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dangerous programming
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=24439		 Page 1 of 1
Author:  naturist [ Mon Sep 17, 2007 6:09 pm ]
Post subject:  dangerous programming
I just survived a near miss. No wreck, but I'm sure the trucker who had to stand all over his brakes hates my guts.

I pulled out onto the highway in the shadow of a blind curve, looked in the rearview and saw the truck come around the corner. I floored the CRD, and it immediately went into major limp mode. Barely enough power to hold the 25 mph I was doing at the time. The trucker had to hit the brakes as I got as far onto the berm as I could. Bumped the shifter into neutral, switched off the engine, and restarted about the time the truck passed me in the other lane.

It had enough power then to accelerate slowly to highway speed, and got me down the road to the nearest dealer, where the replacement of the fuel filter solved the problem.

Clearly some idiot programmed the computer to utterly kill power unless there is enough fuel to yield full power, and made it so a reboot of the computer was needed to restore normal operation, a really stupid way to handle the situation, in the opinion of myself, a truck driver, the parts guy and service guy at the dealership, not to mention my wife, who was seated beside me and is ready to wreck mayhem on Chrysler Corp.

I _WILL_ be filling a complaint with the National Highway Safety Commission, but I wanted to be sure everyone was aware of what amounts to a major flaw in the programming of these vehicles.

I've experienced the power loss that happens when my Jetta TDI filter starts to clog. You lose a bit off the top, enough to alert you that there is a problem, but if the filter will pass enough go-juice to give you, say, 50% power, it's 50% power you get and that's all. The Jeep, you can either have 100% or zippo.

The filter was just replaced about 15,000 miles ago, and wasn't due yet. But that's not why I'm peeved. I'm furious because I was almost squashed like a bug due to SOFTWARE, dammit! This vehicle is drive-by-wire. There is NO hardware connection between the go-pedal and anything connected to the engine. It is strictly a computer programming error. When a filter starts to clog, it doesn't shut off fuel suddenly and completely, it slowly loses maximum flow rate. And it sure as hell doesn't allow fractional flow AFTER it has clogged enough to completely block up on full flow demand.
Author:  BBB [ Mon Sep 17, 2007 6:53 pm ]
Post subject: 
Scaaaaarry. Other diesels I have driven had a slow loss of power over a few days as you mentioned and yes that was your que that the filter was getting clogged (GM 6.2's and Ford 7.3's) Maybe the programmers initiated the limp mode so the fuel pump would not starve completely and you would have some means of movement instead of just dying? Could you mount a pressure guage to monitor the filter's flow rate?

Wow... I'll have to let the Queen know to think twice before pulling out in front of a 80,000lb truck. You know... physics, inertia and all.
Author:  BlackLibertyCRD [ Mon Sep 17, 2007 7:01 pm ]
Post subject: 
Gald to hear that no one was hurt and you are still with us. I think it's the CRD losey fuel system that makes the problem worse. I hate the limp mode too wish it wasn't so sudden when it happens. Maybe we should all complain to NHSC about the limp mode being too dangerious and would be better we broke a part than lose a life.
Author:  UFO [ Mon Sep 17, 2007 7:08 pm ]
Post subject: 
I'm glad you are still around to report this issue.

Definitely need a fuel pressure monitor. A vacuum gauge on the output of the filter should do it.
Author:  Cowcatcher [ Mon Sep 17, 2007 9:45 pm ]
Post subject: 
I would be willing to bet that you filter was just fine. The CRD will always wallow and do nothing if you "stomp" it. Somehow I always forget that and do it anyway :oops: , and always when I really need the power. hit it lightly until it spools some then hit it and it is a rocket. If that wasn't the issue it was what BlackLiberty ID'd, air. Since you shut it down and restarted right away if it was still sluggish it was likely because you had not let it rest long enough for the air to self purge some.
Author:  retmil46 [ Mon Sep 17, 2007 10:24 pm ]
Post subject: 
Been there, done that, not once but twice within the first 6 months of owning this beast.

I've adopted the mantra of replacing the filters once a year, regardless of mileage, just before winter.

Hard lesson learned - don't change your fuel filter based on mileage alone, but also on the quality of the fuel that's available.

Prior to installing the Stanadyne filter, but after getting the Suncoast TC and lift pump installed, on that tank I was somewhat puzzled because fuell mileage looked to be decreasing. I wrote it off to the tranny having to relearn to live with the new hardware at first, but I had a sneaky suspicion due to how slow the pump had operated on the prior fillup.

When i did install the Stanadyne and change out filters, well, Cowcatcher posted the pics of the "coffee grounds" that came out of both filters - enough rust, dirt, and water to choke a moose. And even more inside the filters when i cut them open. If I'd still been operating a vacuum system with two filters in series and that amount of crud in them, that Jeep would have been DOA long before that point. With a clean set of filters, mileage on this tank jumped back up noticeably, 285 miles with 5/8 left.
Author:  Joe Romas [ Tue Sep 18, 2007 8:09 am ]
Post subject: 
I've experienced this a couple of times also. Push the peddle down and nothing happens as traffic comes barroling down on you :shock: I suspect the real problem is, like BlackLiberty says, is air in the fuel system. But if you have a plugged filter it would cause it also. I've owned about 20 diesel vehicles since 1978 and have not gotten a bad tank of fuel yet (knock on wood) :? I've gotten some that didn't run well though :roll: I'm sure it can and does happen but is not as bad as it could be :) Mine has had air in fuel symptoms since the very first trip home from the dealer. Bucked like it was running out of fuel with a full tank :twisted:
Author:  boilermaker2 [ Tue Sep 18, 2007 8:21 am ]
Post subject:  I don't think it is air
Some have CRD's that will smoke the tires. Mine never has. After a car wash, it will jerk sideways at 20 mph as the turbo spools up. :twisted:
The only time I have noted the air issue is when I let off the gas, not get on it.

My jeep has never jumped but it will respond quickly if I take one second to get it to the floor. Anything faster and I think that too much fuel is dumped into the system, the turbo doesn't spool and your on the outs.

I have noticed that the jeep seems to accellerate quicker which I think is dumb. After all, I thought O/D Off at most changed the RPM shift point and at its least just kept the machine from going into overdrive.

Neither situation explains what happened to you. I am curious, were any codes thrown? I think we would all like to know that.

Boiler
Author:  Jeger [ Tue Sep 18, 2007 8:33 am ]
Post subject: 
I vote for air also. Bleed it once a week, a bet you get air more often than not. Although it does take a good bit of air to cause a limp mode, you should notice it bucking a bit here and there before it completely craps out.


If it was the traction control/esp it wouldnt have ran bad after you got off the go pedal. And you should have seen the traction control light flashing.
Author:  Joe Romas [ Tue Sep 18, 2007 8:38 am ]
Post subject: 
Boilermaker2.

As was mentioned earlier this a a drive by wire vehicle :lol: Our peddle has no direct connection to the pump. It's all computerized. Your noticing air in the fuel when letting up on the peddle was my first symptom of air :roll: Recently I put a small O ring in the filter head and in the process bled every bit of air out of the filter head and it ran fantastic untill I filled it up 400 miles later and think got air back into it. The bleeder nipple is not the hightest place on the head and will not let all the air out. I bled mine from the output port to the pump after putting in the o ring. I think the pump is starving for air and easing down allows it to purge the air and when it's totally down the air is purged.
Author:  naturist [ Tue Sep 18, 2007 8:51 am ]
Post subject: 
It wasn't air in the lines, sorry guys.

Once it went into limp mode, it did not un-limp until the engine was restarted. This "effect" happened a couple more times (but not under such, er, urgent pressure) on the way to the dealer, so I had lots of chances to test theories other than limp-mode.


Mine would smoke the tires until the F37 recall. (For what it's worth, I'm ok with the lower power after that recall in the cause of better driveability.) And driving it 41,000 miles has schooled me in how to drive with the turbo lag. It has NEVER bogged badly when you jump on the go pedal, it merely moves off initially in a leisurely fashion until the tubo spools up, then delivers a firm kick in the butt. And when I saw the truck in the mirror, I didn't "jump" on it, but I did push my foot down firmly.

After the fuel filter was replaced, I tested it by several foot-stomping accelerations, and it behaved normally.

As to the question of breaking something, remember, there is NO throttle plate here (discounting that darn EGR/Flow Control valve). A diesel is supposed to take in all the air you can cram in there ALWAYS. There is ONLY fuel amount/turbo boost to control engine output, and both of those are firmly under control of the ECM. A limp mode is fine, when things are about to break, I have no problem with that, although this limp mode seems just a bit too underpowered. What I am not fine with is the computer deciding to give you far less power than you could otherwise get. There is no reason why the computer seeing a fuel pressure problem, has to essentially kill the engine entirely. The binary full-power/nothing situation is not applicable here.
Author:  boilermaker2 [ Tue Sep 18, 2007 9:05 am ]
Post subject:  A couple more questions
Naturist:
Do you conduct a WOT periodically or do mostly baby the machine?

Do you switch fuel, B levels or fuel stations? (I have but I am very consistent on B2-B5-B20 blends from the same refinery and source stock)

This is not accusatory, I am trying to walk through a potential cause-effect without pouncing on one issue.

The rest of the group:
Does the fuel pump change pressure/rate of fuel due to demand or is the rate/pressure constant and the amount is regulated at the fuel rail? (24 atmospheres- a built fuel heater 8) - kept constant and excess fuel routed back to the tank)

I've been watching black CRD's posts about a lift pump as well and am just doing some cross-threaded ( :shock: ) observations.

Boiler

Sorry: This post was being written after Naturist had already replied. Not going to delete it though, some of the questions have not been answered.
Author:  naturist [ Tue Sep 18, 2007 9:19 am ]
Post subject:  Re: A couple more questions
boilermaker2 wrote:
Naturist:
Do you conduct a WOT periodically or do mostly baby the machine?

Do you switch fuel, B levels or fuel stations? (I have but I am very consistent on B2-B5-B20 blends from the same refinery and source stock)

This is not accusatory, I am trying to walk through a potential cause-effect without pouncing on one issue.


I did conduct several WOT tests both before and after the filter swap: consistently went into limp before, consistenty did not after. Also consistently refused to return to normal after limp mode until engine was shut off and restarted. I also tend to drive like I stole it normally. I've noticed that if you baby it for a few days, then stomp it, you can get a cloud of smoke, which I do not like to see, so I tend to "clear" that out at least once a day.

This was all on the same tank of fuel. I get almost all my fuel from the storage tanks on my farm. Before anybody hollers, this is taxed and undyed on-road fuel delivered by the local distributor. And before it goes into my vehicles, it goes through a 10 micron filter/water-blocker. I did put one tank of ULSD from a station I'd never visited a couple tanks ago on another trip. But that fuel had been all run out and I was back on 100% fuel from my tanks when the incident happened. So I may have gotten a bad load causing the filter to fill up. But there was no change in the fuel before/after/during my "adventures."
Author:  Jeger [ Tue Sep 18, 2007 9:29 am ]
Post subject: 
You will know soon enough if it was in fact your filter getting clogged...unless you fill up at the station next time.

I do agree though that it does sound more like a clogged filter than air.

BTW...maybe there is something wrong with the filter on your tank at home, it should filter just as good as the stock CRD filter, and should therefore be clogged as well? Unless you have some algae growing in the KJ's tank.
Author:  nix [ Tue Sep 18, 2007 11:12 am ]
Post subject: 
This is rather interesting, as I just replaced my fuel filter for the first time. (at 27,000 miles) I replaced it with another OEM filter since I've had no bucking or air in fuel problems. When I put the new filter on (I did not pre-fill the filter with diesel as I had none around) I did the whole bleed the air procedure. (open the screw, pump away and wait for diesel only to come out) I swear I filled up 4 cups of diesel and air was still spitting out of the bleeder screw. I finally just pumped it until the first sign of a steady stream of diesel was coming out then closed the bleeder screw. I'm sure if I let it go a second longer it would spit air out. Since my filter change the jeep seems to be slightly lounder and clattery-er (is that even a word?) But no bucking or power loss. Is it normal to bleed that much air out? Should I go and keep bleeding the air out or leave it be? I don't want to be squashed by a semi :shock: on the interstate.
Author:  Cowcatcher [ Tue Sep 18, 2007 11:22 am ]
Post subject: 
nix wrote:
This is rather interesting, as I just replaced my fuel filter for the first time. (at 27,000 miles) I replaced it with another OEM filter since I've had no bucking or air in fuel problems. When I put the new filter on (I did not pre-fill the filter with diesel as I had none around) I did the whole bleed the air procedure. (open the screw, pump away and wait for diesel only to come out) I swear I filled up 4 cups of diesel and air was still spitting out of the bleeder screw. I finally just pumped it until the first sign of a steady stream of diesel was coming out then closed the bleeder screw. I'm sure if I let it go a second longer it would spit air out. Since my filter change the jeep seems to be slightly lounder and clattery-er (is that even a word?) But no bucking or power loss. Is it normal to bleed that much air out? Should I go and keep bleeding the air out or leave it be? I don't want to be squashed by a semi :shock: on the interstate.


Did you close the bleeder each time at the end of the stroke? If not it ingested air on each repeated pump.

I know this is a common diesel design but in my old age it is harder to manage. I wonder if you could add a check valve at the bleeder so you could just pump it. You would still need a valve or plug after the check valve.

In the spirit of full disclosure I have pumped air twice in 33K miles. Once when I ran the fuel too low and the second time when I changed the fuel filter at 28K miles. I had one experience of fuel starvation at about 25K with a less than 1/4 full tank on a hot day after a sharp, low speed 90 degree turn in traffic. I think it was air injested from the tank and there was no CEL. I will be looking at BlackLiberty's lift pump/check valve solution as I think with it the air would have cleared and enough fuel would have made it to the pump. The fuel filter may also have been a contributing factor at 26K but mine didn't seem all that dirty when removed.
Author:  Joe Romas [ Tue Sep 18, 2007 11:23 am ]
Post subject: 
What if one of the conditions that sets limp mode is low fuel pressure. and that low pressure was caused by air in the system :?:
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