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1970 Cadillac gas tank has white powder in filler neck

Started by Scot Minesinger, October 28, 2015, 08:56:22 AM

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Scot Minesinger

This 1970 RWD Cadillac has had the tank re-done at Loopers in Rockville where it was opened up, baffles re-secured, and then resealed guaranteed for life back in 2010.  The tank does not leak.  The metal fuel lines front to back have been replaced, along with sender, and rubber fuel lines.  The car was run infrequently until 2012 when it was parked and most gas drained out.

Then the engine was removed for valve job, and other work plus detailing.  The carb and fuel pump were replaced and have not seen fuel yet.

I'm getting ready to start this car up again and the tank has a white powder like stuff on filler neck (which were exposed to fumes only).  I hear that this can pass right thru fuel filters and gum up the carb if not removed.  Is this true?

I'm willing to drop the tank and wash out this loose powder with fresh gas and blow out fuel lines with compressed air - is that enough?

Thoughts, ideas, experience are sought here.

Thanks,

Scot
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

I have not noticed the white stuff in fuel tanks but have seen it in carbs.  I thought it had to do with a combination of moisture , alcohol, and the aluminum.   If you are seeing it in the tank it must not be related to aluminum.     I have seen it be both a fairly easy to crush and dislodge powder like build up but also a tough limescale like build up.    I have actually seen both in the same carb so it must have something to do with how often it gets wet with fuel.   Its usually not at the bottom so its not like its from water that separated and sat.  It usually seems to be in higher spots so maybe it does have something to do with vapor?   For me its been happening since ethanol popped up which is 20 some years now.   I don't know if filters catch it or not since I always find it in carbs.  Where I saw it most recently was a golf cart that has a clearish plastic fuel tank that looks clean inside so at least in my recent case it was not like it got to the carb from the tank.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Caddyjack

Jack Larson
Philadelphia, PA

Jon S

Scot -

Is it possible to get a chemical analysis of the powder?  Maybe an agricultural analysis ... Say you found it on your lawn or on a tree?
Jon

1958 Cadillac Sedan De Ville
1973 Lincoln Continental Coupe
1981 Corvette
2004 Mustang GT

Scot Minesinger

This white powder-ish stuff is a known by-product of ethanol gas break down.  Just wondering what will get rid of it.  The issue is it comes off during normal operation and clogs carb.  If this is true, I'm think I can scrub it out now before re-filling with fuel.  Plus Eastwood and others sell fuel tank cleaners too.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

James Landi

If you've an in line "micron" filter, you've no need to worry, as any small particles will either disperse in fresh gas or larger ones will be trapped in the paper filter.  Running the car frequently on ten or more mile jaunts keeps all the mechanicals in good working order.  James