2150 Carb Bowl Draining Overnight

[letank]

Hmmm, I wonder. I certainly hope that's not the issue.

It does seem really strange to me as that vacuum port is at the back of the carb, which is surely well away from any fuel passages?


Also, I've just had a look on Summit at carb spacers, and realise that I do already have one!
My intake manifold has exactly this on top, which then has a thick gasket between it and the carb.

https://www.summitracing.com/parts/cwa-j3240515

Is that enough spacer?

enough, yes.
Do not forget the thin paper gasket between the intake and the plastic spacer. The TSM says mount dry... I use a small bead of Hylomar, last year I did not put enough or missed a spot and it resulted in a intake leak 12 month later...

[wiley-moeracing]

Can be a cracked bowl, would need to get some crack detection fluid/spray to see. But honestly you may be better off getting another carb to work with first, would be cheaper than going through all this work.

[Brynjminjones]

Thanks both

The paper gasket is in place and hasn't been disturbed. I'm pretty confident it's not leaking as it runs perfectly and I was able to tune the carb very easily.

I'll inspect closely for a cracked bowl next time I have it off, but to be honest I probably won't play with it much more as it really does run beautifully!

It's only if the bowl keeps draining that I'm concerned, but I expect we'll find it's okay now the weather has cooled down.

Thanks everyone for the help with this, I'll report back if I have further problems!

[Brynjminjones]

Now the weather over here isn't so hot, I thought I'd report back my findings!

After being parked for several days, the Wagoneer is back to being able to fire right up with no problems at all.

I guess the gas must just have been evaporating really quickly after parking in the garage with a very hot engine bay on a hot day.
I've often noted in the past just how long the engine seems to stay hot for in the garage, so that must have been accelerating the gas evaporation.

It probably doesn't help that my air cleaner doesn't have any of the flaps to seal it off, so it probably vents almost as easily as an open element cleaner.

Thanks again for the help, carburetors are still a learning curve for me!

[FSJunkie]

The evaporation of fuel from the float bowl varies greatly with ambient temperature and the volatility of the fuel.

It's possible that the fuel you are buying has a high volatility rate that makes it evaporate very quickly. This would be more of a "winter blend" of gas rather than a "summer blend". High volatility fuel in hot weather can create all kinds of problems.

Opening the hood after you shut the engine off will aid greatly in preventing the fuel from evaporating. Most of the evaporation happens within the first few hours of shutdown while it's still very hot under the hood. Opening the hood lets most of that heat out.

[Brynjminjones]

I expect you might be correct.

I don't know if we use winter blends for fuel here as it very rarely gets below 25F, but since the weather has cooled down from ~90F I've not had another problem with the Wagoneer.

Fingers crossed it was just a very heat soaked engine bay, being parked somewhere it wouldn't cool down quickly.

[Brynjminjones]

I've been keeping an eye on this for a few weeks now and I think it's acting fairly normally, evaporating about as quickly as I'd expect.
This is verified from taking the top off the carb.

There is one strange thing though, which is that the engine will still often cut out ~5 seconds after starting it from cold. It will restart after about 5 seconds of cranking.
The strange thing is that it's now doing this every day. even in the cooler temps. Previously it was only this bad when the weather was hot.

I've fixed and tweaked a few things with the carb that may or may not be linked, as discussed in this thread here: http://www.ifsja.org/forums/vb/showthread.php?t=189057


Today I checked the oil, and I'm pretty sure it smells like gas. I'm not 100% sure on that, but I got my girlfriend to sniff it too and she said, without prior explanation "smells like gas".
It also doesn't seem to have dropped at all in level, yet usually it leaks quite quickly!

The question I guess is, could a failing fuel pump be causing this problem with cold starting? I'm wondering if it just takes a little too long to prime, allowing the bowl to drain before managing to refill it again.

Incidentally, I've also complained about poor gas mileage in the other thread. I guess these two could go hand in hand?

Any opinions would be much appreciated

[babywag]

A bad fuel pump diaphragm can leak fuel directly into pan.
A bad power valve will dump loads of fuel 100% time and some fuel will make it into oil.
A malfunctioning/misadjusted carb and/or choke will make it run very rich and some fuel can make it into oil.

Just because you have "new" parts doesn't mean they are all good.

[Ristow]

yah,not to shock anyone here but these carb rebuilding places are not scouting the few remaining carburetor gurus in the world to rebuild their products.



the guys "rebuilding" your carburetor dont even know what its purpose is.

[Mikel]

Yeah but you have Free Health Care in UK I was in France 15 years ago and a pair of $30 Levis were costing $120 there. I also spent 2 years in Germany [1989-91] and couldnt believe the cost and expense of everything. Plus, over there you cant register a road vehicle if its modified/lifted /has bigger tires etc. No/Nope, Ill pay for my own Health Insurance and Small Government. Not that our Government and Fake News aren't Corrupt--Im not Blind

If you think things are expensive, wait until they are free

[Dorien Berteletti]

Have a similair problem. I mounted an electric fuel pump with a seperate switch
on the floor behind the frt seat. I use it to prime the carb and it's also a good back up.

[Brynjminjones]

Thanks all for the help, as always. The problems can often seem obvious when reading back, but I can be slow at times and need things put into plain English for me!

Ristow, it doesn't surprise me at all that rebuilt carbs aren't done to the best standards. This one is the original though and mostly rebuilt by me, so it's probably even worse!

A bad fuel pump diaphragm can leak fuel directly into pan.
A bad power valve will dump loads of fuel 100% time and some fuel will make it into oil.
A malfunctioning/misadjusted carb and/or choke will make it run very rich and some fuel can make it into oil.

Just because you have "new" parts doesn't mean they are all good.

Thanks Tony, sometimes I just need a simple breakdown like that to work things out!

In response to those points:
1. I'm suspecting this. The pump wasn't replaced when the engine was rebuilt, and I'm sure that oil smells gassy. This would also explain why it's slow to fill the bowl and using too much gas.

2. The power valve gasket was originally leaking. I replaced the whole lot but didn't realize that I split the new valve open whilst installing! I've now put the old valve back in with a new gasket and it's sealing perfectly, and no longer running rich.

3. I did have to spend some time sorting this, but the choke is now dialed in nicely. My previous adjustment was done with the leaking power valve, but now that's fixed I was able to set everything as per the factory service manual.


I've got a new fuel pump that should be arriving today, so fingers crossed we'll know before too long if that really was the issue.

[Brynjminjones]

I've had some time to work on the Waggy, although no real results yet.

New fuel pump and filter have been installed and work just fine. I also changed the oil as a precaution, as it really did stink despite only having 500 miles on it.

One positive thing I observed is that the carb seems to be holding fuel well. I took the top off to manually fill the bowl (to help prime the new pump) and there was probably still 1/4" gas in there after a week of sitting.

After driving it yesterday, the only thing I noticed is that I could hear a kind of hissing noise after I parked it. I took the top off the air cleaner and there was definitely gas residue on the choke plate.

Is that the gas in the bowl boiling out?

[Brynjminjones]

Sorry to dig up an old post, but I've resolved this problem now and thought the information might be helpful to somebody one day.

I finally settled on the fact that my carb does just evaporate over night. It's much worse when the weather is hot, but it always does it pretty quickly.
Fixing the carb vent solenoid actually made it evaporate even quicker, but fixed my hot start problem (discussed in another thread).

I finally realized that the problem is not that the gas in the bowl is evaporating, the problem is that the fuel pump wasn't then able to refill the bowl quickly enough.

If the bowl was totally empty it would take sometimes over 30 seconds of cranking.


The fix was simple - I just needed to replace the rubber fuel line at the tank end. It was an original hose, plus the clip had rusted off completely.

The end result is that the bowl will fill from empty in about 5 seconds maximum, so it now doesn't matter that it evaporates overnight.

It now starts basically as quickly as my fuel injected cars in all conditions!

[tudrewser]

For what it's worth, I'm glad you dug it up and gave us an answer...I found this whole thread very helpful. Has given me some things to look at.