Electric Fuel Pump and Mechanical Fuel Pump Combined Use
To be able to obtain quick starts is it possible to setup an electric fuel pump and a mechanical fuel pump in-line to work in conjunction with each other? Near the tank should I install in-line a clear filter to the electric fuel pump, which then sends gas to the mechanical fuel pump at the engine, which then pumps gas to the carburetor?? After the mechanical pump is primed by the electric pump will I be able to switch the toggle switch off to the electric pump and the mechanical pump will fuel the carburetor? Or will I have to setup a bypass line? For judging purposes I am trying to keep the vehicle as original as possible. I AM UNCLEAR ON HOW TO ACCOMPLISH POSITIVE RESULTS. I NEED EXPERIENCED INPUT. If you have knowledge of a publication that I would be able to refer to for illustrated information, please recommend.
Thanks.
W.W.
W.W.-
I can answer part of your question, based on my own experience. My '36 Plymouth had a 6 volt electric fuel pump and rubber fuel lines when I bought it in 1990. It ran well with that setup until last summer, when it stalled on the highway, probably due to hardened fuel lines and an aging pump.
I replaced the lines with new rubber lines and a 6 volt electric pump (Carter) from Summit racing. Shortly after this, the car began stalling on the highway, and I thought it was due to vapor lock, as it was 90 degree summer weather.
After some investigation, I now believe it was actually a flooded carburetor causing the stalling, due to the fuel pump putting out 6? 1/2 PSI. My various manuals (MOTOR'S,? '36-41 Plymouth repair manual, etc., all disagreed on the PSI for the original mechanical? fuel pump, citing anywhere from 2? 1/2? to 4? 1/2? PSI.
So I bought an adjustable fuel pressure regulator from Summit racing, and after some experimenting, it is now set at 3 PSI, and the gas mileage, which had plummeted to 8 mpg with no regulator, is now between 12-13 mpg, on a engine with 110,000 or so miles on it.
The setup, proceeding from the fuel tank toward the carburetor, is: clear plastic fuel filter, fuel pump, fuel pressure regulator.
If you only intend to use the electric pump for quick starts, it may not be critical to have a fuel pressure regulator in your system. If you intend using the electric pump for highway use, you may want to determine the PSI of your mechanical pump and match the electric pump to that PSI as close as possibe.
I'm sorry, I can't help with the other part of your question, about having both pumps operational.
Regards,
Pat O'Connor
My e-gaspump setup is only used for the starting procedure, as the mechanical pump is in good working condition. I just wanted to avoid to have the starter move the whole engine just to get some gas to the carb. Gas line shunt is fuel hose just clamped together. Will not be electible when judged.
Greetings! Go
One thing I didn't mention in my earlier post about 6 volt electric fuel pumps:
After my original (in the car since 1990) pump failed, I replaced it with a bellows type pump made by Walbros. It ran OK for about a month, then it stalled (fortunately, right by a gas station). I went in the station to get some jumper wire to wire the pump directly to the battery.
By the time I got the wire (about 5 minutes), the Plymouth started without a jumper wire, and I made it home (5 miles).
No longer trusting the Walbros pump, and wondering if gasahol would attack the bellows, I spent just over 100 bucks on a 6 volt rotarty vane type Carter pump from Summit Racing. Much of the available fuel around north central Illinois has 10% alcohol, so the Carter pump gives me one less thing to worry about.
Since installling the Carter pump and the adjustable fuel pressure regualtor, the '36 has been running fine.
Regards,
Pat O'Connor
Dear WW, got Your e-mail questions:
a) Filter: I have a filter just ahead of the carb. It has a glass housing which is very easy to look for gunk in the filter webs. I never found dirt in there, so I settled with it and didn?t think of another one. I never had the currage to look for the built- in one in the gas tank port. It should be a kind of metal mesh, and I feared to mobilize unwanted quantities of dirt history.I will do if I have to take the hole tank out one day. If You want to put a filter, which is a good idea anyhow, You better choose the high point ahead of the carb. If choosing the low point ahead of both pumps You will have to drain the hole gas system when taking the filter mesh out for cleaning. I don?t think that both pumps are too sensible for small dirt particles, it?s more the carb with its tiny pin holes.
b) Yes, I switch off the e-pump as soon as the engine starts running. I don?t need it any more than. Consider too, that in case of an accident the e-pump is an additional fire hazard continuing to spill gas on the ground. For 12 V You find an electronic savety device for switchuing it off, but I didn?t find one for 6V. Alsoo, You don?t have the overfilling problem of the carb. If the mechaninical pump fails on the road, You can use the e-pump to reach home, too.
c) I use plastic gas T- Tubes fitting right in the (ruber?) gas hoses,and metal clamps to fix all. The mechanical pump doesn?t need a directional valve, as the built in valves do.
Greetings! Go
sorry, I was early this morning at 5:30 AM, so please ignore all the double characters.... Go
The early V8 Fords (32/53) were very prone to fuel pump/vapor lock problems because the fuel pump sits on top of the engine and the pump push rod had a habit of wearing down causing a short throw on the pump arm. I learned in 1954 that the only true way to solve/eliminate the problem was to install an electric fuel pump in the fuel delivery system. I have a '36 Ford coupe which I have had since 1952, I installed an electric pump, as a backup to the mechanical pump in 1954 when the mechanical pump failed while driving between Las Vegas and Los Angeles late one night.
As a general rule electric pumps push better than they pull so it is best to mount them as close to the tank as possible... There is no need to remove the mechanical pump if the diaphragm is in good shape. If the diaphragm is ruptured/split it will allow raw fuel to enter into the engine oil supply. I have installed the electric pumps two ways.
1. Installed directly into the fuel line...
2. In a loop around the main fuel line....
I prefer the direct line connection because you don't have to mess around with valves to stop the fuel from just returning to the tank.
A word of caution !!!!! To correctly hook up an electric pump.... you need to install a pressure switch into the oil pressure system, ie; between the oil pressure sender and the block. The pressure switch will turn the electricity to the electric pump off in the event of an accident. The engine will supply enough oil pressure to activate the switch when the starter cranks the engine over....... The only problem with the pressure switch is that you can't turn the electric pump on to pump fuel into the system on a vehicle that has been sitting for awhile..... if you are using the electric pump as the only source of fuel delivery, then the pressure switch is a good idea.
I have found that unleaded fuel is not friendly to the older fuel systems. I have electric pumps on several vehicles, they have all failed in the last few years, as have all of the rubber fuel lines, fuel pumps and carbs. If you purchase a new fuel pump, parts for your carb or rubber/plastic fuel line, make sure that the products you purchase are friendly to unleaded fuel.
I have an electric fuel pump in my '39 Plym... the pump is tucked up into the frame back by the hump over the differential. If the car is up on a hoist you can see it but when the car is on the ground it is very difficult to find. The pump is only used to aid in starting the car if it has been sitting for awhile....Bill
I also forgot to mention previously that my electric fuel pump is wired to a toggle switch, so that I can prime the carb after the car has been sitting for a few days (or weeks).
This is not as safe as a pressure switch, but it does allow you to prime your carb, and in the "off" position, it is also a theft deterrent.
Regards,
Pat O'Connor
Pat,
Thanks, you and Dennis have been of GREAT HELP. I now have a better understanding.
W.W.
Bill,
Thanks also to you "Bill" for your help.
W.W.
I prefer to run electric fuel pumps, mounted as near the tank as is reasonably feasible, on our vehicles. Its prudent to carry a new spare electric fuel pump when any distance from home, tho, as they can and will fail without warning.
On some of the vehicles, I've run the lead to the fuel pump from a terminal at the battery, or starter switch/solenoid, with an in-line fuse, and a manual switch concealed up under the dash.
On others, the fuel pump is fed from the accessory or ignition side of the ignition switch, with the same sort of in-line fuse, and concealed switch. If the ignition switch is capable of feeding the electric pump load as well as the regular ignition load, that is preferable, in my opinion, as you neen't always remember to switch off the pump before stopping the engine.
A well-concealed fuel pump switch, assuming you're not running the mechanical pump also, is a reasonable theft deterrent, as a thief may jump the ignition, but not know about the fuel pump and its switch, so he'll not get very far. It also works to have the fuel pump switch right in plain sight, but with an old label, such as 'siren' or 'siren brake', fog lamps, or some such.
I've set up a number of the old Dodge/Ply cars and trucks with a blanking-plate on the block for the original mechanical pump mounting, an electric pump, with the fuel tubing ran as far from the manifolding as reasonably possible, and wrapped in thermal insulation.....this does make a difference on really hot days, particularly at high elevations.
cheers
Carla