1988 - 1998 (GMT400) Section for all discussion related to the 1987-1998 Chevrolet and GMC trucks.

1998 1500 Cold Start issue

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Old Dec 22, 2018 | 7:16 AM
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Default 1998 1500 Cold Start issue

I have a 1998 Chevrolet 1500. When it’s below 60 degrees it will turn over fine but will not crank. I can pour a little bit of gas in the throttle body and it cranks on the first try. When temperature warms up durning the day it will crank fine. I have changed the temperature sensor, fuel pump about a month ago (AC DELCO) and the filter about 5 months ago. I have over 60 psi of fuel pressure on the rail. Any suggestions would be greatly appreciated.
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Old Dec 22, 2018 | 11:25 AM
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Once you pour the gas does it continue to run on it's own?
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Old Dec 22, 2018 | 4:09 PM
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I don't know if your unit uses a cold start valve that may not be working.

I see you mentioned that you replaced a temperature sensor, but there may be a separate coolant thermo-sensor which tells the PCM to enrich the fuel mixture when the vehicle is below a certain temperature.
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Old Dec 22, 2018 | 4:40 PM
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Originally Posted by Rednucleus
Once you pour the gas does it continue to run on it's own?
it does. It will run all day. Crank it as many times as you want after the first time
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Old Dec 22, 2018 | 4:45 PM
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Originally Posted by Kazoocruiser
I don't know if your unit uses a cold start valve that may not be working.

I see you mentioned that you replaced a temperature sensor, but there may be a separate coolant thermo-sensor which tells the PCM to enrich the fuel mixture when the vehicle is below a certain temperature.
i don’t think it has a cold start valve. If it does I can’t find any info on it. The coolant thermo-sensor that you’re talking about is the one that I changed. It made the most sense because something not tell the PCM that it needs more fuel because it’s cold.
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Old Dec 22, 2018 | 4:50 PM
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Does it try to start or absolutely no fire when cold?
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Old Dec 22, 2018 | 8:19 PM
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Originally Posted by Marcus Stacks


i don’t think it has a cold start valve. If it does I can’t find any info on it. The coolant thermo-sensor that you’re talking about is the one that I changed. It made the most sense because something not tell the PCM that it needs more fuel because it’s cold.
What engine do you have?
Where was the location of the switch?
Can you upload a picture of the switch you took out?
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Old Dec 23, 2018 | 7:14 AM
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Originally Posted by Rednucleus
Does it try to start or absolutely no fire when cold?
it will just spin over. I have good fire from the plug wires.
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Old Dec 23, 2018 | 7:16 AM
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Originally Posted by Kazoocruiser
What engine do you have?
Where was the location of the switch?
Can you upload a picture of the switch you took out?
The engine is a 5.7 vortec. The sensor that I changed is located beside the thermostat on the intake. It has 2 wires going to it, black and white.
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Old Dec 23, 2018 | 1:03 PM
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Since the problem doesn't seem to have gone away so far, and with your additional information, I found this information which might be helpful, at this web address:

https://itstillruns.com/install-1993...p-8531973.html

I know it is showing information for a 1993, but it says this:

Locate the coolant temperature sensor; the location depends on which engine your 1500 pickup has. The 4.3-liter's sensor is on the right cylinder head, beneath the rear of the exhaust manifold. On the 5.0- and 5.7-liter engines, the sensor is on the right cylinder head under the exhaust manifold. On the 6.2-liter engine, the sensor is on the right cylinder head, in front of the exhaust manifold. The 7.4-liter's sensor is found in the center of the right cylinder head, above the exhaust manifold.
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Here is another site that places a second switch on the driver's side of the engine.
https://www.gmt400.com/threads/are-t...tec-5-7.26214/

Here is a website with diagnostic help.

https://troubleshootmyvehicle.com/gm...-temp-sensor-1

Maybe the wire connector itself is corroded internally, so you replaced a good switch with a new switch, but the wire connectors got antifreeze on them or something. By analogy, when a table lamp goes out, and you replace the bulb, and it doesn't fix the problem, maybe the bulb was not the problem. It could be a whole lot of other things.

I had that problem on a Nissan Maxima.

keep us posted.

Did your engine light ever come on, or were you ever able to pull any codes?

Last edited by Kazoocruiser; Dec 23, 2018 at 1:08 PM.
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