Difficult hot start/ choke problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

s10mk · 04-02-2018, 07:13 PM

Hi everyone, my truck starts cold really easily, but I've been having a slight issue with hot starts. I think I figured out my problem, but I wanted to get some opinions, this is my first time working on a carberated engine. But anyway, when my truck starts, the choke is completely closed, then the vacuum break pulls the primary choke open slightly. The engine will then warm up, but the choke never moves. I read the temp just under the bi-metal coil on my intake, and it heats up to 175 degrees, but still the choke won't open, and it doesn't appear that the choke rod moves any amount at all. Am I correct in assuming that my bi-metal coil is bad?

s10mk · 04-02-2018, 07:14 PM

Engine warm and running

s10mk · 04-02-2018, 07:16 PM

Choke linkage

geezer#99 · 04-02-2018, 07:54 PM

Coil might be fine.
Crossover might be plugged.
Check the temp in the same area on the other side of the intake.

**Steeveedee** · 04-02-2018, 07:57 PM

That linkage rod appears to be pretty close to the heat shield in the pic. Is it free to move? You can remove that shield to see if that helps. It may well be that either the linkage on the carburetor or the rod are adjusted so that the choke never opens. Take the shield off and reinstall the rod; then verify that the rod can be moved far enough for the choke plate to be completely open, by hand. That's a first pass at a diagnosis. You might try this and let us know how that worked.

ETA- this can make it hard to start hot, if the mixture gets too rich. But I suspect that the hot start issue is one that haunts these trucks, and has to do with the starter being hot.

s10mk · 04-02-2018, 08:25 PM

Quote:

Originally Posted by Steeveedee

That linkage rod appears to be pretty close to the heat shield in the pic. Is it free to move? You can remove that shield to see if that helps. It may well be that either the linkage on the carburetor or the rod are adjusted so that the choke never opens. Take the shield off and reinstall the rod; then verify that the rod can be moved far enough for the choke plate to be completely open, by hand. That's a first pass at a diagnosis. You might try this and let us know how that worked.

ETA- this can make it hard to start hot, if the mixture gets too rich. But I suspect that the hot start issue is one that haunts these trucks, and has to do with the starter being hot.

I know the rod itself moves freely, I can grab the rod and use it to manually open and close the choke. But to be sure, ill remove the cover and reinstall the rod to see if that helps.

**Steeveedee** · 04-02-2018, 10:10 PM

OK, the choke coil could just be toast. They wear out like everything else.

stsalvage · 04-02-2018, 10:36 PM

I know a lot of people like to stay factory.But in some ways its best to go better with alum intake newer carb and use a manual choke cable.One other thing i like using the straight out water out let that the 1964--67 V8 used and they have a hose for it as well.Reason for that is i like running the temp sending unit on top of the intake next to the intake water inlet.Fram makes a wonderful alum gasket and it reusable so no more having to use the paper gasket one an you use NO gasket sealer on that new one from Fram there a little pricey at 22-25.00 a peace

Here is a pic of the intake with the sending unit

I put in a picture of the sending unit on the side of the head wire always get toasted plastic and heat don't work well together

04-02-2018, 07:13 PM	#1
s10mk Registered User Join Date: Jul 2017 Location: herminie, pa Posts: 313	Difficult hot start/ choke problem Hi everyone, my truck starts cold really easily, but I've been having a slight issue with hot starts. I think I figured out my problem, but I wanted to get some opinions, this is my first time working on a carberated engine. But anyway, when my truck starts, the choke is completely closed, then the vacuum break pulls the primary choke open slightly. The engine will then warm up, but the choke never moves. I read the temp just under the bi-metal coil on my intake, and it heats up to 175 degrees, but still the choke won't open, and it doesn't appear that the choke rod moves any amount at all. Am I correct in assuming that my bi-metal coil is bad? Attached Images __________________ 2009 GMC Sierra 1500 2006 Buick Lacrosse 1987 Chevrolet V10 1972 Chevrolet c20 350/350 1967 Chevrolet Biscayne ls3 swapped

04-02-2018, 07:14 PM	#2
s10mk Registered User Join Date: Jul 2017 Location: herminie, pa Posts: 313	Re: Difficult hot start/ choke problem Engine warm and running Attached Images __________________ 2009 GMC Sierra 1500 2006 Buick Lacrosse 1987 Chevrolet V10 1972 Chevrolet c20 350/350 1967 Chevrolet Biscayne ls3 swapped

04-02-2018, 07:16 PM	#3
s10mk Registered User Join Date: Jul 2017 Location: herminie, pa Posts: 313	Re: Difficult hot start/ choke problem Choke linkage Attached Images __________________ 2009 GMC Sierra 1500 2006 Buick Lacrosse 1987 Chevrolet V10 1972 Chevrolet c20 350/350 1967 Chevrolet Biscayne ls3 swapped

04-02-2018, 07:54 PM	#4
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: Difficult hot start/ choke problem Coil might be fine. Crossover might be plugged. Check the temp in the same area on the other side of the intake.

04-02-2018, 07:57 PM	#5
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,676	Re: Difficult hot start/ choke problem That linkage rod appears to be pretty close to the heat shield in the pic. Is it free to move? You can remove that shield to see if that helps. It may well be that either the linkage on the carburetor or the rod are adjusted so that the choke never opens. Take the shield off and reinstall the rod; then verify that the rod can be moved far enough for the choke plate to be completely open, by hand. That's a first pass at a diagnosis. You might try this and let us know how that worked. ETA- this can make it hard to start hot, if the mixture gets too rich. But I suspect that the hot start issue is one that haunts these trucks, and has to do with the starter being hot. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

04-02-2018, 10:10 PM	#7
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,676	Re: Difficult hot start/ choke problem OK, the choke coil could just be toast. They wear out like everything else. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

04-02-2018, 10:36 PM	#8
stsalvage Scrapper 1 Join Date: Jan 2007 Location: Riverside Calif Posts: 1,649	Re: Difficult hot start/ choke problem I know a lot of people like to stay factory.But in some ways its best to go better with alum intake newer carb and use a manual choke cable.One other thing i like using the straight out water out let that the 1964--67 V8 used and they have a hose for it as well.Reason for that is i like running the temp sending unit on top of the intake next to the intake water inlet.Fram makes a wonderful alum gasket and it reusable so no more having to use the paper gasket one an you use NO gasket sealer on that new one from Fram there a little pricey at 22-25.00 a peace Here is a pic of the intake with the sending unit I put in a picture of the sending unit on the side of the head wire always get toasted plastic and heat don't work well together Attached Images



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