A Question for the Injection "Masters" - Page 6 - PeachParts Mercedes-Benz Forum

sasquatchgeoff · #76 09-10-2009, 11:31 PM

Quote:

Originally Posted by jt20

it was previously implied, I believe.

but the system is self-priming, and to add this benefit, the filter is located ABOVE the IP in a relative sense. The air rises quicker than the fuel can be sucked into the IP.

Hence the occasional air bubble in my translucent return line (I have one clear yellow one that connects to the secondary filter canister) I may be wrong, but I would think that the back-flow valve would prevent return fuel from entering the gallery unless the primary filter was plugged up completely (the reason for the valve in the first place) - isn't return line pressure separate from gallery pressure?

sasquatchgeoff · #77 09-10-2009, 11:36 PM

Quote:

Originally Posted by Dionysius

Ye guys are so great. Thank you Sasq for your dedication and thoroughness.

you are welcome

Quote:

Originally Posted by jt20

Yes, thanks again SAS, a thorough thread that is updated with conclusions is always enlightening.

welcome - as always

Diesel911 · #78 09-11-2009, 12:03 AM

You are now the "Injection Masters".

Diesel911 · #79 09-11-2009, 12:08 AM

Quote:

Originally Posted by sasquatchgeoff

For me, the act of replacing the o-rings and the subsequent boost in performance/quality was an indicator of problems in the pump/atmosphere barrier. However, I did simultaneously replace the copper seals as well, so the grease method might work, as long as the grease remained congealed enough to seal the air gap (heat would thin grease).

I am still not completely sure how the air got in. My pump shop's "pump specialist" swears up and down that there is no way for air to get in the gallery unless it comes from the lift pump because of constant positive pressure in the gallery. But, as we have discussed here, the possibility for air infiltration as a result of some negative pressure in the gallery created by the dynamic pressure shifts in the system due to acceleration, shift patterns, slow-down, etc, as well as sitting over several nights with less than 1/2 tank of fuel and the negative siphon pressure possibility therein, still looms in my mind. By that logic, every seal that presents a barrier to gallery pressure/atmosphere should be inspected and replaced.

In my case, the pump sat without injector lines connected to the DV holders for about 5 months while we painstakingly rebuilt the head. Also, there was 246,000 miles on this pump with 60 or 70K of those miles using B99. After touring a biodiesel plant as a research project, I know that there is a crapload of lye and methanol in B99 and both substances are known to deteriorate EPDM - the stuff that o-rings are made of.

I do not think the IP gets hot enough to cause Wheel Bearing Grease to run off. I would stay there long enough for a test.

Dionysius · #80 09-11-2009, 03:11 PM

Quote:

Originally Posted by Diesel911

I do not think the IP gets hot enough to cause Wheel Bearing Grease to run off. I would stay there long enough for a test.

This could then be a good strategy for troubleshooting. Since work and expense is involved in proving it to the Injectors or the DV & O Rings area I wood suggest this as a first line of attack to eliminate the O Rings & DV area.

So the logical, minimally invasive, minimum cost, troubleshooting approach is as follows:

1. For diagnostic isolation carefully apply bearing grease to DV Valve fittings on the IP to seal any possible air ingress. Test for 200 miles and keep monitoring the persistence of the grease seal.

2. If problem persists examine and repair all air ingress possibilities related to the low pressure fuel supply and return circuits.

3. If problem still persists pull the hi pressure hard lines and Injectors and bench test them plus examine the atomizer and prechamber areas for carbon and damage.

Please feel free to edit or modify this approach since I am sure I have forgotten something. Let me know if you agree with it or if you have any question or suggestion. This is a complex thread and someone one year from now will need a quick final review. I want to hang the final one in my workshop.

sasquatchgeoff · #81 09-11-2009, 03:44 PM

Quote:

1. For diagnostic isolation carefully apply bearing grease to DV Valve fittings on the IP to seal any possible air ingress. Test for 200 miles and keep monitoring the persistence of the grease seal.

2. If problem persists examine and repair all air ingress possibilities related to the low pressure fuel supply and return circuits.

3. If problem still persists pull the hi pressure hard lines and Injectors and bench test them plus examine the atomizer and prechamber areas for carbon and damage.

Thanks Dionysius,
Excellent summary.#2 is almost infinite in possibilities, but for our purposes, in order the isolate the DV seals, this strategy will at least eliminate this pesky phenomenon. Establishing that there is a possibility of negative pressure within the IP is a milestone. Some IP techs disagree that it exists at all.

Dionysius · #82 09-11-2009, 06:52 PM

Quote:

Originally Posted by sasquatchgeoff

Establishing that there is a possibility of negative pressure within the IP is a milestone. Some IP techs disagree that it exists at all.

The scientific approach here would be to instrument the IP gallery with a pressure transducer and set up for electronic triggering when the signal goes negative. The comparative and differential analysis of the recorded pressure signal data whilst driving with good and with faulty O-rings would be very informative. I would have pedal position, rpm, speed, boost-pressure, for correlation on the other channels. Most certainly the Bosch Designers have all of this data in their engineering files but do you think that they would ever break their code of silence and take us out of our misery?? Most unlikely methinketh. I wish I had some insider access into that Fort Knox!!

sasquatchgeoff · #83 09-11-2009, 08:29 PM

Quote:

Originally Posted by Dionysius

The scientific approach here would be to instrument the IP gallery with a pressure transducer and set up for electronic triggering when the signal goes negative. The comparative and differential analysis of the recorded pressure signal data whilst driving with good and with faulty O-rings would be very informative. I would have pedal position, rpm, speed, boost-pressure, for correlation on the other channels. Most certainly the Bosch Designers have all of this data in their engineering files but do you think that they would ever break their code of silence and take us out of our misery?? Most unlikely methinketh. I wish I had some insider access into that Fort Knox!!

That info would have saved me about 3 months of cranium against my garage wall.

It is indeed a stretch to imagine air traveling past that flattened o-ring, through all those threads on the end of the DV holder, and into the gallery fuel - but evidently it happens.

Diesel911 · #84 09-12-2009, 01:22 AM

Quote:

Originally Posted by sasquatchgeoff

That info would have saved me about 3 months of cranium against my garage wall.

It is indeed a stretch to imagine air traveling past that flattened o-ring, through all those threads on the end of the DV holder, and into the gallery fuel - but evidently it happens.

Some of our great minds say that a Bee is not supposed to be able to fly.

Science starts with observation. You had a problem and you observed that replacing the O-rings and Crush Washers solved the problem.

If the exact explanation is lacking it does not matter as the problem is fixed.

The next step is for some more Members with the same problem to do the same repair and see if it also solves their problem.

Dionysius · #85 09-17-2009, 03:21 PM

I have done some serious study on the Bosch In-Line Multi-Cylinder pumps such as Type APE and Type PES. The design has changed little from the 30s to the 80s when Common Rail began to take over. These pumps use a constant stroke with variable volume. The stroke is derived from a camshaft driven from the timing chain located at the bottom of the pump. The variable volume or charge of fuel is derived from a rotation by the rack which alters the length of stroke for the helical fuel path to reach the spill port. The rack is activated by the accelerator and governor.

I cannot conceive of a negative pressure ever being developed in this system which would cause suction of air past the O Rings and Threads of the DVs.

The only explanation I can give is that when a hot engine is stopped the pump casting and components are hot and the standing fuel in the pump is hot by contact. As this fuel cools down to ambient conditions the decreasing volume will draw in the air.

sasquatchgeoff · #86 09-17-2009, 07:59 PM

Quote:

Originally Posted by Dionysius

I cannot conceive of a negative pressure ever being developed in this system which would cause suction of air past the O Rings and Threads of the DVs.

The only explanation I can give is that when a hot engine is stopped the pump casting and components are hot and the standing fuel in the pump is hot by contact. As this fuel cools down to ambient conditions the decreasing volume will draw in the air.

This indeed has been an exploration of the IP and associated components - especially for me. Truth is, this exploration (especially the recent events) compels me to agree with you Dionysius. I guess I should back up a bit here (I might get a little long-winded, so be prepared).

I owe you all an apolgy for not waiting more time to post my remedy. The nailing behavior ultimately returned after replacing the DV o-rings and seals. This time the nailing/rough idle, for whatever reason, took its own sweet time manifesting itself. The following is a coarse synopsis of the 5 or 6 repetitions of the engine (and my own) behavior pattern after each attempt to isolate the problem and subsequent failure. I wrote this after discovering that the nailing/bad performance had returned:

1. Purge pump of air (this last time I REALLY did it good, because the DV holders were removed - I believe air gets trapped in there)
2. Engine runs spectacular first and second day (this last time the engine ran spectacular for about 4 days) - I am grooving on the wonderful high of the "honeymoon."
3. What I call "Dark Morning" - crank car and there is a rough idle - almost as if there is air in all cylinders - eventually smooths out
4. Next day: What I call "Evil Doom Clouds" - engine cranks - idle is really rough and never really smooths out. Injectors begin to get noisy. Chugga-chugga at red lights - I begin looking for a firearms shop.
5. Next day: What I call a "Please Kill Me Now" morning. Rough crank, idle, and very noisy injectors. Minor nailing at first crank - but goes away. Injectors have a peculiar sound, almost like an idle sound from healthy, newer injectors, but present across all the RPM ranges. By this time power is beginning to wane.
6. Next day: The "I'm Gonna Drive It Until it Blows Up" phase. Rough cranking, idling - chugga-chugga at red lights, nailing in the 1500-2200 range, low power, my right hand rests peacefully on the handgrip of a loaded high-caliber sidearm, awaiting the command from my brain to end this misery.

So that was the pattern, with a little humorous embellishment on my part (no I never really considered suicide or firearms).

Last week, I went to the injector shop to get my Monark after-market nozzles installed on the injectors. I spoke with Rod while Kyle fitted the Monarks and tested my injectors.

At this point I will ask you to see post #44 in this thread.

Rod suggested that the only thing that was left was the secondary fuel filter housing. He said he had experience with the 602/602 FF housing cracking because garage gorillas over-torqued the banjo-fittings while reusing crush washer seals. He said sometimes the housing would get hairline cracks on the inlet and outlet part of the housing. After reinstalling the injectors with the new nozzles there in the shop parking lot, I drove straight to the junkyard and picked up a housing I had eye-balled in an '87 SD several days before. I went home, installed it, and waited for the "hammer to drop." It has been over a week now and the start up is smooth as it was when I put the new nozzles in. No smoke, no roughness, and most importantly, no nailing - ever.

Whether it was the FF housing or the new nozzles, I will probably never really know for sure, but I have a strong feeling it was the FF housing.

Again, I apologize for "crying wolf" so many times here. For now, the engine is running great. I will update with any changes/reports periodically.

Thanks to everyone for their fantastic input. And a special "you were right all along" goes out to Dionysius.

- geoff

Dionysius · #87 09-17-2009, 10:04 PM

Sasq........you are a gentleman of great character to keep us all informed even when doing so must have been very difficult for you at times. Integrity is not a common trait in us humans and you have demonstrated it here by not giving up and by coming back so many times after you have sworn the problem was licked. We have all learned immensely along with you on this one and it will remain for me one of the best threads yet

If this is not the final answer still keep coming back without impunity and in any case come back in a month or so to do your final report.

This is such a great thread that I requested Mr Hunter to place the link in his DIY links which will enable it to be located under 'nailing' etc. for future users:
Injector + Heat shield + Nozzle, Prechamber + Collar, and Nailing. LINK THREAD
It is in there now.

Castings and housings can also fail and only the most persistent get to taste the sweet flavor of success by being so committed.

This is a great forum and one thing that would make it even better is if the titles and the conclusions were executed more diligently. All of the Moderators are volunteers and they do a geat job. Perhaps, however, an auto generated reminder email to each OP to file a conclusion two weeks after the posting activity has died off would be a great idea. The editing of the titles to make them accurately reflect the subject would be the other big improvement.

sasquatchgeoff · #88 09-19-2009, 11:29 AM

Dionysius and All,
Thanks for the kind words. All of my effort and learning would not have been as easy without the support of this forum. If PeachParts Shop Forum is an educational tool, then I have exploited that benefit to the fullest with this thread. Thanks to everyone who chimed in - Dion, jt20, Diesel 911, Barry, and anyone else that I might have missed. Your generous comments added to my determination to solve the riddle.

Also a BIG THANKS goes to the Bosch shop Diesel Fuel Injection Service in Portland. If you are out of the area, sending your sick injectors, pumps, or turbos to them is a safe, effective alternative to doing the work yourself or having a local shop take care of you. Mark, Rod, Kyle, Bill, or Daniel are experts and to me, their service is worth every penny. I spent some money with them 4 months ago and they are still giving me free stuff! If you send your injectors to them, you might want to clearly state the desired pop-pressure (otherwise they just use the spec stamped on the holder.

)

- geoff