Delivery valve internal leak as a cause of nailing? Yes? No? Maybe??? - Page 9 - PeachParts Mercedes-Benz Forum

dieselbenz1 · #**121** 05-19-2017, 11:24 PM

I was poking around and found this

Delivery-valve problems are cylinder specific. If the valve sticks open, no fuel passes to the associated injector. Leakage is harder to diagnose. White smoke that persists after all bases have been touched—pump pressure and timing, new injectors, and engine compression—suggests that one or more delivery valves may be at fault. Disassemble one valve at a time, clean the parts thoroughly, and test for leaks by blowing through the outlet port. Older, simpler valves can sometimes be resurfaced. Check piston fit by depressing the valve and placing your finger over the inlet port. You should feel the vacuum as the piston falls.

Diseasel300 · #**122** 05-19-2017, 11:56 PM

Just as an update on the test-mule:

So far I've put ~150 miles on the car since swapping in the polished DV's. No nailing has appeared and I haven't had any problems with starting or rough running. Car is running the same as it was with the known-good DV's installed. Small datapoint obviously, but it does seem to indicate that DV polishing may be a useful solution for some of these persistent nailing issues.

OM617YOTA · #**123** 05-20-2017, 01:12 PM

Quote:

Originally Posted by dieselbenz1

I was poking around and found this

Delivery-valve problems are cylinder specific. If the valve sticks open, no fuel passes to the associated injector. Leakage is harder to diagnose. White smoke that persists after all bases have been touched—pump pressure and timing, new injectors, and engine compression—suggests that one or more delivery valves may be at fault. Disassemble one valve at a time, clean the parts thoroughly, and test for leaks by blowing through the outlet port. Older, simpler valves can sometimes be resurfaced. Check piston fit by depressing the valve and placing your finger over the inlet port. You should feel the vacuum as the piston falls.

This is another good point for mine, I've had smoke the entire time I've owned the engine. I would have thought swapping a different injection pump with different delivery valves in would have helped or at least changed things significantly, but with a used pump who's to say what condition all of that was in.

Diseasel300 · #**124** 05-20-2017, 01:17 PM

Quote:

Originally Posted by OM617YOTA

This is another good point for mine, I've had smoke the entire time I've owned the engine. I would have thought swapping a different injection pump with different delivery valves in would have helped or at least changed things significantly, but with a used pump who's to say what condition all of that was in.

It's important to note that there are a lot of other things besides DV's that will cause smoking. Low compression, injection timing, spray pattern, and of course the SOURCE of smoke are all important factors to consider. If you swapped the IP and had the same behavior, it's probably safe to say that the IP wasn't the source of problems. Used or not.

I'd be looking for oil consumption problems, worn turbo seals, or IP timing before blaming the DV's. It's very common for people to claim they have "grey" smoke when it is in fact "blue" from oil burning.

barry12345 · #**125** 05-20-2017, 10:37 PM

Actually sticking open is an interesting possibility. I was trying to grasp the possibility. A totally dead cylinder seems to be the suspected result.

Over the years non soluble particles in the fuel might get compressed and stick to the seat or valve face. Providing enough of a compromised surface to leak. It would not take much leakage to disable the function in a hydrostatic situation like this. Volume of fuel flow is probably also low so a washing type action may not be strong enough to erode the compressed and sticking contaminates.

I was more concerned with a finding a testing method to find out if leaky delivery valves are present in place. Especially since this threads originator proved we could address the delivery valves at home.

Perhaps taking an old hard line cutting it and brazing or silver soldering a usable attachment on the cut end.

Apply perhaps 25 pounds of air pressure with a gauge in the rubber line that feeds it. . With a shutoff at the end and an air input at the extreme end. A good delivery valve should hold the pressure for days I expect. For testing a more sane period could be established. I think we could quickly develop what a problem delivery valve acts like. Or establish the leakage factor that is acceptable.

You might have to run the injection pump out of fuel and rotate the engine to expose the port in the injection pump element. Giving a route for the air to easily escape if the valve was leaky. May require a few magnets and a degree wheel stuck on the harmonic balancer. As an indicator when a specific fill port was exposed on each element.

All four of my diesel 616 and 617 engines run very well. Although the 616 engine that has rebuilt or all new parts including the basic engine runs just a little better. That engine still has only a very few thousand accumulated miles since it was installed by a dealer.

It is possible in my mind because these cars are so old that there are a lot of sub standard delivery valves out there in service. Not causing any signifigant problem but degrading the engine just enough to notice a difference like I observe. There is no fairly quick test to see what shape they are in that I can think of quickly.

Other than the sitting under a head of air for a period yet to be established. Or taking an old hard line and teeing in a high pressure gauge with an injector on the other end. Building pressure by rotating the engine and seeing if it holds.

Once the delivery valves are removed I think my vacuum pump and one of my better vacuum gauges that reads down to low microns could be used.

If a hose could be clamped on the delivery valve casing. It could quickly pull down to 100 microns and sit there when the vacuum pump is isolated from the circuit with a valve. The test could be done very fast and be very conclusive.

I also think with any leakage it would be obvious with my stronger pump in only a very few seconds. You could evaluate each delivery valve this way establishing if it needs attention. Plus testing after you repair it to verify it is now good to reuse. This to me is a very fast way to deal with them.

What is a little scary is the majority of injection pumps on these cars are still the originals. Very old now with high miles on many of them. I suspect even a little leakage will have consequences. Nothing you might be able to put your finger on but still something. Could be for example fuel milage. A slightly leaky delivery valve might delay the injection for example. Or under fuel a cylinder. Or both.

The much maligned milli volt system should indicate it as one of many possibilities if a cylinder is running cooler. At the same time if an engine is producing no more than .1 milli volts difference between all the cylinders in a power balance test the overall delivery valves are probably very good.

We did experience on this site and in private messages and emails. That some engines settled to a perfect milli volt test after what was wrong was repaired. All the cylinders were exactly the same after in the milli volt power balance testing. Not that many but there were a few of them.

Years ago now when I joined this site there was little known about these pumps by most members in comparison to what now is. Pumps got changed out very frequently when they were either not the issue or we could have addressed the issues.

There are much fewer injection pumps changed out today in comparison. Certain things are and will still remain beyond what we can do. These cars like myself have continued to age over those same years. Delivery valve issues seem to be increasing.

These are just a few quick thoughts. Others can come up with better and easier hopefully. Or perhaps I can with some thought.

packerfan · #**126** 05-21-2017, 12:20 AM

Quote:

Originally Posted by RunningTooHot

Has anyone ever had a situation where the delivery valves were NOT leaking externally, but replacing the crush washer & o-rings resolved a nailing condition at idle? (Or has anyone ever encountered a broken delivery valve spring? (Assuming correctly or not that a broken or out-of-spec DV spring could possibly be causing nailing at idle?)

Reason for asking: My '98 E300 (OM606.92) has been nailing at idle on one cylinder. It's especially bad when cold, and it actually misfires under cold-start conditions. (The glow plugs all ohm out OK - but even if a glow plug was faulty, that wouldn't cause it to nail at idle while the engine is hot.)

I've pulled the factory original injectors out (to have Greazzer go through them) and I temporarily replaced them with a spare (used) set for the time being, but the nailing persists. Granted, I don't know the condition of the spare injectors, but the nailing is consistent – therefore my suspicion about the delivery valve.

It is definitely not a tank of bad fuel, as it has persisted through several tanks. (I also run Power Service at relatively high doses with every fill up.)

Any thoughts, opinions, conspiracy theories, etc. are much appreciated. Oh, and Merry Christmas too!!!

I am experiencing the same problem, how do I contact "Greazzer", I would like my injectors rebuilt?

jake12tech · #**127** 05-21-2017, 12:56 AM

Quote:

Originally Posted by packerfan

I am experiencing the same problem, how do I contact "Greazzer", I would like my injectors rebuilt?

Message grezzer on the forums. He will respond.

Diseasel300 · #**128** 05-21-2017, 10:10 AM

Quote:

Originally Posted by barry12345

Actually sticking open is an interesting possibility. I was trying to grasp the possibility. A totally dead cylinder seems to be the suspected result.

Over the years non soluble particles in the fuel might get compressed and stick to the seat or valve face. Providing enough of a compromised surface to leak. It would not take much leakage to disable the function in a hydrostatic situation like this. Volume of fuel flow is probably also low so a washing type action may not be strong enough to erode the compressed and sticking contaminates.

I was more concerned with a finding a testing method to find out if leaky delivery valves are present in place. Especially since this threads originator proved we could address the delivery valves at home.

Perhaps taking an old hard line cutting it and brazing or silver soldering a usable attachment on the cut end.

Apply perhaps 25 pounds of air pressure with a gauge in the rubber line that feeds it. . With a shutoff at the end and an air input at the extreme end. A good delivery valve should hold the pressure for days I expect. For testing a more sane period could be established. I think we could quickly develop what a problem delivery valve acts like. Or establish the leakage factor that is acceptable.

You might have to run the injection pump out of fuel and rotate the engine to expose the port in the injection pump element. Giving a route for the air to easily escape if the valve was leaky. May require a few magnets and a degree wheel stuck on the harmonic balancer. As an indicator when a specific fill port was exposed on each element.

All four of my diesel 616 and 617 engines run very well. Although the 616 engine that has rebuilt or all new parts including the basic engine runs just a little better. That engine still has only a very few thousand accumulated miles since it was installed by a dealer.

It is possible in my mind because these cars are so old that there are a lot of sub standard delivery valves out there in service. Not causing any signifigant problem but degrading the engine just enough to notice a difference like I observe. There is no fairly quick test to see what shape they are in that I can think of quickly.

Other than the sitting under a head of air for a period yet to be established. Or taking an old hard line and teeing in a high pressure gauge with an injector on the other end. Building pressure by rotating the engine and seeing if it holds.

Once the delivery valves are removed I think my vacuum pump and one of my better vacuum gauges that reads down to low microns could be used.

If a hose could be clamped on the delivery valve casing. It could quickly pull down to 100 microns and sit there when the vacuum pump is isolated from the circuit with a valve. The test could be done very fast and be very conclusive.

I also think with any leakage it would be obvious with my stronger pump in only a very few seconds. You could evaluate each delivery valve this way establishing if it needs attention. Plus testing after you repair it to verify it is now good to reuse. This to me is a very fast way to deal with them.

What is a little scary is the majority of injection pumps on these cars are still the originals. Very old now with high miles on many of them. I suspect even a little leakage will have consequences. Nothing you might be able to put your finger on but still something. Could be for example fuel milage. A slightly leaky delivery valve might delay the injection for example. Or under fuel a cylinder. Or both.

The much aligned milli volt system should indicate it as one of many possibilities if a cylinder is running cooler. At the same time if an engine is producing no more than .1 milli volts difference between all the cylinders in a power balance test the overall delivery valves are probably very good.

We did experience on this site and in private messages and emails. That some engines settled to a perfect milli volt test after what was wrong was repaired. All the cylinders were exactly the same after in the milli volt power balance testing. Not that many but there were a few of them.

Years ago now when I joined this site there was little known about these pumps by most members in comparison to what now is. Pumps got changed out very frequently when they were either not the issue or we could have addressed the issues.

There are much fewer injection pumps changed out today in comparison. Certain things are and will still remain beyond what we can do. These cars like myself have continued to age over those same years. Delivery valve issues seem to be increasing.

It sure is easy to overcomplicate things and do a lot of extra work, especially when so many DIFFERENT things can cause nailing. I'd consider the DV's to be a "major" issue compared to the "usual suspects" such as injectors, compression, timing, and DV seals (on the 60x engines).

Before doing a bunch of work that simply isn't required and spending countless hours worrying about that .1mV, take care of the usual issues first. If the problems don't resolve and the compression is good, move on to DV's.

barry12345 · #**129** 05-21-2017, 10:51 AM

Quote:

Originally Posted by Diseasel300

It sure is easy to overcomplicate things and do a lot of extra work, especially when so many DIFFERENT things can cause nailing. I'd consider the DV's to be a "major" issue compared to the "usual suspects" such as injectors, compression, timing, and DV seals (on the 60x engines).

Before doing a bunch of work that simply isn't required and spending countless hours worrying about that .1mV, take care of the usual issues first. If the problems don't resolve and the compression is good, move on to DV's.

I hate having to pitch milli volts. It is just a tool that more and more is learnt about. .

I believed one gentleman was clearing carbon as his milli volts where growing closer to each other. It really bothered me that his idle was not improving as the milli volts had closed up substantially.

I knew they where still in no way close to what they should be. Yet he saw no improvement. Since there was no compression check done of the engine I was reluctant to speculate. You cannot skip an indicated step in using milli volts in testing without risking getting lost.

Some of the more conventional service types at the time thought his head might need to come off. All I know is when you do not know what is going on. Using any tool that can help establish what is. Is not a bad thing.

Tragically since milli volt application has not caught on yet. Almost ever time it is used something new is learnt.

I suspect at this time. When we develop a workable test for delivery valves. This poster will find some leakage in others in his injection pump. Not as bad as the real offender was. Realistically a good check valve has no leakage present at all.

No absolute reason to address them if the engine is still running normally as far as the ear notices.

Diseasel300 · #**130** 05-21-2017, 10:54 AM

The only reason things keep getting learned about with the milli-volt readings is because they don't identify anything other than which cylinder is "cold". How cold? No telling. All the time spent messing with millivolts could be spent solving the problem. Is it useful for identifying the dead cylinder? Sure. Other than that? I'm not sold.

Show me some peer-reviewed research showing that a glow plug can be used as a calibrated thermocouple and I'll get off your back about it. Until then, I'm not buying it as a tool useful for anything greater than finding a dead cylinder.

barry12345 · #**131** 05-21-2017, 11:15 AM

That's okay. It is a bit of a pain to use anyways. Saved for using when nothing else other than shot guning a situation remains many times.

The fuel system manufacture for this brand patented using it a long time ago. At least one Japanese diesel producer had field reps that used it as part of the company policy. When their diesels used the older fuel systems.

Finding a dead cylinder is simple. No need to use mili volts. Finding a cylinder down 20 percent is another thing. Reestablishing or even an indication that you have a power balance issue instead of say a motor mount issue.

So you change the motor mounts and the engine shaking is still there?

Diseasel300 · #**132** 05-21-2017, 11:19 AM

Quote:

Originally Posted by barry12345

So you change the motor mounts and the engine shaking is still there?

Obviously the engine shaking is the issue, not the motor mount. Replacing the mount for a shaking engine is akin to airing up the tires because the radiator leaks. Find the issue causing the shaking first, then replace the motor mount to isolate any remaining vibration from reaching the chassis. Good repair practices never go away, but they are often forgotten or overlooked.

dieselbenz1 · #**133** 05-21-2017, 02:41 PM

I talked with a caterpillar mechanic who tells me you can detect a bad delivery valve by feeling the injector hard lines with the engine running. Hopefully that test will work but my engine is running great so I have no comparisons. Thank you Diesel300 for all the efforts you put into this thread. He also informed me the delivery valve is designed to suck back fuel from the hard line to abruptly stop injection rather than dribble past the injection period. The softer the feeling points towards a possible delivery valve issue.

Diseasel300 · #**134** 05-21-2017, 10:27 PM

The delivery valve would have to be pretty bad to be noticeable on these engines. The fuel flow is so much less than on a big Cat engine. Even with the nailing cylinders on my engine, I couldn't tell a difference by feeling the injector lines, all of them had a sound "thump" to them. If the DV were worn to the point of causing a miss, I'd expect you could easily feel it on these engines, but not enough tactile difference to detect nailing.

As a followup to the previous updates, I have put another 220 miles on the car this weekend, and still no nailing has returned.

Diseasel300 · #**135** 06-08-2017, 11:44 AM

Progress report time: The DV's in #1 and #2 that were lapped are still quiet as a mouse. I've been through nearly 2 tanks of fuel and they haven't acted up yet. I suspect that they are going to be fine.

However - #5 has started a slight nailing at low RPMs, nowhere near as loud as #4 and #6 were, but still noticeable at low loads and low RPM's such as putting around a parking lot or driving in school traffic. Usually can hear it start ~700 RPM and gone by 850-900 RPM. It is inconsistent and comes and goes. If I crack the hard line to #5, the noise stops and the engine is as quiet as a skipping diesel can be.

I intend to pull #5's DV and do the lapping procedure on it to see if it solves the problem. It may be this weekend before I get around to it, but I'll report back when I've done the deed.

In addition to doing the DV, I'm going to see if the "feeling the hard line" theory has any merit, especially before and after the DV lapping.

Since this is an un-touched DV, it should provide some interesting insight whether or not the lapping procedure is worth anything or not. I'd love to know the history of the IP and why it has so many DV issues, but there are some things we'll just never know...