73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Ben_Greenberg on December 21, 2014, 12:25:18 pm
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Hey guys and gals!
My newish to me 78 c15 heavy half has a TON of trouble with cold starts.
When it's warm out it takes several seconds of the starter cranking and me repeatedly pressing the accelerator to get fired up and occasionally it will die, but if I start back up then it will start and idle ok.
Now that it's consistently 32 or below in northern Indiana I have to use starting fluid about 2 or three times to get the thing to fire up and stay that way.... Aka no longer practical.
What is the correct process to start my truck in cold weather?
I feel like when it was fresh off the line in 78 it would not have had this many problems. Any ideas on how I might help my old guy get back to its former glory?
Thanks everybody! Any and all thoughts are appreciated! I may post a link to a video of the cold start if I get a chance and if it would be helpful.
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Typically when the carb is in good shape and the choke is set up correctly you only depress the accelerator to the floor once to set the choke and high idle. Turn the key and it should come to life. My 1984 C10 starts great and have no issues through warm up
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In warm weather, I push the accelerator once to the floor, then turn the key and it's on. In winter, I push the pedal to the floor several times to prime the manifold, turn the key and it's on.
Things to check: Is the choke working? Is the choke adjusted properly?
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Rich,
When I depress the accelerator once the choke does close, or at least close to being fully closed. Should it close completely?
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No, the engine needs air even when choked.
What's your timing set at? All the air pollution crap still on it? Have you set the idle mixture?
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Rich,
There are a lot of questions there that I'm afraid I don't have the answers to.
When I first got the truck I took it to my mechanic that has a dedicated classic car mechanic and he noticed that I don't have a timing marker or a balancer with marks, so timing... Not so sure.
Idle mixture, also not sure. I had it tuned and timed by ear by my mechanic, but that's about it.
As far as any EGR or any other exhaust related item my truck doesn't have that.
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your mechanic should have tuned the idle mixture and timed it by using a vacuum gauge. not by ear
that could be a huge part of the problem
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For extreme cold, fully depress the pedal and depress the pedal again about 1/2 way, now crank the engine. Once it starts, foot off the pedal. This is assuming it's properly tuned, stock configuration. If it's not starting this way, you need to do a complete engine performance tune-up. Start with the ignition system, set timing and adjust idle mixture & idle speed. Allow it to cool and check/set the choke coil and fast idle speed.
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The choke should close all the way when could,in fact it should have some tension to it in the closed position.
The colder it is the tighter it will be.Hit pedal 1 time to set it and turn the key.It should start and run at high idle.
If it starts and dies then there is not enough tension on the choke or the choke pull off is not set right pulling it open to far
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Hey guys! So I finally got a chance to mess with my 78 with apparent choke issues. So I have a few questions
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When I depress the gas, it engages the choke and it closes almost all the way. Now when I push it closed, the truck starts right up! Which is great! Now how do I make sure that I get the proper amount of tension to close the choke completely? Any helpful tips are appreciated! Thanks everyone!
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Do you still have the owner's manual and can you post a pic?
In the meantime, i think this is a very good article:
http://www.chevelles.com/techref/Adjusting_Automatic_Chokes.htm
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P.S.
Before i stupidly overheated my 305----and you can say what you want about 60 year old technology, my rochester 2G started up as fast as any fuel injected car. And in some cases FASTER than some fuel injected cars---like my TBI cavalier.
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How tight the choke sets is all relevant to ambient temps.the coider it is the tighter it will shut thus taking a little longer to fully open
It should be like my 78 and have a choke stove mounted on the pass side of manifold under the carb with a rod running up to the choke plate
shaft.You can take it off and wind it some to get ckoke to close fully when cold,just be gentile with it.It may take a couple tries.Of couse
assuming its original stuff
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How tight the choke sets is all relevant to ambient temps.the coider it is the tighter it will shut thus taking a little longer to fully open
It should be like my 78 and have a choke stove mounted on the pass side of manifold under the carb with a rod running up to the choke plate
shaft.You can take it off and wind it some to get ckoke to close fully when cold,just be gentile with it.It may take a couple tries.Of couse
assuming its original stuff
Thank you! I will definitely check this!
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could it be that the gas isn't staying up in carb ? I have found this to happen to both my 79's and my 86 K5 blazer and had to replace either part or all my gas line. once I did that they have been fine but before that I would have to pump the gas while cranking over and would take one or two tries before they would stay running.
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I had wondered that for a long time, but when I manually closed the choke blade with my finger then walked over and turned the key the truck fired right up
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I will be checking out the choke stove tomorrow and report back! Love this forum otherwise I probably would have bought a new carb and other useless stuff since I am still very much an amateur learning as much as I can.
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Alrighty. Sooo I feel really stupid. The previous owner claimed that the truck had been tuned by a gm mechanic, so I took his word on it. When I finally got around to checking the choke stove to adjust it I noticed that the pull off spring was bound up and after I fixed that.... All my starting problems are gone.... Man... I am a dumb dumb
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Hey I'm sure we have all been there at one time or another.Glad you got it worked out
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Alrighty.... Back on here. Is there any way to keep the spring for the pull off from binding? The end of it keeps getting caught in the arm that it's supposed to be compressing against. Otherwise the truck starts up great!
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If you can post a pic
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This spring for the choke pull-off gets bound up on the "arm" that it compresses against. Am I missing a piece? Or is the spring the wrong size? All help is appreciated!
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Bump for suggestions
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Does it look like that linkage should be pushed further through the pull-off arm, and a cotter pin put through the hole?
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Ok just looked at a carb I had laying around and the lower link should have a little tab on the bottom side below the hole .Remove the dashpot and rotate and push the link in further where te hole is on the inside of the dashpot.Once in there it cant come back out