Re: [doc] Cold Start Switch?

[Martin Gutkowski <martin@xxxxxxxxxxxxxx>]

What I'm about to write assumes the engine -did- run fine and has gone 
wrong, not having been fettled with by anyone.

When the lambda system fails (duff sensor, stuck full throttle switch, 
duff thermal switch) it results in the lambda system setting the mixture 
rich. As the mixture needs to be rich when cold, this usually results in 
just fairly heavy hunting at idle at all times, and when revved, black 
smoke comes from the exhaust.

When a CPR dies, it -usually- gets stuck at 3.5bar control pressure 
which is correct for a hot engine. This results in a lean running 
condition when cold and causes hard starting, poor idle and the 
inability to rev (accompanied with pops and bangs from the air intake). 
Things really get messy when the CO screw is messed with to account for 
this. This is the most likely cause of John's problem

I've also seen CPR's die showing cold control pressure (1-1.5 bar), 
Primary pressure (5 bar or thereabouts) and the wierdest one of all 
which showed complete open bleed-off - ie control pressure of nearly zero!

The hot start relay is redundant on cars with fuel accumulators and 
won't do anything unless the missing ground wire is added.

Martin

Nick Tomlinson wrote:

> I have seen the K-Lambda Jetronic engines run a bit naff if they are 
> not set correct, yet run OK once warm because the Oxygen sensor over 
> compensates.
>
> The Duty cycle of the frequence valve via fuel computer (or diagnostic 
> plug) should be checked for best tolerance, or use an oscilloscope on 
> the oxygen sensor.
>
> The best course of action would be to check fuel pressures etc and do 
> a full diagnostics.
>
> There is another white relay holder (3 wires) for hot climate 
> countries to pulse the cold start valve during engine cranking. This 
> is normally shoved out the back near the fuel pump relay.
>
> NickT.







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