'49 248 Fuel Pump

[OOPSETTER1]

As some of you already know, I'm running an electric fuel pump on my '49 Super. They're just not holding up, I've replaced three of them within the last year. I'm getting the low pressure pumps, 4 - 6 PSI, which is *supposed* to work well on Straight 8's. And they're not cheap, I'm getting sick of changing them every 300 miles or so.

Ideally, I want to go back to using a mechanical pump, and perhaps just keep the electric pump as a starting aid by putting a toggle switch somewhere.

The mechanical pump is still on the engine, but the fuel lines no longer go to it. However, the wipers work fine, which I assume means that the vacuum part of the pump must still be working. The engine was rebuilt when the car was restored, but I have no way of knowing whether the fuel pump was rebuilt or replaced, I did not own the car when it was done. It had only been driven about 500 miles since restoration when I got it, and it had an electric pump mounted on the frame near the rear axle. It had fuel problems when I got it after it had been sitting over 5 years without being started...trash in the tank, and carb problems. The first pump that went bad I attributed to gunk from the tank. However, the other pumps that have failed have all been after I had the tank cleaned and the carb rebuilt. The car runs GREAT while the pump is working, no problems at all...starts well, runs out wonderful. But, after 250-300 miles, the pump always goes out, without any warning. No sputtering, no coughing, it just dies. The fuel filters are remaining clean. The new pumps all come with a new small filter attached, and I have changed the inline filter near the carb each time I put on a new fuel pump.

Is it reasonable to assume that the mechanical pump could still be good, since the vacuum works? I'm thinking that perhaps the shop that restored the car was experiencing the same carb problem I had when I got the car...stuck needle and seat...and maybe thought it wasn't getting gas due to a fuel pump failure...and just stuck an electric on it.

[Bob]

The vacuum and fuel parts of the pump are separate and do not indicate much about the performance of the other part. That doesn't mean it does or doesn't work.

There is a typical pump rebuild in the reference section if you would like to have a look at it. A good source for a kit is Egge.

[OOPSETTER1]

There is a typical pump rebuild in the reference section if you would like to have a look at it. A good source for a kit is Egge.

Thanks, Bob. I had already looked at the information in the reference section. I found a rebuild kit at another site, but thanks for letting me know about Egge, I've not checked there yet. I may try plumbing lines back to the mechanical pump and then disabling the electric pump while the car is running to test it. I had thought about just hooking up some temporary lines, long enough to reach a container, to see if the pump would pick up gas and pump it while the car is running.

The real mystery is what is causing the electric pumps to fail so quickly. A mechanic friend of mine theorized that since these older cars do not have a return line to the tank, and given that electric pumps actually "push" fuel more than pulling from the tank, that it is overheating and burning up due to pushing against so much force.

[Bob]

You could test it just as you say. Your friend is probably right. There are probably ways to make the electric pump work, like running a return line or by putting a pressure regulator switch. But usually the best fix is to fix the original.

[OOPSETTER1]

But usually the best fix is to fix the original.

I totally agree! I want it to be as original as possible anyhow.

[Jyrki]

Most electric pumps need to be gravity fed, that is, their inlet port must be mounted lower than the gas level in the tank. Otherwise it will cavitate. In addition, a pressure regulator always makes it easier on the pump, even if the pump has an internal bypass valve to regulate the pressure.

[rockin-bones]

Hmm...interesting. I just had a new one installed on my '48 a few weeks ago, and soon after the engine just quit at the most inconvenient times (such as at a light). I wonder if there's a connection....

[OOPSETTER1]

Most electric pumps need to be gravity fed, that is, their inlet port must be mounted lower than the gas level in the tank. Otherwise it will cavitate.

Thanks for the input. The electric pump is located lower than the fuel tank itself, although not by a lot. It's mounted just forward of the rear axle on the inside of the frame.

[Straight80]

I think Buick knew what they were doing by 1949 with the mechanical fuel pumps. But I know of an electric fuel pump that will probably out last the car!!! I worked on Thermo King, and Carrier transport refrigeration units for over 14 years, and I only changed about 6 fuel pumps. These fuel pumps are almost indestrucible. I only know of a 12 volt version, if anyone is interested. I think I still have one in a box, that I used for a very short time for diesel fuel. The one I have has a glass bowl on it so you can see whats in the fuel, these fuel pumps were mounted on the fuel tanks which were mounted under the belly of 53' trailers. The snow, ice, mud, and rain didn't bother them at all, as long as there was no water in the systems. Even then, when the ice was melted. They pushed the fuel just fine. Once a fuel line is primed, the fuel pumps can push as far as 50 feet, or more!. The Buick straight eights only need 4 PSI of fuel, to maintain proper operation.

Anthony

aka Straight80

[OOPSETTER1]

My friend and I tackled testing the old mechanical fuel pump yesterday. We hooked up a piece of fuel line to the old pump, and while the engine was idling using the electric pump we put the end of the fuel line into a shallow pan with some gas in it. The old pump was trying to work, you could feel a little pressure pulsing on the outlet side, but it would not pick up the gas. We thought that perhaps the pump needed some type of priming, so we just hooked up the fuel line that was in use coming from the electric pump to the mechanical one, and turned the switch on. We immediately saw the problem, it had a MAJOR leak around the fuel bowl on the bottom of the mechanical pump. We got a new gasket for the fuel bowl, put it back together, and hooked the gas line back up from the electric pump so we could idle the car, bypassing the mechanical pump. While it was idlling, we again put the short piece of fuel line into a pan of gas, and WOW! It pumped great, looking like a geyser! After seeing that we were getting good pressure from the mechanical pump, we plumbed all the lines to it, disabled the electric pump, and held our breath! I started the car, and it ran flawlessly! I drove it to a local parts store, and we got a toggle switch to mount under the dash for the electric pump. I guess we put around 25 miles on the '49 yesterday, and so far the old mechanical pump is working great. I like the idea of having the electric pump on there too, "just in case", and to use as a starting aid after the car has been sitting for a week or so.