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89 with 4.2 will crank on half a turn if it has been less than a day since I last drove it, but if it sits for a few days, I have to crank on it for a good 20-30 seconds before it will fire. It runs great, and only does it after it has sat for a few days. It is parked on an incline. I think it's probably fuel draining out of the fuel line, and I remember seeing a post linking to a valve that was supposed to fix this, but for some reason all my searches on the forum no longer return any results. Does anyone have any ideas?
 

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The thread is called "Hard start after two days".
In essence it recommends a one way valve between the fuel filter and the return line that runs back to the gas tank. When our carbureted YJ were built the factory installed a tiny valve in the hose that goes from the fuel filter to the return line. It's easy to not see this valve and discard it when changing the fuel filter. The valve is "No Longer Serviced".
Several years ago another poster discovered this and we started installing aftermarket one way valves to help the situation. When I did it, it helped for a while then the long cranking issue returned. Then we all went with metal one way valves, thinking the plastic ones didn't hold up to gasoline with alcohol in it. My long crank after two days came back again.
I just live with it. If someone ever comes up with a permanent cure, they'll be a Jeep Hero.

Pics are from 2016 when the other poster (I don't remember who) discovered this. One way valves in the pics are plastic. I'm currently running a metal one but it doesn't seem to help. If you want to try it, search EBAY for "One way fuel valve" or similar.
@Got it at last is running a Motocraft carb and I think he has a valve on his return line. Maybe he'll chime in to let us know if he's experiencing the long cranking issue.

Good Luck, L.M.

EDIT>>> The vent outlet goes to 12 o'clock (top), not like the pics show.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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This Video pretty much describes what we are talking about.

It was done for a 91 which is injected and therefore should be installed before injection. On our Carbed lines we install on the downside of the fuel system after the filter on the line returning to the tank. Often the factory valve gets cut out and tossed when fuel lines get replaced without the owner ever knowing it's installed since it was inserted in the fuel line at the factory. I use them on both my 4.2 YJ's and they help keep the carb bowl from emptying out when sitting. I drive mine daily or sometimes let it sit for a week still starts up pretty consistent either way.

If you've just expaerienced a severe weather temp change that can also give you a hard start and you may need to check your electric choke.

Good Luck, hope that helps
 

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Wow.
I replaced my fuel lines when I replaced my carb and this issue arrose. I presumed it was an issue with the fuel draining or evaporating out of the carb and was thinking it was something to do with the float, seat, or evap door.
I was thinking of swapping to an electric pump so I could prime it before cranking.
Now I know.

Since Luckymac says his returned despite the valve.
From what I know on an FI car the fuel pump itself normally has a check valve.
So if we put one right after the pump, and one right after the filter to the return, it might solve the issue.
I imagine the return line drains on shut down, and can suck air afterwards. And with air coming in the fuel can probably just run backwards through the pump back to the tank clearing the lines.
Can anyone think why that could be a bad idea?
 

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Wow.
I replaced my fuel lines when I replaced my carb and this issue arose. I presumed it was an issue with the fuel draining our evaporating out of the carb and was thinking it was something to do with the float, seat, or evap door.
I was thinking of swapping to an electric pump so I could prime it before cranking.
Now I know.

Since Luckymac says his returned despite the valve.
From what I know on an FI car the fuel pump itself normally has a check valve.
So if we put one right after the pump, and one right after the filter to the return, it might solve the issue.
I imagine the return line drains on shut down, and can suck air afterwards. And with air coming in the fuel can probably just run backwards through the pump back to the tank clearing the lines.
Can anyone think why that could be a bad idea?
I had considered this some time ago, although I never acted on it. I thought the mechanical fuel pump might have a anti-return valve so I put a new fuel pump on. That didn't change anything.
I have a couple spare one way valves. I'll put one inline between the fuel pump and the fuel filter. We'll see what happens.

Good Luck, L.M.
 

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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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The restrictor was designed to apply backpressure to the float bowl to keep it full, also why we put the filter return at 12 o'clock to feed the float bowl from the center main line first.
The one way check valve will allow the return line to drain, but the purpose is to have a full float bowl at startup. If the bowl is draining between starts we are looking at a float bowl issue with the valve sticking open or something similar. I would suppose the same thing would hold true for putting one before the filter on the supply line side, but I wouldn't want to add anything extra the would interupt the supply side at all.

Of course all this is theory until proven, so please experiment and report back what you find.
Other things that may come to mind,

Kink in the rubber supply line at the pump where it does it's Curly Q.
Kink in the rubber lines at the tank.
gunk buildup in the lines.

All the above would restrict free flow to the pump and may require the pump to crank a few times to develop pressure/suction to supply Carb.

I dig all this trial and error stuff by everyone as it gets multiple fixes across multiple issues, which may work for some and not others, but gives us options to try.
 

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I've been banging this around in my head all afternoon. What might be happening is the fuel filter is draining back into the gas tank. With the one way valve between the fuel pump and the filter it may stop the filter from draining. After a couple days it takes several cranks to fill the filter and pressurize the fuel feed system.
It seems unlikely that so many of us would have faulty needle & seats in the carburetor float bowl. I'm not convinced it's not related to the fuel bowl though. If a person pumps the accelerator pedal several times prior to cranking, he should get some sort of firing, even if it doesn't start up.

I'm also wondering if the overflow valve plumbing to the charcoal canister might have something to do with the carb float bowl going dry (if going dry is actually what's happening). Hopefully with our collective experience and ideas we can cure this once and for all.

I didn't install the one way valve today. I ordered an assortment of hose clamps off Amazon that'll be here Monday.

Good Luck, L.M.
 

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I've been banging this around in my head all afternoon. What might be happening is the fuel filter is draining back into the gas tank. With the one way valve between the fuel pump and the filter it may stop the filter from draining. After a couple days it takes several cranks to fill the filter and pressurize the fuel feed system.
It seems unlikely that so many of us would have faulty needle & seats in the carburetor float bowl. I'm not convinced it's not related to the fuel bowl though. If a person pumps the accelerator pedal several times prior to cranking, he should get some sort of firing, even if it doesn't start up.

I'm also wondering if the overflow valve plumbing to the charcoal canister might have something to do with the carb float bowl going dry (if going dry is actually what's happening). Hopefully with our collective experience and ideas we can cure this once and for all.

I didn't install the one way valve today. I ordered an assortment of hose clamps off Amazon that'll be here Monday.

Good Luck, L.M.
My carb is a brand new Crown replacement, so I would hope it's not something wrong with the seats.
If I pump the throttle it'll fire for a second then starve and die.
 

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My carb is a brand new Crown replacement, so I would hope it's not something wrong with the seats.
If I pump the throttle it'll fire for a second then starve and die.
That's what makes me think that it's the fuel filter that's draining and not the carb. It appears that you still have fuel in your fuel bowl, although it may just be some fuel left in your accelerator pump well.

Yesterday I put a one way filter at the input side of my fuel pump. I had intended to put it between the fuel pump and the fuel filter but when I did so, it pushed the metal line between the pump and the filter into a position that hindered access to my oil filter cap.
I reasoned that a one way valve anywhere between the carb and the fuel tank would prevent the gasoline in the filter from draining back into the tank. With the current Covid business keeping folks home it may be a few days before I drive the Jeep anywhere. Once it sits for a few days, I'll report back to let everyone know what happens.
Got it at last is concerned that any restriction in the fuel line may hinder acceleration or highway driving. I share that concern so I didn't do anything that I can't reverse if I have problems. When I was done I didn't take the Jeep out onto the county road (speed limit is 45MPH so that isn't a good test). I only drove it the 30 or so feet from the shop to the garage. Right now my concern is the long cranking time after sitting for a couple days. If this cures the long crank issue and I have starvation issues at highway speeds I can always get a one way valve that allows a greater flow of fuel.

Now I've got a bug up my butt that want's me to figure out a cure for this pain in the neck issue that has been bugging me for the past 6+ years.

Good Luck, L.M.
 

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Update...

I let my Jeep sit for the past 3 days after installing a one way valve between the fuel pump and the gas tank.
I went out early this afternoon to start the Jeep. Outside temp was in the high 20s overnight and in the low 40s in the garage when I went to start it. Usually I would expect the Jeep to crank 15-20 times before starting in those conditions after sitting for 3 days. This time it took about 5 cranks (or revolutions of the engine to be more precise).
While I'm not certain that the situation is cured, I'm hopeful.
If it turns out that this is the cure for me, I'll make this thread a sticky.

Thanks to @madmatt41 for bringing this up again.

Good Luck, L.M.
 

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That's a nice easy place to put one, I ordered one, I'll put it there too and try to update.
There seem to only be two manufacturers out there for them, at least on ebay and amazon. I think it's 5/16ths fuel line.
 

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That's a nice easy place to put one, I ordered one, I'll put it there too and try to update.
There seem to only be two manufacturers out there for them, at least on ebay and amazon. I think it's 5/16ths fuel line.
Please let us know what your experience is with the one way valve a between the fuel pump and the gas tank is.

My current position is "So far, so good. We all may be on to something here. Let's keep digging at it".

Good Luck, L.M.
 

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I keep meaning to try it, but I have to go and make sure the fuel line is actually 5/16. Almost everything under the hood is replaced, and I want to make sure of the size, but it's also below freezing and raining outside. I'll update when I try it.
 

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Update...
It's been cold here South and east of Denver. Overnight low was 12* and it's currently 15*. This morning it was 30* in my garage with no heat except one wall it shares with my house. Luckily I have heat in the shop.
I drove the Jeep two days ago and it sat until today. Jeep started right away with 2 strong pumps of the gas pedal and then crank. With a carb, it ran rough for a second or two but then smoothed right out.

I'm even more hopeful that we may have found the cure. I'm still not doing the Snoopy dance, but I am smiling.

My one way valve is a 5/16".

Good Luck, L.M.
 
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