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Working on my 1937 Twelve. Car ran & drove great for many years. Starting around 2003 car was only started & driven a short distance once or twice a year with some fresh gas put in. Car still ran & drove great 3 years ago (key point here), but wheel cylinders started getting sticky from inactivity so I laid it up to go over through the brakes. At that time I drained the gas tank and had 13 gallons of varnish on my hands. I got the brakes put back together last October. During the down time I also installed a new electric fuel pump (normally used for priming only). The old one was one of those cylindrical ones from the 1960's with points in it. It didn't work anymore, so I replaced it with an new Airtex rotary type pump. I put fresh gas in the car, started it up & it still ran great. Since the engine hadn't run in two years I let it run for probably half an hour, also using the hand throttle on the dash to run it at higher rpm. Everything seemed fine.....until I tried to drive it on the road.

After pulling out of my driveway and driving it maybe a mile up the road it started to buck like it was starving for gas. It couldn't be vapor lock I thought. It wasn't hot out, and when I tried driving it, it wasn't even fully warmed up. It never had a vapor lock problem in the past either. I turned the electric pump on and that seemed to help. If I turned it off again it would start the same symptoms again after a short time. The car would also die on occasion when coming to a stop at a stop sign. One time I drove down the road without the electric pump and it literally ran out of gas. I pulled to the side of the road, stopped, and tuned on the electric pump and it had to run for a good 15-20 seconds before the car would start again.

My thought was that the fuel pump diaphragm had weakened from sitting for 2 years with our modern alcohol laden gasoline. The pump was last rebuilt in 1999 in preparation of driving it to Warren, OH for the Centennial. So, this spring I had the fuel pump rebuilt by Antique Auto Cellar in MA. Put the rebuilt pump back on, drove the car, nothing changed or improved. Car still acted like it was starving for gas.

My next thought was either the gas tank has crap in it and is clogging the pick up tube, or the carburetor is gummed up. Since it's a lot easier to throw a kit in a carb than it is to drop the gas tank, I did the carb first. My thought was maybe it's gummed up or the accelerator pump was bad. Upon taking the carb apart I found the fuel bowl part did have a bunch of loose crap in it, and the accelerator pump has largely disintegrated. The carb had not been apart since the 1960's. I thought for sure this was my problem. I took it all apart, cleaned it thoroughly, used compressed air to blow out all the passages and put it back together
with new gaskets and a new accelerator pump.

Got the carb back on the car today. Drove the car, same results. Still starves for gas after driving a short distance. Still runs out of gas & needs the electric pump run to get it to start again. If I keep the electric pump on while driving it, it will stay running & drive OK.

So now my thought is that it is the gas tank. I think there's crap floating around in there and it's getting sucked into the pick up tube when the car is driving at a higher rpm. I'll post a picture of the electric fuel pump too. I don't think it's blocking the flow of fuel as the car will idle in the yard all day long. It's just when it's under load at a higher rpm that the symptoms emerge. But why would it run in the yard OK with the throttle pulled out to say, 1500 RPM, and not starve for gas?

Before I put the car away for the winter & pull the gas tank I'll ask: What do you guys think? The gas tank was last done in the early 1970's. The Bill Hirsch treatment was used at that time: the tank was sloshed with rust remover, then sloshed with a neutralizer, and then some type of sealer put in. I'm wondering if the alcohol in the gas has loosened the sealer.

If the electric pump is in series with the mechanical pump I would temporarily take the electric pump out of the fuel line and see how it does with only the original. You mentioned installing a rotary pump. While the pulse types generally have no issues with pass thru, some rotaries will not allow the mechanical to pull much fuel past them when the pump is off.

images.oreillyauto.com/parts/img/large/pfp/e16371_p04_ang.jpg

This is what I installed. I have heard of that happening in the past. I think I will try your suggestion before taking down the tank. I may drain the tank as well into a very clean container and see if there's any crud.

Flow thru rotaties really depends on the pump construction. On some of the roller rotaries and rotary vane types, as long as the pump is off and spring pressure or centrifugal force is not keeping the vanes tight to the cavity wall there is enough space between the vane and side walls that some fuel can get pulled past -- albeit not at full flow. On the gearrotor types there is generally minimal to no clearance and fuel is totally blocked unless pump is running.

The use of a check valve and tee setup is recommended for rotaries in series. In that setup a checkvalve parallels the pump. The mechanical pump can still pull fuel thru the checkvalve and the pump (if it lets any fuel pass) for complete flow yet when the electric pump is on the checkvalve closes so fuel cannot go back into the tank and has to go to the fuel line.

Yes, I do remember seeing a diagram showing the proper set up for those in the CCCA Bulletins in the past.

Yikes. You toss 13 gallons of bad gas on the ground? No wonder you don't give your address. Hope you don't live near us. Next time, take stuff like that to a recycling center.

"The car built by gentlemen for gentlemen," remember?

If he dumped the gas tank onto the ground how could he say there was 13 gallons in it?

If he lives in a rural area he can go ahead and burn it. Although I did hear that EPA is putting out a regulation to control God. They want to fine God for the west coast wild fires. Those fires are polluting more air than every power plant and automobile in the nation.

Anyway, I used to hook up a gas can to the fuel pump and run the car on that. If starvation is gone then the problem is in the delivery side of the system.

The technical term for this procedure is "dividing the circuit."

I had an electric fuel pump looking like the one you show in the picture. It is a rotary vane and you cannot pump through it. It has been awhile since I have done this, but as I remember one way to check if your original mechanical diaphragm if moving enough. Take off the air cap (cannot recall the exact name) on top of the pump. Stick a small rod or screw driver in the hole. Turn the engine over and make sure the rod moves up and down about 1/4 inch or more.

Get the GLUE/Old gas out of the lines and carb.?? With a car with bad gas u have to flush the lines or that GLUE coated to the walls breaks loses and gives u hell sticking the Needle and Seat and if didnt go into the carb ur N&S could be coated with the stuff and sticking.

BUT could b another thing. Just when u think u have seen everything something new pops up.

I remember when I had to replace the fuel pump on a '49 Chevy about 50 years go. I bought a new and installed it. Everything seemed OK except when I would get going about 50 mph it would be fuel starved. The condition started occurring at lower speeds. I then replace the pump with another new and the condition was fixed.

I think if I were try to fix the problem I would; 1) disconnect the fuel lines from the pumps & carburetor, 2) fill them with carburetor cleaner & let sit for and hours so hen flush with solvent, 3) replace any filters with new ones, 4) reconnect all of the lines except at the carburetor, 5) turn on electric pump long enough to fill and purge the lines, 6) connect a pressure gauge & measure just before the carburetor to ensure that you at least 3 psi, and 7) measure the volume pumped (refer to specs for the electric pump). If all is well then the last links in question would be the carburetor or a breakdown in the spark side of the issue.

Several notes about electric pumps; 1) place close to the tank as they are designed to push not suck, 2) ensure they have a great ground, 3) place a large filter between tank and pump, & 4) don't skimp on wire size use at least 10 gauge.

Good luck on solving it.