Fuel pump loosing prime?

[Flex BT]

Reading the other thread, I just had a thought... I have the charcoal canister in place in my system and a non-vented gas cap. Is it possible that my (and possibly OPs) gas systems are creating a vacuum in the gas lines and pulling fuel back to the tank after shutdown if the canister isn't functioning as it should?

 

[Posi]

You should have a vented cap.
Try a stant 10811 cap.

 

[Flex BT]

Well damn, that looks just like mine, I thought it was non vented because it says "warning contents may be under pressure" or something.

 

[Lumpy Grits]

You should have a vented cap.
Try a stant 10811 cap.

That's the cap I'm use'n.
LG

 

[IrishCJ6]

I'm glad someone else has this problem because I had the same thing with mine. I stripped and rebuilt the carb twice, replaced the pump and checked all the fuel lines and filters. It got to the point that I would kill the battery or cook the starter before it would fire. Same thing, dry fuel bowl and stubborn fueling. I solved this by installing a electric pump in parallel to the mechanical one. I have it on a momentary switch so use it to prime the carb only. Once primed it fires first turn of the key. Benefits are if my mechanical pump ever fails I can very easily wire the electric one in order to get home. Not perfect but it works for me and it's similar to the old heat coil on a old diesel.

 

[Flex BT]

Are you all using the Weber 38/38 as well or something else? I have that as well as the wrangler charcoal canister conversion.

 

[mriplaybass]

I'm glad someone else has this problem because I had the same thing with mine. I stripped and rebuilt the carb twice, replaced the pump and checked all the fuel lines and filters. It got to the point that I would kill the battery or cook the starter before it would fire. Same thing, dry fuel bowl and stubborn fueling. I solved this by installing a electric pump in parallel to the mechanical one. I have it on a momentary switch so use it to prime the carb only. Once primed it fires first turn of the key. Benefits are if my mechanical pump ever fails I can very easily wire the electric one in order to get home. Not perfect but it works for me and it's similar to the old heat coil on a old diesel.

This is what I have considered doing it. I have been trying to figure out just how to plumb things in though. I am not sure if it is possible to put the electric pump in line with the mechanical pump, thereby using the electric pump to prime the mechanical, or if I should run a "T" in the supply line, and run a separate supply to each pump, then another "T" at the carb for each pump.

Some of my thoughts are: #1 If run in series, will the mechanical pump be able to draw fuel through the electric pump if the electric is not running.
#2 If run in parallel, would the mechanical pump force fuel back through the return line and then backwards through the electric pump if the electric is not running.

I know, why is this guy going through all this convoluted plumbing?!! Why not just go electric only and solve all the problems at once? . Because that would just be too easy! What else would I do with all my spare time?
But seriously, I kind of like the idea of a redundant fuel system given that we do go well off road, and often out of necessity, we go by ourselves.

Flex: I have the Motorcraft 2100 carb. I don't think the Weber 38 was used on the V8's.

 

[Torxhead]

I think you should try the #2 route, just to see if it works. This is an issue that I have seen numerous times before from guys on the forums. I had the same problem with my oem setup prior to installing a t.b.i. I did try the #1 route with a cheap fuel pump that did not last long. I am thinking fuel evaporation though and was hoping you would do some more research on it. Good luck on however you set it up.

 

[Neuner]

Not sure I understand why you want to run both a mechanical and an electrical version? Why not just the electrical?

If you believe it's a must, I think you'd want to run them in series. Also wouldn't have to worry about check valves with that setup. Not sure if the pressure would go through the mechanical when it's disabled but you should be able to check with a simple test.

Seen quite a few use a low pressure carb pump in series to help prime their high-pressure fuel injected pumps because they don't prime as well. Didn't read of anyone having any issues over time.

 

[Posi]

The Jeep I'm building now has a rebuilt 2100, new fuel pump, and new lines. My engine is finished, the only time I start the engine is to move it out of the garage, which can be anywhere from 1 week to 4 months. When I want to start the engine it always starts because there is always fuel in the bowl. It even starts without the choke connected, a few pumps of the skinny pedal and a short cranking period and it fires. Of course without the choke connected I have to feather the pedal until it warms up a bit (it's on the to do list).

I also have a stock CJ in the back of my shop, I always have to add fuel to the carb to get it to fire. The difference between the two, one has fuel in the bowl, one does not.

You can install an electric fuel pump and it will 100% correct your symptoms. The electric fuel pump will pressurize your systems filling the fuel bowl until the float rises to a set level thereby cutting off fuel to the bowl. Adding a E-pump will not correct the problem but will cure the systems. E-pump is a nice upgrade.

Anyone running an electric fuel pump should always carry a spare when offroading.

 

[mriplaybass]

Neuner, as I said before, I just like the idea of a redundant system. I am also a bit of a dinosaur. I like doing things old school. I am slowly learning the electronic end of the hobby, but I still trust the old mechanical parts more. I probably will end up going electric pump eventually, but for now I still like the OEM pump.

Posi: I know switching to an electric pump will solve my problems. I agree, carrying a spare would be a necessity. It drives me crazy because electric was the original plan, but at the last minute last July, I changed my mind, sent the electric pump, pressure regulator, and gauge back to Summit! Now I wish I had kept them.

Any one know how much pressure the OEM pump puts out? Not sure if I need to go the whole route with a regulator and gauge.

 

[Posi]

4-5 psi 6 cyl
5-6.5 psi 8 cyl

 

[Torxhead]

To be on the safe side Bass, I would suggest installing an oil pressure switch for if the engine quits the loss of oil pressure will shut off the pump. Like if you are in an accident on the road or have a mishap in the dirt.