Packard Forum Index » Post-War (1946-54)

I'm sure this has been addressed a million times, but when I do a search I don't really get an answer to my question. I recently purchased a 1949 Custom 8. It's completely stock with the exception of the addition of an electric fuel pump. I've asked another member of the Packard club why this is necessary and he said it just provided some redundancy to the system. However, when I test drove the car prior to buying it, at times it would run rough, particularly during acceleration, and the owner told me to switch on the electric pump, and sure enough, it would smooth out. I've since experienced this same problem many times and I sometimes have to leave the electric pump running continuously. Is this simply a vapor lock issue? It's been in the 90's and low 100's here lately. Why does this not occur with my '50 Ford under the same environmental conditions. The fuel pumps in both cars appear to be in the same temperature environments. Thanks.

Most of us just use the electric pump for priming after a long sit or the occasional "vapor lock" situation. It should not be needed for routine running so I would wonder if the mechanical pump or other parts of your system are up to par. Perhaps something is restricting flow and the extra boost of the electric pump is overcoming some other issue.

If the mechanical pump has old rubber and you use ethanol fuel that could be a problem. There is also a screen in the bottom bowl of the mechanical pump which could be clogged. There is another screen in the carb under a large brass plug just behind the fuel inlet.

Some possibilities others have run into is the rubber hose between the steel line on the frame and pump might be old, internally cracked or has flattened due to a bend and has less flow capacity. If you have the optional ceramic filter next to the carb, if gas was allowed to dry out in the glass bowl varnish could have deposited within the filter element. The usual symptom there is reduced flow and the feeling of inadequate or running out of gas. Diagnosis is a bit hit or miss because air can pass easily leading to belief the element is clean but fuel flow is actually restricted. Frequently the glass bowl never fills up and car runs with a good portion of the element exposed.

The "redundancy" of the electric pump is twofold. First, and most importantly, it cycles fuel through the system more quickly than with a mechanical pump to help prevent vapor lock, but this will only be effective if the system is plumbed with a return loop. Instead of any vaporized fuel or air pockets needing to be pulled through the returnless system and the carburetor by the factory mechanical pump, vaporized fuel is returned to the tank, and the carb can draw from a more solid stream of cooler fuel.

Second, it takes some work away from the mechanical pump, extending its life somewhat. Note that an electric pump can fully replace a mechanical pump, if the pressure doesn't pulse too much and the pressure regulator is set properly.

Regarding the problems while driving, vapor lock is most likely while restarting the vehicle after a heat soak. Engine and chassis heat bleeds into the lines, with no fast-moving air to cool it, and vaporizes some fuel. It is definitely possible to have this problem while driving, but I suspect a weak mechanical pump delivering substandard pressure is a more likely culprit.

Am assuming by your description of having to turn the pump on to alleviate the problem the pump is located inline and pushing fuel thru the mechanical pump. If so, another possibility is the electric pump itself is restricting flow.

Solenoid or pulse types similar to those made by Airtex have regular in and out valves and usually allow fuel to be pulled thru without restriction. A few pulse types can restrict a bit and many if not most rotary types will restrict or even completely block fuel if they are not running.

Lex you are spot on about electric fuel pumps, vapor lock, etc. You may be interested in what I did for my 1956 Packard Panther Restomod:

1956packardpanther.com/Panther/fuelSystem.html

I said when I posted this and others have agreed, this is an "overkill" solution, but it is in the same family as what you were talking about. My solution is race-car based with 115F temps at 3,000FT altitude conditions in mind.

Craig

Added benefit of electric pump is it saves the starter motor from having to fill carb after long or hot shut down also saves the battery. A piece of fuel line to by pass the pump in case of mechanical pump fails on the road is good thing to carry and takes up little space. The electric pump makes for a lot better starting when hot with aupercharged V8 as my 57 clipper has do to carb being inside the box which tends to get hot after shut down.

I don't understand all these problems with the original equipped cars. What did people do in the forties and fifties when the cars were new? My dad had a 58 Buick which we drove until 1966 and we never had any cranking problems. the air conditioner was a problem and it ate up mufflers but that was all. It never failed to crank. I have had my "48 's fuel pump and carb rebuilt and mine is not perfect but I don't think the mechanic has it adjusted and tuned properly. I am using ethanol free regular gas.

I'll second that motion, we've owned hundreds of collector cars from 1924 to the 70's, only one has ever had an electric fuel pump, our 1930 Packard. It has a vacuum tank and due to its previously finicky nature it was fitted with an electric pump in the 60's which it still has.

I drove my 49 Custom Eight hearse 8,000 miles in 5 weeks, cross country and back in 100 degree weather in Mexico and Texas and 12,000 ft elevation crossing the Rockies. Never a missed beat or difficulty running or starting. I always kept it in tip-top mechanical condition.

Our two most driven cars are a 52 Patrician and a 55 Caribbean. They are equipped as original and perform very well.

Thanks for the input from everybody. The guy I bought it from said the mechanical pump only had a few thousand miles on it, so I assumed it was ok. I looked a the sediment bowl today and there was quite a bit of residue on the bottom and the final screen in the carburator inlet was a little bit dirty, but I wouldn't think enough to really limit the fuel flow appreciably.

The sediment in the fuel pump bowl means your tank is most likely rusty inside. It is not the sediment in the bowl that causes a problem, what you see are the larger and heavier debris. The fine brass screen at the top of the fuel bowl traps the silt-fine debris and thus becomes partially or fully blocked.

In the short term I'd suggest you remove the bowl and screen and clean well. Let us know how much the screen is blocked. Clean the carb screen. Then drive the car and see how it goes, after that look at the fuel bowl again.
If dirty at all, subest you remove, clean and seal the tank.

Let us know how it works out

Good luck