COLD START PROBLEMS 1978 Caddy

[R Schroeder]

I'm a little down here. I let the epoxy cure for 24 hours and started the car, on the second day. This morning was the third day. Checked float and it was at the bottom. Car started a little hard again, but quicker.
I'll have to get another gasket before pulling it again. Seems something didn't go right. I believe these are all of the plugs that need epoxy, so something must not have taken.
Will get back to you all in a week or so , after I get some time to do it again.
I will get it right in time.
Roy

["Cadillac Kid" Greg Surfas 15364]

Roy,
You need to clean off all the old gunk on the bowl sealing plugs down to the bare metal and then apply the epoxy (or JB) generously (I use my finger ((with latex gloves)) to ensure it is completely covered).  Let the Epoxy cure, exposed to the air for at least 24-48 hours before you re assemble the carb.
Greg

[TJ Hopland]

Next time you shut it down hot and are going to be close by perhaps keep checking back at regular intervals, like 15-30 mins to see if perhaps the fuel is boiling or just being cooked out after shut down.  Try to set the air cleaner lid back on and close the hood between checks, you want to do your best to duplicate a normal shutdown situation.   I would not think ambient temps are that high yet but with the ethanol and other goodies we get in our $4 fuel now its possible that its not leaking.   IF you have a partially plugged cat converter or a stuck 'heat riser' exhaust valve you may be running hotter than normal which is just going to make things that much worse for the fuel.  

Before I did the efi on my 73 I could shut the engine down on a warm day and stand next to the car and listen to the fuel boiling in the carb.   The temporary (9 year) cure for that was an electric fan on a mechanical timer that I would set for about 10 mins every time I shut it down.   Worked great except on the 100*F days.    If I had non ethanol fuel it was fine to about 85*F without the fan.

[R Schroeder]

I did clean the plugs very good before putting on the epoxy. You can see that in the pictures. I did apply a good amount over the plugs.

T.J. the car only has 16,900 miles on it. I think the converter is in good shape. I do have the heat riser in an open position, as I need to address the situation on that yet. Want to lube, and check vacuum diaphram on it soon.

I do feel there is something removing the gas, as I mentioned before. I thought the hose running to the float bowl may be removing it in the form of vapor, when its hot.
What I did today was to start it and shut it down. I'll check tonight and tomorrow morning if it went down. If it didnt , I would be leaning to something else.

The beat goes on.....

Roy

[R Schroeder]

Started it this morning and shut it down. Cold engine.
Checked it tonight and float was up. 13 hours it sat. I could bounce it in the gas. Will check tomorrow if it is still up.
If it is , I believe it could be something else .
Roy

[R Schroeder]

Well, I checked it this morning after it sat for 24 hours and the float was down. She bleed out.
I guess I'll have to do what Greg said and let the epoxy  set for a couple of days. Will be pulling the carb again.
Hope it works the 2nd time around. Haste makes waste I guess.

[R Schroeder]

Pulled the carb again today. I couldnt see any wetness around the plugs ,but coated them again anyway. I'll let it sit for a couple of days now, before I put it back on.

Any place else this might loose gas from ?
Roy

[Glen]

One possibility is the fuel pump check valves.  If they leak back it will pull the fuel out of the carb.  But I’m not sure how that would be affected by heat/time.   

Also how does the float valve play into this?  If it is closed the fuel would not be able to flow back.  But if the float valve was to open up later and the check valves were leaky, the fuel would then drain out.  Just something to think about. 

[R Schroeder]

That is something I'll have to check I guess. Carb will be going back on tonight. Will take a couple of days to check out.
I suppose I could remove the gas line over night and see if gas level stays up. If it did , then at least I would know something more.
Thanks Roy

[R Schroeder]

Gasket didn't come in yesterday, so I'll see if it comes in today.
While on the bench I did notice the rear choke pull off was not correct. The rear one opens the choke to .250 on warm days and doesn't work on cold days. 68 degrees is the temp change for the rear to kick in. It was opening the choke way to far. This caused a flat spot during warm weather take off. Front choke pull off opens it to .140 on cold days.
Hopefully that will take care of the warm weather take off problem. Cold weather , it was fine.
Epoxy is hard and it looks like I covered everything, so we will see tomorrow, if I get it back together today.

Later
Roy

Late afternoon.--- Its back together ,and choke is working nice now.
Will check tomorrow for leak down on float.

[R Schroeder]

Back to more testing. Float was down this morning after running car around yesterday. At least I know its not the plugs that are leaking. They are covered and covered very well now.
I will disconnect the gas line tonight ,after running the car, and see if there is gas in the bowl tomorrow.
It has to be the fuel pump, or the vent line that is removing the gas from the bowl. I'll test both of them out.
So, the mystery continues.
Roy

[dadscad]

To my pea brain way of thinking, the fuel level in the bowl is below the float needle and seat. There would be no way for fuel in the bowl to siphon back through the fuel pump to the tank, because the needle and seat are not in the bottom of the fuel bowl.

Are you sure the bowl gasket to base is sealing and not leaking fuel into the manifold or outside it? Have you put the carb on the work bench and let is sit with the fuel bowl full of fuel and the top off the carb so you could see all around for leakage?

David

[R Schroeder]

David. It is positively not leaking. Was on the bench for 2 days .
I know the in feed is higher, but this sure has me puzzled. It doesnt all drin out. There is some in there to start the car.  Has to be something to do with the gas line. Gas line is empty when I remove it from the carb, the next day.
Car is starting OK, and it runs beautiful . Just has this disappearing gas problem...............ha

[R Schroeder]

Here is the reason I believe it might be going back down the gas line.
The brass piece that holds the needle shut off, has slots in it ,near the bottom. If the float moved down just a little the gas would drain back down the line. Not all of it though. There was enough for 4 pumps before it stopped pumping gas.
It would come to the level of the slot in the fill bushing.

[dadscad]

Wow....I stand corrected!! It has been so long since I opened a Quadrajet, that I have forgotten the needle and seat were actually on the bowl floor. Sheesh.....talk about egg on the face! In this case the pea brain moniker fits! 

Looking at the picture, is the gasket under the seat in good condition? That would let fuel back down the fuel line until the level reached the bottom of the seat where it screws into the bowl. Is there a tiny crack in the bowl into the seat threads?

David

[R Schroeder]

Everything is brand new in the carb. The bottom of the seat for that bushing is about 1/3 the way up from the bottom. Like I said , there is a slot , on each side , cut in the side of the bushing to allow gas to come in faster. This puts the height of the gas right at the bottom of the seat, or about 1/3 to 1/2 up from the bottom of the bowl.

Couldn't see any cracks or other problems with the carb.
I think maybe its a fuel pump problem now.

Normal gas level in yellow. This is above the fill area.
Blue is where the slots are in the bushing that holds needle valve.

[dadscad]

I'm going to type my random thoughts, you may have already been there.

As you have already tested, the carburetor will sit for days on the workbench with the fuel bowl full and not leak down. To me that indicates the floats "float" and the needle and seat seal against the weight of the fuel in the bowl.

If the fuel pump has a leaking valve allowing the fuel in the fuel line to the carburetor to fall back into the supply line side of the fuel pump, there should be a slight vacuum in the line on the underside of the needle. If the needle and seat has any defect it would allow fuel to migrate slowly, overnight, into the fuel pump, eventhough the seat will hold fuel above the needle seat without vacuum on the supply side of the seat.

Have you tried to pull a very slight vacuum on the fuel line to see what happens? You would think, a slight vacuum would help pull the needle against the seat making a better seal.

David

[R Schroeder]

No , I have not tried a vacuum on the fuel line.

I was reading about the fuel pump yesterday. Funny thing about it, is when you do a fuel pump pressure test it tells you to pinch off the vapor line from the gas tank to get a accurate reading. To me that sounds like that line is open from the carb to the tank. It sounds like its on the upper side of the pump, or the same side as the feed to the carb. It would be a source for the gas to run back down the line, I would think.
Why else would you need to pinch off the vapor line to get a pressure reading ?

Also got my flat spot back today too. Dam. I'll have to go out and adjust everything again. Just a slight hesitation now and then when you step on the gas. I had that out of there for a few months now, and since I put the carb back on this last time , it is back.
Driving me nuts.

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One hour later - I put the tach back on the engine along with a vacuum gage and readjusted the carb. Air fuel mixture screws needed to be adjusted. Flat spot is gone again. Guess when you put the carb back on you need to re-adjust. Also checked the timing, and that was still good.

Anyway ,  I ordered a new fuel pump for the car. Should be in next week.  This one is 33 years old, so maybe its got problems. Car only has 17,000 on it, but the age is my concern.

[TJ Hopland]

Ever try or notice any signs of pressure or vacuum in the fuel tank when you remove the cap after a nice drive?    I have had cars that have has some sort of a venting problem that would end up putting the tank under vacuum.   One car it was actually strong enough vacuum and weak enough tank that it collapsed the tank.

[R Schroeder]

Have not noticed anything like that on my car T.J.
Never had it spew pressure , or had a sucking sound , when I have been on a trip and stopped to fill it either.
I suppose that vent line to the charcoal canister up front , keeps that in check.
Just my thoughts.