Carburetor: First we have to understand how the Pierburg carb 2E works in order to know that is wrong. The carburetor has and automatic choke. The design has a spring like bimetallic strip connected to the choke flap. When the engine is cold, the bimetallic spring has the choke closed. The bimetallic spring is located within a housing through which water from the engine passes. After the engine starts, the water in the engine begins to warm up also warming the bimetallic spring via circulation through the spring housing. As the bimetallic spring warms up it begins to open the choke. A stepped cam is located on throttle butterfly shaft which is influenced via a link connected to the choke. This mechanism allows the engine to run at fast idle during the warm up period. Blipping the throttle deactivates the fast idle feature. In addition to all this there is also two other items of note. There is an accelerator pump and a second barrel opens at more than half accelerator. The accelerator pump squirts fuel in the first barrel when the accelerator pedal is pumped. The second barrel opens to allow double the fuel air mixture in the engine at about 75% accelerator opening.
What I found was (a) The choke flap had been forced open. (b) The choke linkage was broken. (c) The accelerator pump was not working. (d) The diaphragm operating the second barrel butterfly was not working. That pretty much explains the poor starting in the cold and poor acceleration. I was able to get a carb rebuild kit from UK. The kit contained all the required o-rings, gaskets, pump diaphragm etc. for the proper functioning of the carb. For the broken choke (plastic) linkage, I was able to fabricate it from steel. In this way the carb functionality was returned to the way it was supposed to work. A replacement second barrel diaphragm returned the proper operation of the second barrel.
Water pump/thermostat assembly: Again here too we need to understand how this system works before knowing what is wrong. When the engine is cold, the thermostat is obviously closed. In this state certain water ports are open and certain ports are closed while certain ports are always open. The “always open” ports are (a) the flow to the carb bimetallic spring housing discussed earlier and (b) the cabin heater. In cold condition the ports that the thermostat valve keeps open allows the water to do what is called short circulation, i.e. circulation just within the engine block. When the water reaches 82 degrees, the thermostat opens and water is no longer allowed to do short circulation and directed to the radiator also obviously called long circulation.
What I found was that the mechanics in their attempt to “fix” the overheating problem, remove the thermostat and weld shut the short circulation port. Also I was informed by one of the mechanics who worked on this van that the pump had been found to have corroded impeller, and that it had been rebuilt with a Toyota impeller. I have to say that certainly the impeller job was well executed. But the port welding job basically ruined the pump. My plan was to restore all the original function of the carb/engine cooling system. So a new pump and thermostat was imported from UK. Oh BTW they also made the electric radiator cooling fan direct with ignition switch (another popular local overheating fix). Now with the Choke system operational, it is essential that the thermostat be working or the choke will remain "on" for longer than necessary. This is certainly not desirable at all.
Distributor: The distributor is of a breaker less design there is a magnetic pickup that sends a signal to the engine computer. Quite simple.
What I found was that the four wires had broken or got cut pretty close to the pickup element inside the distributor housing. Then on the way to the computer there were many joints in these four wires. At the computer end of these four wires there is a connector which looked pretty bad to me. I decided to replace the pickup assembly with a new one. There is a company in the UK that offers the pickup complete with base plate. This was imported and fitted. Hence now I can be assured that the spark will be reliable.
I reassembled all these parts back to see if there was any improvement.
There is mixed news to be reported. The starting issue is completely resolved. The car starts first time from dead cold, runs on fast idle till it warms up. While on the road the acceleration is quite good for a van. In fact I was very surprised that it just shoots ahead on pressing the accelerator. However the overheating problem became worse than before. Very disappointing. I felt very dejected that all my work on the cooling system has gone to waste. I was at my wits end and decided to let this be for the time being until I do more research to get to the bottom of the overheating issue.
In the mean time I decided to strip the van completely. It had to go for a full re-spray so the exterior and interior trim had to be removed. Also it was time to get busy with ordering new parts from overseas. Here are pictures of what happened next: