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Old 03-03-2021, 06:56 PM   #1
jason78613
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Default carb leaking gas, what did I do wrong?

Got a rebuilt Stromberg 81 carb from Uncle max, and a new fuel pump from Charlie NY for my '38 60hp. Car is smooth at idle but sputtering when I accelerate hard. After extensively reading through the forum, figured I'd check the float level...

I removed the screws around the top of the carb and lifted the top, cranked the engine a bit and it filled up the float bowl just fine... I'm not an expert, but everything looked right based on reading.

I put the top back on, tried to start the car, but it wasn't starting at all, and after a bit of cranking, quite a bit of gas seeped out of the hole where the accelerator pump goes into the top of the float bowl. (see attached picture) I removed the top again and checked the accelerator pump rod and the felt washer is there, along with the metal washer, springs, etc, but not sure if I'm missing something else?

Did I do something wrong? What typically prevents gas from coming out of that hole? what is causing gas to come out of that hole now?

I'm a noob, go easy on me.
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Last edited by jason78613; 03-03-2021 at 11:32 PM.
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Old 03-03-2021, 07:02 PM   #2
petehoovie
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Default Re: Not sure what I did wrong, carb leaking gas

Quote:
Originally Posted by jason78613 View Post
Got a rebuilt Stromberg 81 carb from Uncle max, and a new fuel pump from Charlie NY for my '38 60hp. Car is smooth at idle but sputtering when I accelerate hard. After extensively reading through the forum, figured I'd check the float level...

I removed the screws around the top of the carb and lifted the top, cranked the engine a bit and it filled up the float bowl just fine... I'm not an expert, but everything looked right based on reading.

I put the top back on, tried to start the car, but it wasn't starting at all, and after a bit of cranking, quite a bit of gas seeped out of the hole where the accelerator pump goes into the top of the float bowl. (see attached picture) I removed the top again and checked the accelerator pump rod and the felt washer is there, along with the metal washer, springs, etc, but not sure if I'm missing something else?

Did I do something wrong? What typically prevents gas from doing out of that hole? what is causing gas to come out of that hole now?

I'm a noob, go easy on me.
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Old 03-03-2021, 07:26 PM   #3
Ken hash
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Default Re: Not sure what I did wrong, carb leaking gas

The 81 is a nice carb. When you take the top of the carb you see a float that is attached to a needle. When the gas rises the needle goes into the seat and stop the gas from coming in. It could be that the float is not correctly adjusted. Stomberg has a website with lots of information and diagrams. Good luck
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Old 03-03-2021, 07:35 PM   #4
51 MERC-CT
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Default Re: Not sure what I did wrong, carb leaking gas

Sputtering on acceleration seems to indicate issues with the accelerator pump (bad pump leather/rubber etc.)
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Old 03-03-2021, 10:04 PM   #5
Charlie ny
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Default Re: Not sure what I did wrong, carb leaking gas

Jason,
Your pump delivered 2 1/2 psi on my test motor, it should be very close to that
on yours. I'm upset but never surprised when something like this occurs. Uncle Max
will be here shortly....I think I just heard him.
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Old 03-03-2021, 10:06 PM   #6
jason78613
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Default Re: Not sure what I did wrong, carb leaking gas

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Thanks Charlie, I’m sure your fuel Pump and Max’s carb are good based on all the forum reviews and recommendations, I’m just wondering of I did something wrong?

It was running without leaks until I opened the top of the carb... so not sure what the culprit is. I just wished I hadn’t messed with it.
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Old 03-03-2021, 10:07 PM   #7
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Default Re: Not sure what I did wrong, carb leaking gas

Nothing keeps gas from coming out of that hole where the accelerator pump plunger rod enters the float bowl. That felt washer is only there to keep dirt from getting in; there is no pressure seal because the float bowl must be vented to atmospheric pressure.

So, your test proved that under low fuel pressure from the fuel pump at cranking speed, the float needle shut off fuel at the correct level. When running, I suspect that fuel pressure from the fuel pump is exceeding the pressure that the float needle can withstand. Anything over 3.5 psi can cause problems. I use a pressure regulator set at 2.5 psi, and that is still plenty of flow for drag racing (just kidding; don't do that any more).

If too much pressure is the case, the bowl will fill too high and tend to flood the engine. It will run really rough. You will probably have a strong smell of gas under the hood, or even in the car.
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Old 03-03-2021, 10:35 PM   #8
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Default Re: Not sure what I did wrong, carb leaking gas

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Originally Posted by drolston View Post
Nothing keeps gas from coming out of that hole where the accelerator pump plunger rod enters the float bowl. That felt washer is only there to keep dirt from getting in; there is no pressure seal because the float bowl must be vented to atmospheric pressure.

So, your test proved that under low fuel pressure from the fuel pump at cranking speed, the float needle shut off fuel at the correct level. When running, I suspect that fuel pressure from the fuel pump is exceeding the pressure that the float needle can withstand. Anything over 3.5 psi can cause problems. I use a pressure regulator set at 2.5 psi, and that is still plenty of flow for drag racing (just kidding; don't do that any more).

If too much pressure is the case, the bowl will fill too high and tend to flood the engine. It will run really rough. You will probably have a strong smell of gas under the hood, or even in the car.
I have a rebuilt fuel pump from Charlie set at 2.5 psi, and it was running fine with no leaks before I opened the carb... I didn’t change anything else??

I just tried it again and it started up but after a few seconds, the gas started pouring out of that hole, so I shut it down again! Don’t know what else to do, :-(

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Old 03-03-2021, 11:36 PM   #9
Charlie ny
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Default Re: carb leaking gas, what did I do wrong?

Jason,
Let's do this....send me the pump and carb, I'll install both on my test motor
and get back to you on the Barn with an assessment. No charge. I'll cover return

shipping. The moment the parts get here I'll install them and have them heading back

to CEDAR PARK the next day.
Charlie
Charles Schwendler
5845 Cole Rd.
Orchard Park, N.Y.
14127

Last edited by Charlie ny; 03-03-2021 at 11:36 PM. Reason: h missing in chalie
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Old 03-03-2021, 11:56 PM   #10
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Default Re: carb leaking gas, what did I do wrong?

Sure sounds like a problem with the float needle valve. I am curious to learn what Charlie discovers.
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Old 03-04-2021, 05:19 AM   #11
moefuzz
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Default Re: carb leaking gas, what did I do wrong?

.Your fuel pump is mechanical or electric?

The original mechanical fuel pump on top of your intake may be pushing to much pressure.

Your carb is not designed to handle over pressure for very long and can be over
powered by the fuel pump in a matter of seconds, minutes or hours...
...until it can't physically hold back the excess pressure anymore and it will finally give up.


Quick and easy fix=


You can add an extra gasket (or 2) underneath the fuel pump stand at the intake,

this has the effect of shortening the fuel pump pushrod and will decrease fuel pump pressure somewhat.

The longer the fuel pump pushrod "appears" in relation to the physical height to were it is mounted dictates fuel pressure.


So Hypothetically, if you (don't do it!) were to grind the fuel pump push rod a 1/16th or an 1/8th inch, it would have a shorter stroke and would not push the pump as far or as hard.

Adding an extra gasket under the fuel pump stand at the intake
has the effect of shortening the rod and lowering fuel pump pressure.
You can add one or 2 extra gaskets and experiment.

Don't ever grind the fuel pump pushrod to lower fuel pressure or push or stroke at the fuel pump as this is not easily reversible and over time the mechanical fuel pump looses some of it's pressure at which point you can always pull one of the extra gaskets out.

Also, there are 2 different fuel pump pushrods lengths depending on your intake.

Check that yours is close to the below specs dependent upon aluminum or cast intake manifold.

52-9400-A Push Rod - Fuel Pump (V8-60hp) - Alum. Intake (5.625")

52-9400-B Push Rod - Fuel Pump (V8-60hp) - Cast Iron (6.375")



Back in the old days gaskets were relatively thick,
now a days gaskets are less then paper thin so you may have
inadvertently/unknowingly "adjusted" the fuel pump pressure
upwards by installing a paper thin gasket and you wouldn't
even know it until the needle and seat (float) are
over powered and flooding happens..


Extra gaskets are cheap,

...Cheap enough to buy a couple and still have money for your morning donut






.
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Old 03-04-2021, 05:54 AM   #12
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Default Re: carb leaking gas, what did I do wrong?

Top quality service there from Charlie NY. ^^^^^
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Old 03-04-2021, 07:30 AM   #13
Terry,OH
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Default Re: carb leaking gas, what did I do wrong?

I can not say what Max did to the Carb. except he does excellent work and so does Charlie! if the input valve has the two steel balls that control fuel flow they are somewhat sensitive to dirt. I note you are using a fuel flex line to feed fuel to the Carb. If a piece of rubber gets into the input valve the two balls will not be able to control fuel level properly. This can lead to excessive fuel level and fuel coming out exactly where you have fuel. I suggest you change the rubber fuel line to a new steel line with the proper fittings. The input valve can be removed and cleaned, without taking the Carb apart.
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Old 03-04-2021, 07:45 AM   #14
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Default Re: carb leaking gas, what did I do wrong?

Regarding #11....a V8 60 does not have a separate f/p stand....the stand is integral with the intake. Terry has good ideas as always but my offer works best if I can put
the patient on the table direct from the accident scene.
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Old 03-04-2021, 09:18 AM   #15
jason78613
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Default Re: carb leaking gas, what did I do wrong?

Quote:
Originally Posted by Charlie ny View Post
Regarding #11....a V8 60 does not have a separate f/p stand....the stand is integral with the intake. Terry has good ideas as always but my offer works best if I can put
the patient on the table direct from the accident scene.
Charlie ny
Thanks Charlie!... I’m going to open the top of the carb once more to check that the valve/needle is seating correctly, and that the float is controlling the fuel correctly...

I’m hoping it’s an easy fix since it was working fine before I messed with it. Perhaps Terry’s note about a piece of rubber (or simmer other crud) getting stuck in the valve is the culprit.

if I can’t figure it out, I’ll be sending the pump and carb to you.
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Old 03-04-2021, 09:22 AM   #16
Jake dalka
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Default Re: carb leaking gas, what did I do wrong?

Very impressed with Charlie ny offer....
Willing offer to help solve the issue.....
I’ll remember that and share with others....
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Old 03-04-2021, 10:28 AM   #17
jason78613
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Default Re: carb leaking gas, what did I do wrong?

UPDATE:

I took the top off the carb, removed the inlet valve, all looks good and clean, no crud. float moves up and down just fine...

I left the carb open and cranked the engine (I have a button on the starter solenoid so was able to watch it)... the fuel bowl started filling with gas, but the float never rose up! I stopped cranking when the gas was starting to overflow out of the bowl.

Then I noticed small bubbles forming (see attached pic). I read you're supposed to check for float leaks by submerging in hot water, but do those bubble also indicates a pinhole leak in the float? Or is that just a small air leak somewhere in my fuel line (quite possible as I have a small drip at the gas tank where I need to replace the fitting).

Any other reason why the float would not lift?

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Old 03-04-2021, 11:25 AM   #18
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Default Re: carb leaking gas, what did I do wrong?

Can you lift the float up manually? Also try to push in the metal ball of the input valve to see if its sticking.
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Old 03-04-2021, 11:48 AM   #19
jason78613
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Default Re: carb leaking gas, what did I do wrong?

Quote:
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Can you lift the float up manually? Also try to push in the metal ball of the input valve to see if its sticking.
Yep, the float moved up and down freely.
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Old 03-04-2021, 11:53 AM   #20
51 MERC-CT
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Default Re: carb leaking gas, what did I do wrong?

Pull the float to determine if it has gas in it.
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