Hard Start When Engine is Warm
#1
12-09-2015, 10:41 AM
Hard Start When Engine is Warm
Does anyone know EXACTLY how the cold start/hot start works in these W engines? I suspect coolant temp sensor is out of spec but still working. I get instant start dead cold colorado winter. warm engine, hard to start need to hold pedal and 'chugs to life.'
I went through an ignition module issue before, very hard to diagnose but it is possible for it to spark but prohibit fuel from injecting. noid light and weeks of testing with computer hanging from harness to learn this. I got good pump, test pressures, ignition components, etc.
Hopefully someone can tell me resistance or voltage values as function of temperature for coolant sensor, air temp sensor, etc? My old volvo manuals had graphs of this so you could verify the sensor was reporting the correct data. I have not found such details for the S-10, mine is 94 with quarter million. the hard start warm has been going on for about 3-4 years. anyone know exactly what the engine does based on sensor inputs for warm start versus cold start? the cold start is remarkable...it is running upon the first cylinder to fire. it cranks less than one revolution to be running at cold high idle....just perfect. when it is hot, it behaves like it is too warm, not getting any enrichment at all hence need for some pedal during crank.
I went through an ignition module issue before, very hard to diagnose but it is possible for it to spark but prohibit fuel from injecting. noid light and weeks of testing with computer hanging from harness to learn this. I got good pump, test pressures, ignition components, etc.
Hopefully someone can tell me resistance or voltage values as function of temperature for coolant sensor, air temp sensor, etc? My old volvo manuals had graphs of this so you could verify the sensor was reporting the correct data. I have not found such details for the S-10, mine is 94 with quarter million. the hard start warm has been going on for about 3-4 years. anyone know exactly what the engine does based on sensor inputs for warm start versus cold start? the cold start is remarkable...it is running upon the first cylinder to fire. it cranks less than one revolution to be running at cold high idle....just perfect. when it is hot, it behaves like it is too warm, not getting any enrichment at all hence need for some pedal during crank.
#2
12-10-2015, 07:00 AM
Does anyone know EXACTLY how the cold start/hot start works in these W engines? I suspect coolant temp sensor is out of spec but still working. I get instant start dead cold colorado winter. warm engine, hard to start need to hold pedal and 'chugs to life.'
I went through an ignition module issue before, very hard to diagnose but it is possible for it to spark but prohibit fuel from injecting. noid light and weeks of testing with computer hanging from harness to learn this. I got good pump, test pressures, ignition components, etc.
Hopefully someone can tell me resistance or voltage values as function of temperature for coolant sensor, air temp sensor, etc? My old volvo manuals had graphs of this so you could verify the sensor was reporting the correct data. I have not found such details for the S-10, mine is 94 with quarter million. the hard start warm has been going on for about 3-4 years. anyone know exactly what the engine does based on sensor inputs for warm start versus cold start? the cold start is remarkable...it is running upon the first cylinder to fire. it cranks less than one revolution to be running at cold high idle....just perfect. when it is hot, it behaves like it is too warm, not getting any enrichment at all hence need for some pedal during crank.
I went through an ignition module issue before, very hard to diagnose but it is possible for it to spark but prohibit fuel from injecting. noid light and weeks of testing with computer hanging from harness to learn this. I got good pump, test pressures, ignition components, etc.
Hopefully someone can tell me resistance or voltage values as function of temperature for coolant sensor, air temp sensor, etc? My old volvo manuals had graphs of this so you could verify the sensor was reporting the correct data. I have not found such details for the S-10, mine is 94 with quarter million. the hard start warm has been going on for about 3-4 years. anyone know exactly what the engine does based on sensor inputs for warm start versus cold start? the cold start is remarkable...it is running upon the first cylinder to fire. it cranks less than one revolution to be running at cold high idle....just perfect. when it is hot, it behaves like it is too warm, not getting any enrichment at all hence need for some pedal during crank.
#4
03-13-2016, 04:08 PM
I notice no one mentioned the oil pressure sending unit.The oil pressure sending unit on certain year blazers, works injunction with the fuel pressure/fuel pump.If you have a defective sending unit,this will cause a hard start, or no start at all.The oil pressure sending unit is a great safety device.If you have no oil pressure, the engine won`t start.,Let`s say if your driving down the freeway, then your oil pump fails..The sending unit will signal to the pump to deactivate, which will kill the engine immediately.
Totally incorrect. GM has not used that circuitry since the mid 1980's, (before S&T series were produced).
There is a circuit on 1995 and older S&T that goes through the oil pressure sending unit. It provides an additional path for current to flow to the fuel pump when oil pressure is above ~7psi, but it can not disable the pump. In 1996, GM realized the circuit was not necessary, and quit using it.
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