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560SEL hard start /low rough idle
Have been struggling with this prob as follows:
-After sitting overnight at about 60 deg F ambient cranks hard (5-8 sec) , starts, idles slow and rough and stalls. Third try seems to work and idle is smoother and sustainable at normal 700-800 rpm. Alternately, on cold start if i hold the gas the car will continue to run and then idle smoother and sustain. -I initially thot the problem was coolant temp sensor related but the sensor tests good with normal resistance values. -I now believe what is happening is something in the fuel delivery and a fuel starvation issue. -Does my logic make sense and would fuel pressure measurements to det if pressure damper and/or accumulator is bad make sense. -Is another way to validate this to turn key on (dont engage starter but turn on the fuel pumps) and then engage starter to see if startup is smoother???Or do I have to jumper connections in the fuel pump relay ciruit to turn on the pumps?? I have replaced the following parts -- fuel pump relay, OVP,dist cap and rotor, plugs,cold start injector (valve).--and none to these components changes the startup problem. In the course of diagnosing the coolant temp sensor i did observe that if i disconnect the coolant temp sensor from the CIS control unit the engine starts right up , but then stalls with rough idle. My guess is the EZL is sensing high res - full enrichment and then chokes the engine. Any help appreciated. |
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