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  #21  
Old 11-15-2022, 12:00 PM
coconup coconup is offline
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Quote:
Originally Posted by ngoma View Post
Not understanding this. The idea is to install the low pressure fuel pump at the fuel filter inlet. This pressurizes the entire fuel circuit between from the filter (including the fuel filter) to the IP (including the IP)(at least to its centrifugal vane pump). Should be no chance for air intrusion EXCEPT: possible scenario of clogged fuel pickup in tank?
Yes that is pretty much the setup I had all along: hand pump before the filter inlet. Air must have come in from somewhere at the filter (either the outlet or the fuel preheat plastic valve - aka the knackfrosch). Today I took the filter out, replaced all pipes going in and out of it, replaced the o-ring on the plastic valve and bubbles are finally gone.

Earlier I tried the trick of creating a vacuum at the IP inlet with a hand pump, and the the vacuum would hold. I could not hear any hissing sound from anywhere, so I concluded the IP and everything downstream from the filter is tight.

I have now put the hand pump between the filter and the IP just to check that the filter outlet was not the source of the air ingress, but I will move it back to the filter inlet eventually. The important bit is bubbles are now gone

Quote:
Originally Posted by ngoma View Post
Sorry at work and can't view YT videos. Thought you checked the injectors? Is the IP dialed in (fuel screw, and LDA preloads)?
I checked all injectors, yes, nr. 6 is still installed and that one had a slight drip before opening pressure. But I doubt that would be the cause of the final cloud of smoke in the video. As for injector 1 (the totally screwed up one), I already replaced it with the best of the bunch I had left from the ones I originally took out.

The two new injectors are still on their way, they will arrive tomorrow.

I have not done anything to fuel screw and LDA preload, they are set as the workshop set them when they reconditioned the pump.

I had the fuel screw on my list of suspects, but I'm not sure that would explain rough-ish idle. Also as a side note, the turbo is currently disconnected from the air intake, so I'm assuming the LDA would just sit there at any RPM. I'm not very familiar on how to tune the LDA and smoke screw though, so these two might very well need some adjustment.

When you have a minute to check the video, that might make it more clear what the remaining symptoms are: bumpy idle (but better than before) and clouds of smoke when revving.

Quote:
Originally Posted by ngoma View Post
Did you strip the threads in the block or the teeth in the bolt head 12-point inhex?
The teeth, it was one of the hard bolts to reach and one of the first ones I torqued.. the bit didn't sit all the way down into the bolt head and I didn't notice, so I screwed up. Afterwards - and after a lot of fighting - I was able to force the m12 bit to the bottom of the bolt head, so I'm hoping I can now pull it out without it stripping again. I will then replace it with a new one a torque it fully.. assuming I don't have to take out all of them and repeat the whole torquing from scratch (seems overkill?).

As you can imagine, I was beating myself really hard about this.. but now that I got the bit to fit the bolt head again I'm a bit more optimistic.

Last edited by coconup; 11-15-2022 at 12:08 PM.
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  #22  
Old 11-17-2022, 11:26 AM
coconup coconup is offline
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Any tip on what would be a good next step? Adjusting the smoke screw and idle perhaps? Still unclear how the LDA would play a role right now, grateful for any hint
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  #23  
Old 11-18-2022, 10:53 AM
ngoma ngoma is offline
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Stumped for now, sorry.
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  #24  
Old 11-18-2022, 11:08 AM
v8volvo v8volvo is offline
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To me it seems like it has to be a fuel pump condition or calibration issue. I'm sure this is not what you want to hear, but I think your best move is to remove the injection pump and bring it to a certified local Bosch fuel injection reconditioning center and ask them to run the pump on their test bench. It should not be too expensive and at least removing the pump is relatively easy with the engine still out of the vehicle.
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  #25  
Old 11-19-2022, 07:17 AM
coconup coconup is offline
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Quote:
Originally Posted by v8volvo View Post
To me it seems like it has to be a fuel pump condition or calibration issue. I'm sure this is not what you want to hear, but I think your best move is to remove the injection pump and bring it to a certified local Bosch fuel injection reconditioning center and ask them to run the pump on their test bench. It should not be too expensive and at least removing the pump is relatively easy with the engine still out of the vehicle.
Thank you for the answers @v8volvo and @ngoma. So you reckon it's not even worth trying to adjust the smoke screw and idle screw myself? As in, those cannot explain that the engine is running like it does?

Also, I assume the Turbo being disconnected should also not make a difference with regards to black smoke when revving?

Now looking for Bosch diesel services around me, I'm just wondering if there's nothing I can try myself before taking it all down.

Last edited by coconup; 11-19-2022 at 07:39 AM.
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  #26  
Old 11-19-2022, 08:06 PM
ngoma ngoma is offline
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Quote:
Originally Posted by coconup View Post
So you reckon it's not even worth trying to adjust the smoke screw and idle screw myself? As in, those cannot explain that the engine is running like it does?
Seems like what you are describing is an overfueling behavior. Sure, worthwhile trying some adjustments before sending out the IP. Make sure you mark the screws or adjusters before starting so you can return them to baseline.



#10 is what we refer to as the fuel screw, sometimes the smoke screw.

The LDA preload (AKA starwheel) is #5, the other smoke screw is unlabled, at the very top of the LDA.

Here is some random explanation (pretty good I thought) I found in a quick internet search:

"TURBO DIESELS WITH MECHANICALLY CONTROLLED FUEL INJECTION PUMP

Until the early 1990's, nearly all small turbo diesel engines had a mechanically operated diesel injection pump with fuel delivery directly controlled by a mechanical throttle linkage. So that by and large the more the driver opened the throttle, the more fuel was injected into the engine.

Apart from a cold start arrangement and a fuel enrichment compensator mounted on the pump, no other sensors had an influence on fuel delivery, although some models did introduce other controls before going fully electronic.

The pump fuelling on most vehicles can be adjusted with the pump on the engine by turning the main fuel screw after removing the seal. There are other adjustment screws, but generally do not attempt to adjust these unless you are having a pump overhaul, in which case the pump will be removed from the engine. Other pumps will have the main fuelling adjustment screw under a cover at the rear of the pump or under a plug on the side of the pump. If this is the case, fuel will be drained out of the pump when the plug is removed. You will then need a small mirror and a light to identify the position of the internal adjustment screw. With the car in gear, roll the car forward until the screw comes into view inside the pump. Generally turning the screw clockwise just a few degrees gives an increase in fuel delivery. An exhaust smoke test should be carried out after these adjustments if there is any doubt that the vehicle would not pass the MOT test. When increasing the fuelling in this way the increase will be from tickover right upto maximum r.p.m. This is not exactly what is required for optimum fuel economy, or smoke emission. So unless the volumetric efficiency has been improved by other modifications, such as an improved induction system, uprated turbo, increased boost or larger intercooler, it will often only be necessary to adjust the compensator. (On some engines the compensator cannot be easily reset without some modification).

The compensator is a device mounted on the pump which increases the fuelling in response to turbo boost pressure. Most mechanically operated pumps on turbo diesel engines are fitted with one. Boost is fed from the pressure side of the turbocharger or manifolding via a small bore pipe to a chamber above a rubber diaphragm. Below the diaphragm is a rod and linkage to the internals of the pump. Boost moves the diaphragm and rod linkage which moves the fuelling rack to increase fuelling. More boost moves the linkage further for increased fuel delivery, until it reaches a stop.

Fuelling adjustments are best carried out by adjusting the compensator, as this will be the most fuel efficient way because extra fuel is injected primarily only with increasing boost, when the extra fuel is most needed. Too much fuel at the bottom end before sufficient boost is available will produce excessive black smoke.

It is not usually necessary to remove the pump from the engine to obtain the correct curve. Although if the pump needs a rebuild or you are willing to spend an extra �300-�400, you can have the pump rebuilt to give an uprated fuel delivery where it is most needed in the r.p.m. range to suit your particular requirements."


From https://www.brick-yard.co.uk/forum/f...opic91110.html

Seems unlikely that the LDA is causing your overfueling, as the LDA is actually a fuel-limiting device, when not under boost (to limit overfueling and smoke in low-load situations)(while the IP is still base-tuned for proper fueling in high-boost conditions). It gradually allows more fuel as the boost builds. And as your turbo is not adding bost, the LDA should be keeping fueling to low-boost levels as there would be no signal pressure to move its mechanism. Unless #8/9 is sitting too low for some strange reason.

Quote:
Originally Posted by coconup View Post
Also, I assume the Turbo being disconnected should also not make a difference with regards to black smoke when revving?
Sounds logical, but not 100% sure.
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  #27  
Old 11-20-2022, 08:56 AM
v8volvo v8volvo is offline
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Yeah, I agree as well on the above. Nothing to really lose by trying some adjustments.

I think I would focus on the smoke screw above all else. If it were turned too far in I think it could contribute to the kind of behavior you have seen. The touchy throttle response and instantaneous smoke are the telltales on that I believe.

Agree that the lack of the turbo in the intake stream should make no difference in the particular symptoms your video showed. The engine is obviously overfueling and the unstable idle is due to the governor barely being able to keep fuel rates under control with the current settings. The big black clouds that occur pretty much immediately as soon as you touch the throttle reveal the fact that the turbo cannot really be part of the story. It happens faster than the turbo could ever respond so you couldn't rely on the turbo to "clean up" that smoke with more air.

Misadjustment of the LDA seems slightly more plausible as a partial factor, for example if the smoke screw is close to the right setting but the LDA is not performing its limiting job and thus the engine is able to access full fueling even when off-boost. (The LDA is meant to keep full fuel setting from being available except when turbo pressure is moving the LDA diaphragm.) However that wouldn't explain the unsteady idle speed, so it would be a partial contributing factor at best, if any factor at all.

Another thought I am having after again watching the behavior in the video: the hydraulic dampening circuit (not shown or described in the info above that is focused on adjustments that can be performed on the engine) could also be affecting the pump's ability to manage a stable RPM. It's meant to help avoid sudden or oscillating movements in the governor and is set only on the test bench, can't access it or really adjust it at all with the pump on the motor.

Two more good resources to add to the above that go into detail on that hydraulic dampening function, as well as all the other things the VE pump does.

https://www.dieselduck.info/machine/...ion%20Pump.pdf
https://injectionpumps.co.uk/pdf/bosch_ve_pumps.pdf

I still stand by my (perhaps pessimistic) assessment that you probably unfortunately bought an injection pump that was not calibrated correctly and it may need to get put on a proper Bosch test bench at the end of the day if you really want the engine to run at its best. The seat-of-the-pants adjustments you can make with the pump running the engine can help but will never reach perfect setting, especially since if you find that those are misadjusted it should make you presume that all the other bench settings you can't adjust in-situ (eg dynamic timing advance curve, hydraulic dampening, etc) are also wrong. But it is logical to try the adjustments you can get to before taking any further steps, even if for no other reason than to confirm the theory that pump miscalibration is the root of your problems. And who knows, maybe you will manage to get it to a satisfactory place just with those changes.

Let us know what you learn!
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  #28  
Old 11-20-2022, 11:49 AM
coconup coconup is offline
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All of this is golden, thank you so much. Unfortunately right now I am blocked by sub-zero temperatures where I live but here's my battle plan for next week, hoping for a more forgiving weather:

1. Replace the injector that had a slight leak with the new one I got in the mail, after testing it on the bench, and see if that leads to any improvement
2. If no improvement, swap the pump with the old one the engine originally mounted, which I still have with me. I think that would be the easiest way to assess whether the pump is to blame

I'm also thinking of running the engine with coolant up to operating temperature in order to see if performance improves once warmed up. Stupid idea given I still need to break in the pistons? I read on the page @ngoma linked that ideally the engine should run as little as possible before being put under load, in order to ensure proper break-in.

Thanks again for all the info and tips, I will report back once I have some news
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  #29  
Old 11-22-2022, 08:13 AM
v8volvo v8volvo is offline
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I can sympathize with what you are facing there. This November here where I live has been the coldest anybody can remember. We have already had a total of almost three feet of snow in the past three weeks and many nights below 0F. Looks like more on the way. Certainly not good weather to be working in the garage unless you have heat.

I guess I had not realized you still had your old IP available. If so, installing it is a great way to determine whether the current replacement IP is responsible for the trouble!

Did the engine run in a satisfactory way with that original IP? One thing I cannot recall (apologize if you already told us earlier) is what was your reason for removing this engine for repairs in the first place. Was it just proactive reconditioning? Or did it have operational issues as well? If the latter is the case, then installing the old IP may not be as conclusive of a step.
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  #30  
Old 11-23-2022, 09:00 AM
coconup coconup is offline
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Quote:
Originally Posted by v8volvo View Post
Did the engine run in a satisfactory way with that original IP? One thing I cannot recall (apologize if you already told us earlier) is what was your reason for removing this engine for repairs in the first place. Was it just proactive reconditioning? Or did it have operational issues as well? If the latter is the case, then installing the old IP may not be as conclusive of a step.
@v8volvo I had bought the engine with 270k km on it. It was running ok but a compression test revealed all cylinders were below the recommended wear limit, so I decided to rebuild it. One thing after another I ended up getting all new components, although some of the old ones (like the pump) didn't show any obvious problem.

Today temperatures were less hellish and I managed to spend the afternoon in the garage. To my disbelief, one of the two "new" injectors I got in the mail is junk. The second one also leaks slightly when held just below opening pressure (see below). At this point I will just return all of them and move on to a different shop, I don't trust this one anymore and it might very well be that the overfueling issues I'm seeing come from one or more injectors.

While I patiently wait for a new batch of injectors, here's a video of the "leaky" injector (the second one I mentioned above): https://www.youtube.com/watch?v=lvSHxDQ6pco

Sorry if the video is shaky, I only have two hands . In the video, I'm holding the pressure tester at just below opening pressure. As you can see towards the end, a drop of diesel forms underneath the nozzle although opening pressure is never reached. Just so I have a good reference point when the new injectors will come: is this considered "ok" or even normal? Or would you say that injector too is bad?
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