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Won't Start In Cold Weather

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Old 01-30-2010, 10:15 AM   #1
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Question Won't Start In Cold Weather

Well here goes, I have a 86, 2.5L, S-10 long box 4x4 that I have had trouble starting in the winter time. When the temp. is above say 40 deg. it will sart no problem but when it's below that is when I start to have trouble. I put a inline kats heater on it and that will help a little but does not solve the problem. I have good fuel pressure, I have replaced the hall effect switch, dis cap & wire, plugs, manifold & gasket, all the sensors, tried a different ECM, but not the chip, a different coil (used), I have not replaced the power modual although I have one which I can use but usually when they go bad it's all at once. Just wondering if anyone out there has had this problem before and what you might of done to fix it. I'm open to ANY and ALL ideas that might help. Thanks for your time!
Old 01-30-2010, 02:21 PM   #2
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Re: Won't Start In Cold Weather

Check the CTS in the water neck and also the IAT in the intake behind the alternator (both of your ECM's temperature sensors.) Pull a plug after a starting attempt to see what its condition.... Wet/ Black/ Clean/ ETC.
Old 01-30-2010, 02:56 PM   #3
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Re: Won't Start In Cold Weather

I have replaced the CTS in the water neck but what do you mean by the IAT? Is that the same as the Idle Air Control Valve up next to the firewall? I don't see any wires or plugs in that area behind the alt.. My alt. is on the front of the motor up next to the fan.
Old 01-30-2010, 03:22 PM   #4
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Re: Won't Start In Cold Weather

its the inlet air temperature sensor. It is in the 1st cylinder runner on the intake right behing the alternator.
Old 01-30-2010, 04:50 PM   #5
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Re: Won't Start In Cold Weather

I have checked my intake manifold and there is no sensors or wires on Any of the intake runs.
Old 01-30-2010, 06:14 PM   #6
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Re: Won't Start In Cold Weather

I also checked the 86 S-10 GM service manual and I don't see any refrence to a "IAT sensor" what so ever. Maybe I'm looking in the wrong section, if there is such a thing do you know what page or section it is in?
Old 01-30-2010, 07:30 PM   #7
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Re: Won't Start In Cold Weather

well thats weird. I looked it up here http://www.autozone.com/autozone/cat...&parentId=59-0 for my 87, but it dosent list one for an 86. I guess they made some changes in between years.
Old 02-01-2010, 07:57 AM   #8
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Re: Won't Start In Cold Weather

Any More Ideas???
Old 02-05-2010, 09:29 PM   #9
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Re: Won't Start In Cold Weather

My bad, no iat on 86 man.....
Old 02-06-2010, 10:41 AM   #10
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Exclamation Re: Won't Start In Cold Weather

Quote: Originally Posted by lesterl
My bad, no iat on 86 man.....
===========================
WOW--

Learned something new today!!

Wonder how GM controlled spark retard in these year models without the Intake Air Temperature (IAT) sensor?? It must have been based on coolant temperature only...??

That also means that the 86 chip is different, too.

To the original poster: Without an IAT sensor, that means the the reading of the coolant temperature sensor in the t-stat neck becomes that much more critical for a proper fueling at cold start. You can check it with a meter.

Goes to show that GM was changing the specs right along.---

Last edited by Steady Eddie; 02-06-2010 at 10:46 AM.
Old 02-09-2010, 10:10 PM   #11
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Re: Won't Start In Cold Weather

Yeah, I forgot on my 85 it had no IAT, there ya go!!!!
Old 02-10-2010, 10:29 AM   #12
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Re: Won't Start In Cold Weather

I had the same problem. I checked everything then I realized it was the IAT
Old 02-10-2010, 08:47 PM   #13
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Re: Won't Start In Cold Weather

Quote: Originally Posted by jackmp32010
I had the same problem. I checked everything then I realized it was the IAT
Check posts 7, 9, 11 man....
Old 02-10-2010, 08:48 PM   #14
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Re: Won't Start In Cold Weather

Will it fire up with a shot of carb cleaner?
Old 02-10-2010, 11:16 PM   #15
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Re: Won't Start In Cold Weather

I checked the coolant sensor this P.M., with the ingnition on and the wires unpluged with the test leads on the black and yellow it read 5.2V, then I pluged it into the sensor and probed the black and yellow leads with one lead to the wire and one grounded to the frame. The yellow showed 4.27 V and when I probed the black it showed .02V. Should the black show the same as the yellow if the sensor is OK? Hope this makes sense. Also is there a way that you can test if the sensor is OK or not? I have looked, in the manual but it's a little fuzzy on that.

Last edited by sotte01; 02-10-2010 at 11:19 PM.
Old 02-12-2010, 05:35 PM   #16
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Re: Won't Start In Cold Weather

To test the CTS, unplug it, hook your meter across the 2 terminals on the sensor (in OHMS scale.) Compare the reading to the link in signature.
Old 02-12-2010, 07:35 PM   #17
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Re: Won't Start In Cold Weather

OK if I understand you right let's say it's 32 Deg. the reading should read somewhere around 9420, is that right? Thanks
Old 02-12-2010, 09:15 PM   #18
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Re: Won't Start In Cold Weather

Yeppers.... These sensors are known to both read too cold when they fail as often or more often than opening up....
Old 02-12-2010, 10:54 PM   #19
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Re: Won't Start In Cold Weather

When your trying to start it, does it seem like the starter is having a hard time turning it over?
Old 02-12-2010, 10:55 PM   #20
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Re: Won't Start In Cold Weather

I know thats a relatively stupid and obvious question ^^^^^^ but I couldnt help myself.
Old 02-13-2010, 06:05 AM   #21
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Re: Won't Start In Cold Weather

No problem with the starter.
Old 03-05-2010, 02:35 PM   #22
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Re: Won't Start In Cold Weather

It didn't take long to find my posible answer, my 87 is doing the exact same thing
Old 03-07-2010, 03:40 AM   #23
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Re: Won't Start In Cold Weather

tectron1, your posible answer IS???
Old 03-20-2010, 09:41 AM   #24
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Re: Won't Start In Cold Weather

Just a note to let everyone know I think I might of found the problem of my s-10 not wanting to start in cold weather. Over the last two yrs. or so I have used the starter quite a lot trying to start it in cold weather and in the process it finally took a dump about a week ago. I replaced it with a new NAPA rebuilt and from then on it has started within the first five sec. or so each time. This morning it was 18 deg. out so I tried it and walla about 3-4 sec and she fired right off. The old starter seemed to work OK but it must of been getting tired or worn out. bagged 87 sorry to of told you it wasn't the starter but I thought it was working ok and shortly after that it died. I have had it at the local shop and they had tried everything they could think of and still didn't help, just lighten my wallet. Thanks for all the help and ideas now I'll start on my wiper!!
Old 03-20-2010, 11:49 PM   #25
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Re: Won't Start In Cold Weather

Yeah, they get worn out and dont turn as easy (and draw more current when cranking usually as they age.)
Old 10-12-2010, 04:26 PM   #26
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Re: Won't Start In Cold Weather

Well I hope this the finall post on this subject. As soon as it started to cool down this fall I started to have problems with the starting when it was cool in the morning. I finally changed the ignition module useing a new GM one that I had gotten on Ebay and that did the trick. The old one was a after market one and was starting to go bad. I have had this problem when I used to run a citiation 2.5 on the mail route. I have tried it when it was 32 deg. out this fall and it starts right off no problem what so ever. Just thought I would relay the information if it might help someone else out.
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