What injectors are these? - PeachParts Mercedes-Benz Forum

jtrnw · #1 11-05-2017, 10:46 AM

Hello! This is my first time on this forum, but I plan to stick around. I recently bought a 1969 w115 220d in semirunning state. I'm located in the bay area, CA. Right now its injector nailing real bad. I'm going to try diesel purge, but I'm sure the injectors will need a rebuild. That leads me into my question. I searched the internet high and low and I cant find any reference to the kind of injectors that are in this car. I'm confused by the hard return lines on the injectors, and that it appears they're threaded into the block with thread tape. Any wisdom?

Diseasel300 · #2 11-05-2017, 10:57 AM

I can't help you with the injectors, I'm not familiar with diesels of that vintage. What I can tell you is that the thread tape doesn't belong there!

BillGrissom · #3 11-05-2017, 11:25 AM

Thanks for posting since very interesting and the photos will help somebody. Where the injectors screw into the head look perhaps the same as 1980's 4 & 5 cyl OM617 engines, as does the top tube connection. That suggests that a later injector might fit. But, the supply tubes are very stiff, so unless at the exact same height, a swap wouldn't work. Of course, the return would be easy to re-plumb on later injectors w/ rubber hose (viton best).

Even simpler, the innards (nozzle) might interchange and that would let you keep the original housings (keep it real and looks cool). If doing yourself, you might buy a later used injector assembly on ebay ($15 or so) to check. Before removing an injector, be ready w/ new heat shields that fit under each injector tip. If the same PN as later diesels, heat shields are cheap. Indeed, Bosch injectors for other Euro diesels (VW, ...) are similar/same. I know that turbo and non-turbo injectors in 1970-80's engines interchange because my 1984 had 3 non-turbo injectors (housing stamped "110 bar" and pop-tested 1600 psig). BTW, the engine ran about the same after replacing w/ turbo ones (135 bar).

I agree, no teflon tape. The heat shield is the gasket at the bottom and just metal-metal at the supply tube where pressures are highest. If anyone gets a leak at the top tube, one thing to try is a thin copper or aluminum "soft seat" which is common in aerospace, Voishon being one brand. Teflon tape would be very bad there since pieces could clog the injector passages. Good luck.

R-3350 · #4 11-05-2017, 11:34 AM

those are the early om621 type injectors the return line banjos take two small crush washers on either side of the hard line. other than that the injectors themselves are exactly the same as the latter style.the nozzles and heat shields are entirely interchangeable. if you chose to rebuild them yourself the return line fitting is retained by the injector line nut and the large check nut under that and will come off when it is loosened i cant remember if it uses a crush washer or if it mates like the injector body half. you may need to lap the return fitting disc to get it to seal if there is no crush washer. you will need to remove the return fitting to get a socket on the injector. good luck with the car.

jtrnw · #5 11-05-2017, 11:57 AM

That all sounds very optimistic. The guy I bought it from didn't seem very mechanically competent, and I don't think he did much with the car at all, but the guy before him bought a full injector rebuild kit with the bench tester and all. It doesn't look like he used it though. I've got 4 new nozzles and shims and such. I haven't found heat shields yet, but they're probably in the bottom of a box somewhere. Is there any advantage to the later style body, besides ease of disassembly? If not I like the idea of hard return lines. That's what my land cruiser has, and I'm a fan of them in that application.

I think my order of attack will be; change injector pump oil, one can of diesel purge, pull injectors, rebuild, remove teflon tape, etc, reinstall with new fuel filters, drive til the wheels fall off. Am I missing anything else major that should be done before I rebuild them?

R-3350 · #6 11-05-2017, 12:33 PM

the early injectors are no better or worse really just different there are more potential leak sites from the banjoes but crush washers are less likely to leak than rubber return lines. i might consider re-sealing the delivery valves and replacing all the soft fuel lines (not the plastic just the feed and return lines plus any other rubber fuel lines) as preventative maintenance. also change your fuel filters after doing the diesel purge.

BillGrissom · #7 11-05-2017, 04:16 PM

Your Injection Pump looks different than mine. If like my 84 & 85, the IP shares oil w/ the engine, so gets changed with that.

If you run out of shim washers, search for my post w/ PN's of stainless shim washers I bought from McMaster-Carr. I just added the thinnest (recall 0.1 mm) one in a few injectors, which raised pop pressure ~100 psi. I think getting a fine & uniform spray is more important than pop pressure.

Diseasel300 · #8 11-05-2017, 08:23 PM

The old pumps have their own oil charge (red cap in the back). They don't share common oil like the 617 and later engines do, so they need the oil changed from time to time.

Injector pop pressure AND spray pattern are both important. The pop pressure sets the timing, spray pattern is important for proper vaporization/combustion. If the pop pressures are off very far, it will affect the spray pattern and cause uneven power and a rough idle.

Diesel911 · #9 11-05-2017, 08:39 PM

Quote:

Originally Posted by jtrnw

That all sounds very optimistic. The guy I bought it from didn't seem very mechanically competent, and I don't think he did much with the car at all, but the guy before him bought a full injector rebuild kit with the bench tester and all. It doesn't look like he used it though. I've got 4 new nozzles and shims and such. I haven't found heat shields yet, but they're probably in the bottom of a box somewhere. Is there any advantage to the later style body, besides ease of disassembly? If not I like the idea of hard return lines. That's what my land cruiser has, and I'm a fan of them in that application.

I think my order of attack will be; change injector pump oil, one can of diesel purge, pull injectors, rebuild, remove teflon tape, etc, reinstall with new fuel filters, drive til the wheels fall off. Am I missing anything else major that should be done before I rebuild them?

How to Rebuild Injectors
http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

Diesel911 · #10 11-05-2017, 08:45 PM

The outside of your Injectors will not look the same as in the attached pic but the parts inside will be similar.

When you take apart the Injector be sure to not how the part the gree arrown is point is oriented. If you assemble it back wards you are going to crack off the part that the orange arrow points to.

The parts of the Injector Nozzle that are in the square are mated to each other and they need to be kept together as an assembly.

jtrnw · #11 11-05-2017, 10:28 PM

Thanks for all the great advice. My intension is to get the injectors perfect while they're out. I'd really hate to have to pull them twice.

My IP is definitely the early style with its own oil, so that's first on my list to change since I doubt its been done in a while. Right now I'm waiting on a new hand priming pump, the one in the car mostly just primes the ground underneath the car.

jtrnw · #12 11-29-2017, 01:54 AM

Its been a while, so I thought I should give a progress update. It ran like absolute garbage. Full throttle and its making all kinds of noise and not really running more than 1500rpm I estimate. Certainly some of the noise is the exhaust, but that doesn't explain its lack of ability to rev or make power. I pulled the injectors and pop tested them. I don't particularly trust the pressure gauge on my tester, but the all tested between 109 and 117 bar, and the patterns seemed not to bad. I was hoping they were really bad, and that was most of my problems, but no luck.

Next step is to pull the valve cover and look the top end over.

BillGrissom · #13 11-29-2017, 10:14 AM

Quote:

Originally Posted by Diseasel300

... pop pressure sets the timing ... If the pop pressures are off very far, it will affect the spray pattern and cause uneven power and a rough idle.

Pop pressure has a very small effect on injector timing. The IP is positive displacement and the fuel is very incompressible, and the tubes very stiff, so the nozzle will open in sync with IP piston motion, i.e. it keeps building pressure until the spring pressure is overcome and the nozzle pops open. To be exact, raising the pop pressure will delay opening, but very slightly and only due to the very slight compressibility in the system (i.e. negligible).

If pop pressure is so critical, why did I notice negligible difference from changing the 3 injectors in my 1984 w/ 1600 psig pops to the spec'ed 1950 psig? And, yes I tested on my electronic pop tester. On a related note, I can't say I noticed a difference from changing the injector timing (start of delivery) from spec 24 deg BTDC to 27 deg, in both 300D's.

Spray pattern is very important since small droplets are critical to combustion and a uniform mixture, but the non-turbo 1600 psig injectors give about as good a pattern as the 1950 psig turbo injectors, as they should. Most of the time while driving the turbo is not adding significant boost. Does anybody know why the designers made the turbo injectors pop higher?

jtrnw · #14 11-29-2017, 03:46 PM

I tend to agree. It seems to me slop or stretch in the timing chain would have a much larger effect of timing.

Maybe it's just perception, but the other diesels I have experience with (toyota) don't seem to be too picky about timing.

Alec300SD · #15 11-29-2017, 04:00 PM

Quote:

Originally Posted by BillGrissom

Does anybody know why the designers made the turbo injectors pop higher?

My WAG is that at boost conditions in the cylinder you get a poorer spray pattern (larger fuel droplets) at 1600 psi vs 1950 psi and hence poorer combustion.