Cold Start Issue....ideas?

[Coley]

Ok...I'm just starting to get the truck ready for summer with it having been in storage and I'm noticing something.
This started late in the fall...as follows:
Pump the gas and truck pretty much immediately fires...then immediately dies as soon as the key is released.
It seems to be getting enough fuel...the choke is opening correctly.
Is this something in the ignition switch? or coil?...or wiring? ...or electrical at all?

So, I thought I read something here about this maybe being a faulty ignition switch or???....so when I tried it again...i left the key (and starter) spinning for an extra 1/2 second and it fired right up. (naturally I won't make a habit of this...lol)
Once warm, it does start without issue and it runs great the rest of the time....but the initial cold start incident of it 'snapping off' is a little confusing....because it does want to start and it does fire...it just quits as fast for some reason.
I'm not too worried about it and I will recheck the choke business....but I just want to make sure that there is nothing else to be looking or checking for.

Any thought or input on this is welcome.
Thanks!
Coley

[tutone]

Just a guess. My 55 does this after sitting for a few days sometimes. I think my issue is the carb losing prime. The fuel in the bowl either evaporates or you may have a slight fuel pump issue. Once it cranks, it uses what is in the fuel bowl and dies for lack of fuel. As soon as the bowl is reprimed it will run. I found tightening my fuel lines around the filter helped. I also find it hard to believe that it is an electrical issue, since it runs fine warm. Let us know when you do find it.

[67 chevelle]

Coil is suspect also , when in the start position the coil gets 12 volt [aprox] , when in the run position it should have around 9 volts [aprox] , id check the positive side of the coil with a volt meter , if its getting these voltage readings you might have a bad coil , if its not getting these voltage readings , in your case most likely in the run position , it may be wiring or ignition switch related .

[Coley]

Great info guys....I'll check this out.
This is the kind of stuff that is somewhat interesting to do....noting that there is no 'show stopper' event here with respect to driving the truck...just an interesting initial start issue.
One of the great things about these trucks is that when something is considering crapping out or stopping...they tend to start warning you to pay attention...thus giving you the opportunity to figure it out.
The same can't be said of a newer vehicle....when they quit....you are usually done and out until the service tech gives you that fateful callback....lol.

Let's see here....a new coil and maybe a new ignition switch....what is that $100?...$150?.....lol, sort of 'required engine shampoo' money these days in most certified repair shops...
We'll see.

All good
Coley

[geezer#99]

What's your initial timing?
Ported or manifold vac to the dizzy?

[Coley]

Originally Posted by geezer#99

What's your initial timing?
Ported or manifold vac to the dizzy?

The last I recall, my initial timing was somewhere in the 10-12° I think....and I use the standard ported vacuum off the front right of the carb.

Note: just gave a quick start up in the driveway to warm it up a bit...started up fine but again, with that same initial 'immediate shut-down'.

Sidenote: the weather here has been so frikkin' crappy, with rain and cool temps I haven't had the motivation to put the plates on it and get it on the road....and it looks like things are changing much for the weekend.
Sad trombones....lol


All good
Coley

[geezer#99]

Try switching to manifold vac.
Dying cold like that is often lack of timing.

[LongBox]

Hey Coley: I'm in Vancouver, and it's been raining almost every day since I bought my truck. It has the opposite problem to yours: starts beautifully when it's fully cold; but starts then dies when it's hot. Go figure.

Let us know how you solve this problem.

[geezer#99]

I had another thought!!
I know, I know... I'm only allowed 1 a week!! LOL!!

Perhaps your choke is set a touch lean. The choke blade opens a bit too far on initial fireup.

[Coley]

...well some very good points and ideas here guys.
If it stops frikkin' raining for 20 minutes I'm hoping to check and try a few things on it today.
The vacuum change up (to manifold vs ported) is easy enough.

Question: does anyone remember off hand the best way to check a coil...isn't it so many (qty. ?) ohms resistance across it that is a good indicator?
I might have a spare coil and if not, they are cheap like soup down at the supply store.

I will also check the choke position, both as 'cold start' set and then also track the opening upon starting. (I know the choke pull off is working ok).

I am tempted to give it the ol' 15 minute full carb re&re removal and take the carb in the basement for a nice, serious carb clean out session with compressed air and carb cleaner. Pretty easy stuff...and doesn't take that long and always cleans up the carb to run a little better, quicker and cleaner.

Separately, I have a couple of great (quadrajet) carbs to substitute for general testing as well....which I was thinking of doing last year anyways.
(...always a good idea to keep an eye out at the swap meets for a similar, reasonable, quality quadrajet if you get the chance...you never know?)

More to come on this...and the good news is there are no show stoppers here...just some interesting checks and tests to get the quick start back.
It is one of the great things about these vehicles and this level of technology...ironically considered 'antiquated' these days.

All Good
Coley

[Steeveedee]

As stated earlier, if it runs fine hot, your ignition is good. Check to make sure that the choke closes all the way, and then use a vacuum pump to see how far the choke pull off opens the choke plate. If you have the factory service manual, you can find out what the opening value is. It may need adjusting.

[Coley]

Ok...update....problem solved!!
I took the time to look a little closer at the electrical and two things were clearly amiss. (...there was an interesting, but good reason for that)
One: the coil wire was not pushed firmly into either the coil or the distributor...a little loose and 'just hanging' for sure.
two: One of the distributor 'hold downs' (spin & turn) was not fully seated so the distributor was not stable or fully down and a little loose.
Solved both of those and...ba-da-bing.....quick start time again!!
Tomorrow when its cool I will recheck the cold start deal.

On the very big upside....I licensed and put the truck on the road today and drove it all afternoon after washing it up....Loved It!!...ran like a top, but no surprise there....it has always been a good running truck....plus got a bunch of 'thumbs up' on the truck as I was out and about.
Even my wife was glad to see it on the road...she too, is a big fan of it and says...'wait for it'....its almost time to repaint it. Damn.....love that special woman..lol!!

The only thing now or 'next' that I want to take on is a brake pedal that after braking....starts to 'leak down' or get soft?....hmmm?...however, I will maybe post up a new thread to take on that little idiosyncracy.

...love these trucks and this technology tho'....super simple 'low stress' stuff.

All good
Coley

[Steeveedee]

On the brakes- stand on the pedal hard, and then slowly release the pressure. If it sinks down, the master cylinder is bypassing and should be rebuilt or replaced. Sooner rather than later!