M38A1 fuel tank cleaning?

Casey B · #1 03-11-11, 00:18

Hi Fellows..
Well I have to start from the begining again and do it correctly and see if the engine will run better. I cleaned and rebuilt the carb...the kit has two different springs for the accelerator pump and short one and a longer one...NOT the the spring for the metering rod. So I used the longer one like it had.

Put an inline fule filter in between the tank and pump. It caught a lot of large particles from the tank.
I took the sending unit out as well the pick up tube and it was fine except the element was loose so things got past it.
Then I see this stuff on the bottom of the tank. It appears to have gone in as liquid but then dried but can be rubbed off with your finger while still wet with fuel.

Any ideas what it is/ was for?

What do you recomend I clean the tank with when I do the final cleaning out and any tips on how to do it efficiently would be great?

Once cleaned I will rebuild and clean the carb, blow the lines with compressed air and new fuel filter.

I was told I should maybe consider an electric fuel pump as the old one has the rubber diaphram which may not be compatable with the alchol in todays fuels? YES/ Don't Bother?

Thanks to all again...!

rob love · #2 03-11-11, 00:35

Not sure what that crap is that's in your tank. I would suggest taking the tank to a radiator shop where they can properly clean it out, and seal the tank or repair any leaks.

I am still running on an original fuel pump just fine. There are kits out there with fresh alcohol compatible diaphragms and check valves, but mine will be an original. Zero issues.

The inline filter is important. Best to have one before the fuel pump, as the sediment can clog open the little check valves in the pump and cause it not to pump fuel. I install a second one at the carb just to make sure everything is good.

Phil Waterman · #3 03-11-11, 15:15

Hi Casey

Great pictures inside the tank, looks like the tank is in good condition other than what ever that gunk in the tank is. This doesn't look like normal varnish from evaporated gas, almost looks like something was dumped into the tank. Is all the gunk on the bottom of the tank?

Robs comment about taking it to a radiator shop is a good one, but be careful some shops use an etch solution which is OK on brass used in radiators but might take the coating off the steel.

So back to the gunk, it looks like the your fingers have made marks in it, can you get some out of the tank with out scratching the inside of the tank? If so try you might try the following to see if it will dissolve:

Really hot water ( I sort of suspect this may work)
Acetone
Straight alcohol
Automotive paint gun cleaner

Reason I suggest doing this on small samples is so you don't make the problem in the tank worse, for obvious reasons don't mix them together.

I would not use anything abrasive, as it looks like the steel in the tank is other wise in good condition.

One of the old methods of dealing with a problem like this was to use a gas tank sealant to seal the junk down, but as the new fuel mixes have dissolved two older type of tank sealants resulting in the same type of problem you already have I would not suggest using a sealant.

Please keep us posted on how you make out as your problem is one which any of us can end up dealing with.

Cheers Phil

cletrac (RIP) · #4 03-11-11, 15:58

I'd try taking it to the car wash first and see if that removes the gunk. If you get one with really hot water and lots of pressure it should work.

rob love · #5 03-11-11, 17:33

The tank appears to be one of the replacement tanks from the 80s. The give-away is the welded edges instead of the rolled edges of a factory gas tank. I'll check my spare one and see if the same gunk is on the bottom. It may be there to help seal the drain plug area as well as some of the welded seams. It is possible this was put in by the manufacturer and was never intended to see alcohol.

IIRC there is a baffle in these tanks which would make scraping half the tank impossible, but as suggested by the others, heat or solvents may remove the gunk.

Casey B · #6 03-11-11, 23:47

Is all the gunk on the bottom of the tank?

Yes it looks like it is only one the bottom of the tanks and from what I can see only on one side of the baffle and looks like it was poured in then the tank tilted to the same position as when I took the pictures.

Really hot water ( I sort of suspect this may work)
Acetone
Straight alcohol
Automotive paint gun cleaner

Please keep us posted on how you make out as your problem is one which any of us can end up dealing with

Well I am going to try just plain old gasoline first to see if it loosens then as you said Phil try the Hot watr from a kettle and a wood scraper then the others and see what this stuff is Feels and looks like fuel varnish. No holes in tank so we'll see have a radiator shop in mind to take it to but will try these first!

Rob where do you fit the upper fuel filter before the carb? just along the fuel line that runs to the input on the distributor side of the engine I am guessing?
A plastic fuel line filter is okay there...? heat? or would you go with a metal one? I used a plastic one on the fram rail pass side just near the spring shackle.
Thanks again and will let you know!

Casey B · #7 04-11-11, 01:36

Okay well here's the update.
Before puttinaanything in the tanks I tried to wipe with my hands and it just rubbed off in little flakes that were slightly shiny. So I am going to say a petrolium based productNow it was only in the one side of the tank nothing around the drain which is on the filler side.
I took a clothe an wiped the residue off which except for some globs which look like drippings from a fat fryer it all came off. I then poured HOt Boiling water in and agitated it and the stuff seemd to melt and wash away with help. A wood paint stir stick helped.
Then after pouring that out and wiping dry with a clean clothe I decided to try a little gasoline and it did nothing to the stuff except turn it to a greasy gooy substance that smeared rather then wiped away...So much for the petrolium based substance.
It is curiously where the pick up tube goes and is the same colour as the element the strains the fuel at the pick up tube.
What is that made of...? Spongy red pourus material in a cylinder? Could be that is not compatible with todays fuels. Or the goo could have been an additive poured in that did not mix with the feul aka STP? something like that Or even sugar as it does look like varnish or burnt caramel! The pattern of the goo seemed to radiate outwards from the pick up tube in a radial pattern as the paicks show and then drip down.

Well there you are mystery not solved but problem gone.

The tank Bottom has some small patches of surface rust so I will look at getting it coated for new fuels.
Do radiator repair places do sealing of fuel tanks? Or I can google I guess!

Thanks fellows!

rob love · #8 04-11-11, 02:01

Rad places do gas tanks. Or you can source some POR15 and do it yourself. I believe Lordco carries it in your province. It is not rocket science to apply.

Casey B · #9 15-11-11, 19:14

here are some pics of the tube i am speaking of It is in very tight and i do not want to wreck it if it is not supposed to come out...You can see there is no real palce for this to go even if i did get it loose unles it folds or over laps to fit through the neck opening? I tried to gently pry where the indents are and nothing...tried a puller on the bottom and like I said am curling the lip over...Any thoughts other than heat and penitrating oil if this pieces does come out?

Casey B · #10 15-11-11, 19:57

after cleaning some rust off i found the spot weld no need to go on it does not come out...fixed the tube bottom ready to seal now thanks for all the help!