1940 Fuel Issue

[Daves1940Buick56S]

All:

Well, I thought my fuel pump etc. was OK but now I am not so sure. About 2 weeks ago I moved my 56S up to a neighbors while its carport was being constructed. On Saturday I tired to start it to move it back but had a devil of a time. Obviously the fuel bowl had drained but I could not seem to get enough fuel pumped into the bowl using just the starter (I have "temporarily" installed a glass inline filter before the carb so I can visually see what the pump is doing). Even 4 separate shots of ether and resultant short periods of running didn't help. So I finally just pulled the brass filter plug on the WDO and filled the bowl. It started right up and the glass filter showed good pumping action.

So it looks like I should take a closer look at the pump and line. I have the spec on pressure - about 5 lbs, correct? I also want to do a flow check. What should I expect for 15 secs of cranking? About 4 oz? I seem to recall that the "modern" ('60s!) fuel pumps were expected to do a pint in 30 secs, and the older pumps to do a pint in 1 minute. Obviously I don't want to sit there and crank the engine anywhere near that long. I have also seen a test where you actually start it and let it idle on just what's in the bowl for 30 secs. I would expect with it running that a pint in 30 secs would seem about right.

I know that if I see a starvation problem that it might not be the pump, it may be in the line or pickup. Unfortunately I just filled up the tank so that will complicate things.

I tend to be a bit sensitive on this issue since I had a slow starvation problem with my old '66 Fairlane-289 and ended up burning out all of the valves without realizing it (hey, I was 18 at the time!) and want to be careful now since the rings and valves have just been done.

Cheers, Dave

[Mark Shaw]

Dave,

Many of us straight 8 drivers have installed electric fuel pumps near the tank to help prime the original pump for starting. It also helps while driving on hot days at high altitude & pulling hills to overcome vapor lock. I don't use my electric any other time. The original pump works well after it starts and for normal driving conditions.

My $0.02

[FLYER15015]

Dave,

My '40 LTD came with an electric pump mounted back @ the tank, just AFTER a huge clear plastic filter. I use a hidden toggle switch mounted under the dash. Sure comes in handy after she sits all week, and we want to take a drive on Sunday. A whole lot less grinding on the starter. Also works great for driving in the mountains, where vapor lock is a way of life.

If you have not replaced/rebuilt your mechanical pump, to accomodate the corn-gas we are forced to use, I would recommend that you do. This would also give you the opportunity to blow some LOW PRESSURE air from the fuel pump inlet tube, back to the tank, just to check the line and pickup tube, Makes you feel better once you do this.

My $ .02

Mike in Colorado

[Daves1940Buick56S]

Thanks Mark and Mike! I should have looked more carefully at the shop manual before I posted. It says the pump should put out a pint in 45 secs with the engined running at a speed equivalent to 30 - 35 mph (I assume in 3rd gear!). So that would be about, what, 1800 rpm? I can do that with what's in the bowl but it may not make it at that rpm for 45 secs - but, assuming the pump is first order linear on rpm vs capacity, I can figure it out.

I am not sure of the lineage of the pump. My seller did not know. I know the engine was overhauled (rings and valves) but do not know if the pump was looked at. It sure looks clean like it hasn't been on there long but you never know.

I will blow some air thru the lines - my air compressor goes down to about 15 lbs/in^2, is that low enough?

I am hoping to avoid the electrical booster pump but we shall see - not worth starving the engine and burning up the valves - been there, done that.

Cheers, Dave

[trp3141592]

Hi,

From my experience, I suggest that you remove the gas cap from the tank before back-blowing the fuel line. You could otherwise quickly overpressurize the tank and pop a seam or make a pin hole worse.

Been there.

-

-Tom

[FLYER15015]

Dave,

Tom is right on....

To blow the line, I hooked up a length of rubber hose to the inlet side of the fuel pump, removed the gas cap, and had a buddy listen for the bubbles in the tank, we then switched roles, and I satisfied myself that the line was clear.

As for the mechanical pump, have you pulled the bottom bowl from it to check for trash ?

Bob's has a diaphram and stuff that is "corn-gas" tolerant, and considering how easy it is to pull and rebuild them, I would do it just to raise my comfort level.

Mike in Colorado

[Guest SteveAS]

Bob's has a diaphram and stuff that is "corn-gas" tolerant, and considering how easy it is to pull and rebuild them, I would do it just to raise my comfort level.

I'm also having problems with the fuel draining back when my car sits for several days. I understand the practicality of an electric fuel pump, but I'd rather not have one if I can avoid it. Would the kit that Bob's sells solve the problem by making the seals fuel- and air-tight?

[FLYER15015]

Steve,

To answer your question.

No, "Bob's" kit will not solve your drain-back problem when the car sits for extended periods. The mechanical pump sits way down on the block, the carb sits clear up at the top, and the float valve is not capable of creating a super tight seal, so natural siphoning takes place, back to the level of the tank (Bernoulli's principal).

Back in the day that these cars were dailey drivers this was not a problem, however in todays world where we only take them out on weekends, at best, an electric pump, used only for "priming" and vapor lock is a very good idea. Has saved a lot of starter grinding....

Heck, my '53 MG-TD only had a Lucas electric pump on the fire wall. I put a good Bendix pump back at the tank, because Lucas was known as the "prince of darkness" back then

Q= Why does an Englishman drink warm beer ? A= He has a Lucas refridgerator !!!

Mike in Colorado

Edited October 9, 2012 by FLYER15015
spelling (see edit history)

[Ben Bruce aka First Born]

Steve, my '50 fuel pump was rebuilt by Terrell Machinery, in TX, and does not seem to drain back. Others may have different experience.

Ben

[Guest outlaw car man]

I have to agree with Mike on the seals- I rebuilt my pumps with new stuff, but they were OK anyway. At least I know. I've had the vodka gas eat old seals, turns to a goo like stuff, then you are screwed.

I don't run elec pumps on my cars, never have.

Of course I put on about 300 miles every two weeks to keep things up & running, usually run over the mountains and back with the big 344 engine. Hell going over the snowy mountain passes, at 10,000 feet, but this is Colorado, normal driving, just chain up.

whew ! deep in Colorado too.

[Daves1940Buick56S]

Update:

Finally got a chance to work on it again today. Pressure check good - 5.5 lbs/in^2

at idle speed. Capacity check also good - 1/2 coffee can filled in 25 secs, also at idle.

But I will go ahead and rebuild this Spring anyway. Just wanted to be sure for the short term.

Cheers, Dave

[Bob Engle]

You probably got trash in the fuel pump valves, causing a temporary problem. I had this happen and eventually found little bits of rubber showing up in the filter. A rebuild with alcohol resistant materials corrected the problem.

Bob

[trp3141592]

Hi,

Terrill Machine in Deleon, TX, rebuilt my '40 LaSalle pump with alcohol-resistant parts. Nice job, nice folks.

--Tom

[FLYER15015]

Dave,

Did you put a BIG clear plastic filter back by the tank yet ?

You might be getting come crud off the bottom of that 70 year old tank, which has probably evaporated dry a couple of times.

You put "corn gas" in it and all of a sudden, some old sludge breaks loose and heads for the carb.

One of the FIRST things I did to the "Baby" was to pull the tank, and clean it out @ the car wash.

You know the fuel pick up tube does not have a filter on it. It will take in anything that's in that old tank.........

My $ .02 And worth every penny.........

Mike in Colorado

[Daves1940Buick56S]

Thanks Mike and all! I think the gas tank is either new or rebuilt from the looks of it but I will take a closer look. I know I need to look at the tank sending unit as well since my gas gauge always points to 3/4 full no matter what.

Cheers, Dave

[Dynaflash8]

Because of EPA requirements that we use Ethanol here, none of my '39 Buicks will run without vapor locking in hot weather over 85-90 degrees. I have mounted an electric fuel pump on all of them with an on/off toggle switch under the dash. When it begins to stumble I flip on the switch and straighten it out. Of course you could do away with the fuel pump in some way but that would look non-authentic. You don't want to run the electric fuel pump all the time, because if the fuel pump diaphram fails you wouldn't know it and then you'd pump gas into the crankcase. My electric pumps are not back at the tank, but hidden up in the x-member and they work fine there. My '41 has so far not exhibited the need for the electric fuel pump, but I have one installed anyway. Ethanol is so lousy that I've installed electric fuel pump on the '69 driver as well, and once the Riviera is through all of the AACA judging, I'll put one on it too. I also use Startron (available from NAPA) in all of my gas tanks on the old cars because Ethanol will ruin every part of the fuel system if left untreated.....fuel pump, carburetor, even neoprene rubber gas lines. On the '39's I've also insulated the fuel lines in the engine area with pipe insulation you can buy at Home Depot to wrap home water heater pipes....it is split, so if you wire it on with thin wire, you can remove it for a judged car show. If you think Ethanol is bad now, wait until they require and institute 15% Ethanol.