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)
