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Fuel problems 1940 Buick Super Eight in MD


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When I brought the car home a few months ago it started and ran fine. Now it will not start. I have fuel in the clear fuel filter (before the fuel pump). I disconnected the fuel line from the front of the carb and when I crank it over nothing comes out. The fuel pump that is on the car was changed recently looking at how clean it is. Is there a common problem with these old fuel pumps that I can look for?

I am a mid 60s Chevrolet guy so when I look at all of the lines that come from this fuel pump, I get scared. :-)

Any ideas?

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Just because you have gas in the bowl does't mean it is picting it up from the tank-----------take line off the incomming side of pump and suck the line ----see it you are getting gas ????????????--if so it is your pump take it off and opperate it manually and see if it is sucking check the tank maybe it is empty or the line in cloged or there is a break in the line---- my car has a bowl under the car right at the tank check yours

Edited by broker-bob (see edit history)
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I have not run across any cars with a sediment bowl on the fuel tank, outside of Model T Fords.

By 1940, most cars had a sediment(filter) bowl either on the fuel pump, or right before the carburetor.

Possible fuel supply problems can include:

- no gas in tank (gauge lies?); also pick-up tube rotted away, no longer reaching bottom of tank ?

- blocked pick-up tube in tank (rust, water, ice )

- collapsed / deteriorated rubber flex-line at tank and/or at pump.

- fuel-pump: bad diaphragm, check-valves blocked-open due to debris, bad gasket on sediment bowl

- rust-perforated steel fuel line between tank & pump ( holes may not be large enough to drip fuel, but large enough (or enough of them) to allow air to bleed into the suction line). If fuel-line, brake lines, or under side of car look really crusty / flaky, then examine the fuel line very closely.

- Real long-shot: if at some point the gas tank has been sealed with a pour-in DIY tank liner, that could be "Shedding", and strands/blobs of sealer are clogging the fuel system. ( This was a constant problem I had with a '48 International pick-up I had around 1993 - kept pulling long pink strands of sealer out of fuel lines, pump, carb...).

I would suggest starting at the tank and working forward: disconnect fuel line at the tank-side of the fuel pump, then go back to the rear of the car, remove the gas cap, put your mouth up against the filler neck, and blow into the tank, and hold some air-pressure on the tank for about 1 minute... if all is well with the tank, pick-up and line, some fuel should start to run-out at the disconnected end by the fuel pump.

If this technique (quick and dirty) doesn't appeal to you, and you have a source of compressed air, you could gently apply 5-10 lbs of air to the tank line where you disconnected it from the fuel pump... if all is well, you should hear air moving through the line and gurgling through the fuel in the tank ( remove filler cap first !)

Fuel pumps on these cars aren't inherently more problematic than they were for your 1960's Bowties... just older. If your Buick has more than two lines going to the fuel pump, it is probably equipped with a combination fuel and vacuum pump, to boost vacum for the windshield wipers.

One thing that has been plaguing older cars in recent years has been the increasing use of alchohol-blended fuels - these can attack older rubber parts in the fuel system ( hoses, diaphragms, etc). If you're buying replacement hoses or fuel pumps, make sure the rubber is alcohol-resistant. Don't waste your money on NOS rubber parts.

If the fuel-pump turns-out to be the culprit, don't waste your time with NOS pumps or kits; send your existing pump to Antique Auto Parts Cellar, in Weymouth, Mass. Tom Hannaford will completely rebuild it with nitrile neoprene diaphragms, etc, and it will work "better than new". Visit them at "www.then-nowautomotive.com"

One last thought, since gasolines were re-formulated to work best with fuel-injected cars, about 15 years ago, many of us have noticed that the carburetors in our pre-1980 vehicles go dry after sitting un-driven for two to five days; when we go back to the vehicle, we either have to grind on the starter until the carb fills ( 20-30 seconds on my De Soto), or prime the carb with fuel / starting fluid. I don't have a problem with cars that are started every one to two days, but if they sit longer, the carbs dry-out.

Good luck with your Buick !

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some on mentioned about the fuel disapering in the carb bowl ---that happens on my 36 did'nt know why--what does the fuel have to do about ???? does it evaperate-?---------------Broker Bob

Broker Bob,

When computer-controlled fuel-injection replaced carburetors on gasoline-powered vehicles (early 1990's), consumer gasolines were reformulated for peak-performance and lowest emissions when used in fuel-injected systems.

One of the results was an increase in the volatility of pump gas ( its tendency to vaporize ). This is not in issue in fuel-injection systems which are "closed", and the fuel pump is located in the gas-tank, and "pushes" the fuel under fairly high pressure up to the engine; if you put a liquid under pressure, you increase its boiling point (same principle as the pressurized cooling system and the Presto pressure-cooker).

When you put this new, easily-vaporized gasoline in an "open" system, and one where the fuel is "pulled" a long way from the tank, under reduced pressure, there is a greater tendency for the fuel to flash into vapor, causing vapor lock / fuel-starvation.

When the warm engine is switched-off, residual heat in the engine causes the fuel in the carb bowl to evaporate through the vent tube or anti-percolation valve, and if the vehicle sits unused for enough time, the carb bowl goes dry.

How long this takes depends on the vehicle; I have found that my 1940's & 1960's MoPars dry-out if unused for more than three or four days. If they are run every day or every other day, eneough fuel remains in the carb for a quick start.

I believe this is less of an issue with post-1970 vehicles that have "closed" fuel systems, where the fuel tank and the carburetor are both vented to a charcoal canister, so that raw fuel vapors are captured and scavenged by the engine through a small vacuum hose.

There are also certain carburetors whose float-bowls have passages sealed with lead soft-plugs, which sometimes weep fuel, allowing the carb to leak-down.

Our cars still manage to run on modern fuel, but it's not the same stuff we were getting 25 years ago, lead notwithstanding.

De Soto Frank

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  • 3 weeks later...

OK I disconnected the line at the fuel pump that goes back to the tank. I blew air thru it and found that I had a leak at the rubber hose just outside of the tank. I put two new clamps on there and seemed to have that taken care of.

Will I have to prime the fuel pump before it starts pulling fuel again or should it just pull it out of the tank?

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When my '41 De Soto carb goes dry from sitting, it takes about 15-20 seconds of cranking to fill the carb. Don't know how long it would take to pull gas all the way from the tank.

Would suggest pouring about 1 shot-glass worth of gasoline down the carb throat, and starting the engine; if it dies after 5 seconds or so, repeat. By the third time around, the fuel pump should have "picked-up its prime" and be delivering fuel to the carb.

If you don't like messing around with raw gas, you could use starting fluid sparingly...

One trick I've used is on vehicles that have carbs with "bowl vent tube" ( 1/4" diameter tube sticking into the carb throat at an angle), is to take a pump-type oil can, fill it with clean gasoline, and using some 3/16" or 1/4" rubber vacum hose, slip one end of the hose over the vent tube, and the other end over the oil-can spout, and use the pump oiler to fill the carb bowl with gasoline. Stop when you see gasoline start to weep out around the throttle shaft.

With a full float-bowl, the engine should idle for at least 30 seconds to a minute... repeat a couple of times, and your fuel pump should catch-up.

In this freezing weatherm, would also suggest adding a bottle of "dry-gas" to the fuel tank.

Good luck !

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