The question may sound silly to most of you, but it's because I have no experience on electric pump based fuel systems - Never had to mess or repair even a modern car fuel pump, only mechanic pumps... Q: When I install an after market electric pump in a car that originally ran a mechanic pump (now removed) - do I need to have a pressure switch (or something similar) to regulate the pressure (and flow)? The car is 40's Buick with two carb set up. The original mechanic pump has been removed and lost by previous owner. The electric pump is unbranded aftermarket unit. I have no idea of the flow capacity of the pump, but if I leave it on, the carbs start to flood. (It may also be that the carb float chamber valves are worn) However, my question is; are the electric pumps generally "self regulating" or does one need to install a pressure switch to shut off the pump when the fuel line is full and pressure builds up?
You need to know what pump you installed. There are 140 GPH pumps on the market for fuel injection systems that will require a carburetor, bypass style regulator to knock that pressure down to 4 or 5 psi. Many pumps are built for carbureted vehicles that are self regulated.
I tried to search the pump performance figures in web - Most probably it's 2-3 quarts/min at 4.5 psi. small pump. In case it is self regulated - how the regulation is built in? What is the mechanism that makes the pump self regulated? I suppose it must have something to do with the pressure, but which way? Is there internal by-pass valve or is it simply the pump "dies" when the pressure builds up? i.e. there's no power to pump against high pressure in the line?
You need to install a fuel pressure gauge to start with and check your pressure, you are most likely going to need to run a fuel pressure regulator. Those old carbs on that motor probably won't handle much more than about 2 PSI.
It's kind of like women, I have one but I don't understand her. I have several in-line pumps that I pulled off of cars over the years, never seen inside them. I also run a 140 GPH pump in a couple of cars, there is a big difference in volume between fuel injection pumps delivering 45 psi and 110 + GPH and 25 GPH carbureted pumps delivering 4 psi. What does yours look like? (the pump, not your woman)
The fuel pressure gauge is a great idea! Assuming the dual carb setup is original, the carbs could be either Stromberg or Carter. Both were designed to be adjusted with 5 psi at the entrance to the carburetors. Jon.
Thanks Jon. I wasn't sure what the old carbs took in the line of pressure and was being on the safe side of ignorance.
I have an Aeromotive 11209 pump with a 13222 regulator. The pump has an internal bypass at 7psi, but I needed it more like 3-4 for the carbs on the 3x2, so the 13222 will let me set it that low. Also have a gauge on the regulator.
Just out of curiosity, can you not get a mechanical pump for that car? Sent from my iPhone using Tapatalk
Looks like this... Now that I searched for the picture, I noticed that it looks just the same as a Facet-brand pump. Also the same flow volume, a bit over 2 quarts/min.
Well, I COULD, I suppose... Seen used ones at eBay at $120...160, rebuilt ones $180...250. I would like to have one, but... 1) I'm in Finland - takes time & money to get one from there 2) possibility that second hand pump from eBay would have issues 3) do not know the reason why the original was removed and delete plate put on (is the cam running the pump OK?) 4) just need to get the car running for now to be able to move it during my re-build project 5) I do have this un-used electric pump in my garage, just need to make it work in this car for now...
I'm in Sweden, and that looks like Biltema's universal fuel pump (scroll down on the page) that comes in two versions; 130 l/h @ 0,38 bar OR 130 l/h @ 0,56 bar (34,3 gallons/h @ 5,5 psi OR 34,3 gallons/h @ 8,1 psi). Note that the pump is a pressure pump, that should be mounted near the fuel tank, not in the engine compartment. If 0,38 bar/5,5 psi is too high for your carbs, get an adjustable pressure regulator and a gauge, then dial in the correct pressure for your carbs. There are simple regulators that works without a return line. Something like this should work: https://www.summitracing.com/int/parts/hly-12-803/overview/ In my Model A I built a full return system, but that was because of my concerns regarding vapor lock in the cramped engine compartment (hood/hood sides and Cadillac 390).
Hi Kaspar, You got it right, I bought this pump from Biltema years ago (for another car, which in the end did not need it...) Did not mentioned Biltema here, because I assumed no-one would know it anyway... I mounted it next to tank and it is pumping OK, the flooding is the problem. Thanks for the advise, I'll get me a regulator. Still this leaves me wondering; will the pump be running all the time, even if the pressure would be 0,5 bar and the lines full?
Yes it will be running, I guess you can say that the pump will work "against" the regulator when it drops the pressure. Here's an article on the subject: http://www.onallcylinders.com/2017/...ressure-regulators-low-pressure-fuel-systems/
I see the issue! You will have to have a regulator. The pump runs all the time and the floats and needle and seat stops the flow AT the proper pressure. The pump is over powering your floats. Holley makes a simple regulator which you can change the dial on to lower the pressure. About $40 USD. All the regulars like Jegs, Summit, Speedway has them. Sent from my iPhone using Tapatalk
Just make sure you get a regulator that goes down to low single digits, say 2-4 psi, there are regulators that only dial down the flow to 14 psi, that wont help you.
Reading the rest of this thread, I agree with what everyone is saying for the most part. Pressure regulators are often required when using an electric fuel pump on an older carbureted engine. It also sounds like you haven't ever had this car running without the carbs flooding out, and I would hate to see you chasing your tail with fuel pressure to cure a bad float or needle and seat. I don't know if you guys have ethanol in your fuel in Finland, but here in the states we have it and the ethanol plays hell on the old school carbs.
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