More on auxiliary fuel pumps





Well, I guess I did it again and got another argument started. It is always flattering when my articles are copied by other Regions and/or by the national The Self-Starter.


After all, I write these articles for two reasons. First of all, to share experiences that may be helpful to other lovers of these fine old LaSalles and its companion car Cadillac. The second reason is for the thousands of dollars I get for writing them and the additional royalties I get from the reprintings. The latter seems to have fallen by the wayside, so I guess I’ll just stick to the former reason.


Last January, The Self-Starter reprinted an article from our Regional newsletter about hot starts on these old cars. In that article was incorporated some information from an article a few years ago that had a full explanation of the reasons for parallel installation rather than series for auxiliary electric fuel pumps. Since Mr. Fay or Mr. Bentwrench may not have read that article, and for some of you Regional members that might have missed it, we will review some of those reasons.


Those of you who are acquainted with me personally know that I have worked on and loved these old flatheads since the early 1940s. Included is a fair amount of competitive racing, most of it being in the high altitudes and mountain roads of Colorado. We do have some differences in performances, problems and solutions than those cars at sea level.


First of all, let’s review the needs and benefits of installing an auxiliary electric fuel pump. Primarily it is to recover from, or prevent, vapor lock. Secondly is that it makes it easier to start one of these old cars after sitting a while and makes it much easier on the starter motor.


The third reason is to keep from starving the engine on long uphill pulls, mountain passes, high altitudes and hot days, no matter where you are. When the car is starting to starve, it starts to lean out the fuel mixture. The car runs hotter and adds to the problem of overheating, especially on a long, hard pull.


In addressing the problem of judges and modifications, I have been judging at Grand Nationals and Regional Cadillac-LaSalle Club meets for several years as well as the CCCA. At judges’ meetings it almost always comes up about electric fuel pumps. The rules are simple: first, it must be auxiliary, not primary (or only) and the mechanical pump has to be working. Secondly, it must be neatly installed in a workmanship manner.


Speaking of installation, now would be a good time to mention a few installation tips before continuing. You should have a replaceable inline filter above the rear axle higher than the tank. Then you can change the filter frequently without spilling a lot of gas. As for the fuel pump itself, the best place is on the frame about mid-car, lower than the tank, but high enough to be as much out of sight as possible.


Personally I prefer the Carter P4259 (6V) rotary—it is much more silent than the pulse type. When wiring in the pump, there are three pieces of advice. First, get your power for the pump from the accessory side of the ignition switch so there is no possible source for power when the key is off. I’ll let your imagination figure out the safety reasons for this.


Second, use a push-pull switch rather than a toggle switch and mount it in an unobtrusive but handy location. That way there is no confusion as to which way is on or off. Third, be sure of your polarity. You don’t want to be pumping gas from the carburetor back to the tank.


As for under the hood, rather than hooking the line directly to the carburetor, install a tee at the “out” side of the mechanical fuel pump. That way most of the plumbing is low, mostly out of sight and neat.


Down to my reasons for parallel rather than series (inline) which are really very simple. The first obvious reason is that the mechanical fuel pump works easier when it doesn’t have to pull through the electric pump, just like Mr. Bentwrench stated. Actually, that is more than you might believe. If you doubt this, try hooking up a hand vacuum pump on the “out” side of the electric pump, test it and then do the same thing on the line before the pump. I know that test impressed me when I tried it.


The second reason is that pressure from the electric pump into mechanical pump can cause premature failure of the diaphragm, and if the diaphragm ruptures, you could still run the car but you could be pumping raw gas into the crankcase. If you are in parallel, your mechanical can fail completely and you can still drive the car without serious side effects.


For many years I used and installed electric fuel pumps inline or series, and agree with many of you and that it worked fine on my own ’40 LaSalle. I changed over to the rotary pump several years ago and enjoyed the silence. About four years ago I reluctantly changed over from series to parallel.


The following results were experienced. An immediate improvement noticed was the fact that I didn’t have to use the electric pump nearly as much. Secondly, I have not had to rebuild or replace the mechanical pump since. The car seems to run cooler, especially on long mountain passes. By switching on the electric pump on a hard pull before really needing it, I can drop 15 degrees of temperature on a hot day, especially at our high altitudes. As the old saying goes, “Nothing succeeds like success.”


I’ve learned a lot since the mid- to late ’60s, when I wrote articles for the old mimeographed The Self-Starter and they carried me as a tech advisor for 1940 LaSalles. Some methods have stayed the same and some have improved. After all, someone once said, “The glory of youth is in strength and agility, while the glory of our elders is in wisdom and experience.”


See ya next month,