The 505 carries Ktronic Injection and the problem you mention must be sought by parts:
to check the cold starting injector drive: it is located in the admission collector. Without taking it out, it will be checked with a voltmeter if it reaches current, this injector only works while the start and whenever the engine temperature is below 20ºC for a period of between 8 to 15 seconds, then despite continuing to turn turning with the start, the injector should not receive current.
To check the tightness of the cold starting injector, it is necessary to take it out of the collector and bridge terminals 30 and 87 of the tachymeter relay, when doing this, the pump will send gasoline and if the injector does not close it will begin to drip or drip gasoline (possible reason why it is drowning).
If the cold starting injector does not reach current, the cause must be sought in the timed thermocontact.
To check the timed thermocontact: it is located in the cylinder head. With an ohmmeter you have to disconnect the plug and measure resistance between each of the two terminals of the thermocontact and mass. In one of them there must be continuity and in the other a resistance of between 25 to 80 ohms. If the resistance terminal is fed with battery voltage, mass continuity will be interrupted in the other terminal after 8 to 15 seconds.
To check the additional air valve: it is located near the probe plate and the gas butterfly, in the intake manifold to check it, you have to disassemble the tubes and look through them to see if the sheet is completely open with the cold engine and the contact removed. To measure the resistance, the plug must be disconnected and measured with an ohmmeter, the resistance value must be between 14 and 21 ohms and check if it reaches current you have to bridge terminals 30 and 87 of the taquimetric relay and measure tension in the connector of the aforementioned valve. After about 4 or 5 minutes, the bimetallic sheet should have completely closed by obtaining the air passage through the tubes.
Mechanical checks:
Adjustment and focused of the probe plate: it is enough to remove the air filter and look below, apart from being centered, by pressing it with the finger, it must have some resistance and show how \ "chillan \" the injectors. The course of the dish must be homogeneous at all times and after moving it several times, the resistance to movement will disappear due to the pressure drop in the regulator.
Pressures:
The pump pressure when reaching the regulator must be between 3.4 and 3.8 bar with the engine at service temperature. This test must be done with the engine stopped, and it is necessary to have a pressure gauge and an T to splices the tube that reaches the pump to the distributor dosing, since it is the latter that regulates the circuit pressure.
To act the pump with the stop engine, the 30 and 87 terminals of the tachyymmetric relay must be bridged. The pump flow must be around two liters per minute.
A possible cause of the breakdown you have is the regulator of the heating phase. Its mission is to enrich the gasoline air mixture while the engine is cold until the service temperature reaches.
This regulator I do not know where it is exactly in 505, but to locate it you just have to follow the fine tube that leaves the center of the distributor dosing. This tube will take you to an aluminum box about 6 centimeters long by 4 wide and 3 high, with three pipes, two gasoline and one vacuum, and a connector with two terminals. It is very possible that you are screwed to the engine since it needs to heat itself as the motor takes temperature.
The failures that this regulator can give are:
1st breakage of the electrical resistance that heats the bimetallic lamina, (unlikely) which takes much more than normal to impoverish the mixture when the engine is heated and the engine ends up drowning.
2nd accumulation of shit and deposits in the steel sheet that acts as a valve inside the regulator, (very likely) leaving it open and falling the regulation pressure (which produces an automatic enrichment of the mixture).
3rd Break of the vacuum tube that goes from the regulator to the collector, (quite probable) so that the regulation pressure is incorrect at a slow and a half load, which ends up drowning the engine.
4º in some engines flooding of motor oil inside the box because it oozes from the vent (especially in the old Mercedes).
Checks of the regulator of the heating phase:
The pressure of this regulator must be between 0.8 and 1.2 cold bars and when it reaches operating temperature it must be around 3.5 bars. If empty in the tube that communicates the regulator with the gas butterfly, the regulation pressure be the temperature will fall to 0.5 bar (which produces an automatic enrichment of the mixture when accelerating).
To verify the current arrival to the regulator connector of the heating phase, the 30 and 87 terminals of the taquimetric relay must be bridged. And to measure resistance, the regulator plug must be disconnected and measured with an ohometer, the resistance value must be between 20 and 30 ohms.
This regulator has a very high price (around 600 euros) and Bosch does not guarantee that it has it because it is very old (it happened to me with the Mercedes 300 of 81).
So I recommend that you go to scrapping, and take three or four regulators like that, do not have to have the same reference but they have it much better. And that with a lot of patience you take out the 505 motor regulator, clearly, clean it with solvent and the pieces that you see are wrong (especially the stainless steel laminite that acts as a valve) you change them for those of the regulators that you have brought from the scrapping.
Do not change the dock or the bimetallic sheet that is inside the regulator because they are the ones that determine the pressure depending on the temperature. The rest of the pieces are all the same.
In the event that the regulator was well or that you repair it and give the right values (it can be tested outside the car before riding it, it is what I do). The breakdown must be looked at in the same distributor dosing, either because the probe plate has some point where it is too hard, or because the pressure regulator that is attached on one side of the dosing is wrong, if the regulator is wrong, the regulator is going to sing the pressure gauge when doing the pressure test with the hot engine.
Anyway, after reading this, if you have not died, print it and do what I tell you step by step and tell me your advances.
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