Delivery valve internal leak as a cause of nailing? Yes? No? Maybe??? - Page 4 - PeachParts Mercedes-Benz Forum

spock505 · #46 02-03-2017, 03:59 PM

Happy to be corrected, although during observation the DV and copper washer are the only (and last in chain) components to provide a seal (and lock).

This seemed logical given to how sensitive they are to over torquing/dirt, The gallery rack is something I would like to learn more about but that would be pushing my luck, perhaps that plays a part in fuel measurement too?

Diseasel300 · #47 02-03-2017, 05:57 PM

There's a lot more going on below the DV and the copper washer. The DV sits on top of the pumping element. It is a metal-metal contact to provide a seal, the copper washer sits on top of the DV body and is there to provide the final seal between DV and DV holder (the part you unthread). Torquing seats the copper washer and ensures that the DV is seated against the pumping element. If the torque is wrong, the washer is scored, dirt is in there, etc, you won't get a good seal and fuel can find a way to bypass the injector line.

The gallery rack is what determines the metering of how MUCH fuel is pumped by each element. It's position is controlled by the governor in the back side of the injection pump. The accelerator pulls on a spring connected to the rack moving it forward, the governor actuator pulls it back. The firmer you push the pedal, the firmer the spring and the harder the governor has to pull to cut back fuel.

spock505 · #48 02-04-2017, 06:00 AM

Cheers Diesel, I think that's what I said but less eloquently, but we are on the same page.

Thinking about it further, perhaps the spring is not that important after all, it's only really there to unseat the valve during the next cycle. The spring in inside the injector does the reverse, seating the nozzle but more importantly opening under correct pressure via shims.

A job worth doing but very fiddly, testing, undoing holder, grinding shims refitting, testing, repeat.

If anyone is thinking of doing this in conjunction with DV's, worth getting a large gauge tester around the 115bar mark for accuracy.

I had this one made with that in mind.

Diseasel300 · #49 02-04-2017, 08:48 AM

The springs in the DV's perform an important purpose. They both provide the push to close the DV when the supply pressure drops AND they keep it firmly closed to prevent the fuel in the hard lines bleeding off and draining back into the IP. It's a completely passive system.

Using a pressure gauge on the fuel delivery circuit won't get you anywhere. If you've ever felt the hard lines when the engine is running, the delivery duration is so quick that it feels like someone simply tapping the hard line. The delivery quantity at idle is tiny. To properly set your pop pressures using shims, you MUST use a pop tester. It's the only accurate way to set the pop pressures of the injectors.

spock505 · #50 02-04-2017, 09:08 AM

Quote:

Originally Posted by Diseasel300

Using a pressure gauge on the fuel delivery circuit won't get you anywhere. If you've ever felt the hard lines when the engine is running, the delivery duration is so quick that it feels like someone simply tapping the hard line. The delivery quantity at idle is tiny. To properly set your pop pressures using shims, you MUST use a pop tester. It's the only accurate way to set the pop pressures of the injectors.

That is a pop tester??

Diseasel300 · #51 02-04-2017, 09:12 AM

Edit: Paid better attention. Not enough coffee in system.

gmog220d · #52 03-14-2017, 11:25 PM

Weather Sunday was nice, finally, so I spent some time with the E300. The summed up version is I replaced the delivery valve spring and seals on one cylinder, #6, and the difference made is "better" but inconclusive.

With the crossover tube and plastic engine cover off, engine idling, using tubing and my ears I ended up between #5 and #6. Loosening the injector lines at the injectors showed up #6 as the culprit, so that's what I focused on. I pulled the intake off and removed #6's line, the delivery valve holder and compression spring. I left the delivery valve assembly in place. The fuel was clean and clear, and I let some flow through before clamping both return and supply hoses.

I laid the old and new springs out side by side and to the eye their lengths are the same. I was a little bummed about that. I was hoping for a broken or obviously stressed spring - no dice!

After getting it running it sure sounded nice before #6 bled out the air and starting firing. Once #6 cylinder starting hitting the nail was back, and louder than ever it seemed. I let it idle for a few minutes and shut it down. I fired it up again 10 minutes or so later and it ran smooth and quiet for a few seconds, and then the nail returned. I've driven it to work and back twice now and I believe it's quieter at hot idle and about the same during those times when crawling along at low speed, engine turning between 1000 and 1500 RPM, when it nails every revolution.

So, my thoughts come back around to the injector, the delivery valve assembly, and even the pre-com chamber. Thinking of having my spare injector rebuilt by a known quantity, installing it in #6, and going from there.

Maxbumpo · #53 03-15-2017, 09:52 AM

An easy / cheap test would be to swap #6 injector with #1, then you'll know if the problem is the injector or the DV. Inspect the pre-chamber to make sure the ball is there, compare with #1.

If the problem doesn't follow and you've got a couple spare copper washers, you can swap #6 and #1 DV's to see if you can narrow it down to the DV assembly. A faulty DV is not unheard of.

Diseasel300 · #54 03-15-2017, 11:34 AM

Swapping injectors is definitely a good idea. That'll tell you real fast if the nailing follows the injector or stays with the same cylinder.

Mine has been quiet for several weeks, but after the last fuel fill up, ye olde low speed nailing is back. The engine is running a hell of a lot smoother than it did before the DV job, but that irritating nailing is back between idle and 1300 RPM. Additionally, idle overall is much louder - sounds like a Cummins! None of that behavior was present before refilling the fuel.

When this tank of fuel runs down, we'll see if fresh fuel from a different source shuts it up. In my case I know that all of the "balls" are present in each prechamber and the injectors are of known performance. Additionally, the old springs in my IP were definitely compressed by ~1mm compared to the new ones. Should have taken a picture, but that 20/20 hindsight...

gmog220d · #55 03-15-2017, 04:52 PM

Thanks for the replies D300 and Maxbumpo. Agreed that simply swapping the injectors would be a good next test. Any reason I shouldn't swap #5 and #6? That way I only have to mess with one set of fuel line clips. Also makes sense to swap the delivery valve assemblies around as a next test if the nailing isn't related to the injector. Yeah, I have plenty of the copper sealing washers and injector heat shields.

I did have a look at all the pre-com chambers when I had the injectors out for rebuilding a couple months back. They all looked good, balls intact and in place. Kinda wish I had figured out which cylinder was nailing before the injector rebuild.

D300, sure hope fuel quality from that last fill-up is all you've got going on.

spock505 · #56 03-15-2017, 05:28 PM

Spring is around the corner depending on location, fuel companies do change their mix to avoid waxing, i.e winter fuel.

Low sulphur diesel may also change combustion dynamics, a nip of two stroke per tank can help in the short term but best get the problem solved.

Diseasel300 · #57 03-15-2017, 06:06 PM

Quote:

Originally Posted by gmog220d

D300, sure hope fuel quality from that last fill-up is all you've got going on.

I was down to 1/3 of a tank, so I filled up from a Shell station this afternoon to test the theory. That 1/3 of a tank could have lasted another couple weeks, but I'm sick of the noise.

Sure enough, within ~3 minutes of filling up, the mechanical "ping" went away. I still have a loud injector (you can hear it clacking above the rest), but the metallic "ping" noise that was driving me up the wall is gone. Overall the engine is significantly quieter, especially at idle.

Since that worked to quieten things down, I decided to crack injectors to find the "clacker". Narrowed that down to Cyl 4. Crack that line and the noise stops immediately and entirely.

New nozzle coming to Cyl 4 in the near future. Currently has Bosch India nozzles and they seem to have a poor reputation for reliability.

Maxbumpo · #58 03-15-2017, 06:39 PM

Quote:

Originally Posted by Diseasel300

New nozzle coming to Cyl 4 in the near future. Currently has Bosch India nozzles and they seem to have a poor reputation for reliability.

I recently received a set of Monark nozzles from Technikexpert in Germany, about $150 with shipping for six. Greazzer has cleaned / installed / balanced the set, I'm about to head out to the drive and install them. They _should_ fix a persistent nailing problem that has been plaguing me for some time now.

gmog220d · #59 03-15-2017, 09:43 PM

Quote:

Originally Posted by spock505

Low sulphur diesel may also change combustion dynamics, a nip of two stroke per tank can help in the short term but best get the problem solved.

I wonder how some B90 or B100 would make it run. That stuff ran super quiet in the '73 with OM616.

Anyway, I use Stanadyne lubricity formula, and sometimes a shot of Lucas, in all the diesel I run in order to counter ULSD.

gmog220d · #60 03-15-2017, 09:48 PM

Quote:

Originally Posted by Diseasel300

New nozzle coming to Cyl 4 in the near future. Currently has Bosch India nozzles and they seem to have a poor reputation for reliability.

Quote:

Originally Posted by Maxbumpo

I recently received a set of Monark nozzles from Technikexpert in Germany, about $150 with shipping for six. Greazzer has cleaned / installed / balanced the set, I'm about to head out to the drive and install them. They _should_ fix a persistent nailing problem that has been plaguing me for some time now.

I'll be curious about both your results with new nozzles. All six of my recent rebuilts got Bosch because of convenience. This angle is why I thought having my extra injector gone through and given a new nozzle might be worth the trouble and cost.