I have rebuilt many sets of injectors over the years but it has been a while. Anyway, maybe a year or so ago I rebuilt the nozzles in my 99 E300 using Monarch 314 nozzles. As typical they were noisy at first but then settled in and were quiet. I was having an issue with them pinging when under throttle. I suspect I might have had them set a tad low. I decided I really wanted to just run the correct 310 nozzles because I was not getting the economy I thought I should so I ordered a set of Firads. When I installed the Monarchs I had to add shims to get the pressure up. With the Firads, only using the shims that came in the nozzles originally the pressures seemed to be at about 2k. I usually aim for a little on the high side. The injectors were really noisy, but quieted down a little. Even after thousands of miles on them, I still have 2-3 or more that nail at idle. If the car is driven at a high rate of speed for hours on a road trip, it will be somewhat quiet but not like it should.


The other day, I pulled them back out to test them again. It seems I may have got them set higher than I thought. Most of them seem to be popping off at around 2100psi, with maybe 1 or 2 getting closer to 2200. If you pump them rapidly the spray pattern is fine. If you slowly bring up the pressure to the point of releasing, they seem to start streaming before the actually pop. First question, could this be due to them being set to high, or are these nozzles just bad? Second, could this be my nailing? I would assume so.



I guess I may need to either order some shims to lower the pressure (all of mine are thin because I have usually always had to raise it a bit), or go back to the Monarch nozzles and set those correctly.


A couple of other points. The delivery valve seals were replaced well before I installed the initial set of Monarchs and I did not have the nailing issue. It has been suggested maybe I did not have them torqued correctly but this problem did not really start until I switched to the Firads. I thought about pulling the manifold and double checking them. The other thing is I do have some bubbles in the clear lines even though all of the plastic lines were replaced in the last year, along with the shutoff valve and o rings. Car has plenty of power and no smoke, just the darn nailing at idle.

The fact that they are streaming before opening as well as the high pop pressure is likely the cause of your problems. When I rebuild injectors, I bring up the pressure slowly and hold it right before pop for several seconds to make sure there is no streaming or leaking.

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Garage:
1983 300TD
1985 300D
1993 190E 2.6

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That was what I thought but just wanted to confirm. Even though the pressures are set high, they still should not be streaming when bringing the pressure up slowly. I think this weekend I am going to pull them back out and put the Monarch 314s back in. They ran just fine but were pinging a bit because I those set to low.

I await the final resolution here .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

My experience with high pop pressures and pre/post-streaming is that the lower injector holder half has rust or corrosion on the lip that's causing the nozzle to sit slightly off. DILIGENT cleaning is a must and usually resolves it. I've never had a nozzle be the culprit, it's always been the injector holder.

What's a good source for the 310 nozzles these days? I have a set of Monark 314 nozzles, ordered them from eBay Germany, but now I realize that they are wrong for my '95 E300 and I need the 310 nozzles.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Today I reinstalled the Monarch 314s and set them all to right at 1950. The results were drastic and immediate. It has returned to a nice quiet idle. I do still appear to have the stumbling when returning to idle. This seems to happen with the AC off, but does not do it when AC is on. I had an issue where at certain temps with AC off it will miss when its in park. Does not miss in gear or with AC on. I am getting a lot if bubbles in the line out of the bottom of the pre filter, as well as some bubbles out of the fuel heater. I am guessing perhaps this might be causing that. All of the plastic lines have been replaced semi recently and I just replaced the shut off valve and o ring. I am thinking about figuring out what size all the o rings are, pulling the plastic lines and replacing the o rings with new viton rings. Perhaps that will cure the bubbles and the stumble. Does not have any hesitation or stumbling on full throttle.

My experience with injectors is elementary but when installing new monarch nozzles all the injectors streamed if I pumped the pressure slowly even with the pop pressure exactly according to FSM specifications.

If I'm remembering correctly folks here who had a lot of experience with injectors told me to apply pressure pretty quick. I assumed the IP didn't put pressure on the fuel until it was time for the injectors to pop.

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84 300SD
85 380SE
83 528e
95 318ic

I know bupkis about W140's but the W126's that use the Diesel fuel heater have endless problems with them leaking, maybe by pass it to see if the bubbles stop appearing .

I'm betting your intermittent miss is the air bubbles you're seeing .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

A lot is made of pop pressure, but I found 3 injectors in my 1984 300D were for an earlier non-turbo engine. They were marked thus and popped at 1600 psig. The other 2 popped at the proper 1950 psig. I swapped in a set from my failed 1985 engine. Didn't notice any difference in idle noise, certainly not as much as I notice between using fossil diesel and renewable diesel. The later idles noticeably smoother and quieter (higher cetane). I used a pop-tester with electronic pressure xducer and data acquisition, which I detailed earlier. I use shim washers from McMaster-Carr (posted PN's before). You can get finicky about pop pressures, but I doubt it matters as much as having a fine spray.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Return to idle could be associated with base idle setting. The electronic system can do a lot, but it has a latency. SoId I’d look into how you adjust the IP for the return to idle. I’d also look if any cruise control linkages are binding up. Btdt. Granted a 99 has more throttle by wire than the older cars, but you need to look at the IP and determine what adjustments may be viable.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

FWIW ;

Many cars but have a device that slows the return to idle as over run (using the engine to slow down) produces a lot of emissions .

Fuel injected cars tend to have a valve that's adjustable .

Carburated engines tend to use dashpots .

This might be work looking into - way back in the 1970's I was driving a Ford Currier pickup delivery truck and down shifting was useless until I discovered there was a switch on the clutch pedal's arm that activated this device .

When VW Bugs went to fuel injection in 1975 they used a remote vacuu
m delay valve to operate the dashpot, it was adjustable .

I hope you get this sorted and let us know what the end fix was .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better