https://vimeo.com/user127974939/review/484189440/32ce61c642

jimmyjames · **Posted:** Thu Dec 03, 2020 12:20 pm

I replaced the CranK position sensor, and unplugged the FCV, just in case that was somehow causing problems. Haven't driven it much so far, but it seems a little more sure of itself. I think I can hear a difference in how it shuts down. When it seems apt to stall, the shutdown feels very sudden and immediate. When it seems more stable the shutdown feels more gradual and almost like the engine rotates another 1/2 rev as its coasting to a stop vs. falling flat on its face. Might just be in my head though...

I'll post an update if the CKP sensor fixed the mysterious stall issue (as it has for a few other 'stall while driving' posts). No fuel leaks and I definitely still have pressure to the filter head priming pump (cant even move it with my thumb).

Thanks again for all the help and ideas to work through this, I really appreciate it.

WWDiesel · **Posted:** Thu Dec 03, 2020 2:08 pm

Until you get the EGR delete kit installed, you may want to totally remove the butterfly plate out of FCV.
Reason being: If the gears strip in the FCV and allow the butterfly flapper to suddenly go shut, it would starve the engine for air.

The butterfly plate is real easy to remove, there are only two small torx screws holding it in the cross shaft. see picture
Removal can be done in about 10 minutes. :wink:

rankom · **Posted:** Sun Dec 06, 2020 8:16 pm

I would install fuel pressure gauge in between fuel filter and cp3 pump zip tie to wiper arm and monitor your fuel pressure. like ww did.

WWDiesel · **Posted:** Sun Dec 06, 2020 9:54 pm

The beauty of having a viewable fuel pressure gauge after both the OEM water separator filter and the 2 micron secondary fuel filters in real time, it allows you to monitor the status and current condition of both the fuel filters. If for any reason the filters start showing any resistance (D/P) across the filters feeding the CP3, the pressure gauge will show a decrease in filter outlet pressure and alert you it is time to replace both filters.
It is nice changing filters based on actual DP versus just changing them on a time based schedule which might not always be accurate.
I went two years on my previous filter combo before the gauge started showing a decrease in pressure (performance).
Gauges don't lie and removes some of the unknows....

jimmyjames · **Posted:** Thu Dec 10, 2020 5:03 pm

I just ordered parts to make the fuel pressure gauge like you have shown. Makes sense to change filters based on a drop in pressure VS mileage or time interval.

I replaced the crank position sensor and have run 300 miles with no issues. I have my fingers crossed that it was the issue all along, but in a couple hundred more miles I'll know for sure.

Thanks again for all the help!

WWDiesel · **Posted:** Thu Dec 10, 2020 6:44 pm

jimmyjames wrote:

I just ordered parts to make the fuel pressure gauge like you have shown. Makes sense to change filters based on a drop in pressure VS mileage or time interval.
I replaced the crank position sensor and have run 300 miles with no issues. I have my fingers crossed that it was the issue all along, but in a couple hundred more miles I'll know for sure.
Thanks again for all the help!

Tip, you may have to install an inline snubber to keep the gauge from bounding to bad. :wink:

Jeep dies while idling - NOT air in fuel

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