1988 C126 Idle and Starting Issues
 

Hi All,

I have been in the process of rebuilding my 1988 560SEC california compliant model and I have had siginficant difficulty with a number of (I assume) fuel related issues. I have been in the weeds on this one for over a year now and I am hoping for some outside perspective on my issues.

So when I start my car it will turn over but then it will choke and die. To get it to start properly I need to unplug my EHA. So I start the car without the EHA plugged in and the vehicle will high idle around 1,000 RPM. I can then plug the EHA back in while it is running however this does nothing to the high idle. The on board diaognostic does not recognize a fault. I have a video of this if anyone would find it helpful.

New Parts: fuel distributor, injectors & seals, intake temp sensor (4 prong), fuel pump relay, OVP, fuel pump, accumulator, fuel filter, cap, rotor, plugs, plug wires, cold start valve... I'm sure theres more I cant remeber.

Please offer any advice. I just want to enjoy my C126.

What are your fuel pressures-system, differential and volume test? That's where I would start. Also, check for vacuum leaks .

In addition to fuel system pressures, the zero position and idle position of the air flow sensor have considerable influence. What adjustments of the air flow sensor, and/or the basic fuel distributor mixture adjuster were made at the time of installation of the fuel distributor?
The four-pole temp sensor is a coolant temp sensor.
A 1000RPM cold idle speed is normal; it should drop with increasing coolant temp.
That the engine can be started w/o EHA suggests a possible fault in the ECU.
The 1988 & later Calif. versions incorporated a sensor unique to Calif.: An EGR temp sensor! If grounded, or open circuit, it may have some influence.