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Electric Fuel Pump Questions

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CamJam View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Topic: Electric Fuel Pump Questions
    Posted: Jul/15/2017 at 11:33am

I'm thinking of trying a low pressure electric fuel pump as a fix for vapor lock problems on my '72 Javelin.  My question is whether I should also plan to install an inertia safety switch or some other kind of safety switch in the event of a collision?  I'm just wondering what others have done?

Looks like it would be fairly simple to mount a pump on the frame rail near the tank, and then it's just a matter of getting 12 volts to it.  I'm thinking that I could maybe get that from the line that feeds the trunk light?
'69 Big Bad Orange AMX 390
'72 Baja Bronze Javelin SST
'70 Opel GT
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rockAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 1:58pm
I use the smallest pump I could get from summit racing (Professional Products 10700) to use as a helper pump, but kept the mechanical pump. I wired a toggle switch under the dash to operate the electric pump. Turn the pump on for 10-20 seconds to prime the carburetor then turn it off before starting the car. You need to install a check valve near the fuel tank so the electric pump doesn't just pump gas back to the gas tank. Is it just a hot start problem?
DWR
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 2:08pm
Originally posted by rockAMX rockAMX wrote:

I use the smallest pump I could get from summit racing (Professional Products 10700) to use as a helper pump, but kept the mechanical pump. I wired a toggle switch under the dash to operate the electric pump. Turn the pump on for 10-20 seconds to prime the carburetor then turn it off before starting the car. You need to install a check valve near the fuel tank so the electric pump doesn't just pump gas back to the gas tank. Is it just a hot start problem?

Thanks, that's kind of what I had in mind, though I thought I could just keep it running as a helper pump all the time. 

It sometimes dies on hot days while driving too. At first I thought it was a coil problem, but there's definitely no fuel at the carb when it happens. I've replaced the mechanical fuel pump and tried moving/insulating fuel lines, but it still happens on occasion.

I'm confused about the check valve. Won't the fuel pump pump in one direction only?
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'70 Opel GT
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Post Options Post Options   Thanks (1) Thanks(1)   Quote rons Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 4:59pm
First, why is your car vapor locking? I live in Tucson, so we have similar temps. Does the '72 have a feedback system. That is, is there a 1/4 fuel line going back to the tank from the gas filter. The fuel filter will have two outlets ... 5/16" to the carb  & 1/4" to the gas tank. This is there to prohibit vapor lock/starvation. The later nipple must be in the top position. Have you checked the fuel pump outlet pressure? When Fpumps get weak from age they lose efficiency... hence fuel starvation, especially under load. I believe that the Professional 10700 is a pump that is designed to  replace the mechanical pump entirely(AKA geroter pump) . I would advise after verifying that the system is up to par, then add an Airtex 8012. It is a full flow style, meaning that fuel will have very little , if any, resistance, passing from the tank to the mech pump. Solenoid style( like this one) are made to be installed in line. They can be turned off whenever you wish to run on the mech pump alone.  They are good for priming when the car sits for more than week or so. There are some issues running any electric pump full time through the mech pump. Collision is one. Oil pressure two pole switches are made for that. When oil pressure drops to below 15psi the current is halted to the EPump.  2nd. running gas pushed by an Epump through the mech pump depends on the mech pumps diaphrams not leaking, but if they do fuel can enter the crankcase. Keep this in mind. Best of luck. Ron

Edited by rons - Jul/15/2017 at 5:07pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rockAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 5:06pm
The pump I use is self-priming. Not sure about Airtex which is a much bigger physical size. Below is a diagram of what I did. It has worked well for me. I would not install an electric pump inline with the mechanical pump. The mechanical pump will have trouble drawing fuel through the electric pump if the electric pump is switched off.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote rockAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 5:30pm
There is also the consideration that the electric fuel pump must be mounted above the bottom of the gas tank and the outlet side (pointed towards the front of the car) mounted at a 45 degree angle upward. That places a heavy limitation on the size and style of electric pump to use. I bought the Airtex pump - it is cheap and easily available - but it was too big to meet the mounting requirements. I never run the electric pump while the engine is running.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 5:47pm
Originally posted by rons rons wrote:

First, why is your car vapor locking? I live in Tucson, so we have similar temps. Does the '72 have a feedback system. That is, is there a 1/4 fuel line going back to the tank from the gas filter. The fuel filter will have two outlets ... 5/16" to the carb  & 1/4" to the gas tank. This is there to prohibit vapor lock/starvation. The later nipple must be in the top position. Have you checked the fuel pump outlet pressure? When Fpumps get weak from age they lose efficiency... hence fuel starvation, especially under load. I believe that the Professional 10700 is a pump that is designed to  replace the mechanical pump entirely(AKA geroter pump) . I would advise after verifying that the system is up to par, then add an Airtex 8012. It is a full flow style, meaning that fuel will have very little , if any, resistance, passing from the tank to the mech pump. Solenoid style( like this one) are made to be installed in line. They can be turned off whenever you wish to run on the mech pump alone.  They are good for priming when the car sits for more than week or so. There are some issues running any electric pump full time through the mech pump. Collision is one. Oil pressure two pole switches are made for that. When oil pressure drops to below 15psi the current is halted to the EPump.  2nd. running gas pushed by an Epump through the mech pump depends on the mech pumps diaphrams not leaking, but if they do fuel can enter the crankcase. Keep this in mind. Best of luck. Ron

There is a second line going back to the tank, but I believe that this is just a vent line.  It goes to a small rollover valve on the driver's side above the tank.  In the engine bay it connects to the vacuum canister, not the fuel filter or pump.

I changed the fuel pump when the problem first started. The new mechanical pump is a NAPA B-0107-P.  I also just picked up an electric pump from Napa, but I haven't installed it yet. 

Good thought on the diaphragm. If I have to run a wire to the oil pressure switch anyway I  might as well just run it to a toggle under the dash instead and turn on the electric pump only when I need it.
'69 Big Bad Orange AMX 390
'72 Baja Bronze Javelin SST
'70 Opel GT
'07 BMW 335i
'13 Ford Focus ST
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 5:49pm

Duane, thanks for your diagram. It explains why you have the check valve.
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'70 Opel GT
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rons Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 7:29pm
I have a '78 Concord "6". So, there are many more lines under the hood. The line from the tank to the charcoal canister in your car is a vapor line. The fuel tank vapors are purged from a vacuum port on the carb base. I wonder if you could run a second 1/4" fuel line back to the tank. I did that in my Hudson. The fuel is returned in a circulating path cooling it off and eliminating " bubbles" in the fuel line. That required me to make a hole in the fuel filler pipe, and add a .030 restrictor fitting in line, to maintain fuel pressure. I also wrapped the lines in mylar  ( obtained at Jegs).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 8:42pm
IMO I would start insulating the lines before installing another pump. I have a feeling that's not going to cure your problem if you really do have vapor lock in the lines. Try insulating the lines where it's closest to heat sources like the exhaust and the line that runs from the pump to the carb since it's close to the block and heads. If you notice an improvement, keep going and you'll probably fix it. I've used "Cool Tube" from Boom Mat on several cars with very good results.
In order for that pump to overcome vapor lock, the pressure will have to a lot higher than you needle valve and float can handle.
As for a return, believe it or not, you'll add more heat to the fuel than cool it which will make the problem worse. That's one of the reason the OEM's did away with it on FI systems.

"It was long ago and it was far away, and it was so much better than it is today" Jim Steinman
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