Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: rosch on January 04, 2024, 16:27:00
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Years after my 230SL restauration and engine overhaul some known fuel issues started to develop : increasing difficult starting hot &cold , rough idle,hesitating etc.
The IP was overhauled and adjusted and injectors professionally cleaned during the engine rebuilt. Used last year injection cleaner additive without any noticable improvement.
Time to start troubleshooting this winter !
I started at the tank fillercap (where the fuel gets in) and systematically worked all the way forward to end where the fuel gets out : at the injectors.
Checked all the internal fuel lines and flowerpot openings ,vent lines and filter in the tank, cleaned fuel feed pump,checked its inlet filter and outflow checkvalve and replaced the O-rings .
Checked fuel pressure and flow volume and discovered the first problem : the pressure regulating valve in the returnline fitting of the IP caused the fuel pressure to be just 0,4 bar...
After polishing the little plastic valve inside and adjusting the spring pressure , now I have good pressure and flow . Check !
After disconnecting the fuel lines to check the condition of the IP checkvalves and injectors I started with the injectors first.
I used a home built poptester made from a bottle jack and discovered that none of them had a good spray. They looked more like showerheads, spraying little jets all over the place.Hmm...not good !
( For making a low budget poptester without welding see one of my replies on this topic)
Now time to start cleaning !
After watching several YouTube Mercedes source video's from Kent, I started with his cleaning techniques including backflushing,as well as ultrasonic cleaning. Still no luck !
Repeated the process ,got some slight improvements but still no desired results . 6 out of 6 injectors junk ?
Read the forum searching for helpful tips and found someone used the tip of a zip tie and rotated it under the tiny valve . Again some improvement but still spraying little jets and no "chirp".
Now what ?
At this point I was on the verge of buying 6 new injectors ...
If my injectors seemed junk anyway I remembered something I did years ago with my leaking CSV...
The design of the SL injectors is no rocket science,. Basicaly it consists of a metal body with a metal mesh filter in it and at the tip a valve seat with a springloaded valve. Thats all !
( see this video from Kent : https://www.youtube.com/watch?v=-kR1Lrmi5Uw ) or my drawing
To start with the final result first: My "junk" injectors turned into 6 injectors chirping nicely with perfect atomized spray patterns.
You may try it yourself. To help other members please reply on this topic if it worked for you or you have additional suggestions.
What you need (see photo) :
- a poptester with carbcleaner , injectorcleaner ( I used kerosine ,aka parrafine and sold here as "Lamp oil ")
- some thin plastic packaging material and a scissor
- metal polish
- a small flatnose plier
- brake cleaner
First some warnings:
-working with fuel (vapours) is dangarous, take all required precautions.
-always try the simple things first ! , i.e. use of additive , ultrasonic bath cleaning with poptester etc
-NEVER EVER use any metal tool to pry open the injector valve at the tip , instead use the thin plastic material as mentioned.
-Before you proceed be absolutely sure the metal mesh filter is not clogged ! If so: try to backflush to clear it.Flushing in step 4 is essential !
- Don't use too much force when working on the valve/valve seat Do it gently !
- Always end with step 4
Step 1 :
make some V -shape plastic tools to slide under the valve to keep it open or for cleaning and (back)flushing purposes. Use a bent v-shape tool for backflushing so you can slide a hose over the tip side of the injector.
Step 2 :
make a sharp edged plastic "scraping" tool ,something like the one on the photo .For clarity I marked the edge to work with green .
Step 3 :
Over time hardened deposits or gunk will stick at the valve seat (the opening under the valve) , due to ethanol fuels, long periods of stand still etc.These are difficult to remove with solvents
This is where the "scraping" tool is used for. Don't worry , plastic is way softer than metal.
Gently lift the valve with your fingernail and slip the (green) point under the valve and try to get its point into the valveseat opening .
Let the valve return to hold the plastic tool in place . You may add some cleaning fluid if desired.
Now start turning the "scraper" a couple of times and remove it afterwards.
Step 4 :
A very important step !
Insert the little v-shape tool to keep the valve in the open position .Now use your poptester or blow compressed air and/or spray brake cleaner in the fuel INLET side of the injector to clean out any left residue or dirt. This is why your mesh filter must be clean/open.
Remove the v-shape tool.
This may sometimes be sufficient to restore your injector. (2 out of 6 of my injectors worked fine after this step)
Test with your poptester for "chirping"and spraypattern.
Remember : according to Bosch a good atomized spraypattern is only obtained by an oscillating "chirping" valve. Oscillating (rapid opening and closing of the valve) will only occur if the valve is perfectly closing in its seat.
Rule of thumb : NO CHIRPING = NO GOOD
Repeat if necessary or desired..
Step 5 :
If everything fails you might try this step as a last option:
Put a mark (off centre) on the valve, like shown on the photo.
Lift the valve with your figernail or insert a v-shape piece of plastic.
Put some metal polish between the valve and valve seat.Try to distribute it as evenly as possible.
Remove the v-shape tool.
Get your tiny flatnose plier and grip the valve on the OUTSIDE edge (see drawing) .
Now gently start turning the injector body several times in both directions .
Look at the mark and check that the valve is turning relative to the body instead of just slipping in your plier.
Clean the outside of the injector
Return to step 4 and repeat steps 5 and 4 if required.
It took me two applications before my remaining 4 injectors started chirping and spraying correctly. It saved me a bundle !
This process with metal polish was also used to clean and restore a leaking CSV an IP check valves ( plunger type)
SHARE YOUR EXPERIENCE
Good luck and regards from Halle , the Netherlands
Rob ( Rosch)
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Most impressive results, shows what persistence and patience can achieve.
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Excellent, thank you for posting Rob.
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How would you describe the thickness and strength of your plastic tools? Credit card material? Cheap water bottle material? Other? Thanks for the post. I'll probably have to clean up my type 1 injectors.
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Creditcard material is too thick and too stiff. Should have mentioned it.
I made it from a lid of a bowl of a grocery product which was about half the thickness of a creditcard and more flexible. That worked out nice.
Just find something similar that works best for you.
It's the cutting edge of the scraper tool that does the work.Renew when it gets blunt .The v-shape tools are not that critical , they only serve to keep the valve open just a little bit for flushing/cleaning or applying metal polish.
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Nice write up, thank you. It is good information.
A while ago I pulled mine out and pretty much did what you did, but several wouldn’t give me a good spray pattern. I didn’t try the polishing trick though.
I bought 6 new ones and all but maybe 2 had terrible spray patterns. It was disappointing and I returned them.
I thought about making a tool to uncrimp the end of the injector to remove and properly clean the injector valve but haven’t gotten around to it.
I had the engine rebuilt and the injection pump, CSV, and hopefully the injectors also were sent to a specialist (sent by Metric Motors) to be refurbished. I’m hoping they checked the spray pattern and corrected any deficiencies.
My engine is still out so I don’t know how it runs yet.
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Uncrimping and opening the injectors is not a good idea. Inside the injector tip is just a spring which determines the opening pressure.Nothing to clean there.The mesh filter can simply be cleaned with (back)flushing.
Valve and the critical valveseat surfaces are on the outside and can be reached from the outside with a little effort.
Besides : How do you get your injectors properly crimped again without leaking ? Bottom line ? Don't do it !
A good spray pattern can only be obtained when the mating surface's between valve and valveseat form a perfect clean seal thus closing completely in the closed position. That wil cause the high frequency oscillation ("chirp") at opening pressure and should give a good spray pattern.
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Great write-up Rob, thanks!
Instead of, or in addition to, the metal polish I was thinking some fine valve grinding paste could be effective also. I will have to make or get me one of those pop testers for sure and check my 'new' (bought new around 23 years ago) injectors.
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@ Cees :
Valve grinding paste might be too coarse .Not sure though .Have considered it as well ,but didn't dare to apply it.
I'd rather used the metal polish and repeat it more often if needed.
Maybe you could start with a single application of fine valve grinding paste and then start the final polishing stages with metal polish to get an optimal result.
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I've added this to the technical manual, i must confess i had to Google to find out what a pop tester is!
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I’ve already taken an injector apart and seen how it’s made. If done right I think it can be uncrimped and recrimped again. If I can fix the pattern using your techniques that would be great. If not it’s no loss whatsoever to take one apart and try to reseat the tiny valve and recrimp. Testing it on the injector tester will show whether it leaks or not.
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Very informative write up. Thanks for sharing!
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Hello Rob!
Thanks for your excellent explanation .
I followed your advice and looked at some video's of Kent and I cleaned my injectors.
I had to go for the grinding paste. First one was too coarse; bad result.
Then I used some fine paste that I use to polish watch glasses. Much better result.
I see a nice spray pattern now.
One question however. If I build up pression in the pop tester very, very slowly I don't get a nice and even pattern.
If I build up pression a little quicker the pattern looks OK.
Is that what you observe as well??
Dank!
Halvor Sens
Drunen
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Hello Sens,
Good that you were able to save your injectors like I did !
Maybe we should draw the conclusion that it is better to use a fine (metal)polish or similar product and repeat the treatment a couple of times if required.
Regarding your spray pattern there might be an explanation :
By applying pressure very ,very slowly you will come to a point that the pressure buildup in your fuel line / pop tester exactly equals the opening pressure of the injector (caused by the internal spring in the injector). Adding then a very tiny bit of pressure (maybe the volume of just a drop of fuel) the injector will open just a fraction of the normal opening gap and also over a very short time ,just to let this tiny little bit of extra fuel escape. Then the equilibrium occurs again causing the injector to close.The minimal amount of escaped fuel may be too little to see a nice vapor spraypattern.
If you pump your poptester just a little bit quicker and you get a nice audible high frequency "squirt" and spraypattern , you should be OK.
You might doublecheck by connecting your injector to a fuel line only and observe your spraypattern at starter RPM.
A little bit of background information:
Your fuel injection pump is also pumping fuel to the injectors in a quick ,more or less pulsating way.
A simple calculation:
Lets assume your engine idles at 720 RPM ( 720:60 =12 rotations per second) . This is the cranckshaft RPM .In a 4-stroke engine ignition and fuel injection occurs every second rotation of the crackshaft , so at half the speed ,which is 6 times per second per cilinder. How quick is that ? And we're only talking idle . Try to match that with a poptester !.
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Hi Rob,
Wonderful explanation!
Thanks; I agree 100%.
The first coarse paste gave a terrible result, which I was able to "repair" with the finer paste.
I used some watch tweezers to turn the little valve and that worked pretty good.
Regarding the start pressure I was just a little confused by Kent's the video, where he very slowly increased pressure to see the correct pattern. In my case that happens if I apply pressure a little quicker.
But again, I follow your explanation and saved my injectors!
Thanks again!
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Hey Rob - would you mind sharing how you made your pop tester, what parts you used? I would like to make one for myself. Or borrow yours (or Halvor's) if that's possible!
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I bought this and a correct pressure range dial from this guy to use as one.
https://www.ebay.com/itm/401303812709?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=PxAzvc7yQma&sssrc=4429486&ssuid=d6KftIEWT_6&var=&widget_ver=artemis&media=COPY
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@ Cees,
I have the same one.
https://mercedessource.com/store/bosch-mechanical-fuel-injector-mfi-tester-and-cleaning-kit
After initial issues, it worked quit well for my injectors. I you attend the pagodas and beer event next month, I will bring it and you can borrow and or copy.
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Cees,
No problem to borrow it, but I am in the Netherlands...
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Rob, you're awesome!...and for me your posting is very timely.
Regarding my newly acquired 280, with my hood/bonnet, valve cove linkage and manifolds off for deep cleaning my thought is that this is an opportune time to remove the fuel injection lines for refurbishing.
The car runs just fine now so I don’t want to do anything that might require some sort of recalibration of the fuel system and introduce unnecessary complications etc., for a tune up.
So…. are there any precautions that need to be taken during removal or reinstallation of the lines which will ensure that everything works fine after re installation?
Also, photos of FI pump refurbishing (eg SLShop) show what appear 6 plastic acorn nuts on the pump presumably to prevent ingress of dirt while the lines are absent. Where can these be sourced?
John
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@Dirk and @Sens, thank you both for your generous offers!
Given the low cost of the Ebay one, under $100, it probably makes most sense if I just order my own for delivery to France where my injectors are (all 14 x 6 = 84 from all the engines I acquired over time). When I'm done with all of those I should be an expert cleaner!
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Here's how to make a poptester
There are several tutorials on the internet, but most of them require some welding .
This one requires no welding , but you still need a rather large size tap :
www.youtube.com/watch?v=s9A4Y-oS7tU
Watch this video first and the rest will make more sense.
I modified it a bit to make my low budget poptester without any welding or using a large tap (see photo's):
step 1: Starting with a standard bottlejack ,remove the fillerplug on the side ,drain the jack oil .
step 2 : Remove the large nut on top and pull out the plunger.You don't need the plunger anymore.
step 3 : Remove the reservoir,the inner ( high pressure ) cilinder with its inside chamfered top is now completely visible. Install a hose connector where the filler plug used to be.
step 4 : Somewhere near the top ,most likely in the threaded area there is a very tiny hole , it is barely visible. Plug it with something like JB Weld.Keep the thread usable !
step 5 : In the large nut , there is also a hole. Plug it .You can screw in a small bolt and file off the excess material
step 6 : Using a thick steel or aluminium piece of material ,make what I call a lid with a chamfered edge that will fit on top of the inner cilinder. Drill a hole in the center for the size of fittings you are going to use. I used 1/4 " BSP thread fittings which will do fine. (for the injector you will need a M12 x 1.5 mm adapter fitting) Install the first fitting(s) on your lid.It has to protrude the large nut in such a way that you have sufficient grip with a spanner when installing other fittings
Now make a "dry" fit first : install the reservoir ,then install your just made lid. Screw on the large nut on top and check that you obtain a snug fit with your lid and reservoir. If there is any play between the large nut and the lid ,add a suitable spacer right between the large nut and lid.
step 7 : If everything fits OK ,remove the large nut again and add some JB Weld or similar between the chamfered mating faces of the inner cilinder and lid.Screw on the large nut and let dry .
step 8 : install the required fittings and adapters for attaching a fuel line and injector . If desired add a T-coupling with pressure gage if you want to check the opening pressure of the injector.
step 9 : fill the reservoir with cleaning solvent, remove the air from the system and you are ready to go !
Remark : some bottle jacks have a safety valve ,adjustible with a screw ,sometimes hidden under a small cap.You may have to adjust it to obtain good pressure
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Poptester Photo's