Carb Crud Origins?

[Dave Wildrick]

Maybe I’m using the wrong brand of gas. I took the motor out of my 65C about 2 months ago and put it on my engine stand to check for a leaking oil cooler. The motor ran fine on the stand, and there was no oil cooler leak, but I did put in a new clutch assembly, crank pulley seal, and throwout bearing.

Then I had to have surgery on my left foot and was unable to drive the car and have been recuperating while the motor remained on the stand for about 2 months. A week ago I put the motor back in the car, but I was surprised when it would hardly start and wouldn’t idle.

It has the 123 ignition, and the timing was right on. I put in new plugs and checked valve adjustment while the motor was on the stand. I suspected a carb problem with the IDF40 Webers, which surprised me because the gas tank is only a couple years old, the petcock filter is clean, and I have a G2 Fram filter ahead of the fuel pump and a Purolator glass filter on the output side.

The left Weber’s accelerator pump jets were not squirting. So, I removed the carb, took off the lid and found white/gray somewhat granular crud deposits in the carb bowl bottom. I hosed it out with carb cleaner after removing the idle jets, mixture screws, accelerator pump jets, and the accelerator pump diaphragm. I flushed all passageways with carb cleaner and blew everything out with compressed air; also put in a new pump diaphragm. Reassembled the carb, installed it, and the motor still didn’t run right, although the accel. pump jets now worked.

Then I found that the idle jets on #1 and #2 cylinders were clogged (no rpm drop when leads for #1 or #2 are lifted from distributor cap), i.e., in the right side Weber. I took that carb apart and found the same kind of carb bowl deposits I had found in the left Weber. I cleaned it as I had done on the left Weber (did not change accel. pump diaphragm; already done a year ago), put it back on the motor, and everything is now working great.

The question is: How do you get carb bowl deposits like this when you have lots of filters ahead of the carbs?
If your gas is too cheap, can crap precipitate out of it in the carbs in a matter of a couple months while the motor sits on an engine stand? Should you always run the carbs out of gas if you know you won’t be driving the car for a month or two?

[David Jones]

Dave, I am not certain of this but I think it is a combination of things. If water dissolves in the gas because of it's hygroscopic nature it does not drop out as the gas evaporates but exists now as a compound and as such may combine with any salts in the gasoline fractions that go to make up the gas. Once everything has evaporated you are left with what you found. I would think that if no air had gotten to the gas it would have been OK.

[Dave Wildrick]

Dave, I am not certain of this but I think it is a combination of things. If water dissolves in the gas because of it's hygroscopic nature it does not drop out as the gas evaporates but exists now as a compound and as such may combine with any salts in the gasoline fractions that go to make up the gas. Once everything has evaporated you are left with what you found. I would think that if no air had gotten to the gas it would have been OK.

I didn't think about the possibility of more air getting in while the motor was sitting on the stand with no gas line (full of gas) connected to the carbs--speeding up evaporation. Maybe the ethanol in the gas also allows it to absorb more water than if ethanol free.
I was just shocked that the motor didn't run well when put back in the car after what seemed like not that long of an interval and couldn't believe what I found in the carbs.

[David Jones]

If it were ethanol and lead free I think you would find nothing after evaporation. Only way to find out is to put a jar of each in a corner of your garage and wait for it to evaporate. Leaded gas will leave a brownish powder which cakes to the walls and also plugs jets. This was the brominated and also chlorinated compounds which were additives designed to scavenge the engine of lead deposits. An obvious problem back in the day.

[WilliamVaughan]

Let's assume you have your filter near the OEM fuel pump. I do too. The steel lines from the fuel pump to the carbs can also release crud. Especially during high flow. I experienced this recently.

Separated them and sent some steel ball bearings through them with house water pressure over a white polyethylene bucket. Repeated the process till crud stopped appearing. Blew them out and toasted them dry.

[Dick Weiss]

Dave,

I received my '58 Speedster after 1-3/4 years in the body shop after my incident in Put-in-Bay's Race Reunion,
Lake Erie, OH and the engine fired right up after about 1-1/2 minutes of 15-20 second intervals w/the starter and
some gas added to almost an empty gas tank. Didn't do anything w/the carbs (Solex) and the fuel didn't show anything in the 4-cam pressure regulator/filter; The 4-cam engine was replaced w/a Super 2-years ago due to a
'holed piston' after 55 years.

Of course, the twin electric pumps worked OK producing 2.8 PSI like they should, and no further work was needed
The car ran fine--good to be "back on the Road Again". I never used or added extra in-line fuel filters in any cars
I work on and W/long storeages, I do use Stabile.

Dick

[Alan Hall]

I have always thought that the whitish granular crud sometimes seen in carbs is the result of water in the gas settling in the float bowl and reacting with the zinc carb material and forming something like zinc oxide, but have never researched it enough to determine if this is correct. It generally cleans up fairly easily when re-building a carb with severe cases needing a mild acid solution to dissolve it all.

[Wil Mittelbach]

Should you always run the carbs out of gas if you know you won’t be driving the car for a month or two?

Absolutely! As such, I always run my 65C cab's Zenith carbs dry when knowing I'll not be driving the car for about a week or more. Accordingly, never had carb problems upon restart after carb refill via the under floor board elec priming pump.

[George Walling]

I use the non ethanol fuel in my speedster and use Stabil fuel treatment in the fuel, on my 65 Ford Falcon which is the wife's daily driver I use the 10% ethanol but still use the stabil even though the car is driven daily and refueled usually several times a month. I have found that this has helped keep my fuel system clean. The non ethanol lead free fuel here in Oregon is usually about a buck more per gallon than the premium ethanol fuel so that is why I don't run it in the Falcon.

[Charles H Jacobus]

Should you always run the carbs out of gas if you know you won’t be driving the car for a month or two?

Absolutely! As such, I always run my 65C cab's Zenith carbs dry when knowing I'll not be driving the car for about a week or more. Accordingly, never had carb problems upon restart after carb refill via the under floor board elec priming pump.

Wil:
Do have the specific pump brand / specs and installation pictures?

ChuckJ

[Jim Liberty]

I put elect pumps in all my cars under the passenger floorboard too. Pep Boys, Auto Zone, etc have them. Stoddard/NLA and Siera Madra also.

[Charles H Jacobus]

Are you using 4 or 8 PSI pumps and do you use a regulator?

ChuckJ

[Jim Liberty]

I've not measured the output of the electric pumps I use as primers only. The spec sheet says 4/5#. I run one full time on my Sprite, and have both a regulator and pressure gauge on that system. 2 to 3# works fine on carburetor cars.

[Dave Wildrick]

Dave,

I received my '58 Speedster after 1-3/4 years in the body shop after my incident in Put-in-Bay's Race Reunion,
Lake Erie, OH and the engine fired right up after about 1-1/2 minutes of 15-20 second intervals w/the starter and
some gas added to almost an empty gas tank. Didn't do anything w/the carbs (Solex) and the fuel didn't show anything in the 4-cam pressure regulator/filter; The 4-cam engine was replaced w/a Super 2-years ago due to a
'holed piston' after 55 years.

Of course, the twin electric pumps worked OK producing 2.8 PSI like they should, and no further work was needed
The car ran fine--good to be "back on the Road Again". I never used or added extra in-line fuel filters in any cars
I work on and W/long storeages, I do use Stabile.

Dick

You may be right about my fuel filter overkill because it seems clear that the stuff forming in my carbs is not coming past the filters but is instead forming in the carb bowls as the gas evaporates.

I will invest in some Stabil and will try running the carbs dry when I anticipate not running a car for a couple of weeks.
I only have one C coupe at home right now. The other one is not back from the body/paint repair shop yet, but I hope to have it in my garage again soon.

I don't use an electric priming pump, just an outboard motor type rubber squeeze bulb, which fills the carbs fairly fast.

[Jim Liberty]

Running the carbs. dry for a two week layover is an overkill. You'll kill your starter.