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Old 12-11-2010, 04:02 PM   #1 (permalink)
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Date registered: May 2008
Vehicle: 91 420 SEL
Location: Macon, Ga
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Cold weather start issues

With the turn to cooler temperatures a cold starting problem has started with my 91 420 SEL. The colder the temp on the first start of the day the longer it takes to get started. There is definitely a correlation between ambient temp, time since last shut down, and follow on start duration. At 57f start time is 3 seconds, 46f time is 8 seconds, 37f time is 11 seconds, at 25f I had to go with 4 - ten second pulls on the starter; she finally got going on the 5th try after about 8 seconds. Once she does catch, it’s a real rumble-y affair for several seconds, then everything cleans right up. Over the summer, and on warm afternoons, Grumpy fires right up. I suspect cold start valve. I put a volt meter on the leads to the cold start valve, and when starting the car I get a monentary voltage of or maybe 3 or 4. How would I test this? Would a weak ignition be the culprit? Plugs have 10K on them.
I have replaced the Overload Protection Relay. The battery voltage at rest is right at 12 volts, and voltage while running is a shade over 14. Using jumper cables doesn't help, using starter fluid doesn't help. Lambda while running is around 55 ~ 60% (7.5 volts average).
Suggestions?
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Old 12-11-2010, 07:20 PM   #2 (permalink)
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Cold start valve is a good place to start. When they go sometimes you won't notice it until the weather gets chilly. When folks say they get the hard start/rough running until warm symptoms in the cold weather where it didn't exist before I always think CSV first. Its easy to either confirm/eliminate it as a suspect so you can either replace it or move on with your diagnosis of the problem. If you put a meter on the leads and crank the engine you should get 12v (or minus 12v depending on how you attached the leads). Another way to check is put the CSV while attached to the pigtail and fuel line in a mason jar and crank the engine with the coil disconnected but if you choose that way do be careful of the gas that will be spraying if its functioning properly.

If the CSV tests check out, next would be the thermo time switch. Occasionally the wiring of either of these components is the culprit.

Good luck making grumpy a little less grumpy.
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Old 12-12-2010, 01:08 PM   #3 (permalink)
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I agree cold start valve is a good place to start. How long will the 12 volts be supplied to the CSV? At what temperatures does the CSV function? Also, why would the starter fluid have not helped the situation?
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Old 12-12-2010, 04:13 PM   #4 (permalink)
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Maybe it will run for 5-10 seconds if the coolant temp is less than say 90 or 100 farenheit. Thats where the thermo/time sensor part of the equation comes in. If you need more technical data than that you will have to wait for someone that has the exact specifications to chime in. I can't tell you why you can't get it to run on starting fluid.

Last edited by LG500SEL; 12-12-2010 at 04:20 PM.
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Old 12-13-2010, 06:09 AM   #5 (permalink)
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Cold Start Issue Update

Grumpy sat over the weekend, and the temp for the start this morning was 34f. I took some wire and jumped directly the CSV to the battery (car not running). I heard a very distinct clicking each time I touched the leads to the valve (pig tail removed, wire was put to the top of the CSV contacts). I did this 4 times. Then using my volt meter I checked the pig tail side of things while the wife tried to start the car. I got a solid 12 volts while the starter was engaged. I told her to only hold it for a "4" count, but on the second turn of the key, Grumpy fired right up after 2 seconds! So, the CSV is functioning, and signal is being delivered. I'll be curious to see how things go tomorrow after the engine cools overnight. I wonder if maybe the valve was gummed up and putting 12 volts straight off the battery (with the high amperage) might not have loosened things up a bit.
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Old 12-13-2010, 04:00 PM   #6 (permalink)
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Your computer (aren't they fun?) may think your engine is hot all of the time - ergo no cold start regulation which on the old cars was handled by a mechanical box. The cold start valve only gets the engine started - which should be obvious by the name. although if you flood it a bit with the cold start valve it will also keep it running long enough to stay running due to the engine building a little heat in the cylinders.
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