Cold start Issue- Update, info & Tips

[Coley]

Ok, I had another thread going about a cold start issue I was having on my truck...and at the time, I thought I had resolved it, and thought that it had been a minor electrical issue.
I was wrong....and the issue persisted.
Quickly...again, what it was doing on a cold start was starting then immediately 'snapping off' and quitting.
The only way to start it was to floor it...and hold it down and keep reasonable throttle on it until it warmed up.

The thing about these kinds of 'minor' issues as that they can be 'liveable' but if left unchecked or 'un-fixed' they can become annoyances....so its always best to figure out these 'little things' sometimes rather than to live with them or start buying new parts and doing the ol' re/re for the general sake of it....which can be expensive and often (usually?) not required.

So here was the issue and the resolution....and this is important if you guys ever run into this yourself on your truck.

I pulled the carb completely off the truck and put it on the bench. Then I removed the top 'air horn' of the carb which is the top section of the carb.
(note: this isn't hard to do...just take your time, be careful and pay attention to what you remove and how you remove it....it takes maybe 5-10 minutes to do this).

When I got the air horn off, I carefully removed the upper gasket so I could reuse it.
Then I pulled out the top plastic retainer that keeps all the jets and rods and float alignment down and in position.
Low and behold....as I looked into the float bowl area with everything intact (using a bright flashlight)....I noticed that tiny, tiny, tiny little clip that connects the back pivot of the float to the inlet needle (and seat) was missing.....ahh haa.
So I peered down into the float and there in the bottom of the bowl was that little dinky clip.
I re-installed it and then re-assembled the carb. After that I gave the entire all ports a very good clean with carb cleaner and compressed air, then re-installed the carb.
It started right up...but the test would be this morning on a cold start.

So this morning, I gave it a couple of pumps to set the choke, spun the key and ba-da-bing....fired right up immediately and went to the high choke setting.
I think I got it.

So....that tiny, tiny little clip coming off that connection within the carb could really play havoc with cold starting....so if you find this happening to your truck....there is a tip and some insight and don't hesitate to pull the carb and take a quick look inside. If you are careful you don't need any new parts to do this, you just have to ensure that clip is one there correctly.
If you good Quadrajet rebuild on Youtube you will probably see this clip and its assembly procedure in a lot of the videos.

All Good
Coley

[geezer#99]

I think you're dreamin' Coley!!
Must be the warm weather!! LOL!!
So when you start it and it quits and you try to start it again, does it start right back up and keep running?

[Coley]

Yep, its working like it should ,or more particularly....'starting' like it should.
No more need to keep it 'floored' for it to 'catch and keep' going....had it out yesterday, running great. Today, I might do the plugs if it stays nice

All the choke, timing and carb adjustment in the world won't put that little connection clip back on if it has disconnected the inlet needle from the float.

This can be the kind of event that causes someone to dole out several hundred bucks on a new carb due to not being able to find or solve the issue....so it was a very interesting find.
I'm glad I took the time to pull the carb and investigate inside it a bit.


All Good
Coley

[geezer#99]

I was wondering about how it acted before you found the clip gone.
Did it start right up after the first try?

[68gmsee]

I think what may have thrown people off is that in your original post you mentioned that once engine was warmed up it ran fine the rest of the day.

It's possible that when cold the needle may have been sticking some after sitting all night and engine cold. Depending on the fuel pump pressure, it can actually force fuel into the carb and by gunning it and running it at higher rpms, the needle valve became unstuck and you were able to keep the truck running.

[Coley]

Originally Posted by geezer#99

I was wondering about how it acted before you found the clip gone.
Did it start right up after the first try?

Well...that was the whole thing that got me thinking about it.
It would 'fire' but then immediately and abruptly stop...this would continue until finally the accelerator was depressed all the way down...then it would 'stick' and finally run.
So if I sat in the truck for 5 minutes it would warm up enough to head out...but unless you were using the accelerator...it seemed to struggle...and I had to watch this at stoplights too...because it would want to stall. (this makes sense if you think of the inlet needle wanted to shut off flow under minimal (mechanical pump) pressure....but under higher speed/pump action...it was good)
In my initial visual checks I checked to ensure the choke was open (yes)...that it would pump fuel if the accelerator was pumped (yes).
However, without the accelerator 'pumping' apparently fuel would not flow in to facilitate idle, etc....certainly at idle/slow speed.
Interesting stuff these trucks and their technology.....great, often simple puzzles on certain days.

All Good
Coley

[geezer#99]

Well now!!
You've opened a new can of worms!! LOL!!
You describe the symptoms of a cold intake plenum. Common in our humid climate.
Think on that for a bit.

[Ironangel]

Coley, are you sure that wasn't a minnow trap handle down there? On a serious note, thanks for the heads up...But now I am confused, because I can't find my minnow trap!

[Coley]

I think I might be missing something here with the last couple of 'comments'.

Let me clarify.
The issue was that the very small clip that connects the fuel inlet needle to the fuel float inside the main carb body, had disconnected and falled down into the float bowl.
This required taking the top air horn of the carb off, and then carefully negotiating the top gasket off as well as temporarily removing the primary rod/jet assembly as well as the float and needle assembly.
Re-attaching this tiny clip (wire 'hanger') correctly....restored the slow speed fuel operation back to correct operation.
Anyone who wants to know how this disconnection would create the situation the carb was experiencing need only technically think on it and it will make sense.

Now, most importantly..the net result is: I jump in the truck in the morning and give it 2-3 pumps and turn the key and it now immediately starts and kicks up to a nice 1500/1600 (cold start) idle, then kicks down nicely a minute or two later when I head out.....just like it did before....ba-da-bing.
The carb will now continue to supply fuel at idle without needing the accelerator pump in action and engine speed creating more fuel flow from the fuel pump......so the float bowl will now 'self-fill' as the float settles...typical of the idling (low speed) circuit and operation.
To further show this connection/attachment issue go to approx. the 4:50-5:00 up to the 8:00 minute mark of this quadrajet assembly/repair video and you will clearly see the little clip/hanger and its important and attachment within the carb...very interesting and important stuff when it comes to the workings of these Quadrajets.
https://www.youtube.com/watch?v=bhH5A0ql3Qk&t=1s

The main reason I posted this up was so that other members who experienced a similar condition could solve this for their situation and in doing so, realize that all the outer screwdriver adjustment in the world...or timing adjustment, was not going to fix the problem.
You have to open the carb to fix it.

Now it seems to me that sometimes these small 'finds' can solve some problems and annoyances for people enjoying their trucks who may not yet have found 'the culprit' behind their issue....so hopefully it it helps the next guy...then it was worthwhile to post it up.

C

[68gmsee]

Originally Posted by Coley

.....hopefully it it helps the next guy...then it was worthwhile to post it up. C

This is very true. And thanks for posting the fix.

I've always said that we should always post what fixed a particular problem so others can benefit from it. It's very disappointing when you do a search and find your problem but there's no fix posted.