I'm not sure about the switches, but I have a keyed-power fuse block on my firewall with a relay to power the Edelbrock EFI sump and Holley Mighty Mite 'lift' pump on the frame to keep it fed - the Edelbrock Pro Flo MPFI ECU handles rollover cut-off duties. When I install the E-Street EFI on my '71 Mach 1, it'll be the same, but for now it just has the same fuse block/relay set-up along with a Mighty Mite as the primary electric fuel pump feeding an Edelbrock 1406 4bbl carb. I turn the key, wait for the pump to quiet down, tap the throttle once and turn the key - fires right up every time. Both Holley and Edelbrock make electric fuel pump installation kits with wiring, relays, and instructions on how to install for rollover safety. Here's a JEGS kit (Doesn't mention rollover cut-off, though) that could get you started: https://www.jegs.com/i/JEGS/555/10564/10002/-1

 

This is a classic example of 'shotgun' troubleshooting.

Even if there is no fuel in the lines, your carb bowl should have gas...enough gas to start the jeep.

I think you have 2 problems...

1. Leak in the carb causing the fuel to drain out. If your oil has a gas smell.....guess what....it's all going down there and diluting your oil.

2. Cracked rubber fuel lines. If you have the original fuel lines, chances are they are old and cracked. Which lets the suck air. They may not leak oil....but will let air in.

 

I would agree on the shotgun approach, but it's a bit warranted. I struggled to find a quality mechanical fuel pump, all the quality brands kept having issues with the diaphragm tearing free.

As a side note, I did just happen to read the recent post regarding the carb not staying primed. Kinda sounds similar, but for me this is something that occurs only after it sat for a long period without starting, so probably not poorly vented tank.

 

Ok....if you're having mechanical fuel pump issues.....electric is an option, In tank is best. But it needs to be near the tank. The rail in front of the tank is a good spot.
That is how I have mine now.....but I'm going to in-tank....mainly for the noise.

Dropping the tank is not a whole lot of fun....but it gets easier after a few times.
Replace ALL of you rubber lines if they are stock.

Make sure your fuel filter is installed correctly (return line on top)

And smell your oil.

 

Cut open your fuel filter. I found rust in mine. I had the same problems of having to crank like hell after the Jeep sat for a few days. It got to the point that it wouldn't start because the fuel pump could not draw fuel at cranking speed even with a new battery. Once the engine is started, it will continue running. Removing the gas cap while cranking didn't do anything so apparently venting is not the problem. I did the troubleshooting procedure using a fuel pump test gauge as per the FSM and it points toward a restricted fuel line.I changed the fuel tank and sending unit 4 or 5 years agos so that should not be the source of the rust. I finally got a new fuel lines (tank to pump and return line). I need to find some time to change the lines.

 

Hard starting after been sitting could still be the choke setup and/or the float level. When was the last time you serviced the carb and set it up as per the manual? This may be a contributory factor, that even when you do get fuel it takes some time to start.

The 3 way fuel filter was designed to be mounted horizontally and slightly above the carb inlet level (about 1/2") , with a U shaped piece of fuel tube between the two. The tank return has to be at the 12 o'clock position. If this configuration is followed you would have around 4 to 5 ounces of fuel in or next to the carb which cannot be siphoned back to the tank by the tank return.

I would still suspect that you may have air leaks and the best way to identify is to put in a short length of clear hose just before the filter. If you see large bubbles, you have a split between tank and pump.

Another test, after it has been sitting for a few weeks, is to open up the hose after the filter and put in a jam jar. Crank the engine until you see a healthy spurt. It should be less than 10 seconds even on a completely empty system.

 

If you do want an electric fuel pump, I suggest a solenoid type. They cost very little and tick away and stop when pressure builds up against the spring. They are not capable of overpowering the inlet valve of a Weber or Carter etc. Having one moving part they are reliable. They suck well so do not need to be near the tank, I mount them on the fender in the engine bay.

Something like $12

They draw very little so perfectly safe just to attach them to the ignition circuit.

You could arrange relays so that it is controlled by the light blue wire at the solenoid, live in Start, and the auto choke wire which should only be live when the oil pressure switch closes. This will only power up the pump in Start and when running.

 

...

Relay wires

• 30 power
• 85 ground
• 87 to pump
• 86 to "S" terminal and oil pressure switch?

Ahhh, no, Once the oil pressure switch is activated you would be supplying power to your "S" terminal also which will keep the starter running.

I would run an push button override the relay momentarily or one of those timed relays to activate the fuel pump as soon as you turn the ignition ON.
The timed relay is like the one that will operate your dome light after you turn the car off so the dome light will activate for a set time so you can get out of the vehicle.
Some thing like this.

Time Delay on Release Relay - 12V DC, 30 Amp | Del City

Time Delay on Release Relay - 12V DC, 30 Amp: Optimize vehicle lighting and other applications with this 12-volt change over relay featuring adjustable timing from 2 seconds to 3 minutes. Easily modifiable using a waterproof cover and potentiometer, it fits standard 5-terminal configurations and...

www.delcity.net

What will happen is once you turn the ignition to ON, the timer relay will run the fuel pump for what ever time you set it for and then shut it off.
If you have'nt started the engine, then the fuel pump will shut off. If the engine starts, then the other relay will keep the fuel pump running.

But you might not need any of this. most likely you will build up oil pressure fast enough to start the pump up anyway when cranking the engine.

Some other Ideas with a push button, There are other configurations.

 

Ahhh, no, Once the oil pressure switch is activated you would be supplying power to your "S" terminal also which will keep the starter running.

I would run an push button override the relay momentarily or one of those timed relays to activate the fuel pump as soon as you turn the ignition ON.
The timed relay is like the one that will operate your dome light after you turn the car off so the dome light will activate for a set time so you can get out of the vehicle.
Some thing like this.

Time Delay on Release Relay - 12V DC, 30 Amp | Del City

Time Delay on Release Relay - 12V DC, 30 Amp: Optimize vehicle lighting and other applications with this 12-volt change over relay featuring adjustable timing from 2 seconds to 3 minutes. Easily modifiable using a waterproof cover and potentiometer, it fits standard 5-terminal configurations and...

www.delcity.net

What will happen is once you turn the ignition to ON, the timer relay will run the fuel pump for what ever time you set it for and then shut it off.
If you have'nt started the engine, then the fuel pump will shut off. If the engine starts, then the other relay will keep the fuel pump running.

But you might not need any of this. most likely you will build up oil pressure fast enough to start the pump up anyway when cranking the engine.

Some other Ideas with a push button, There are other configurations.

As usual John has the best solutions.

Mine was just two ordinary relays. One energises the pump in Start, the other when the oil pressure switch is engaged from the auto choke. There would be no feedback to the Start circuit as the relay would be open.

But John's solution is so much better I feel ashamed of my inadequacy.

 

If you only need the e-pump for priming the carb, why not simply use a momentary-on switch? Would there then be no need for safety interlocks?

 

The 3 way filter is set up as described, I do have some clear inline fuel filters, I'll toss one of them on when things warm up some, to check for bubbles right before the carb.

I really like the idea of a momentary switch, keeps things simple and easy. I only really would need to prime it on occasion when I haven't started it in a while.

 

just repairing the problem and staying with mechanical pump is the simple solution
handy that it shuts off when engine does to limit the after crash fire
has worked in the carb fed jeep engine for how many decades?

 

Well considering I've gone through 4 fuel pumps, including the old pump. Then had to Frankenstein the arm onto a new body for the fuel pump to work correctly, a mechanical pump is no longer the simple solution.

The new fuel pumps that are being produced do not match the old ones. Wish I could tell you when they changed but ik they are different, the arm angle changed causing to much pressure, then in about 3hrs of drive time the diaphragm blows open and you got gas puking out as your going down the highway.

My problem may not be solely mechanical fuel pump related, but now that I don't 100% trust these new pumps might as well go with an electric

 

John, kind words but my ideas are rarely right.

BUT TOPLESS TODAY, WAY HAY!!!!!!!!

 

I use NAPA part number ECH OP66256 oil pressure switch wired as in the diagram. This switch allows power when the starter is engaged, and when you let go of the key the oil pressure keeps the switch in contact. I also buy a three prong headlight pigtail which plugs right into this switch. For my relay I run the ground wire through a Ford intertia switch which will kill the pump in an accident, but is easily reset.