fuel pump

fuel pump
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bullpup10

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Las Cruces, NM
I was just wondering if an electric fuel pump can be installed and used in series with the mechanical fuel pump. I would like to do this but am afraid to much fuel will be pumped reducing gas circulation which could cause a vapor lock. thanks:confused:
 
An electric pump can be used as a pusher for a mechanical, but unless you need to do this, it's not necessary... Is there a reason you would need an electric pusher?
 
Thanks for responding CJ. After the jeep sits for a few days if becomes a pain to get it started again. An electric pump would help get gas to the carb much faster. I think what I will do is add the pump and a switch to turn it on and off as needed.
 
How long is it taking to start and what motor/year are we talking about? Maybe your jeep start times are normal for carburetion. These days we are spoiled with fuel injected quick starts and lack of warm up time. If you do install an electric pump the excess gas will return to the tank through the return line (depending upon year) if still installed. Also you will need a kill switch such as modern fuel injected vehicles have in case of a crash or the gas will keep right on pumping and subject you to a potential fire. Who is to say the on/of switch you install doesn’t get bumped or shorted out in a crash?
 
The jeep is a 79 CJ7 . AMC 304 with a 500 CFM Edelbrock carb. It had a 750 CFM before which was way to much. I replaced the sending unit and all the 5/16" rubber fuel lines are new. The fuel filter with the return line. I added a see through fuel filter near the carb so I could see if it was flowing gas. I have read where someone said this wasn't a good idea, don't know why not. If the jeep sits for a few days I sometimes have to add gas to the carb before the battery runs down and it's a new one.
 
I have the opposite problem (1974 AMC 304 in a 1979 CJ5 ). Mine starts up fine after sitting - just push the pedal to the floor to engage the choke...are you doing that?

But once started if mine sits for more than 5 minutes or so it doesn't fire right up. A push of the pedal to the floor I think gives it too much gas? It fires up...just takes about 3 seconds of jiggling the gas pedal.

Depending on how long yours takes to fire, I might suggest testing the battery or alternator if you lose power before it starts. Sounds like a long time.
 
Bit of a guess here but is there air in the second filter? If so then maybe the second filter is slowing down fuel getting to the carb. We know air compresses, when the pump is activated by cranking the motor it may take a little longer to push gas through the line to the carb. This also could be a carb problem. Floats, jets, choke? You were right to go smaller on a AMC 304 . I would take out the extra filter and see if that helps. If that isn’t it look at the carb.
 
One other idea, the fuel pump might be bad and letting the fuel leak back to the tank.
As far as running two pumps you can but I wouldn't, I'd go for one or the other. Your choice.
 
aye, all opinions are valued. 2nd filter is full and only 1/2 full with mech pump. Have installed elect pump with killer switch and functions correctly. Waiting on some parts before I can start jeep. All I can say is I should have gone to Napa or Autozone for ordering these parts. They gave me a time table of 1 day and I've been wait 5 days so far. Talking about frustrated.
 
If I was to do this....
I'd wire the electric fuel pump thru a oil pressure switch, wired to run the fuel pump ONLY when the oil pressure is at/near zero. Then add a rollover cutout switch to that so in case of a roll over, it wouldn't keep feeding the engine with fuel.
Then I'd put a bypass switch on the electric pump, so in case of a failure in the mechanical pump, I could flip the switch and use the electric pump to continue down the trail.

AH but what do I know? My mind wanders sometimes... :laugh:
 
mylittlecj5 said:
If I was to do this....
I'd wire the electric fuel pump thru a oil pressure switch, wired to run the fuel pump ONLY when the oil pressure is at/near zero. Then add a rollover cutout switch to that so in case of a roll over, it wouldn't keep feeding the engine with fuel.
Then I'd put a bypass switch on the electric pump, so in case of a failure in the mechanical pump, I could flip the switch and use the electric pump to continue down the trail.

AH but what do I know? My mind wanders sometimes... :laugh:
Click to expand...

Now there is an example of redundant safety :rolleyes:
 
you lost me when you said "If". I just want it to run down the road and maybe a little bit of playing, no rock climbing.

1 thing that has been bothering me. I just read where someone suggested the fuel filter return port be above the port going to the carb. Someone else suggested the opposite. Which one is correct and why.
 
Adding parts on top of parts that do the same thing is pointless. I would go back the the stock arrangement and make sure it's working correct, there are tests that can be perfomed on the pump or just replace it and make sure the filter is installed correct with off center and smaller outlet on top and going to return line.
My 2C's
 
I agree that the least amount of mods would be best especially in my case. The people I know that have jeeps have the newer ones and don't know how to help me with my issues. Although frustrating I have enjoyed my attempts to fix this one. I have yet to see one like mine so I could get a visuel and to ask questions. For now it's just me and my neighbor. We have done the best we could and is now running. In my case we came to the conclusion that the carb was starving for fuel at higher speeds. We went directly from the fuel pump to carb eliminating the return line for now. Electronic fuel pump will only be used during starting or if mech one goes bad. Now to get rid of those noisy headers.
 
bullpup10 said:
I agree that the least amount of mods would be best especially in my case. The people I know that have jeeps have the newer ones and don't know how to help me with my issues. Although frustrating I have enjoyed my attempts to fix this one. I have yet to see one like mine so I could get a visuel and to ask questions. For now it's just me and my neighbor. We have done the best we could and is now running. In my case we came to the conclusion that the carb was starving for fuel at higher speeds. We went directly from the fuel pump to carb eliminating the return line for now. Electronic fuel pump will only be used during starting or if mech one goes bad. Now to get rid of those noisy headers.
Click to expand...

The other thing I would suggest as you get started with your project is to track down an actual factory repair manual ("factory shop manual") for your Jeep. It is a very important asset that can help you, whether making repairs or mods.
 
I had trouble resolving my fuel issues so I finally had to go to a local shop who works on 4 x 4's and he told me that the fuel lines had been run incorrectly(previous owner) and showed me how to. All new fuel lines, filter in the right place. I did keep the electric fuel pump in line. I turn it on for a couple of seconds before starting to make sure the fuel lines are full. So far the CJ cranks over with very little effort. Now on to the next issue.
 
I would be looking for an air leak in the fuel line between the pump and the tank. It is like a straw in a soft drink, if you put your finger over the end you pick up liquid that stays there until you lift your finger and let the air in. Usually, when the pump diaphragm goes bad it pumps fuel into the oil pan.:cool:
 
I had a problem trying to start my CJ7 . It has a AMC 304 with motorcraft re-built carb. I would have to pump the pedal and keep turning it over to prime the system. Finally someone told me about the fuel filter ( top one with one inlet and 2 outlets) and how it was probably installed incorrectly. Seems as though the side with 2 outlets has to be configured with the outlets lined up, one on top of the other. The outlet that is inline with the inlet is the bottom outlet. The other outlet goes on top. If it isn't configured this way it will siphon the gas back to the tank, purging the system.
I tried this on my jeep and it works. I tried it on my dad's CJ8 and it works. I would try it, doesn't cost anything but about 5 minutes of your time.
 
The first thing I did was replace all of the fuel hoses and yes there were cracks on some. But still the filter was in the wrong location. The 4 x4 shop showed me the correct location for the filter and now that issue is resolved. Thanks for all the inputs.
 
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