(Cold) starting issue- input welcome

[Coley]

Ok, I've had a very recent 'cold' starting issue show up on '72 / 350-4bbl.

The carb is the original quadrajet (good condition) and the distributor is mostly original (all original?) with the ignition as an 'in-cap' pertronix system.
So over the last couple of weeks when I go to start it in the morning...it seems to crank and crank and crank...all the while working towards flooding.
Now, if I continue to pump it and crank it, it might back fire and it has done so and you can smell the fuel in the system, even in the exhaust that 'lit' up and thus played a role in the backfire.

Now that said, it will start up...it just takes a minute or I, at some point, have to 'floor' the carb to open the throttle plates and allow it to start.
Now, when it starts...its fine for the rest of the day. No problems or stalling, accelerating, etc anywhere...parking lots, at home or otherwise, etc.
It runs as normal, nothing weird or lagging or rough...business as usual and its always been a great running truck and engine.

So just under a cold start condition....noting that a 'cold' start condition this time of year is a relative term, lol

Any intelligent ideas or good points or things to check? ...carb? or distributor? or fuel pump? or fuel filter? or...not enough air in the tires, lol.

Any input is welcome.

Thanks
Coley

[VetteVet]

Do a search for quadrajet well plugs leaking.

[Steeveedee]

If you are still using the yellow wire from the "R" terminal for ignition power during cranking, take it off the coil and put a test light on it. These can get corroded and weaken the contact. It could be just enough when it's cold that the metal shrinks and the contact is weaker. When it's warmed up, the contact and conductivity will be better. If you get a weak brightness, that would be an issue. You know what no light means. As far as starting hot, the engine is spinning faster and can catch when you let go of the key so that it returns to the "On" position. One of my sons had a Dodge Dart that was always hard to get going. In that case, I finally traced it down to a replacement ignition module that only had four connections on it, but the harness had five wires. That one wire went to the "Start" side of the dual ballast. Once I put a 5-prong module on the car, it got instant starts. It helps to send power to the ignition during cranking.

[Coley]

2 good responses for sure...
If I can't immediately find the issue with the carb on the engine I will pull it and give it a quick disassembly to check a few internals including the condition of the well plugs.
(luckily I have a couple of spare quadrajets in good condition to put on/exchange while I do some checks, etc if extended time is needed)
As for the ignition wire...I thought about that.
Last year I ran a new wire to provide 12 volts to the coil/pertronix system due to poor low speed operation where it was not producing enough initial voltage at idle.
I can test this by installing the same test wire from the battery over to the coil in order to see if it starts up quicker.

By all accounts it appears to be getting fuel at the carb and when the accelerator is pumped....so still not solved but a few places to start looking I suppose.

Coley

[TheSeeker]

Could the choke possibly be sticking?

[bill3rail]

What is your starting procedure?
Pumping the pedal 4 times or 24 times then crank?
I know it is a silly question but some people think they must be over pumped to start (and some trucks need it). Have you tried different methods of starting like not pumping the pedal at all before cranking?
Do you just crank until she kicks over or crank for 4 seconds then stop?

Have you looked at the choke mechanism to see if it is operating as it should be?

Bill

My procedure is pump the pedal 6 times, crank for 4 seconds.
No start? Repeat.
Usually starts on the second try when cold.

[Coley]

Good questions guys, responses as follows:
Backstory: the truck and carb have always performed and started well and similar to factory choke/start set up.
Basically, I usually have pumped the throttle probably twice in the summer months (maybe 3+ times in the colder periods) then turned the key....no further pumping, etc.
The truck has always fired up nicely and gone into a nice medium/fast idle.
I kick the choke off in about 30 seconds and drive away....no stalling, no problems.

Now with the current situation....after the truck starts, it is an easy driver...no stalling, no acceleration problems, no idle problems etc.
I have checked the choke mechanism and its not closed or stuck shut, etc...its open (not fully or wide open) and set at a reasonable angle and the connection lever down to the divorced choke is intact and connected as well.
Just seems to be getting over the hump of the actual engine start/firing operation....go figure?

Interesting stuff and many thanks for the info so far guys...it all helps.

All good
Coley

[Steeveedee]

The choke plate should close completely when the engine is cold. Then, the CPA opens it so that it isn't too rich after startup. If you have cold start problems and the choke isn't all the way shut, that's the place to start.

[demian5]

Have someone look down carb after sitting over night while you pump the gas. If there is good gas flow, then its not the well plugs, but my vote is well plugs like VettVet

[dmjlambert]

"look down carb after sitting over night while you pump the gas", note this means while the truck is off and cold, and not while cranking. Just look into the carb and pump the throttle a couple times before cranking and verify you see gas squirts. If the accelerator pump squirts gas that means the bowl is not dry. If it does not squirt it could be either bowl is dry or accelerator pump doesn't work properly.

[Coley]

Okay quick update....(I've been busy so I haven't been able to focus completely on this).
I took the top air horn off the Quadrajet and had a good luck in there. Everything looked good and seemed to be operating correctly..ie: float, linkage, accel pump, rods, inlet valve, etc.....hmmm.
So closed that up and checked the fuel filter at the inlet...not too bad, cleaned that out.
No difference in the constant cranking effort.

So I hooked up a 12 volt wire direct from the battery over to the coil to ensure a full 12+ volts and the pertronix system.
Again, no difference in the constant cranking effort.

So again....I can get it started...but it takes a minute and might give a backfire while doing so...and again, once its started its good for the day and runs great on all fronts.
...bit of a mystery still.

So apparently I haven't solved it yet. I have a few spare quadrajets that I could try to see if that makes a difference.
As well, I haven't had the distributor cap off yet....maybe something in there?

Again...any ongoing input, tips or recommendations welcome.

All good
Coley

[geezer#99]

What are you running for initial timing?

[HO455]

As previously mentioned the well plugs are common issue. These are the plugs the factory used to seal passages after they were machined to specifications. Over the years they get loose and fuel leaks past them. This causes fuel to drain out of the float bowl and into the intake manifold. So when you try start the engine this raw fuel flows into the cylinders unatomized, which is likely the cause of your backfires, as some fuel is getting past the exhaust valves and then burning in the exhaust manifold. Having no fuel in the float bowl prevents the accelerator pump from sqraying fuel when you pump the throttle. You now have to crank the engine over a bunch to refill the float bowl (Assuming you have a mechanical fuel pump) and then the accelerator pump well before you can start to atomize fuel and get a mixture that will ignite. But all that cranking has drawn in the raw unatomized fuel and it has likely wet one or more sprark plugs and they wont fire. Eventually you get some cylinders firing and the engine runs rough for a bit then the wet plugs dry enough to start working again and the engine smooths out.
Eventually the well plug leaks will get bad enough to start affecting idle quality and the float bowl will drain down much faster.
So let the truck sit overnight , pull the air cleaner, open the choke plate, and wing the throttle, idle to full, while watching the primary bores. You should see fuel spraying on the first time. Do it once more and you should see two good solid streams of fuel shooting down into the venturies. If you don't have two nice solid streams then you are either out of fuel or you accelerator pump circuit has a problem. Now you pull the air horn off and carefully look in and take notice of the fuel level. No/low fuel in your case most likely means it has leaked into the intake manifold. If you have fuel then remove the air horn the rest of the way and take notice if you have fuel in the accelerator pump well. If you have no/low fuel in the well and have the proper fuel level in the float bowl it is likely that you have a check ball stuck. If there is fuel in the well then the likely suspect is the accelerator pump. The modern day fuels we must use can cause the pump's seal to swell up and stick in the bore of the pump and not pump.
Now there may be other things contributing to your hard starting issue but this may help you narrow the search.
Good luck!

[Coley]

Ok, time for the next update...and some progress.
As mentioned, I had the top air horn off the carb and everything in there looked normal...and i couple that with cleaning out the inlet filter.

Regardless...the problem of cranking and cranking persisted. Again noting that it would start and run perfectly normal all day.

Ok, so I tried something a little different...I poured some gas down the carb from a squirt bottle first thing in the morning....and ba-da-bing...it fired right up, and away we went for the day again.
So it is a fuel problem that only seems to occur when its cold or on initially daily start-up.

So any ideas as to what this could be?
ie: weak fuel pump? or bad internal accelerator pump? or the well plugs are hooped? (note: HO455 identifies this as the likely culprit so I'll be keen to take a close look at those and I'm probably in agreement that those are the things responsible for this condition) or the float level is way off or ?

Now, if it is the well plugs.....what is the best way to seal them? Seems to be lots of controversy around this....epoxy? JB weld? wriggleys chewing gum (lol)....serious input is always welcome of course.

All input is welcome, particularly for the carb experts.
Luckily I have a couple more spare quadrajets I could put on while I take this one off for a few hours (or days) to troubleshoot if I had to.

All good
Coley

[72LB]

Accelerator pump could be weak. How good a stream of gas do you have when opening the throttle?

[Coley]

Originally Posted by 72LB

Accelerator pump could be weak. How good a stream of gas do you have when opening the throttle?

Good points. I'm hoping to get to the bottom of this tomorrow and ideally get it all buttoned up by the end of the day.

All good
Coley

[geezer#99]

First check on your pump.
Watch how much fuel squirts when you stab open the throttle halfway. Then hold the throttle there and push the plunger down further watching for more fuel. If you get more fuel than the first stab then you might need to adjust your linkage.
I’ve seen some that give very little fuel on the top half of the plunger travel but give a big shot on the bottom half. Yours might be the same.

[HO455]

Originally Posted by Coley

Ok, time for the next update...and some progress.
As mentioned, I had the top air horn off the carb and everything in there looked normal...and i couple that with cleaning out the inlet filter.

Regardless...the problem of cranking and cranking persisted. Again noting that it would start and run perfectly normal all day.

Ok, so I tried something a little different...I poured some gas down the carb from a squirt bottle first thing in the morning....and ba-da-bing...it fired right up, and away we went for the day again.
So it is a fuel problem that only seems to occur when its cold or on initially daily start-up.

So any ideas as to what this could be?
ie: weak fuel pump? or bad internal accelerator pump? or the well plugs are hooped? (note: HO455 identifies this as the likely culprit so I'll be keen to take a close look at those and I'm probably in agreement that those are the things responsible for this condition) or the float level is way off or ?

Now, if it is the well plugs.....what is the best way to seal them? Seems to be lots of controversy around this....epoxy? JB weld? wriggleys chewing gum (lol)....serious input is always welcome of course.

All input is welcome, particularly for the carb experts.
Luckily I have a couple more spare quadrajets I could put on while I take this one off for a few hours (or days) to troubleshoot if I had to.

All good
Coley

Well plug resealing is not simple do to the combination of heating and cooling with the addition of gasoline, which will affect or attack most substances. Best method I have found is mechanically clean with a wire brush. Chemically clean with lacquer thinner. Heat center section in an oven to 200 degrees. Then apply regular JB Weld to the plugs.
The smaller plugs can be carefully repeened if you make a tool to do it in one shot. Not several punches with a center punch (that usually ruins the center section.). I don't recommend trying this in unless you have made a tool and practiced using it on junk carbs. With the larger plugs I have never had success repeening them so I leave them alone and JB Weld them. Occasionally after installation and use you can have a well plug start leaking again. So its tear down and reseal. The difference in the pot metal carburetor body material and the steel plugs used means they expand at different rates when heated and contract differently when cooled.
The hope with the JB Weld is that by heating the body you get a more porous surface to attach to thus, better long term sealing. Unfortunately the JB Weld has its own thermal expansion rate that differs slightly from what you have smeared it on. Eventually it to come loose. We have tried dozens of products and this process works the best. There is a product out there called Belzona that I have used at work (which has done some amazing things) but it is quite pricy and I have been able to try it out in this application. If it worked long term it may be worth the initial buy price.

[brown7373]

I always drill out the well plugs from below, use a tap to thread the holes and screw in short allen screws covered with Marine-Tex epoxy. Just covering the area with JB Weld is hit and miss, IMHO. I think you can order the correct tap and screws from cliffshighperformance.com and also get a kit from there. I bought additional allen screws at Home Dspot or Lowes. Use 10NF32 Tap and #21 (5/32) Drill Bit. Accelerator pumps from Cliff WORK and are guaranteed for life.

[DeadheadNM]

FWIW - I'm grappling with a similar issue with the 72 350 4bbl in my Blazer. Never could get the original Q-jet that was rebuilt by SMI in CA to idle correctly and had it gone through locally by Biggs Performance, who identified some missing pieces. Anyway, it's touch and go with cold starting despite a fresh motor and carb - I suspect the mechanical NOS choke components aren't working as they should (or maybe I'm not following the correct starting procedure).

[Coley]

I'm pretty familiar with the drill and tap process...and I'm pretty sure I have a 10-32nf tap in my group.
I might take a closer look at this today and I'll try to post up some pics to add some clarity.

Many thanks for the ongoing input guys.

Coley

[joeydurango]

I have to "crank and pump" for a good 6-8 seconds when my truck is cold, especially if it's been a few days. On mine, anyway, I'm pretty sure the fuel is draining back toward the pump slowly as the truck sits, and the first several times I pump the gas I'm not getting any into the carb. But I don't have any backfire or smell raw gas... so perhaps it's a combo of my probable issue and the well plugs leaking on your truck.

[AussieinNC]

On a lighter note...where the heck in the US right now do you have a "cold start" temp ?

It ranges from 75 to 90 here right now in NC....

To eliminate the carb...do you have another one laying around ?

A trip to a wreckers yard and $20 will get you another...you really just want to try it in a "cold" start scenario...if it is better...I would commit to a specialist rebuilt one....

Make sure everything else is in good condition first...

[joeydurango]

He's in Canada...

[geezer#99]

He’s not in Canada!
He’s in Victoria!
We kicked Victoria into the ocean years ago!

You know Aussie, it’s about 50F here now at 0600.