VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Fuel problems investigation and fixes

Background:

A few weeks ago, I drove Justin (1928 AB Canopy Express) 40 miles round trip to a car show and swap meet. Was a fun day and I actually sold some stuff! ;-)

A few blocks from home, I got a strong whiff of gasoline. When I pulled into my yard and opened the hood, gasoline was gurgling out the top of the vacuum tank and was cascading down all around.

I traded messages with Chipper, who thought the problem was a float with a leak. I bought a new float from Gary Wallace, installed it, and that seemed to take care of that problem. I took Justin out for a test drive and something else was off. The truck died a couple of times at stop lights and then bucked like a bronco on the way back home. I suspected that the engine was starved for gas.

So, I decided to open up and inspect the fuel lines, the carb, and the vacuum tank. The following posts and photos is what I found and what I did to fix the issues. (crossed fingers!)

Note: I am not a carb or vacuum tank expert. Just diving in to see what I can find and fix.

For safety, I disconnected the battery.

Here are my first impressions of the components.

Carb: The first thing to come off was the carburetor (Carter RAKX-0). Looking back, I have not really looked into this carb since I got the truck. It's been running well for the last 9 years and 2000 miles. ;-)

1. At first glance, the inlet connector had a nice patina, but upon looking closer, it had a coating (gas tank sealer?) all over the outside and inside, which was starting to flake off. I picked off the outside coating and found a welded, cobbled together part that should have been replaced. I have a new replacement part, fuel screen, and a rebuild kit coming from Gary Wallace.

2. There was a half teaspoon of rust-debris sludge in the bottom of the bowl. That would explain the truck bucking as the sludge probably clogged some orifices and passages.

It is interesting that the screen was not clogged. The rust-debris particles are very fine and easily slipped through the screen. How do I know the debris is rust? It sticks to a magnet.

The shop manual (RTFM - read the fine manual!) says:

1. The screen should be cleaned out every 2000 miles
2. The bowl should be cleaned out every 5000 miles.

Lessons learned for the future!

Vacuum tank: The next thing to come off and apart was the vacuum tank. It is the correct one for 1928 with the four-screw stamped steel top. Here's what I found:

1. An old issue with the vacuum tank is that the shutoff valve leaks around the turn-off shaft. I've been tightening the nut and have gone through a couple of o-rings. To fix this leak, I ordered a new shut-off valve (Edelmann 429520 Brass Compression/Pipe Shut-Off Petcock Valve - 5/16" tube X 1/8" Male NPT) on Amazon.

2. There was quite a bit of yellowish crud clinging to the inside of the outer tank and built up on the bottom of the outer tank. I'd say about another teaspoon full of crud. I used an old toothbrush, a dowel with a sharpened end, and a bamboo shish-kabob stick to GENTLY scrape the crud off the sides and up off the bottom. I did not use anything metal because I do not want to scrape away what is left of the original lining. There are also a few surface rust spots in this tank.

3. The inner tank looks pretty good. ;-) Just needs a good cleaning.

I'll make more posts in this thread as I proceed with the work on these items.

That's it for now. Cheers, Dean

Hi again,

The parts that I ordered from Gary Wallace arrived, so I tore into the carburetor.

I held the carb upside down in my vice (with aluminum jaw covers) and measured the float's distance from the bowl surface to the carb body. The float 'height' measured 36/64" but, according to the specs, it should be 31/64". That translates to a bowl that was shutting off the flow of gas before the correct level was reached. Another verification that the engine was not getting the amount of fuel that it wanted.

Before attempting to unscrew the needle seat assembly, I made sure I had a correct-sized screwdriver and ground off just enough of the driver's tip to square it up. This helped ensure that I would not mess up the brass slot for unscrewing the assembly.

I compared the new needle and seat assembly with the old one and found a few differences:

1. The new needle was shorter than the old one by .030 inch.

2. The old needle had a spring loaded head on the end, whereas the new one was just a rounded solid end.

3. The new needle tip was neoprene, as opposed to the old one of solid stainless steel.

4. The hole in the seat assembly that the needle goes into was deeper in the new one versus the old one by .050 inch. This difference together with the shorter new needle means that the new needle sat .080 inch farther away from the tab on the float. Hmmmm.

Okay, the inspection was over so I started cleaning stuff. I used a can of carb cleaner to blow out all the orfices and they seemed to be clear and open. ;-)
There was a little rust debris on the areas where the gas inlet connector seats, so I gently scraped it off with sharp hobby knife.

The next thing I did was test the float for leaks. According to past VCCA posts, if you dunk the float in very hot water, a leak will show itself by a stream of bubbles (the same way a leak in an inflated inner tube will display when pushed under water). Hurray! No stream of bubbles. Just for the heck of it, I grabbed another float from another carb and, sure enough, that one showed a stream of bubbles coming from its leak point.

I screwed in the new needle seat assembly (with a new gasket), put the needle in, and put the bowl back on (with a new pivot pin). At this point, I did not bend the tab on the float that pushes on the needle. I just wanted to see how everything looked together. No surprise, the float was way far down from where it should be.

So, the float came back off and I very gently bent the tab in order to get the correct 31/64 inch clearance from the top of the float to the carb body. I had to bend the tab over 1/16 of an inch. To do this, I cut a slot with a dremel cutoff wheel in a short piece of bar stock as a bending tool, rather than trying to get in there with a pair of pliers. This little tool did its job very well. ;-)

Cheers, Dean

Carb work part 2:

While putting the bowl back on, I noticed a big gap where the center of the bowl will have to be pulled down (by the body and bowl connecting nut) to meet and seal on the bottom of the carb's body. The new bowl gasket that came in the carb kit was .060 inch versus .030 inch for the old one. I decided to make a new gasket out of .030 gasket material so the bowl would be a little closer to the carb body and not be stretched so much to make a seal. The bowl pulled down nicely when I tightened the nut. I will report at the end of this thread whether any leaks are found when I start driving Justin again. Fingers crossed!

With a new gasket and new screen in place inside the new gas inlet connector, I attached the new connector onto the carb and reinstalled the carb.

The next episode in this journey will cover the rehab of the vacuum tank.

Cheers, Dean

Your work so far is top notch. As you have found out available new parts are not always an exact replacement. Some adjustments are often necessary.

I have found over the years and several thousand miles running '28 Chevys that the float position is not critical. Yes it can affect the gas mileage and maybe power but small changes are not noticeable in how it runs.

On the recently completed VCCA four cylinder tour in Park Rapids Minnesota most '28 Chevy cars reported 16-19 mpg. My Coupe was in that range and depended on the amount of travel above 40 mph. I generally average 18-20 mpg when less then 40 mph. At 50 mph I am sure it is closer to 15 mpg. I did run a number of miles at that higher speed on the tour.

The MPG content is not intended to change the direction of this thread, only give an indication of the expected gas mileage with properly running engine. If others want to comment on MPG it MUST be in a separate thread. Dean is free to do what he wants as this is his thread.

Thanks for the kind words, Chipper. ;-)

Gas mileage is a good sidebar. I used to get around 15 mpg with Justin and it will be interesting to see what it becomes after we're back on the road.

Cheers, Dean

Now to journey into the vacuum tank's issues. The next few posts will be about the vacuum tank's disassembly, inspection, fixing, cleaning, and chemically treating.

The phrase 'chemically treating' needs some explanation. I've read many VCCA posts about whether or not to line the inside of gas tanks and vacuum tanks. There are very credible experts on both sides of this issue. I think the original lining of the vacuum tanks was zinc. There is a dull, galvanized look to the insides of my vacuum tank that suggests that a lot of the original coating is still there.

While rummaging around in my shop to see what's laying around, I found a bottle of Metal Ready from POR-15. It is a mixture of phosphoric acid and zinc phosphate. This product is meant to prepare steel for POR-15 Rust Preventive Coating. I only used the coating on the inside of a tool box, but had some supplies left over. The information on POR-15's website says Metal Ready will dissolve rust and leave a zinc phosphate coating. Hmmmm.

I don't want to use the POR-15 Rust Preventive Coating inside the vacuum tank because it might flake off in the future. I decided to use just the Metal Ready mixture to re-coat the vacuum tank and have a zinc coating that will last another 93 years. In 2114, I'll let you know how it worked out. ;-)

Okay, back to working on the vacuum tank. The top just unscrews and lifts off. Notice in the first photo below that the inlet that connects to the gas tank line has a street tee fitting with a plug in the top. This connection originally was a 90 degree elbow. I found that occasionally, the gas would evaporate out of the tank, leaving it empty. I replaced the elbow with the street tee so I could easily unscrew the plug and prime the tank with gas. Here's a link to another post where I describe the whole set primer up: https://vccachat.org/ubbthreads.php/topics/453708/re-1928-1-ton-lp-truck.html#Post453708

The underside of the tank top looks great! ;-) The valves seem to move freely and the screen was not clogged. The screen was, however, stretched and some of the openings would allow large chunks to get through. I don't think I need the screen because I have a cartridge gas filter in the fuel line coming out of the gas tank, but I'll leave the copper screen in the vac tank for completeness' sake. I have a new gasket for the top of the vac tank (also from Gary Wallace) that I will use for re-assembly.

The next item to work on was the inner tank. I lifts right out of the outer tank. As I said earlier, it is in really good shape. There was a little surface rust at the top of it where the gas seldom goes. I used an old toothbrush, a parts cleaning brush with plastic bristles, and a piece of Scotch Brite to gently clean some crud off the sides of the tank and the bottom. The photo with the brushes show how much stuff came off the tank.

The next steps were to wash, chemically treat, and wash the inner tank again.

1. I washed the tank with WD-40 cleaner and de-greaser using a bottle brush with plastic bristles. I rinsed it with house water and then with distilled water to make sure no soap was left on the surfaces.

2. Since I only needed to coat about the top 1/4 inch of the inner tank, I turned it upside down and stood it in a metal can lid. Then I poured enough of the Metal Ready mixture into the can lid to cover 1/4 inch of the tank.

3. I left the tank in the mixture for 2 hours. Then I dipped it in water, washed it, rinsed it off to stop the acid action, and let it dry in the sun. The surface rust was dissolved and the zinc phosphate coating was evident. See the last photo below.

I believe the rehab of the inner tank is done. The next posts will cover the rehab of the outer vacuum tank.

Ever onward, Dean

Dean,
Your vacuum tank is the best condition I have seen. It must not have seen much water. Was the truck from a desert area? Water vapor in the air (humidity) eventually finds its way into gas tanks and starts corroding.

One comment the first photo shows the top with float hanging down. The float should be installed so the loops in the valve wires are in the straight section of the wire on the float. The 90 deg. bend and "legs" on the valves keep the float from rotating. It also reduces the number of times the inner tank is filled, but slightly reduces the amount of gas in the tank when completely filled.

Hi Chipper,

Yes, I am blessed to have this particular vacuum tank. It came with Lurch, when I bought his rolling chassis in 1994. That truck was sitting outside on a farm in Fremont, CA, near where the old GM plant was (which is now a Tesla plant). The location is about 8 miles from the SF Bay, but the humidity is usually quite low.

Thanks for your observations about the float. I'll correct the float's position when I re-assemble the unit.

Best regards, Dean

Here's part one of the outer vacuum tank rehab.

The general condition of the outer tank is not as good as the inner tank, but it is still pretty good.

The first couple of photos show the general condition inside the outer tank. At a lot of the original coating is still intact. A few surface rust spots are along the top sides of the tank. Most of the corrosion was accumulated on the bottom.

To check the flatness of the top surface of the tank, I used a straight edge on a combination square. I found a couple of places where the surfaces were bent down and therefore, could be a possible source for a vacuum leak. I used a pair of channel lock pliers to gently straighten those dips. To ensure that the surface was really flat, I lightly flat sanded the top surface with a piece of 180 grit emery cloth wrapped around a small slab of steel. That revealed a couple of spots that needed a little more work before declaring success.

Next, I used a brush with plastic bristles on the sides of the tank and a pointed dowel stick to root around the bottom. I vacuumed out the loosened crud. I estimate that there were two teaspoons or so of debris.

The last photo attached to this post shows the bottom of the tank at this point in the process. The pointed stick loosened a lot of the debris, but there were good amounts of rust around the two pipe fittings that are attached to the bottom of the tank. This extra corrosion on the bottom is tackled in the next post.

Cheers, Dean

The original coating used on the vacuum tanks was lead,the same as was used on the sheet metal to make the petrol tanks out of,and it was known as "terne plate".

Here is part two of the outer vacuum tank rehab story.

To attack the surface rust and the crud on the bottom, I used a wire cleaning brush with the end bristles bent forward to be able to reach straight down onto the bottom surface. The first couple of photos show the brush with the bent end bristles and it attached to the dowel stick to reach the bottom of the tank. Duct tape to the rescue again!

The third photo shows the bottom of the tank after cleaning with the dowel stick and the steel end brushes. Much better than when scraped with just the pointed dowel stick.

The next step was to get ready for the chemical treating. I screwed a 1/8 inch NPT brass plug in the outlet that normally goes to the carb and a ball valve in the drain plug hole at the center of the bottom.

The drain hole normally has a plug in it and according to the shop manual, lint and debris must be drained out of the tank occasionally from this lowest orifice in the tank. Another lesson learned for the future.

I sealed the threads with some Rectorseal to protect the threads when I flush out the Metal Ready.

To hold the tank in an upright position outside of my shop, I mounted it to a 2x6 that was screwed to a wooden saw horse. The sides of the top of the saw horse were cut at the same angle of the legs, so shaved off a little material to make a short 90 degree surface for mounting the 2x6 board.

To prepare the tank for chemical treating, I cleaned out the two orifices in the bottom of the tank, put a plug in the fitting that is used to deliver fuel to the carb and put a cutoff valve in the center drain hole. The valve will be used to drain the Metal Ready back into the original bottles when I'm done with the soaking the tank step.

I poured two quarts of the Metal Ready into the outer tank. As you can see in the photo below, it did not completely fill the tank. So, I used a solder acid brush (new and clean) with a bent handle to swab the sides and underside of the top. I shemeared the mixture every 20 minutes or so.

Since the inner tank was coated well enough after two hours, I drained the outer tank at this time to check the progress of the treatment. The sides looked okay, but the bottom was not coated satisfactorily. Especially around the two steel pipe fittings.

So, I fill the tank with the mixture again and left it in for another four hours, still swabbing the the sides and under the top surface. By the way, since this was outside, it was in the sun so the tank warmed up a little. The outside temperature was around 74 degrees F.

I drained the tank again and now I think the inside of the bottom tank is conditioned well enough. The eighth photo shows the good coating that was deposited on the bottom of the tank. The next photo illustrates the coating that was deposited on the sides.

I washed out the tank again, but did not use the bottle brush because I did not want to disturb the zinc phosphate coating. So, I sloshed the soapy solution around, drained it, rinsed it, and gently pushed an old tee shirt into the tank to soak up the leftover puddles.

In order to dry it well right away, I put the tank back in my vice in the shop and left it under an articulated lamp for a few hours.

The rehab of the outer tank is completed. The next post will cover the finishing tasks and re-assembly of the vacuum tank.

Later, Dean

Part three of the outer vacuum tank rehab.

As noted in the beginning of this saga, the lid is in great shape. ;-)

I squirted carb cleaner through all the orifices and up the valve stems. There does not seem to be any blockages and the valves move freely.

In the second photo below, you can see the gap between the bottom loop of the two valves. According to the shop manual, this gap should be between .018 and .028 inches. And yes, the gap is within this range. So the lid is done.

The third photo shows the new shutoff valve and brass plug installed in the bottom of the outer tank.

Next on the list is to install the lid. I noticed that the little bolts that hold the lid on have 8-32 threads, so I cut off the heads of some longer 8-32 bolts to use as positioning studs. These studs will guide the lid gasket and the lid into place on top of the tank.

While positioning the lid over the top of the tank, I moved the float up and down to see how it interacted with the bottom of the valves. To my surprise, I noticed that the curvature of the float hanger was preventing the stem from smoothly passing through the valve eyelets. In addition to the curvature, the stem had tool marks on it that caught on the eyelets. Not good.

In one of the photos below, you'll see the new float on the right next to the old float on the left. It is obvious that the stem needs to be straight in the middle to slide nicely up and down through the valve eyelets. After a little bending with pliers and smoothing with 1500 sandpaper, the new float's stem better mimics the old float stem.

I'll finish documenting the work on the vacuum tank in the next post.

Cheers, Dean

Part four of the vacuum tank rehab.

In the first photo below, the new float with the straightened stem is hanging from the lid. Now, when hung through the valve eyelets, the new float is free to float up and down nicely and work according to the original design. Smooth, man! ;-)

The next photo shows the lid dropped onto the tank using the guide bolts for positioning. One by one, I took out the guide bolts and put in the correct bolts to hold the lid down. As per a conversation with Chipper, I did not use any sealant on the gasket. To finish the job, I tightened the bolts a little at a time going around the lid to pull it down evenly.

After reinstalling the tank on the truck, the next step in this process will be take out the gas filter near the gas tank, blow out the fuel line from the gas tank to the vacuum tank, put a new gas filter cartridge in place, and close everything up.

Almost done, Dean

Dean,
You are doing a first class job. They are not too complicated but require some knowledge and attention to make them function properly. I have been running vacuum fuel pumps (vacuum tanks) on all my pre-29 Chevrolets with only minor problems for nearly 30 years.

Last item to take care of in this effort is to replace the paper gas filter that is at the gas tank. See the first photo below.

The gas filter is a Chevrolet Filter Assembly from the Filling Station. Here's a link to it in their online catalog; Filling Station item FS-607

There's not much to tell about changing the filter. I installed this filter after I had the gas tank cleaned nine years and over 2000 driving miles ago. Sooooo, I changed the filter. ;-)

BTW, I set up the gas line with a valve so I could drain some gas into a bottle to enable me to prime the vacuum tank when it occaisionally gets dry. Here's a post that explains this setup: Portable gas station under my truck

Drum roll please! I primed the vacuum tank, took Justin out for a drive, and he's back to normal!!

Project fuel system inspection, cleaning, and re-habbing is complete. The first post-opt drive will be a local Cars and Coffee event. That took place this morning. Here's a link to that outing: Cars and Coffee in San Lorenzo, CA

Over and out. Dean

Congratulations!