I have a couple questions and hoping for some advice. I am in the process of getting my 1933 Chrysler Royal 8 ready to hit the road. It has a 1976 400 for a motor. The mechanical fuel pump is still in it. A friend suggested I get an electric pump. Will a 5-9 PSI 30 gpa pump be sufficient? Also, do I add the electric pump to the existing one or remove the mechanical one? Never did this before. Bought the car last summer from an elderly friend and towed it home,haven’t drove it yet. Thanks for any help you can give. Love this site.
Some people will install an electric fuel pump before the mechanical as a supplement and switch it on to initially fill the fuel bowl(s) after sitting, or to help with vapor lock issues… Otherwise I would probably pick one or the other, ie remove and block off the mount for the mechanical pump, or just run the thing as is. Both pumps have their own issues… Electric pumps can be finicky and unreliable, so you want to be careful which one you pick, and always have a spare. They can also be incredibly loud; I’m talking louder than your exhaust in some cases. Parts store offerings of SBC mechanical pumps lately have been of particular low quality, often outputting 10-12 psi instead of 5-6. I bought an edelbrock mechanical pump ($$) a couple weeks ago because of this. The real question is, what prompted him to suggest that?
If you are not having any problems with the mechanical pump why bother installing an electric pump? Just more stuff to leak or quit working.
I really want to like electric pumps. They take the heartburn out of fuel pumping, not being anchored next to the frame like mechanical pumps. But . . . . they can be unreliable for sure. I put an Carter rotary vane pump on my Willys and ran it for 15 years. Then it just stopped. I got another one and it lasted a couple months, then stopped. I bit the bullet and got a ******** one (Holley?). A tiny bit noisy but not that bad. It lasted a couple months then quit. Am on my second ******** which has been going a couple years. Since I really like the Carter rotary I decided to open it and see what was wrong. turns out the motor runs submerged in gasoline. Over time, the gas precipitates a s*** on the commutator, insulating the brushes from electrical contact. I polished the commutator with 400 wet or dry and voila!, motor runs great. I found a V-clamp that I can ***emble the pump back together, liquid tight so now I have the best of both worlds. A rotary vane pump that I can service. This is the clamp and opened pump. It is actually a 12V pump, not 24V. Don't know why they put that sticker on it. Carter installs a really thick rubber gasket so it seals back together perfectly. I opened the pump by grinding off the crimp of the can all around the top edge. Here is the pump, serviced, sealed back with the new clamp, ready to run another couple months before it stops again!! I don't understand why Carter didn't make them serviceable.
Define "Vapor Lock Issues" Is is difficult to start after sitting for a while ??? Or does the engine cough and splutter when running for a while ??? [in traffic] Generally for safety ,you should not run continuous pressure on the inlet side of a mechanical pump. If there is a leak, it can fill the oil pan with gasoline. If you just need a pump to prime the system for starting the engine, use a cheap Chinese "Facet" [cube] style flow through pump [aka solid state pump] These pumps act like a one-way check valve when not pumping, so the mechanical pump can draw through it easily. Some people connect these pumps to a simple primer ****on, but I've connected them via a relay [that grounds via the oil pressure sender] so when the engine is running the pump automatically switches off. The most reliable dedicated electric pumps are OEM EFI pumps with a return line. You Tee off a deadhead pressure regulator close to the carb. The Fox Body crowd do this ^^^ a lot with EFI to carb conversions Next pump of choice is the USA made Walbro FRB series [these are US Coast Guard rated] but down my way they are expensive
If you install an electric pump, you can use a momentary/full time toggle switch (mounted under the dash), so it has momentary contacts which will let you top up the carb bowl if it's been sitting for a while, and then the standard "full time" on position which lets you switch the pump in to work in case your mechanical pump lets go (as long as you still have flow through the mechanical one).
I have a high volume mechanical pump in the engine and supplement it with an on demand electric pump mounted near the fuel tank. Here is how it is wired, the pressure switch will cut off the electric pump if the engine looses oil pressure ( like in an accident) so raw fuel is not pumped without the engine running. I have switch on the dash that turns the electric pump on when needed.
The issue with running both a mechanical and an electric in series is if the diaphragm on the mechanical ever fails all the gas is going to get pumped into your crankcase and you wont know it's happening until you lose an engine! I'd never use both together in any build I did. I might consider an electric in parallel with a separate fuel line to fill the carb, but not sure it's worth it really. After my hotrod sits all winter I simply pull the air cleaner and squirt gas into the bowls through the vent tube and it fires right off.
The Jalopy Journal
