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Unread 05-01-2013, 06:59 AM   #1
shadoow
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hard starts due to gas draining - fix?

i've got an 85 258 that has a Weber Solex on it. The longer the jeep sits the harder it is to get it to fire up again so i figure the gas is draining back to the tank. If it just sits for a 1-2 days it cranks and starts pretty much normally but at 2 days you can tell it takes more cranking before starting. The longer it sits after this the more cranking it takes. I've made sure the fuel filter is properly oriented. The gas lines are all rubber from the fuel pump to the carb instead of the stock setup with the carter carb. Anyone have a fix to prevent the gas from draining?? Is there a check valve that can be installed in the fuel line??

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Unread 05-01-2013, 07:02 AM   #2
Neuner-9R
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Interested as well. Same issue. Mine will fire over a couple of times with what is still there and then take some longer cranking to fire up again.
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Unread 05-01-2013, 07:13 AM   #3
Matt1981CJ7
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Is your filter sitting at or above the level of the carb inlet? And does it sit level horizontally?

If so, I think the unfortunate reality is, today's gas blends evaporate quicker than the old days. I believe that's due to ethanol.

Post some pics of your setup, perhaps we can spot something.

Matt
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Unread 05-01-2013, 08:42 AM   #4
hp_lovecraft
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Quote:
Originally Posted by shadoow View Post
Is there a check valve that can be installed in the fuel line??
But you should still have fuel in the bowl? Enough to run for 10-20 seconds, plenty of time to get fuel from the tank.

Maybe the bowl is draining, or heat from the engine is boiling it off? or maybe something like the choke is worn out and not closing all the way?
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Unread 05-01-2013, 08:53 AM   #5
jeepwhore
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Quote:
Originally Posted by hp_lovecraft View Post
But you should still have fuel in the bowl? Enough to run for 10-20 seconds, plenty of time to get fuel from the tank.

Maybe the bowl is draining, or heat from the engine is boiling it off? or maybe something like the choke is worn out and not closing all the way?
When mine loses prime and I start it up on the high idle circuit I'd be lucky to get 5 seconds of runtime out of the fuel left in the bowl. If its been sitting for a number of days some of the fuel in the bowl is also going to evaporate.
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Unread 05-01-2013, 09:49 AM   #6
kovic
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I had the same issues. My fuel bowl drains/evaporates. I had to just switch to an electric fuel pump, turn the key to on, let it fill the bowl then bam starts right away. Only fix I could ever find.

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Unread 05-01-2013, 10:01 AM   #7
scrapman
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Everyone I know with a CJ has the same problem.

Has anyone ever tried to change to a normal fuel filter, and get rid of the return line to see if it helps any? I've always thought that the pressure built up in the tank has to go somewhere. So why wouldn't it go up the return line and push the gas out? I don't believe there is a check valve in the system any where, so what would stop the pressure built in the tank after shutdown from doing this?

I know there are check valves for the fuel vapors on the top of the tank going to the canister, but what are they set at? And why wouldn't the pressure that is below that amount not travel up the return line?

I know someone know these answers, but I could never wrap my head around it.
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Unread 05-01-2013, 10:15 AM   #8
Matt1981CJ7
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Scrapman,

I'm pretty sure the vapor purge to the canister is what depressurizes the tank. If not, when you disconnect the return line at the filter, after shutting down, it would spew fuel. It doesn't.

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Unread 05-01-2013, 10:22 AM   #9
19jeep85
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Everyone has gotten too used to fuel injected vehicles and electronic tank mounted pumps and just being able to turn the key to go. Sometimes you just have to pump the heck out of the pedal and crank it a little longer and even use the pedal to set the choke.
The return line helps prevent vapor lock due to the low-pressure fuel system. It may help matters to make sure the filter is above the inlet to the carb, and at a slight downward angle to the carb; fuel line in higher than fuel line out preventing backflow.
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Unread 05-01-2013, 10:34 AM   #10
scrapman
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Quote:
Originally Posted by Matt1981CJ7 View Post
Scrapman,

I'm pretty sure the vapor purge to the canister is what depressurizes the tank. If not, when you disconnect the return line at the filter, after shutting down, it would spew fuel. It doesn't.

Matt
Not true, you know the Pssshh you hear when you open the gas cap? The same pressure would be in the return line, there is nothing to prevent it. So if you took the return line off without releasing this pressure first (and there is gas in the return line) you would indeed get gas spewing from it.

Any pressure in the tank that is below the blow-off threshold of the vapor line check valves, would be in the return line. And if the valves on top of the tank are not working correctly, all the pressure would go up the return line.

Remember, the return line does not go down into the gas tank, it stops at the top.
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Unread 05-01-2013, 10:51 AM   #11
Matt1981CJ7
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I don't get a "Psssshh" when I open the gas cap...hot, cold, or otherwise.

I've disconnected the return line at the filter several times just after shutting off. Some fuel will spew from the filter due to residual pressure, but I've never had any spray from the return line.

Your mileage may vary.....

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Unread 05-01-2013, 10:59 AM   #12
jeepwhore
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Quote:
Originally Posted by Matt1981CJ7 View Post
I don't get a "Psssshh" when I open the gas cap...hot, cold, or otherwise.

I've disconnected the return line at the filter several times just after shutting off. Some fuel will spew from the filter due to residual pressure, but I've never had any spray from the return line.

Your mileage may vary.....

Matt
x2. If you're getting a "Psssshh" something in the system isn't working as it should. If that pressure is present as you say there would always be fuel remaining in the return line....it would prevent most of the fuel in the return line from draining. Of all the times I have ever pulled the return line off the filter, I've never had fuel come out the return line, only the filter.
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Unread 05-01-2013, 11:07 AM   #13
scrapman
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Originally Posted by jeepwhore View Post
x2. If you're getting a "Psssshh" something in the system isn't working as it should.
Good to know! So the roll-over check valves in the 20 gallon tank should let air in and out and keep the gas tank at Zero pressure?

Sounds like it is time to drop the tank again, and replace those two valves.
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Unread 05-01-2013, 12:33 PM   #14
shadoow
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here's my setup. Seems like it would be difficult for the gas to drain from the carb, slightly uphill, thru the FPR, filter, etc. but something is happening.



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Unread 05-01-2013, 01:12 PM   #15
Matt1981CJ7
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I'm not a fan of your FPR placement, or the rubber fuel lines draped over your valve cover. The FPR isn't necessary, anyway.

That said, I don't how see gas could be draining from that setup, either.

Next time it sits, check the bowl and the filter for fuel, before you start it. That's all I got, right now.

Matt
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