Herzlich willkommen

Herzlich willkommen auf der Unimog-Community-Website. Seit 1999 treffen sich hier die Mercedes-Benz Unimog- und MBtrac-Enthusiasten zum Meinungsaustausch und Fachsimpeln.

Spezial-Forum zur Unimog-Baureihe U 404 S.

Moderatoren: stephan, krahola

#572424
Guuden,

angeblich können die Zündungsspülen vom Iltis und von den 24V Puch passen.
Ob es den Wolf Benziner auch mit 24V gab??
Auch wurden bereits 12V Spulen 1:1 verwendet, in diesem Fall würde ich zwei
Wiederstände aus der runden Box in Reihe vorschalten und min. immer eine Ersatzspule mitführen.

Gut 404!
Justus
#572433
Hallo Justus,

eine interessante Empfehlung, hast Du das schon ausprobiert?
Ich sag mal, damit gibt es Probleme.
Der Vorwiderstand dient beim 404 und ähnlichen (Mil-basierten) Fahrzeugen nicht einer besseren Zündung oder höheren Lebensdauer sondern einer Reduzierung der Zündfunken auf ein Minimum während dem Betrieb. Dies war Teil der Teil der Funkenstörung.
Im 404 gab es folgende Zündspulen:

Bosch-Bestell-Nr. Typ Spannung Strom DC-Widerstand

0221 103001 KW 24 V 1,1 A 4,8-5,8 (Zivil) Ohm
0221 108003 KMW 24 V 1,1 A 4,8-5,8 Ohm
0221 112002 KCW 24 V 0,9 A 4,8-5,8 Ohm
0221 112004 KCW 24 V 0,9 A 4,8-5,8 Ohm
0221 112006 KCW 24 V 0,9 A 4,8-5,8 Ohm
0221 115001 KCW 12 V 1,7 A 1,9-2,3 Ohm
0221 115002 KCW 12 V 1,7 A 1,9-2,3 Ohm
Wenn man sich die Liste anschaut, stellt man fest, dass die Spulen unterschiedliche Innenwiderstände haben. Die 12V Typen haben einen kleineren Widerstand, sie benötigen mehr Strom um die gleiche Leistung als Zündfunken zu erzeugen.
Wenn jetzt der Gesamtvorwiderstand für diese Typen wie von Dir vorgeschlagen durch zwei "Keksdosen" in Serie verfdoppelt wird, bekommen im Betrieb eine zu kleine Spannung. Im Betrieb benötigten die 12V Typen wie angegeben bei ca 12V einen Strom von ca 1,7A m richtig zu funktionieren. Das entspricht einem Induktivenwiderstand von 7 Ohm.

Der Vorwiderstand bei der Mil-Ausführung (Schwallwassergeschützt) der 404 hat 4,5 Ohm. Das würde bei den 12V Zündspulen durchaus besser passen als die Verdoppelung. Da unsere 404 heute in den meisten Fällen nicht mehr militärisch genutzt werden wäre dies sogar für einen dann besseren Zündfunken von Vorteil.
YoEddy2 liked this
#572443
Ei Guuden Jürgen,

da sich bisher keine Antwort zur Zündspule fand, habe bewusst im Konjunktiv von den mir bekannten Gerüchten geschrieben.
Schön ist es, dass Du als Elektroniker nun noch mit Deinem fachlichen Wissen die Sache auf stabile Füße gestellt hast. Danke!

Gut 404!
Justus
Jürgen-Fahlbusch liked this
#572598
Dear All,

I am new to all this, but after looking at the electric diagram and noticed that in order to use a 12V ignition coil one needs two different resistors.
During startup, as you can see from the picture below (Blue circuit)
coil_power_startup.jpg
coil_power_startup.jpg (43.5 KiB) 577 mal betrachtet
The resistor is bypassed and the coil receives 24V, so the resistor to be placed in series during this phase should be equal to the coil resistance to have an equal drop of voltage 12v and 12v.
During running mode the resistance should be calculated so that the drop voltage on the coil + the resistance + the resistance to be added equals 24V. I cannot do this because i do not know what is the resistance value of the resistance (item 29) and what is more important is what voltage should the 12V coil have during normal running mode. You can see the running current path in this second picture.
coil_power_runing.jpg
coil_power_runing.jpg (43.6 KiB) 577 mal betrachtet
I ordered a 24V coil i hope it will work, I drove my Uni for a small trip, it is not running good so now i changed all of the sparkplug wires except cylinder 1, but still it sounds that there is a miss fire on some cylinders, I changed the distributor rotor, still not much improvement, i have a new distributor cap, will replace the current one and check if it makes any difference.
#572602
Dear rkharma,
it would be nice if you can sign all your postings with your real firstname. This is a rule for more friendlyness at this forum.
I am not sure what kind of ignition you have and what kind of problems you have.
Do you have a electronic (Transistor) ignition from Laubtec (Laubersheimer) ore a different kind?
Which coil you are using.
Which kind of sparks and sparkplugs you are using, civil or mil kind?
So you must send us all your details that we can assist.
YoEddy2 liked this
#572615
Dear Jurgen

Thank you for the feedback and the note about the signature will sure do so on my future posts

For the ignition system, it is all civil not military. For the ignition and based on previous posts under this thread by Ulli it should be a Laubersheimer in all cases this is a picture.
20231120_180233.jpg
20231120_180233.jpg (1 MiB) 460 mal betrachtet
The ignition coil is a BOSCH 24V, looks a bit old
20231120_180308.jpg
20231120_180308.jpg (1.07 MiB) 460 mal betrachtet
And finally for the spark plugs they were NGK BP6ES, I replaced them recently with HELLA YH7RCP-11U
20231120_180345.jpg
20231120_180345.jpg (1.21 MiB) 460 mal betrachtet
Thank you for the support

Regards
Rabih
YoEddy2 liked this
#572620
Hello Rabih,

Is the coil the same as it was coming from Ulli or is the coil changed on your side.
If you changed the coil why?
Do you have a Bosch No of the coil?
Do you changed any thing in the wiring since the Unimog came from Ulli?
Why you selected the HELLA YH7RCP-11U spark. This is not compatible with your former NGK BP6ES.
The Hella spark has a different heat value than usual for this motor. Also the gap (1,1mm) is a wider as the usual Bosch WR7DC (0.7mm). The original gap for the 404 was 0.5mm.
Did you checked the ignition timing?
YoEddy2 liked this
#572631
Dear Jurgen

I did not change the coil, it is still as it came from Ulli, I only changed the spark plugs and their cables. The new cables are not 90 degrees at the distributer but they are a good fit on the engine as 5 are long and the first one is 90 to fit next to the distributer.
I ordered a coil as spare just not to have a dead machine should something happen to the coil as 24v coils are hard to get. I could not get more info on the coil will try to clean it a bit over the weekend and try to get a model # or the ohms.
Now I understand that the Hella spark plugs are not a good, should have know better than to trust the shop and should have done my research. I did some inquiries today but the best I could find was Bosch WR8DC it has a 0.8 gap which i believe it is better than the 1.1 gap but still did not buy a new set will shop arround a bit more.
For the ignition, I checked it, I have a strobe light and marked the front pully/damper at TDC, might be a bit off but double checked when I removed the engine valve cover and turned the engine by hand. For this I have two issues one is that the wheel has no markings for the degrees, second problem is that when I try to turn the distributer I cannot turn it more because the cover clip is hitting the engine valve cover. I can try to remove it and position it differently but I am not sure if this is correct. For the degree marking, I wanted to measure the balancing wheel diameter and calculate how much each degree woul be in cm on the circumference and mark it on a sticker and stick on the balancing wheel just to fix the ignition.
I noticed that the rotor head is broken, it works but not sure how, I had ordered a spare bosch one but it doesn't fit, have to check the exact model number.
IMG-20231121-WA0002.jpg
IMG-20231121-WA0002.jpg (174.47 KiB) 406 mal betrachtet
Regards
Rabih
YoEddy2 liked this
#572635
Dear Rabih,
with such broken rotor the ignition can't work proper, so first fix this problem.
Also the Bosch WR8DC has not the best heat value, I still recommend WR7DC type. Not only I have good expierence with this type on the 404 engine.
Normaly there are degree marks in 5 degree steps on the front counterweight wheel. Maybe you have to clean it. Otherwise your approach will work.
YoEddy2 liked this
#572659
Dear Jurgen,

Thank you for all the information. For the spark plugs i will try to find the exact model you advised, i might have to import them myself, car parts dealers usually don't hold items that have slow turn over and for this they only know that there is hot or cold spark plug and not a whole range :D

I will replace the rotor head, just to be sure it should b e a 5Kohms one correct? Bosch have a 1Kohms and a 5kohms, the BERU model EVL029 that is there but broken is a 5Kohms.

Just one more question about the carburetor this time, i ordered a choke cable as the one i have is loose and it doesn't pull back properly. But i was wondering about the exact position on the choke when it is closed. When it is activated (lever pulled) if you look at the carburetor from behind (the cabin side), the lever is on the left touching the "stop", when the choke is off (level pushed back down), the lever should be in the middle like vertical or all the way to the right touching the "stop". If i turn mine all the way to the right the engine dies but this is another story first i will get recheck and try to get the timing correct and the rotor head then will try to tune the carbs again. Regarding the timing, should i remove the vacuum cable while adjusting it or not? I know that when i rev up the engine more than 1500 rpm i can see that the TDC move further to the left (looking at the engine form the front) meaning the ignition is happening even further before TDC.

Regards
Rabih
#572663
Dear Rabih,
the 5 kohm rotor is ok, but I am not sure with the correct number as you have a civil not the MIL distibutor cap.
On the MIL version the Beru EVL4/6z1 or Bosch 1 234 332 088 is used.
For adjustment of the ignition timing everything needs to be ormal. So if your ignition has vaccum adjustment so use it also for the right timing adjustment. Same to the centrifugal force adjustment. You have to use the values from the repair manual.
The choke needs to 100% closed in normal running mode of the engine. Only in cold weather conditions the choke needs to be opended just to start the engine. Than as fast as possible the choke has to be closed.
#572670
Dear Jurgen,

Yes the Bosch 1 234 332 088 is 5Kohms and I have one but it does not fit, the axe is too large and the rotor does not go in, I am looking at Bosch 1 234 332 261 which is 5Kohm there is a 1 234 332 271 it is 1Kohms.
For the choke, I just wanted to know if 100% closed means vertical or all the way tilted to the right (looking from the passenger cabin at the carburetors).

Thank you again

Regards
Rabih
#572671
Dear Rabih,
if the axis of the Bosch 1 234 332 088 is to long you can shorten this a little. The reason is not a wrong rotor but the position of the magnetring of the electronic ignition. Normally there is limit other than the top of the carburator axis. But no the ring is limiting the way down. Maybe this is also the reason why the old rotor break.
The choke lever has two mechanical limits on the choke housing. Left limit full open, right limit full closed. For normal engine operation the choke needs to be full closed.

Hallo, danke für eure Antworten. hm, da bei[…]

U411 Bremstrommel Vorderachse

Danke, habe eine gebrauchte Trommel gefunden.

V + R pneumatisch schalten

Hallo, So ich habe jetzt alles an Hardware zusamm[…]

OM636

Hallo zusammen, gibt es noch irgendwo einen guten[…]