Bucking

irunmiles · **Posted:** Tue Nov 04, 2008 12:51 am

I have 98K miles, so my 100K extended warranty is about to end. For the past month, I've had violent "bucking" while travelling at highway speeds and have to bleed the air from the fuel system approximately every 500 miles. The bucking stops after the air is bled. Before this the bucking was rare, and I only had to bleed the system maybe once between 25K mile fuel filter changes. The current fuel filter has less than 5,000 miles on it (I changed it early thinking that it may be the cause of the increased frequency bucking). Should I take the rig into the stealer before my warranty expires? Is there anything that they can do? I doubt that they will offer a fuel pump as a fix.

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

Sounds like your fuel filter head is leaking and you are getting air in the system. Pull the plug on the heater wiring where it plugs into the filter head, look for diesel fuel (will appear moist). If it's leaking there, take it into the stealer for a new fuel filter head. Supposedly, there is an upgraded filter head dealers are installing now (metal in the area where the plug connects, as opposed to plastic on the original).

Lift pump is a nice mod, but it won't fix the problem of leaky head. If you live in a warm climate, unplug the heater and leave it unplugged to avoid this problem.

warp2diesel · **Posted:** Tue Nov 04, 2008 6:25 am

..and you have a leak, the fuel head will leak, any warranty left, they will need to pay up. Pump it real hard, hold it down and check under the heater plug, chances are it will be wet and they should replace it if your warranty will cover it.

Joe Romas · **Posted:** Tue Nov 04, 2008 7:53 am

Mine had "bucking" or what I refer to as "studdering" from day one, mile one. The cummins pump I put on resolved the problem that the dealer could never duplicate :roll:

Having dropped my tank and seen first hand I believe the first place the air leak is the plastic quick connects back by the tank :wink:

They are soo loose they just slide together with little or no resistance at all. My kj now has a whopping 20k on it and the last 10k were with a lift pump. I also believe the at least part of the heater plug problem is caused by air in the filter head

I've found that my dealer is only able to repair what hits them over the head. Anything else and I get a "can't duplicate"

Back when our KJ's were new some dealers replaced these fuel lines to resolve this problem. I don't know if it ultimatly did but they are in front of the tank and I don't think the tank needs dropped to put them on.

I know our fuel head is a piece of plastic crap but I think in a pressurised system is will work. At one point so must have Jeep or we wouldn't have the fuse, relay and wiring for a lift pump.

ATXKJ · **Posted:** Tue Nov 04, 2008 12:01 pm

FYI - if the dealer will replace it - make sure they get the new fuel head - it's got a reinforced heater plug (so they have to change the connector too)

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?p=381161#381161

irunmiles · **Posted:** Tue Nov 04, 2008 3:27 pm

I checked the heater plug months ago when the concern first appeared on this forum. Mine was not wet or burnt at that time. I checked it again this morning, and it is now wet with diesel and burnt ! The stealer is replacing the seperator and pigtail under warranty. The stealer's parts computer system did not have the new seperator part number, so I had to do some "educating".

warp2diesel · **Posted:** Tue Nov 04, 2008 4:23 pm

Like a Buffet, there is a lot of ways to do it right with a lift pump. The only wrong way is the Bean Counter way that tries to defy the laws of physics. Ask a pump to suck up fuel you will sooner or later get an air leak. When the air collects in the filter head around the heater and it can not transfer the heat to the fuel so the heat goes into anything metal causing it to get hot and any plastic next to it melts, breaks the seal and the air leaks in.

grommet1 · **Posted:** Tue Nov 04, 2008 11:22 pm

I have 28K on my 2006. I have often experienced the "bucking" sensation at 55mph. I assumed that this was the torque converter that I have often read about on some of these forums. However, I now experience the bucking after almost all hard accelerations. After reading this string I now believe it is air in the fuel system. If this is the case, what symptoms does a bad torque converter exhibit?

warp2diesel · **Posted:** Tue Nov 04, 2008 11:39 pm

grommet1 wrote:

I have 28K on my 2006. I have often experienced the "bucking" sensation at 55mph. I assumed that this was the torque converter that I have often read about on some of these forums. However, I now experience the bucking after almost all hard accelerations. After reading this string I now believe it is air in the fuel system. If this is the case, what symptoms does a bad torque converter exhibit?

GMCTD is the expert on that one.

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

grommet1 wrote:

I have 28K on my 2006. I have often experienced the "bucking" sensation at 55mph. I assumed that this was the torque converter that I have often read about on some of these forums. However, I now experience the bucking after almost all hard accelerations. After reading this string I now believe it is air in the fuel system. If this is the case, what symptoms does a bad torque converter exhibit?

A shudder can be caused by many things, including the converter or air in the line. Most cases around here it is air in the fuel. Torque Converters do go bad, however.

http://www.aa1car.com/library/2003/ic60340.htm

Joe Romas · **Posted:** Wed Nov 05, 2008 8:52 am

grommet1 wrote:

what symptoms does a bad torque converter exhibit?

One is when coming to a stop the TC clutch does not release and the engine stalls as a result. Like forgetting to push the clutch on a manual transmission :lol:

Another is when the TC is locked slipping is noticed. Preformance increases will bring this out.

As mentioned most studder/shudder problems at this time are caused by air in the fuel :lol:

06 models built after November of 05 came with a different, better but still not good, TC. Those before that date had some kind of plastic cushion that broke big time. Those were replaced under the F37 recall. F37 consisted of two parts. Hardware (TC and maybe pump) and software (a flash). Those built after 11/05 did not get the F37 recall notice but got the flash when they went in for routine dealer service. The flash cut power overall and during shifts. Exact figures are not widley known.

I've been keeping up with this "studdering and Shuttering" since mid 06 when I got mine studdering mule :lol:

There is a lot of information on this forum but it's somtimes hard to dig out :roll:

BlackLibertyCRD · **Posted:** Wed Nov 05, 2008 12:48 pm

grommet1 wrote:

I have 28K on my 2006. I have often experienced the "bucking" sensation at 55mph. I assumed that this was the torque converter that I have often read about on some of these forums. However, I now experience the bucking after almost all hard accelerations. After reading this string I now believe it is air in the fuel system. If this is the case, what symptoms does a bad torque converter exhibit?

My Jeep TC shutter while pulling a trailer up a grade at lower RPM, (not enough fluid pressure). Have to kick it out of overdrive to get it to stop. Don't slip when not towing, I guess it's a matter of time.

edon · **Posted:** Tue Nov 18, 2008 12:39 am

Ever since new I had experienced the shudder feeling after a hard acceleration to which my dealer's answer always was "cannot duplicate customer complaint at this time" and wouldn't you know, they never would let me demonstrate it for them because "its against their company policy for customers to drive with an employee". So I just lived with it for over 2 years. A few months ago I started to notice what I would describe as a "bucking" feeling (kind of like a cylinder misfire) when creeping along in rush-hour traffic. This too could not be duplicated by the dealer... :lol:

So imagine my surprise when after sending it in to have the glow plug system repaired (a whole other story) both the shudder and bucking feeling have been completely eliminated. What supposedly was changed was an air mass meter and boost pressure sensor, as well as engine and transmission flashes. What they think these have to do with the glow plugs (which still don't work properly) I'm not entirely sure I'll ever know. Oh well, maybe I can send it in to have a muffler changed and whatever they do will fix the glow plugs! lol

irboogie · **Posted:** Tue Nov 18, 2008 9:58 pm

I had the bucking, it got real bad after a long idle. Once it even stalled out on me due to air. I wanted to do the lift pump but I decided to try the tank connections first. So far about 3 tank fulls, I've had no problems at all. I still need to check the lines the rest of the way and see if there any more of the little quick connectors.

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midwest · **Joined:** Tue Apr 25, 2006 12:03 am **Posts:** 173

irboogie wrote:

I had the bucking, it got real bad after a long idle. Once it even stalled out on me due to air. I wanted to do the lift pump but I decided to try the tank connections first. So far about 3 tank fulls, I've had no problems at all. I still need to check the lines the rest of the way and see if there any more of the little quick connectors.

[/list]

How about an update, has this solved the bucking problem? How hard is it to drop the tank?

chadhargis · **Posted:** Sun Nov 30, 2008 12:55 am

What's that a picture of?

Goglio704 · **Posted:** Sun Nov 30, 2008 1:16 am

That is the top of the fuel pickup in the tank. Looks like he replaced the factory lines and quick connects with fuel hose and clamps.

irboogie · **Posted:** Sun Nov 30, 2008 1:56 am

So far I still have not had any bucking or other trouble. It is not difficult to drop the tank. I used a jack to help drop it due to the fuel still in it (about 3 gallons). I can't say it will be a 100% fix for anyone but so far I have kind of forgot about it due to no issues.
Good luck

midwest · **Joined:** Tue Apr 25, 2006 12:03 am **Posts:** 173

irboogie wrote:

So far I still have not had any bucking or other trouble. It is not difficult to drop the tank. I used a jack to help drop it due to the fuel still in it (about 3 gallons). I can't say it will be a 100% fix for anyone but so far I have kind of forgot about it due to no issues.

Good luck

Seems this is a big part of the air problem and a great solution. Did you go all the way to the steel lines at the other end of the quick connects? Did you have to cut into the steel lines?

irboogie · **Posted:** Mon Dec 01, 2008 9:47 am

I replaced all the way to the steel lines so I did not have to cut anyting.

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