D-Jetronic fuel injectors for W109 300SEL 3.5: need advice here what to do - Page 2 - PeachParts Mercedes-Benz Forum

Tony H · #16 01-06-2011, 10:32 PM

Looking at my engine with the intake manifold removed I can see the injectors mounted in the head with the tip of the injector about 1.5" from the intake valve. The fuel charge would need to travel backwards the entire lenght of the individual intake runners to reach the plenum.

Quote:

Originally Posted by Graham

Thanks for the explanation of how MS injects. Gosh the original Bosch system has twice as many injector circuits as MS

I am surprised that such a small % of fuel injected near a certain cylinder would end up in that cylinder. That fuel would have to flow back up the intake runner and then find it's way down another runner to a different cylinder - What causes that? Maybe pulsing from the valves?

As you can tell, I don't know beans about this. My diesel injectors squirt fuel right where it is needed

Gurunutkins · #17 01-07-2011, 12:44 AM

Hi Tony and Graham
sorry still working from memory here but yes and no to both of you.

remember the injectors fire from the trigger points in the base of the distributor. there are 4 sets of points and each fires 2 injectors so the pairs are (from memory so excuse errors) 1&5, 3&6, 4&8 and 2&7. however there are 2 cams firing the injectors (1 on each level of points) set 180 degrees apart. following that you actually fire 1&5 and 4&8 together and then 3&6 and 2&7 so even though you are running 4 sets of points its actually firing those in pairs the way the cams are set up so there are really 2 circuits firing 4 injectors each every rotation of the engine. with MS I also fire 4 injectors at a time but I can fire them up to 3 or 4 times per engine revolution depending on the latency in the injector plunger (how fast can I move the solenoid up and down). Hope I got that right I will check my dist tomorrow morning

same thing really with the fuel in the manifold. just at idle I have 16 or 17 inches of vacuum in the manifold, the distributor cam rotates and fires injectors 1,5,4 and 8 all together as cylinder 1 intake opens, cylinder 1 sucks in 562ml of air (not accounting for scavenging and ram effects etc etc) thats 2 and a half cups of air or nearly 1 and a half cans of beer and each cylinder does that 11.66 times per minute (idling at 700rpm) the air is all supplied through the aux air valve at the front of the plenum through 2 pies into the middle of the lower plenum - the turbulence and eddies are huge and you will literally suck from the rear of the plenum to feed the front cylinders. think of the cold start enrichment valve stuck on the front left of the upper plenum and yet it enriches all of the cylinders in the engine until they hit operating temperature.

thats one of the reasons that racers use polished manifolds, just to try and decrease the turbulence with all of the air movement in the planum and manifold tubes. my lotus 7 is tuned to get maximum load into the cylinder thats filling for compression so my cam is hand tuned so that my exhaust valve is still a little open when the intake opens, called scavenging and it allows for a free path so that as the last of the exhaust gasses leave the cylinder they actually start to suck the new charge into the cylinder behind them before the exhaust valve closes totally so I can move more charge in faster and overcome some of the turbulence effects in the manifold.

hope thats some help
cheers
barri

Tony H · #18 01-07-2011, 05:01 PM

Thanks Barri-that helps alot.
Tony

werminghausen · #19 01-10-2011, 04:30 PM

Just to letting you know where I am :
I have taken off all injectors from the rail and disassembled them as much as possible. I took off the pintle cap (I used a M10 Nut, screw it on until the cap started turning on the injector...then pulled it off...this was before I saw Barri cutting the cap off on the side with a blade in the video which is fine because this part gets replaced anyhow)
I also pulled the baskets off by using a sheet metal screw with as slightly bigger diameter than the inside diameter (ID was about 4.1mm and I use a screw with 4.3 AD) screwed it in and then pulled it out. Can be tricky, but I got them all out almost unharmed but full of gunk. I am wondering how much restriction the full basket might have been to the flow of fuel?
I am planning on replacing these baskets too.
Of course I have removed the old rubber hose which was pressed on the injector intake with the metal ring at the bottom. I cut the metal ring with my sharp small cutting pliers which went quite well (while Barri is doing the cut with a small cutting tool in the video which I don't have).
I have soaked all injectors in WD40 for now but will use the Kerosene/ Mineral Spritis 50/50 mixture Barri was recommending.
I will do the flushing with Carb cleaner after a couple of day of soaking.
I'll keep you posted.

Gurunutkins · #20 01-11-2011, 12:22 AM

just if anyone is interested here are the videos I put together for Martin. the first is removing and disassembling the injectors and the second is cleaning without an ultrasonic cleaner. I actually soak mine in kerosene and mineral spirts first them flush them and then clean in the ultrasonic bath. I had to modify the technique a bit as i just didnt have enough hands to hold the camera and show the technique so it too is a bit of improvisation

the removal and disassembly
http://www.youtube.com/watch?v=9VJ1Gy4yKBs
the cleaning etc
http://www.youtube.com/watch?v=yKIg_fLwR5U

cheers
Barri

werminghausen · #21 01-11-2011, 10:31 AM

Thanks so much for the 2 videos Barri! The videos are especially valuable for someone like me doing injectors for the first time.
As you confirmed I will use 50/50 Diesel (substituting the Kerosene) and Mineral Spirits for soaking the injectors a couple days before cleaning with carb cleaner.
Martin

werminghausen · #22 01-25-2011, 10:40 AM

I soaked the injectors (I took off baskets and pintle caps) for some days and then set up the flushing with cables connected to battery with a 12v light in line (in order to see when there is current clowing and to have a 'fuse' in case amperes go higher than expected.
I took a transparent PVC hose, put it on the pintle side (pintle up) filled with carb cleaner and did the back flow flush by connecting the cable to the battery with a frequency of maybe 2/second. I also did some with adding 10 PSI air to push harder.
Same I did for the flush in the regular direction. There came out quite some gunk! You don't believe it if you haven't seen it

JeffreyNMemphis · #23 01-25-2011, 06:51 PM

Barri,

I enjoyed your videos! Thanks for sharing!!

Gurunutkins · #24 01-27-2011, 12:14 AM

no where near as professional as yours and some others on the site. I'm going to have to get a tripod or a helper!
cheers
Barri

Graham · #25 01-29-2011, 10:22 AM

Quote:

Originally Posted by Gurunutkins

no where near as professional as yours and some others on the site. I'm going to have to get a tripod or a helper!
cheers
Barri

Great stuff barri - Wish I had seen the videos before I cleaned mine! I didn't try a backflow and it's hard to know how well my el-cheapo US unit worked.( BTW Notice your accent is a bit mixed up like mine

Similar influences I guess!)

I would like to try bumping the fuel pressure on my car up to 40 psig and maybe the Nissan injectors could be the answer. The Yellow Bosch may work but hard to find at price where I can justify the experiment

I once did some calculations that showed that high RVP winter fuel (Delivered in Fall/Winter/Spring) would flash across the injector at 28psig and under hood temperatures that occur after a short stop. This means a mix of vapour and liquid is injected instead of just liquid. This might be OK, but it reduces the flowrate through the injector orifice. The engine either doesn't start or runs badly for a few minutes until cooler fuel arrives from the fuel tank. And the nice spray pattern obtained under test conditions is altered.

I would hope that the lower flow injectors would also allow the ECU to control the injectors a little better (more pulses needed?) and achieve better mileage.

barri - where did you find the (used?) Nissan injectors? I need a Spring project!