Fuel issue

[dtrojcak]

I have a '78 CJ7 with the 4.2
If I crank it every day, it starts right up.
If it sits for a few days, I have to crank for 30-60 seconds before it will fire up.
What I think is happening, is the fuel is draining back into the tank, leaving the fuel lines empty.
If I let it sit for a few days, it seems the fuel is also evaporating from the carb bowl.

I'm considering adding an electric fuel pump to fill the carb bowl, hopefully eliminating the long crank times.

My questions are:
1. Where should I mount the electric fuel pump? I'm thinking somewhere close to the existing mechanical fuel pump for ease of installation and wiring.
2. Should the electric pump be located before, after, in parallel, or in place of the mechanical pump?

I'm thinking of putting the electric on a switch that I would turn on before starting to prime everything, then shut it off once the engine is started.

Will the electric pump allow fuel to flow through it if it's not on?

Will the electric pump be able to pull/push fuel through the mechanical without the engine running?

If I install the electric in parallel instead of in series with the mechanical, will the mechanical push fuel backwards through the electric pump if the electric is switched off?

Or should I just bypass the mechanical all together and go with just the electric?

Will the electric require a pressure regulator?

I'm leaning towards adding the electric on a switch.
My thinking is that once the engine is started, I turn off the electric pump, and everything works as it always has.
I just need something to get fuel to the carb quicker when it hasn't been cranked in a while.

 

[Torxhead]

Since your CJ has survived this long without an electric pump you might want to try and see just where the problem is. Otherwise setting up an electric pump correctly can get tricky. Two good locations for the pump would be at the lowest point of the fuel system where fuel is siphoned to it or close to the fuel tank where it can suck the gas to it. Not too many guys want to install an in tank pump. You would probably want about 4 p.s.i. at the carb inlet which would require a regulator. I am not sure how running an electric pump parallel to a mechical one, but should be researched. Good luck!

 

[Lumpy Grits]

First, is the smaller dia. return line on your fuel filter at the 12 o'clock position?
If not-Correct that now. When was the last time that f'filter was replaced?
When was the last time the carb was rebuilt? Fuel can be leaking out of the bowl into the engine.
LG

 

[dtrojcak]

First, is the smaller dia. return line on your fuel filter at the 12 o'clock position?

If not-Correct that now. When was the last time that f'filter was replaced?

When was the last time the carb was rebuilt? Fuel can be leaking out of the bowl into the engine.

LG

Return line is on top at the filter.
Filter was replaced about 6 months ago, problem existed both before and after filter change.
Last carb rebuild is unknown. I bought the jeep about 2 years ago.
This problem was there when I bought it.

I installed a second marine-type filter with a clear housing so I could see the fuel in the line.
It is empty of fuel after a few days of not running the engine.
As soon as the starter engages, I can see fuel start to squirt into the clear filter.
It takes about 20-30 seconds for the fuel to fill the carb bowl enough for the engine to try to fire up.
It runs rough for the first 10 seconds or so, then everything is fine.

 

[Jimbos76cj]

Aluminum One-Way Check Valve 10mm Barbed

How about one of these in the soft line right before the pump. Also check your lines to make sure non are rotted and all your clamor are tight.

If it makes you fell better mine does the same thing and the fuel system is 100% new. That why I drive it daily

 

[Lumpy Grits]

Return line is on top at the filter.
Filter was replaced about 6 months ago, problem existed both before and after filter change.
Last carb rebuild is unknown. I bought the jeep about 2 years ago.
This problem was there when I bought it.

I installed a second marine-type filter with a clear housing so I could see the fuel in the line.
It is empty of fuel after a few days of not running the engine.
As soon as the starter engages, I can see fuel start to squirt into the clear filter.
It takes about 20-30 seconds for the fuel to fill the carb bowl enough for the engine to try to fire up.
It runs rough for the first 10 seconds or so, then everything is fine.

It's time to rebuild the carb. Classic 'empty-bowl' deal. Sounds like you have choke setting issues to correct.
Just for 'grins'-Have you ck'd ALL manifold bolts and carb screws/nuts to be sure they are tight?
LG

 

[dtrojcak]

Aluminum One-Way Check Valve 10mm Barbed

How about one of these in the soft line right before the pump. Also check your lines to make sure non are rotted and all your clamor are tight.

If it makes you fell better mine does the same thing and the fuel system is 100% new. That why I drive it daily

That would definitely be easier and much cheaper than installing an electric pump.

And yes, it does make me feel better that your new system does the same thing.
Honestly, it doesn't bother me enought YET, to go through the trouble of adding another pump.
It does get annoying sometimes like yesterday.
The jeep had sat for about 8 days and we had a cold front blow in 2 days ago. It ran down the battery before I could get it cranked. My battery is probably weak and needs to be replaced.

It's time to rebuild the carb. Classic 'empty-bowl' deal. Sounds like you have choke setting issues to correct.
Just for 'grins'-Have you ck'd ALL manifold bolts and carb screws/nuts to be sure they are tight?
LG

I'm curious why you mention correcting choke setting issues.
How would the choke affect fuel draining from the filter?

Excuse my questioning, but other than lawnmowers, it's been a long time since I have worked on a carb'd engine.
How would a carb rebuild and/or tightening bolts/screws prevent fuel from draining back to the tank?

 

[Lumpy Grits]

Choke setting-You stated the engine sputtered when it did start. That could be either to much or to little 'choke'.
You tighten the screws/bolts/nuts I spoke of to reduce vacuum leakage/loss to provide better/stronger air-fuel 'flow'. That helps in starting.
If there's crud in the bottom of the carb's fuel bowl(bet there is!). It may well allow the check ball under the accelerator pump to let the fuel leak into the engine and drain the bowl a good bit.
-----------------------
The fuel isn't drain'n back to the tank-it's drain'n out of the carb
-----------------------
A carb kit doesn't cost much, the kits come with the instructions on what & how for the settings. A vacuum gauge is real handy here for setting idle mix.
LG

 

[dtrojcak]

Choke setting-You stated the engine sputtered when it did start. That could be either to much or to little 'choke'.
You tighten the screws/bolts/nuts I spoke of to reduce vacuum leakage/loss to provide better/stronger air-fuel 'flow'. That helps in starting.
If there's crud in the bottom of the carb's fuel bowl(bet there is!). It may well allow the check ball under the accelerator pump to let the fuel leak into the engine and drain the bowl a good bit.
-----------------------
The fuel isn't drain'n back to the tank-it's drain'n out of the carb
-----------------------
A carb kit doesn't cost much, the kits come with the instructions on what & how for the settings. A vacuum gauge is real handy here for setting idle mix.
LG

Ahh, I'm thinking the sputtering is due to the bowl not completely full yet.
It runs fine after about 5 seconds.

I have a clear housing filter in front of the normal filter.
It is empty before cranking.
The bowl may be draining as well, but the lines are draining back toward the tank.
I believe the fuel is draining down to where the line goes horizontal under the jeep, but not all the way to tank.
Fuel starts pumping into clear filter as soon as engine is cranked.

 

[Lumpy Grits]

The carb's bowl(if it ain't leak'n)holds all the fuel you need to get started.
The fuel is NOT be'n pull'd back out of the bowl. That can't be done--The fuel inlet is above the fuel level.
You also have some fuel sit'n in the FP.
LG

 

[Posi]

An empty clear filter tells you the fuel in the line forward of the filter is draining back. It's NOT possible for fuel in the bowl to drain back in the fuel line.

 

[dtrojcak]

I realize the bowl cannot drain back into the line/tank.
I'm thinking the fuel is evaporating from the bowl when it sits for a few days.

 

[Posi]

I think not. I've removed carbs with fuel still in the bowl from vehicles sitting in the pick and pull yard for I don't know how long. If your bowl is empty after a few days it's leaking. You can install a e-pump and it can fill the bowl by turning the key leak withstanding.

 

[Lumpy Grits]

I realize the bowl cannot drain back into the line/tank.
I'm thinking the fuel is evaporating from the bowl when it sits for a few days.

Nope-That fuel is in a sealed container(IF it ain't leak'n).
My CJ will sit for weeks sometimes. Starts up within 5 seconds of turn'n the key.
LG

 

[Fastatv]

Unless I missed it somewhere, what type carb are we talking about here...Carter, Motorcraft?

 

[Hedgehog]

Frankly I'm always a bit confused when there is a perceived problem when a carburated vehicle starts exactly the way a carbureted vehicle starts. It is my belief that you can't really compare the way a modern multi-computer equipped, fuel injected engine starts to the way a 40 year old 100% mechanical engine starts, especially in the winter. So, after sitting for a while it takes 30 seconds to a minute to start, but once started it runs well. If started within a day or so it starts right up. So, exactly what is the problem? I think you have a CJ that runs great, what more can a person ask?

 

[dtrojcak]

Nope-That fuel is in a sealed container(IF it ain't leak'n).

My CJ will sit for weeks sometimes. Starts up within 5 seconds of turn'n the key.

LG

This definitely changes my opinion.
I was under the impression that the CJ carb would be similar to lawnmower, weed eater, chainsaw, etc. in that it needs to be primed first if it hadn't been started in awhile.
Looks like a carb disassembly will be in my future when I tire of this problem.

Unless I missed it somewhere, what type carb are we talking about here...Carter, Motorcraft?

From what I can tell, it is a Weber type carb.
It was on the jeep when I bought it.
It doesn't say Weber on it anywhere that I can see, but the rectangle Weber air filter fits on it.

Frankly I'm always a bit confused when there is a perceived problem when a carburated vehicle starts exactly the way a carbureted vehicle starts. It is my belief that you can't really compare the way a modern multi-computer equipped, fuel injected engine starts to the way a 40 year old 100% mechanical engine starts, especially in the winter. So, after sitting for a while it takes 30 seconds to a minute to start, but once started it runs well. If started within a day or so it starts right up. So, exactly what is the problem? I think you have a CJ that runs great, what more can a person ask?

The "perceived" problem is that my fuel lines and fuel bowl are empty after a day or two.
My theory of some sort of problem seems correct judging by the responses from others.
I was simply mistaken on the cause of the problem, but a problem does exist.
Is it a big problem? No, it's just slightly inconvenient and annoying.

My first vehicle was a 1970 F100 with a carbureted 360 engine.
The fuel didn't drain from the lines and the bowl didn't empty itself after a few days.
I wouldn't say it's normal for any vehicle to take up to a minute to start because it has to refill the carb bowl after it sits for a few days.
But thanks for the helpful advice.

 

[Hedgehog]

Good luck finding your "problem". It seems to me that you might be over engineering a fix by adding a temporary usage electric fuel pump. But that's just me.

 

[Lumpy Grits]

Post some pics of your carb. Then you will know what kit to buy. Sooner or later your gonna need to rebuild it. You say you have owned this Jeep for 2 yrs and not touched it-Your past due for a rebuild
BTW: All those small gas engines you speak of are a gravity feed in the fuel. That's why you must prime'em. Car engines and such are pressure feed on fuel because of the much higher fuel consumption and the distance from the fuel tank.
I have many years of experience in rebuilding lawn mower/chainsaw carbs. Pretty much the same deal except auto carbs have dual idle air fuel mixture screws and you need to set the accelerator pump adjustment correctly.
LG

 

[Fastatv]

I can't really help you with a Webber, don't know much about them. I have to agree with you tho, after sitting a few days it shouldn't require 30 seconds to a minute to start.....something is wrong. Additionally, turning the engine over for that length of time is hard on starters and batterys, and possibly flywheels. I have read that the ethenol fuel does evaporate faster thn the non E type, but that is something I read on-line so who knows..... As most have said, your carb may have a leak somewhere.
My neighbor has five carbed vehicles, 71 401 cubic inch Gremlin, 72 401 Matador, 72 Rebel with a Pontiac 455 that he installed in the car ( ), 74 360 Jeep Truck, 69 131 CJ5 ( yes, serious gear head ). He continously has problems with these vehicles starting after sitting for three or four days. He has replaced fuel pumps with higher volumn pumps, new fuel lines, wrapped fuel lines to prevent heat.....and on and on. So far, he has added a small electric fuel pump on two of them....uses a toggle switch to turn them on a few seconds, then back off, vehicles start right up.
I think there may be something to this ethenol fuel ( crappy as heck )...or in my area but again, who knows.
Remove the carb and remove the air horn, add fuel ( while on the bench ) and see if you have a leak. This way you will know. Then build the carb ensuring correct float height....can't hurt. Hang in and keep us posted. Many of us are curious....