2BBL carb mystery

SuperDave

A NOS 49 eight stock carburetor. Never seen ethanol...Hard to start after being idle for 24 hours. There is fuel in the glass bowl at the carb. After a L..o..o..n..g cranking session .. it starts and runs fine. If left for several hours it starts quickly. I discovered that the float bowl is empty after a 24 hour period. where the heck is the gas going? It's been this way since installing this carb, so I suspect that is where the trouble is. But what is going on? It's not overheating and boiling fuel out.. Any suggestions.

Park_W

With a good fuel pump, some pressure remains in the line to the carb and in the glass bowl; over 24 hrs the fuel in the carb can evaporate. That allows a bit more fuel to come in from the bowl, and it evaporates too. It's rare that I find fuel in the carb(s) of either of my Hudsons after 24 hrs.

lostmind

This why I installed an electric pump, to fill the carb before start up.

Lee ODell

Also, not as noticable when car setting for extended periods is gas evaporating out the gas tank. With Southern California's gas anyway. While working on my car for 9 mo. the gas gage went from full to 1/3 tank. I suppose some may have gone out the carb too. That figures out to be about 13-14 gals to zero miles. That's about $50 dollars that disappeared at todays price at the pump.
Lee O'Dell

Frankvintagefullflowcom

My unsolicited opinion: If your tank went from full to 1/3 over a period of 9 mos., someone else burned it for you.
Southern Cal gasolines are formulated for lower volatility, esp. during the hotter seasons (that's all the time down there, isn't it?). The industry assumes you will be driving the car within some reasonable period from fill-up so blend changes aren't noticeable. Seasonal changes in fuels are common everywhere to accommodate presumed conditions.
Oddly, I have the opposite experience with gasoline, except for the hot engine/evaporation -from-float-chamber part. I have occasion to prime a carb or such, and sometimes have some of gas left in an open can in the shop. It will still be there a week later, somewhat less, of course, but not gone.
I find modern gasoline to be much more akin to Diesel fuel than the gasolines I remember from the old days. It's safer due to the lower volatility and has lower evaporative emissions but, by virtue of those qualities, our old carbureted engines don't get along well with them. We rely on evaporation to provide the gasoline vapors to get a fire going in a cylinder. Liquid fuel doesn't work. Modern Fuel Injected engines don't have that problem so it works fine for them.
I'm not at all surprised with little (or more) hard starting esp in colder places. Fuel that was put in a tank when the low volatility blends were being pumped might be hard to set on fire when it's finally used months later.
But I might be wrong.......
F

[Deleted User]

If you have a bad gas cap gasket gas will evaporate quickly out of the tank . I learned this the hard way ,putting 2 gallons in and all gone two weeks later. Found the gasket was gone ,new cap and all's well.

Frankvintagefullflowcom

I stand corrected.
There's no gasket at all on our '47 and I've never noticed any loss due to evaporation but it never gets above 37 here.
No single explanation fits all cases. There are a few factors that will affect the rate of evap. I just threw out some thoughts, however, I must amend the "week" claim......it's more like a few days. As Dad used to say, "I've told you a billion times not to exaggerate!"
F

[Deleted User]

It may vary depending on the make-up of the gas . Formula's vary from area to area and season to season. Most areas have a winter blend that's different from the summer gas.

Frankvintagefullflowcom

That was the point I touched on in the first mssg. I didn't go quite as far as you did with the explanation since I tend to get so wordy that the point gets lost. By the time I'm done, I don't even know what I was talking about.
F

MikeWA

"By the time I'm done, I don't even know what I was talking about."

That does it, Frank, I'm throwing your hat in the ring for U.S. Senator, whether you like it or not. After that statement, I know you're perfect for the job. Nancy Pelosi and Patty Murray have been successfully utilizing that technique for decades.

BTW, on the subject at hand, the electric fuel pump on my '48 used to fill the carbs when I turned it on, and car would start right up- then the pump went out, I put a new one on, and now it won't fill the carbs, so quite a bit of grinding before it starts. Guess I'll change the pump- any recommendations? I just got the 30 buck NAPA one before- maybe you get what you pay for!

Frankvintagefullflowcom

Mikey,
That doesn't make any sense......right up my alley.
May I assume (there I go again) that you can hear it running or there is some indication that it is doing so? Do you have the original mechanical pump in the system as well? Do you have any money? Are you 6V? (I should know that one already).
I'll guess the 30 buck NAPA item is an oscillating type gizmo that makes a clicking sound. Only available in 12V (or maybe 24) as I know it. I use a Carter 6v unit but they're a bit costly. Cut Rate has 'em but the best price I've bumped into is Speedway Motors @ about $90. They pump like crazy......'way more volume than necessary and they're noisy, but Made in USA and I suppose a good quality unit. S/M item # 910-4259. Pos or Neg Earth.
If you have the mechanical still in the system, then I'd have to guess that the electric isn't doing anything and you're still waiting for the mech to do the job.
F

SuperDave

I can easily install an electric pump and a momentary switch.. But I shouldn't have to. These things didn't have that problem when they were new. Whether it's ethanol or not, shouldn't make any difference. I'll get to the bottom of it.. I hate "band aids".
My Super had almost the same problem and I found a pin hole leak in the pickup tube INSIDE the tank at the top. The fuel would syphon back into the tank over a 24 hour period. What fuel was left in the carbs would start it but then it was outa gas until I spun the starter a while.The car would start and run about 10 seconds then I would have to crank and crank.

lostmind

Dave , I don't know about new , but every Hudson I had since the 80's needed to be primed or cranked to fill the bowl if it sat for extended times [ a week or more].
The new ones got used every or two , no problem.
I understand that you want to know why. I'm pretty sure if you check back in history ,
this is why we have fuel injection today, carbs weren't that great.

Frankvintagefullflowcom

My intent for installing the electric is just that......to avoid lengthy cranking to get fuel to the carbs after periods of non-use. Most of us drive our Hudsons as often as is practical/possible but they too often sit for quite a while in between. The less I crank, the longer my starters, ring gears and patience will last.
I believe I'm also fighting the "pin-hole in the dip tube" issue in our '47 212. Everything else in the fuel system is new and it still runs out of gas on an upgrade or above 45 mph......sometimes. Tank gets dropped tomorrow to have a look.
F

Park_W

Dave, you're simply wrong in asserting that there's no change in the gas. Even without ethanol it evaporates faster than the stuff we had in the fifties and sixties. Almost all of us have electric pumps to fill the carb(s) after the car has sat. With a 6v car, you have to pull too much from the battery to get that fuel up.

And Frank, do you have a bypass around that Carter rotary-vane pump? If not, that's why you've got a fuel delivery problem on the highway. That pump definitely restricts the flow when it's not running. I went crazy for months trying to find the problem in my '47. Finally realized it was the pump . . . a bypass with a check valve in it solved the problem.

Frankvintagefullflowcom

PW
No, I don't, but I did do some experimenting before the installation and felt that I'd sufficiently demonstrated that the mechanical was capable of drawing through the Carter electric......maybe I was wrong.
As a test procedure recently, I installed a tee in the fuel line at the inlet to the mechanical and affixed a vacuum gauge to observe pressure drop between the mechanical and the electric while driving. The result was < 1 inch Hg which I surmised was insignificant, however, that was a judgment call without any data to back it up.
What's odd is that it will sometimes perform normally. We drove the car from Olympia, WA area to Forest Grove Oregon (~175 mi.) and back with no issues whatsoever. Even at 55 mph and up and over the Lewis and Clark bridge in Longview, Wa. and it never missed a beat. Next day it was back to the same old tricks.
So.....I'll install the chk/bypass and head for the nearest hill. I've come to know the exact spots where it will quit.
Thanks for the tip.
Frank

RL Chilton

Some pumps are "flow-through" pumps, and some are not. Best to bench test them first before installing.

Frankvintagefullflowcom

Doc,
Do you know what the mfgr of your pump is?
I have noticed the possibility of a correlation betwixt fuel level and the occurrence of the problem, but haven't documented it to the point where I can be certain. That could certainly be a factor esp. if it's on the ragged edge of working or not.
Aside from one recent event, it has occurred to me that the success or failure of the mechanical to provide adequate flow may be linked to whether or not I used the electric at some point in the trip. I'm wondering if the rotary-vane pump has a variable flow-through resistance, depending upon what position the rotor stops at when shut down? Carter could probably answer that Q but I'd never get an answer from them. That could explain the intermittent nature of the problem if I can establish a pattern......or just install the bypass.

Park,
I should have inquired as to the type/make of the check in your installation. Light spring-loaded ball chk? Frank

Frankvintagefullflowcom

Update:
Looking at my trusty (and huge) Grainger catalog, I see a likely candidate but it has no opening pressure spec. given, otherwise looks good w/Viton and SS components. $10 +
F

Park_W

Doc, the Carter rotary pump is the only one I know of with this problem. All the "click-click" pumps allow fuel to be drawn through them easily with no problem.

Frank . . . yes, the check valve is one with the lightest spring. The level of fuel in the tank is certainly a factor. When its full, that's extra pressure exerted on the fuel, so it's going to flow better. And I had the same experience as you have . . . the behavior was really erratic. Heck, a couple times it faded on me driving through the neighborhood at 25 mph! Take my word, the bypass will eliminate the problem.

Frankvintagefullflowcom

Ok, OK. I believe you.........but, I still wonder which valve you used. It will take something with a very low opening pressure so as not to behave like what I already have. I located another by Appolo Valve that looks good and shows an opening pressure spec of .5 psi. The downside is that none of these outfits have the guts to say it can be used with gasoline even if it can. I'd be more comfortable if they'd say so. A WOG rating is comforting and I'll bet it's the best I can do.
I'll have $45 into the valve (w/o peripherals) but it's 'way better than the way it is.
I'll report later.
Frank

jjbubaboy

Hey Frank,
I did almost exactly like Park's setup on my 36T. Works like a charm! I run the electric to fill the lines and float bowls and then shut off. With the one way valve the bowls dont empty out. I also check areas on www.puregas.org site and use ethanol free fuel as much as possible. Got most every fitting, and valve at www.mcmastercarr.com. Great to do business with also.
Jeff

53jetman

Yes, I think the descriptions in the McMaster-Car catalog are more complete than in the Grainger books

Frankvintagefullflowcom

I fuel-up at a local station that has non-ethanol gas as often as possible but we're not always near it.
I'll look at McMaster-Carr. I've just been doing biz with WWG for so long it's become a habit. I just call, give 'em my phone # and the item numbers and it shows up on my door step before I hang up.
Grainger typically gives the mfgrs part No. so I can get further info from them if need be.
Thanks for the info.
F

lostmind

I don't think Dave , op , got his answer. He said it never saw ethanol.
Maybe the check valve in his pump is bad , allowing to siphon back to the tank?
Or the bowl plugs are seeping? I know most Carter carbs seep somewhere.
I guess you could run it until it's hot , shut it down and disconnect the fuel at carb and seal the inlet
to see if the fuel is leaking or evaporating from carb. 24 hours seems like it must be leaking.

Park_W

Frank, sorry I hadn't realized you were needing a part source. I got my check valve from McMaster-Carr. Their item nr 7775K52. 1/4" pipe threads. Has worked fine for several years now.

Frankvintagefullflowcom

Park,
Thanks.
Back in High school, I had to PAY to get someone to do my homework for me. Where were you then?
Since I'm a bit more comfortable here now, I'll respectfully disagree with the statement that gasoline evaporates faster these days than back in the good ol' days. In my limited experience, it's of a much lower volatility now.

Lost. You are right that Dave didn't get his answer. This discussion got sidetracked by.....uhhhhh, me.
Let's revisit the original post. Dave says that "the float bowl is empty after 24 hrs." Did you mean float bowl, or the glass sediment/filter bowl to which you initially referred?
F

SuperDave

Frank,
The Carb is empty and the glass filter is full. I am going to investigate the carb closely.. Also it seems like it takes way too long to fill the carb.
It's been a little hectic around here for the last couple days, so I haven't been able to look at it. In my spare time, I have been trying to get a Holley4000 to work right on a 56 T bird.
By the way I sent you a PM on another subject.

Frankvintagefullflowcom

Park, TNX for the McMaster-Carr info. Their valve is meant for gasoline + others so I now have the required warm, fuzzy feeling about installing it, plus a .3 psi opening pressure differential. Cool.
I ordered two so I'll have one to drop, never to be seen again after launching off of my boot toe and under something that isn't worth $15 to crawl under even if I could see it.
Frank

Frankvintagefullflowcom

Park,
Thanks again for the hot tip. I re-plumbed system to include the bypass/check valve set-up and road tests have indicated a successful job. No more of keeping one hand on the switch on the hills. Fuel pressure is a bit low at 3 psi and drops to 2.5 on a long WOT upgrade but I doubt that it will ever be an issue. Since it takes .3 psi to open the check valve, one could say that it's a gross 3.3 psi, net 3 at the carb.
I'm a happier guy.
Frank
ps No, the spring can't reach the pump.

SuperDave

A follow up.
One of the lead plugs on the base of the NOS carb was leaking a very slight amount which helped deplete the float bowl. It would evaporate almost as fast as it leaked, so it was hard to see any residue. A slight "tap" from a small brass hammer.. fixed. Still was hard starting over night, but slightly better. I then bit the bullet and installed an in line electric pump with momentary switch.. Now.. With fuel available, It would try to start, but the starter would kick out. Took several tries to get her going. The final fix?? Cleaned the spark plugs. They were sooty. Probably from when I had the old carb on there..the metering rods were worn excessively. Starts like it should.
Just for the heck of it. I filled a float bowl on a 2bbl carb and left it open (no top) on the bench. in 24 hours there was only about 1/2" left. The temperatures were in the 70's. With the carb fully assembled, the exposure to the atmosphere would be considerably less. Then figure a hot engine, warm carb would evaporate a little faster. Oh well... it's fixed.