Injector Replacement

[hoot]

Originally posted by Broker:

We are not maxed out on weight all the time.
Sometimes we are running with 4 Bonnevilles
or 4 windstars.That is way below our max.
We along 90% of our competitors are running roughly the same running gear.They run with no CDL and they run real quick compared to a F-650.And when they are empty they are fast.
Brakes are electric over hydrolic on all three axels on the trailer.Bracking is no problem.It is only the hills that kill our speed in Vermont.But we are getting power upgrades as we speak.

Broker.... how dare you. Power upgrades? I thought you stayed away from them.

[N.E. TMRPR]

I have K3500 CC that now has 91,000 plus miles on it. It is totally stock and I fuel it mostly out of my own holding tank in my garage. I have double filters on it and had my first injector problems at 71,000. They replaced all eight injectors and the truck was back to normal and then #8 started leaking. The dealer took the truck in and ordered a new injector and line. The line and injector was replaced and returned to me. After about 150 miles #8 started pouring fuel all over the bottom of my truck. Back again to the dealer and they do #8 again. I get it back and after half a day #2 and #8 are leaking this time. I call the dealer on Thurs. morning at 8 am and tell them to pick it up right away because I needed it for Tues. for a haul job with my gooseneck for a quick $2,500. They finally get it at 1pm on Friday and start working on it Sat. morning. They call me on Monday morning and tell me that the parts will be in on Weds. morning. So much for good service huh! So now my $2,500 is out the window. They finally get the truck done on Thursday and now I'm ****ed. I went to the owner and told him after doing business with him for 15 plus years {Usually buying a new truck every 2 years plus my wife buying a new Envoy} and spending $75,000 in 01 with him I thought they should take care of me with the trade in of my truck and a great price on the new one. I had considered keeping this truck longer but they couldn't seem to fix it and did'nt want to pay for repairs after warranty. I also spoke with the tech who worked on the truck and this is what he told me. If someone can verify this I would appreciate it. The tech said that the injectors have a roll pin in the top of the body and they had been torqueing the line nuts down too much causing the roll pin to break and the injector to leak. Back to my deal. The owner gave me blue book for my truck {$24,000} and took $6,800 off the list of $48,700 plus the rebate it came to $15,000. I thought this wasn't too bad. By the way, I took the truck for a 600 mile tow this past few days and there's no more leaks and the mileage was back to around 12.8 mpgs with the trailer running 80 mph. It's still going this week! I have faith in the truck as the rest of it has been flawless. It still has the original tires {they are about done} over 50% brakes and still is extremely tight. I do beleive GM will solve the injector issue with Bosch. I have three friends with the 6.0 Ford and they have already had injector issues. The requirements for the EPA are whats causing the failures. Sorry for the long post but I thought my case applied.

[Bulldogger]

With all the talk about injectors going south did anybody ever try Diesel Dynamics they offer injectors for $1200 with exchange. If your gonna change them, any idea if these are any good? do they have a truck that shows up at pull-offs or Dyno days. Dave [img]smile.gif[/img]

[blue]

How do people KNOW their injectors are leaking significantly? Is it funky idle, a major miss, major smoke or what?

I have a little ~25-50rpm jump in idle speed, lasts a fraction of a second, every few seconds it happens. I don't care about it, it is no big deal. If it is a leaky injector I don't care.
When SHOULD I care?

[dmaxalliTech]

You will know it, smoke, rough idle, rough running, knocking. fuel in oil, all are signs of injector trouble. Is your truck an 01?

Your idle surge has two fixes, a programming update and if thats not it, its likely a pressure regulator

[whoz]

Dmax pays only about $75 per injector. If you have to pay $6K for a set either GM or Isuzu is making a killing.

[OC_DMAX]

This sounds about right. Parts seem to cost 3 to 4 times at the dealer as to what you can buy through regular part outlets. Case in point, fuel filters for $45 while you can by them online for $18. How about Allison tranny filters for $27 at the dealer while at the Allison shop, filters go for $9. If GM would get their act together and sell the injectors for say $150 (still leaving them and the dealer with 100% mark-up), the repair bill would not leave customers in a state of shock. So much for customer satisfaction.

[Viking]

You can just call it going for the almighty dollar!

[whoz]

Contamination in injectors:

Becareful when replacing the first fuel filter. I know that the majority of Cummins injector problems with the Bosh injectors begin AFTER the first filter change. The break into the system to install the filter introduces contamination after the filter connection which can end up in your injectors.

The Cummins and Dmax injector have the same guts expect with diffent hydraulic orifices to control the injector performance. The components have have different part numbers and are produced in the same equipment.

The Cummins injector body is made from bar stock with a low pressure return at the bottom of the injector. The Dmax injector is made from a forging and its low pressure connection is off a forged ear at the top. A injector with an internal crack will show up as a poor performing cylinder with a high back flow from the low pressure connection. Since the bar stock has a more uniform grain structure then the forging the bar stock (round) injector will probably have a longer life.

Since the Dmax motor came out before the Cummins motor, it had more of the process improvements to prevent body cracking. The Cummins injectors from the get-go should be more reliable relating to body cracks anyway.

Personally being in automotive engineering, I would never buy a product with a brand new system of anything the first year it was out. There is always a learning curve and the products near the end of their market life are the most reliable. Considering the technical challenges with materials (steels) resisting the high pressures it is no wonder there are material problems and cracks. The materials are under severe stesses.

Common rail pressures are pushing the limits of material science. The higher the pressures the more problems there will be.

Anyone jacking the system pressure up with specialmodules to increase performance is killing their injector life at the same time. The injector body fatigues and it has a life measured in pulses at the design pressure.

[OC_DMAX]

Whoz,

I'll ask the obvious, did you participate in the design of the DMAX injector and if so, how many iterations of the design have we been through?

With regard to "special modules to increase performance", most of these boxes do not increase rail pressure on the DMAX above the stock 23Kpsi design (very early boxes did raise rail pressure). However, the rail pressure on the DMAX swings all over the place, depending on engine operating conditions. So,,,those who have these add-on boxes on their trucks have a tendency to push the truck a little harder and thus are operating with a higher "average" rail pressure than those who do not have a box. In any case, the max pressure is always within the stock 23Kpsi design limit.

From my perspective (and after reading the GM injector warranty letter that I received), I came to the conclusion there are multiple problems with the original injector design. Some of these problems the DMAX owner can have an impact on by increasing the lubricity of the fuel (additive) and cleaning-up the fuel (supplemental filtering). Some of these issues, the owner can have no impact on (fundamental design material property issues that you mention). Hopefully, DMAX Limited and Bosch are working off the issues.

By the way, I am an electrical engineer in the Defense Electronics business. Our product evolutions are similar to those that you work on in the automotive area. We design a product to an agressive cost and schedule, then build, test and deliver the product. After delivery, we begin with product updates (usually software). I purposely waited to buy the second year DMAX with the above in mind, looks like I did not escape the injector issues though.

Regards,
Alan

[ 01-27-2005, 04:27 AM: Message edited by: OC_DMAX ]

[More Power]

By 2001, a series of Duramax 6600 engines had already been tested for more than the equivalent of a combined 1M miles in GM's engineering facility. In addition, the first 6600 began durability testing in 1998, and by 1999, fleets of 6600 equipped trucks were being tested in the SW and in AK.

The earliest engines were basically hand built in Japan, and I suspect the earliest fuel injection systems were hand built by Bosch. I tend not to think the injector design is faulty, but rather that the demands of mass production allow problems to creep into the finished product. Up till late 2002, DMAX was producing something on the order of 400 engines per day, then in late 2002 or early 2003, that number went to as high as ~800 as the second line began production. This figure can require as many as ~6,400 injectors per day being built into engines x six days per week.

I'd bet GM has equipped the chair seats in their conference rooms with hot plates (especially for the Bosch engineers).

MP

[whoz]

I did not participate in the design, but I do know those who did. I was more on the processing side. The design it self was very stable, the issue is the processing of the steel components. There were no major design changes within a generation. The customers will not allow that.

The body steel is pushed to the max and all stress concentrations must be removed from the part. That means all bore intersections in the high pressure area need to be ECM deburred and rounded and any chemical process (derusting before phosphating, neutralizing after ECM) need to not attack the grain boundaries in the steel. If the pickling before phosphating is to hard the MnS stringers are eaten away and it leaves a very tiny pit for the pressure to work on and start a crack.

I agree the American fuel is crap. The Europeans have worked a long time on the fuel quality to be able to run fuel lubricated pumps. The Cummins and the Dmax are both fuel lubricated pumps. If the US could get as good of quality fuel there would be a lot less problems with the pump and the injectors.

The newest injector (generation 3 1800 bar) will be made without a phosphate coating. It is a waste of money to have it since the Dmax injectors are covered by the oil cover anyway. The problem is that nobody likes the cosmetic issues with finger print rust, etc. The incoming inspection expects a perfect looking part, or else it is rejected. But, in order to make it look perfect other things unseen might be disadvantaged.

The rail pressure swings because the pump is suction controlled with a proportional valve. If the valve overshoots it give a little more fuel to the compression piston and the rail pressure goes up. And, there is the response time of the pressure regulator so under dynamic conditions I'm sure you have lots of ways the system can over and undershoot.

What is a shame is that there are no passanger cars with common rail in the US. The Bosch Diesl magazine had an article of a new Honda Accord with common rail. It got 75 mpg on the highway. All common rail and unit injector systems have good low end torque and are fun to drive. I would buy such a system if they were available and the US fuel were better. The VWs with the unit injectors are also very fun to drive.

[ 01-27-2005, 12:42 PM: Message edited by: whoz ]

[OC_DMAX]

Excellent discussion here Whoz, thanks for the insight into some of the issues with the injectors and the material processes involved in making them. I need to track down the materials guy here at work so he can educate me on some of the finer details that you wrote about.

Its unfortunate that the US Government / Industry cannot get their act together and clean-up the diesel fuel. I have been following the recent lubricity standards that are being negotiated with industry (as we roll out Ultra-Low-Sulfur Diesel here in the US). There seemed to be an excellent chance to minimize injector system wear by increasing the lubricity of the ULSD fuel. That chance has faded and the final wear standards seem to be well short of what Bosch recommended.

I am also leaning to agree with what MorePower mentioned above (original prototype designs worked fine, but when produced in a production environment little process problems creep in). I have seen this happen before also.

Later,
Alan

[whoz]

The new system for large diesels, to replace the unit injection system, is the pressure amplified system. The high pressure (2400 bar) is isolated to a limited portion of the injector. That means the pump and rail both operate at lower pressures that don't tax the materials so much. The trade off is that the pump has to put out more flow in proportion to the amplifier ratio. In this case a fuel cooler is recommended since the amplifier return fuel is hot. Hot fuel has poorer lubrication properties as well.

The cost reliability trade off is being made once again. The customers are pressuring the injection system designers to design pumps and injectors that can operate with fuel temps. of 90 deg C. That means everything is pushed to the limit to avoid the heat exchanger and its associated costs. To me they are setting themselves up for failure. They are saving money on piece costs and will have the customer pay it back in reliability costs.

It is like the stupid timing belts in cars that have to be changed. I'd rather pay for a timing chain even if it is a little more noisy. The same idiotic trade off was being made with stainless steel exhaust. I gladly pay another $100 on the car price to not have to replace the exhaust system for $125 every two years. Thank goodness the Feds required the manufacturers to warranty the exhaust system for 5 years. They knew what the costs would be and added stainless steel on their own!

The unit injection system in the VW's kicks butt and has the highest pressure of any diesel system.. 2050 bar. I have not heard any big problems with it either. The break even between a unit injector and common rail is after 4 cylinders, so the unit injectors will stay with the pass. cars. It would be cool to see a big V8 motor with all unit injectors! It would kick butt.

[ 01-27-2005, 01:41 PM: Message edited by: whoz ]

[DmaxMaverick]

Whoz

The Powerstroke Diesel engines (Ford) have used the unit injector system (HEUI) for many years. It is different than a fuel pressure only system , as they use an engine oil pressure system that activates the fuel side of the unit injector. A reliable system, but they have their drawbacks, too.

Excellent discussion with some very good info. Thanks for your input!

[whoz]

The Bosch unit injectors are driven off a camshaft with a roller. The roller works on a high pressure piston compressing the fuel and it has a solenoid to control the opening timing. It is like having a one cylinder high pressure pump integrated in each injector. The Bosch UI's are fuel lubricated but can require a weep hole under vacuum at the end of the cylinder to keep the blow by fuel from mixing with the engine oil.

Bosch has some really great technical primers on most of their diesel products. Maybe I scan some stuff if there are any diesel tech freaks here.

[OC_DMAX]

I purchased an excellent text book from the SAE last February. It was written by Bosch and is titled Diesel Engine Management, Systems and Components. Anyone who is interested in reading about the diffenent fuel injection systems,how they are controlled, how emissions interact with these systems plus a whole lot more would be advised to purchase the text book. There is a whole chapter dedicated to the High Pressure Common Rail systems by Bosch.

[OC_DMAX]

Whoz,

Has Bosch and DMAX Limited worked out all the issues with the DMAX injectors or are they still tweaking the material processes (even in 2005)?

With regard to cost cutting on each vehicle, when a manufacture can save $500 per vehicle and they produce 500,000 units (as they do with the GM trucks), these savings can add up. It is a little frustrating like you mention when the sticker price of the vehicle is $40K and the manufacture is going cheap on us. I would rather pay $41K and have the best quality. Maybe someday they will catch on.

[Bugsy]

My 2004.5 D/A is going up for sale next week.
It has 10,800 miles and already a headache.
Never buy Chevy again.
I've had 2 and both were lemons.

Good riddens.
Sure, I'm gonna take a beating but not like I would after 36K miles is up.

[whoz]

Hi OC_DMAX,

As far as I know of the generation 1 injector materials and processes have been stable since the beginning of 2002. The measures taken should provide the specified durability and fatigue strength.

I do not know much about the generation 2 results. Generation two should have been a less expensive injector with more accurate injection quantities.

The latest design, generation 3, is a 1800 bar system with a slightly different steel alloy for the body and elimination of the phosphate coating. There is still a surface treatment for corrosion protection but it is proprietary and was chosen because it was friendly to the steel.