Shudder after WOT Fix

thewalker350 · **Posted:** Sat Apr 28, 2007 9:16 am

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!

Goglio704 · **Posted:** Sat Apr 28, 2007 9:22 am

If I'm reading you right, you're saying the problem is hot fuel rather than air. I know firsthand that the heater can leak, but I can't see it making air. Not being critical, just looking for clarification. I had noticed the other day that the fuel filter on mine seemed too warm for the conditions.

thewalker350 · **Posted:** Sat Apr 28, 2007 9:44 am

That's what it appears to be! For the shudder after WOT why wouldn't you see a drop in power if you were sucking air. Mine will pull the same until I let off the throttle and it will start to shudder once you start applying the throttle to maintain you speed. If it was air I would think you would feel it on acceleration too! I was having alot of no-starts and the only way I could get it to fire was to bleed the air out so maybe the two are related. Will the heater being so close to the top of the assy and air create vapors or more air?

retmil46 · **Posted:** Sat Apr 28, 2007 11:23 am

Could be that if the heater is staying on when not needed, and getting the fuel hotter than needed, that it's causing entrained air and gases in the fuel to come out of solution and accumulate in the filter.

I've noticed on a couple of occasions that after a run my fuel filter was quite warm, but attributed that to radiated heat from the engine itself, given the close proximity of the two. Guess I'll dig out the fluke and check mine as well.

But I quite agree, doesn't seem to be any logical reason that the fuel heater should be on on a 90 F day. Offhand, sounds like a problem either with the programming or the fuel temp sensor causing it to be on full time.

Jeger · **Posted:** Sat Apr 28, 2007 1:11 pm

I thought the fuel seemed awfully hot when I changed my filter the other day. Keep us updated.

You gotta love this place.

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

Would this explain why my CRD will sometimes start running much better (and stops shuddering) after I fill the tank with fuel? I have noticed that this happens regardless of if I burp the air out or not. Sometimes, however, when I get fuel it makes it worse. I suppose if the fuel is warmer, it makes it worse-- if cooler it can't heat it up as bad, so then its better. Coupled with the heated fuel releasing air-- this is starting to make some sense.

I have also noticed that even after burping the air out, it no longer shudders much but is still gutless at random. It does it more in summer or after the engine has been running awhile, so I have figured this was the EGR heatsoaking the innercooler. Perhaps it is the fuel heater coming on-- or sometimes both? Maybe this explains some peoples poor gas mileage as well. (Mine has been doing 27mpg in mixed driving, so it is good there.)

If this is indeed the problem-- what should be the permanent solution? A new OEM heater switch? Is the new one going to break too or did we just get a bad batch of them?

Regardless, it is going to be a chore to convince the dealership to replace the switch under warranty. It does not have a code, so I am sure I will get: "It is a diesel, diesels are supposed to run slow and rough." Haha. Ugg.

thewalker350 · **Posted:** Sat Apr 28, 2007 1:30 pm

Do we know if we have a sensor that controls the heater or is it on all the time? If it is on all the time I would think a on-off switch would be sufficient. If we have a sensor controlling the heater we might need to do some adjusting on the sensor I.E. resistors.

dirtmover · **Posted:** Sat Apr 28, 2007 2:59 pm

Hmm, interesting. I was just thinking yesterday, as it shuddered accelerating onto the highway, how the symptoms have been nowhere near as bad over the winter as they were last summer. They have suddenly got worse again now that the ambient temperature is back in the low teens. You may be on to something here!!!

CATCRD · **Posted:** Sat Apr 28, 2007 3:14 pm

Which plug on the filter housing is the fuel heater?

BiodieselJeep.com · **Posted:** Sat Apr 28, 2007 3:44 pm

The Walker: You get a gold star! very nice catch! Might be a sticky in this one, OldNavy!

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

CATCRD wrote:

Which plug on the filter housing is the fuel heater?

Facing the filter, the fuel heater is the plug on the right. It has heaver wire on it than the thermostat plug wire on the left.

DarbyWalters · **Posted:** Sat Apr 28, 2007 3:55 pm

We might also want to isolate/insulate the fuel filter from the engine bay radiant heat. It might be that the fuel heater is working properly but the radiant heat from the engine bay is causing it to get too hot...meaning that the heater is working properly for the fuel from the fuel tank but the filter itself is getting too hot and heating the fuel more than it needs to.

retmil46 · **Posted:** Sat Apr 28, 2007 4:58 pm

Another thing to look at too - if he had the heater unplugged and it didn't cause a CEL or other codes to be thrown, that means it's pretty much a clear shot, as some have suggested, replacing the entire POS fuel filter assembly with a quality aftermarket unit. Preferably one with 1/14 thread to accept a Cat 2 micron filter.

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

The voltage is supposed to be present at the heater plug/pins at all times. The heater element is self-regulated with some kind of positive thermistor characteristics in the heating element itself. Which is fine, unless the element goes bonkers and stays on all the time. Then you have what's called BDS, or boiling diesel syndrome, which is known to make grown men cry on the side of the road,
sitting beside their CRD, hood up and engine not running. If not under warranty, BDS soon gives way to LWS, or lightened wallet syndrome, which is what keeps the Jeep parts department smiling when you call.

From the FSM, section 14-67:
"The element inside the heater assembly is made of a Postive 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 anytime its temperature is high, which means it will not generate heat when the temperature is above a certain value. When the temperature is below 45F, 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 85F, the PTC elements resistance rises, and current flow through the element stops."

What this means to you :-)

As long as the PTC/heater element is working correctly, the range of temperature when the fuel heater is on full blast will be from 45F (and below) with decreasing heat function all the way up to 84F. Assuming the FSM is correct, that is, and this section wasn't lifted from a catepillar bulldozer manual when the tech writer couldn't get past the engineers voicemail. If the PTC element malfunctions, as in goes out of calibrated resistance design, you could have heated fuel in July. It could boil the diesel as you drive down the road with the AC on high. Unfortunately for us, the FSM does not list the correct resistance range so that we could test for a bad PTC day.

One could take measurements from a known good fuel head at 87F, toss the fuel head in the freezer (inside a plastic bag) when the wife isn't looking, and measure again at 40F. If your wife catches you before you report the results, ask her to spare the punishment long enough to report the results.

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

retmil46 wrote:

Another thing to look at too - if he had the heater unplugged and it didn't cause a CEL or other codes to be thrown, that means it's pretty much a clear shot, as some have suggested, replacing the entire POS fuel filter assembly with a quality aftermarket unit. Preferably one with 1/14 thread to accept a Cat 2 micron filter.

I ran with my fuel heater plug disconnected for 3 days without any CEL, other than the MAF P0201. I had to, as the leaking fuel heater electrical port was burning when connected. However, I did read somewhere that the PCM uses the temperature sensor readings (left plug on fuel head) to monitor fuel temperature and adjusts the pump pressure using this information.

UPDATE - It sets a P0183, fuel heater input A High code. Never mind... it seems the odo trick reads some codes that my obd reader wont.

thewalker350 · **Posted:** Sun Apr 29, 2007 12:45 am

If the PCM monitors fuel temp and adjusts the fuel pressure and that sensor is to the left of the heater then maybe with WOT the fuel temperature is changing quickly with the incoming cool fuel and the PCM is seeing this change and is adjusting the pressure which is giving us the shudder. Perhaps the temp. sensor and the heater are too close together causing them to react too rapidly which changes the fuel pressure too rapidly :?:

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

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.

DarbyWalters · **Posted:** Sun Apr 29, 2007 9:33 am

So do we need a FHDM (Fuel Heater Disconnect Mod) to compliment the ORM? :lol:

thewalker350 · **Posted:** Sun Apr 29, 2007 9:51 am

The FHDM is working great for me and its too soon to tell but I think my fuel mileage may have increased too. :lol:

I just want to know why disconnecting the heater solved the shudder. Inquiring minds want to know!

BVCRD · **Posted:** Sun Apr 29, 2007 10:00 am

DarbyWalters wrote:

So do we need a FHDM (Fuel Heater Disconnect Mod) to compliment the ORM? :lol:

I offered this solution some time back as a fix for those having fried fuel heaters. I asked if it would do any harm during summer driving temps but got no return interest back then. If the fuel is warm, it will ignite better. Only way I can see that it might be an issue is if the fuel is near boiling temps. I once had a fuel leak on top of the intake manifold of my old 65 Ford. Dang Rochester carb was leaking. I smelled fuel and pulled over. The fuel was collecting in the low spots on the intake, and was literally boiling. YIKES!!!! Run, don't walk away. :shock:

Shudder after WOT Fix

Who is online