Shudder after WOT Fix

retmil46 · **Posted:** Sun Apr 29, 2007 11:03 am

Hmmm, I wonder if MrMopar64 or someone else would have access to the specs, if there is an optimum fuel temp range where the ECM gives us "normal" performance, and at what fuel temp the ECM starts cutting back on fuel pressure.

Sounds like Goldilocks and her porridge - you don't want it too cold (gelling/wax), you don't want it too hot (boiling/vapor lock/reduced fuel pressure/melted fuel heaters), you want it just right.

I can see it getting to the point we're going to have so much stuff disconnected on this beast that it really is going to be a major evolution just to get ready for an annual DMV inspection!

oldnavy · **Posted:** Sun Apr 29, 2007 11:19 am

This may be the cause of the few of you having what appears to be air in the line from bad seal at the head or lines. If this thing boils the diesel it will make bubbles and low and behold you have air in the line and stall. You then clear the air in the line and the heater cools down while you do this and maybe even resets itself and tthen do the same thing again when the conditions that trigger the heater is met at some point.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

It could be part of the problem. I don't have an issue with pulling the heater plug in summer and plugging it back in during winter. Just another code to clear before inspection. God help Chrysler if they try to make a living from selling diesels in the U.S. Most customers won't put up with this kind of engineering.

retmil46 · **Posted:** Sun Apr 29, 2007 9:09 pm

Tried this on mine today. Did about a 20 mile run. When I got home, engine was plenty hot, but fuel filter and head were still cool to the touch.

When I did the same check a couple of weeks ago, basically same conditions, fuel filter and head were so hot it was uncomfortable holding your hand on them.

Larry R. · **Joined:** Sun Jan 21, 2007 1:35 am **Posts:** 92

Does anybody know what fuel temperature will yield the highest fuel pressure? I wonder if you could use a resister that will give the computer that reading?

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

With this thing getting so hot, and the assembly made of plastic-- I smell another NTSB investigation and a F38 recall. Hopefully they recall before a CRD catches fire and burns up. I went ahead and unplugged the sucker-- I like my CRD rare, not crispy. Betwixt this, the ORM, a new torque converter, provent and CAT fuel filter-- happier days are ahead. Thanks to all here. I would have had to sell this thing if it were not for you guys, the dealer knows less about it than I do.

msilbernagel · **Posted:** Mon Apr 30, 2007 1:54 pm

You have totally made my day!

I've experienced the shudder since I got the rig last month. It only seemed to happen once it reached operating temp, and then only when letting off the throttle (feathering) as the rig reached 55-60 or when there was a slight downhill grade. It was noticeable and occasionally irritating with 100% ULSD, but when I added the WVO blend it was obviously worse (maybe 2X?). The blend is 80% WVO, 15% RUG, 5% IPA (Isopropyl Alcohol), and Power Service... Seeing this thread, I suspect the RUG/IPA boils much easier... and/or it has enough additional viscosity that when the higher temps are sensed perhaps the ECM drops the fuel pressure too low to atomize well? Or both?

Anyhow, I drove to my AM watering hole today to get the usual cup of Java - and pulled the fuel heater plug there (about 6mi from home, no shudder noticed yet). From there I drove to work (another 20 miles) with NO shudder at all! That (no shudder at all) has never happened before, and I'm running about 50% blend... AND, the MAP/EGR are functioning normally (no ORM).

As far as I'm concerned, you've knocked the ball out of the park on this one. I'll continue to run in this configuration and let you know how things go.

Thanks!

Mark
-

thewalker350 wrote:

I'm new to posting on this forum but I've been reading and keeping up with everything for over a year now. Like everybody else I performed the ORM and love it. The only issue I had left to fix was the air in the fuel issue and the shudder after WOT. I have always felt it was in the fuel filter assy. so I decided to start with it. My plan was to try and seal all the joints somehow or eliminate it all together, and for some reason I disconnected the fuel heater to see if it affected the way it runs, and the all of my air in fuel symptoms went away. I drove it for over 100 mi. and not one shudder, hard start/no start or stall. I thought it couldn't be this easy so I plugged it back in two days later and all the symptoms returned. So, needless to say I unplugged it again and hope we can figure out why they (DC engineers) have the heater turned on on a 90 degree day and why having it on affects the way it runs. It was 87 degrees yesterday according to my Jeep overhead and there was 14.7 volts at the wire connector. I hope this helps some of our problems!

chadhargis · **Posted:** Mon Apr 30, 2007 2:13 pm

So...the real question is, what is the heater for?

Yeah, in cold conditions, I understand (has DC ever heard of a thermostat??), but when it's 86 degrees out like it is here, why are we heating the fuel?

GilaMonster · **Posted:** Mon Apr 30, 2007 3:09 pm

Which plug on the fuel assembly is for the heater? I'd like to try this disconnected and see if it runs better out here in the desert.

BVCRD · **Posted:** Mon Apr 30, 2007 3:15 pm

As you stand in front of the KJ, it would be the one on the right.

GilaMonster · **Posted:** Mon Apr 30, 2007 3:25 pm

BVCRD wrote:

As you stand in front of the KJ, it would be the one on the right.

Thank you.

msilbernagel · **Posted:** Mon Apr 30, 2007 4:03 pm

Ranger1,

Where is the best place to pick up an FSM? Or, perhaps better, is there an online source with schematics & wiring diagrams?

Thanks,

Mark
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Ranger1 wrote:

I'm not too concerned with the proximity of the fuel temp sensor to the heater unit, but I do think if the heater element starts overheating the fuel near the temp sensor, it will cause the PCM to drop the fuel pressure, as noted in the FSM. This certainly will affect engine performance. It could also add to the air in the fuel system by releasing the dissolved air within the fuel itself.

I have no doubt that your CRD ran better with the fuel heater disconnected, especially if it was overheating. Mine did before the fuel head starting leaking so badly that it needed replacement. In fact, my old fuel head heater socket was so overheated that the heater plug is now burnt black on one side. That kind of heat has to effect the performance.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

800-890-4038

or

www.techauthority.daimlerchrysler.com

MOSFET · **Joined:** Sat Feb 25, 2006 11:40 pm **Posts:** 295

Ranger 1 - Thanks for the link. I already have the CRD service manual, but I could not find where to get one for a 1996 Dodge Ram.

oldnavy · **Posted:** Mon Apr 30, 2007 7:36 pm

Checked the fuel filter & head for heat today when wife git home and the head was maybe silghtly above aire temp, but filter was warm. My guess just from the close quarters to the EGR, but it was not so hot as to be uncomfortable to hold. I would discribe it more as warm, not hot.

Now for just an observation of mine and it is by no means scientfific. It just seemed today that the CRD was running quiter and smoother. Is that possible just because of a better filter? I would not think so, but what do I know. Any idea's or have I just had another senior moment. :oops:

BVCRD · **Posted:** Mon Apr 30, 2007 7:58 pm

oldnavy wrote:

Checked the fuel filter & head for heat today when wife git home and the head was maybe silghtly above aire temp, but filter was warm. My guess just from the close quarters to the EGR, but it was not so hot as to be uncomfortable to hold. I would discribe it more as warm, not hot.

Now for just an observation of mine and it is by no means scientfific. It just seemed today that the CRD was running quiter and smoother. Is that possible just because of a better filter? I would not think so, but what do I know. Any idea's or have I just had another senior moment. :oops:

I wouldn't think so either, but who knows? I swear mine was quieter the first time I bled a bunch of air out of it.

BlackLibertyCRD · **Posted:** Mon Apr 30, 2007 8:25 pm

BVCRD wrote:

oldnavy wrote:

Checked the fuel filter & head for heat today when wife git home and the head was maybe silghtly above aire temp, but filter was warm. My guess just from the close quarters to the EGR, but it was not so hot as to be uncomfortable to hold. I would discribe it more as warm, not hot.

Now for just an observation of mine and it is by no means scientfific. It just seemed today that the CRD was running quiter and smoother. Is that possible just because of a better filter? I would not think so, but what do I know. Any idea's or have I just had another senior moment. :oops:

I wouldn't think so either, but who knows? I swear mine was quieter the first time I bled a bunch of air out of it.

Do you think possible that the CAT filter has better flow so not to starve and not cause shuttle after WOT?

oldnavy · **Posted:** Mon Apr 30, 2007 11:37 pm

I do know that air in the lines going to injectors will really make a diesel rattle, I always noticed it on old MB's where you don't have a bleeder screw after changing filters. With this filter being designed for a much higher flow rate (think big V8) then our diesel would ever require, you could have a valid point. The OEM was a minium filter requirement for the system for the least dollar and probably did have flow problems. This higher flow ability, if it does exist, would help eliminate over heating by the fuel heater maybe. I would think that if the filter was not flowing at high enough rate it could cause both shuddering and over heating of the fuel by the heating element. What do you think?

Marlon_JBT · **Posted:** Tue May 01, 2007 12:24 am

Well this is one unplugging that I will do. There's no CEL.

Although I haven't really noticed a difference. We'll see. Maybe I'll have to plug it back in to notice.

DarbyWalters · **Posted:** Tue May 01, 2007 12:52 am

It does make sense that it would or could run quieter. The clatter a Diesel makes is always greater when running under low fuel conditions, like at idle. Also fuel starvation would cause some of the conditions we CRD owners have experienced in the past. Basically everything we are doing/trying is making these CRD operate as they should... :wink:

... Off Road at least :lol:

Shudder after WOT Fix

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