Fuel draining back - JeepForum.com
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post #1 of 30 Old 11-20-2012, 05:44 PM Thread Starter
82JeepCJ7
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Fuel draining back

On my AMC 304, if I let it set over night, it seems as though the fuel drains back from the filter etc, past the fuel pump. It takes some cranking to get it fired back up again. I thought the pump had a check valve in it?


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post #2 of 30 Old 11-20-2012, 06:03 PM
WhatWasThat
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I have the same problem, any help would be much appreciated.

Philip
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post #3 of 30 Old 11-20-2012, 06:11 PM
scottg73
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I had the same problem. Have you got the fuel filter turned so the return to the tank is positioned at 12 o'clock? Mine was down at 6 o'clock so the fuel was draining back to my tank I think. I adjusted the filter and set my choke. That was about 2 weeks ago, its started every time since then. Before that a few days sitting and it wouldn't hardly start without a splash of gas or a shot of fluid. Seems to have worked so far, fingers crossed
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post #4 of 30 Old 11-20-2012, 07:19 PM Thread Starter
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I don't have a return filter on it. Its in/out.

I wonder if its in backwards? Runs good. Just doesn't like to start first thing in the morning.

Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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post #5 of 30 Old 11-20-2012, 08:21 PM
scottg73
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In that case you may be on the right track looking at the fuel pump check valve. It could be just weak enough to drain but not bad enough to cause low pressure and driving problems yet. I was thinking with this new ethanol gas it also evaporates quicker.

I guess if you could pinch the line or add a cutoff valve between the carb and pump. Then you would know if it was evaporation or it was leaking back past fuel pump.
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post #6 of 30 Old 11-20-2012, 09:22 PM Thread Starter
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My Jeep has never had any fuel in it with ethanol. It costs a lil more per gallon but its worth it.

Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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post #7 of 30 Old 11-20-2012, 09:25 PM
wellmax
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I have a 1984 Jeep, the fuel filter on my jeep has one inlet and two outlets, center one goes to carb, the outer one is to be positioned at 12:00 o'clock high and it goes to the fuel tank.

If you position the outside outlet in any position other than 12:00 high your fuel will drain back out of the carb and the jeep will be hard to start the next morning.

Maybe someone has installed the wrong fuel filter on your vehicle!!!!!!
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post #8 of 30 Old 11-20-2012, 10:02 PM Thread Starter
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Well, good thing you ASSUME much...

Beat it to fit, paint it to match!

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post #9 of 30 Old 11-20-2012, 10:08 PM
BuckleshootCJ5
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Mine is the same way... If it sits longer than a day it takes quite a while to get fuel to the carb. I haven't spent a ton of time looking into it, just dealing with it at this point. One thought I had was that my gas tank leaks a little around the fuel inlet and maybe that causes it to flow backwards. Don't know if its a lack of pressure thing or not...?

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post #10 of 30 Old 11-20-2012, 10:41 PM
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Would putting an electric fuel pump on fix the problem?
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post #11 of 30 Old 11-20-2012, 11:42 PM
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The original system had a mechanical pump, a 3 way filter and a U bend before the carb. Fuel was stored in the filter, the U bend and the float bowl. Standing overnight they should start first time, you just pump the throttle twice to get it on the fast idle cam and inject a little fuel and she is good to start.

I had this trouble for years. Then I popped the top off the BBD one morning and realised it had fuel in the bowl and on the second revolution on the starter more flooded in. It was not fuel starved at all, it was a mixture problem.

So I replaced all the vacuum hoses. Some were loose, some perished.

Both CJs now start first time every time. It is uncanny how they just fire up and sit there purring.

An electric fuel pump would only help if you had an issue with fuel draining from the pump to the tank. As the tank connection is at or above the pump this seems unlikely but you could get a syphon effect. The hoses also split at the tank, letting in air etc.

These things were properl built so if you have a problem it is fixable. An electric pump is a sticking plaster over the issue which may be leaking hoses at the tank, a fuel filter wrongly installed or a vacuum leak.

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post #12 of 30 Old 11-21-2012, 12:42 AM
Matt1981CJ7
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82,

What's your reasoning for not running a return on your fuel system?

And I agree with Bagus, it may well be mixture related, or a leak.

Matt
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post #13 of 30 Old 11-21-2012, 07:16 AM Thread Starter
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This carb (Q-Jet) never had a return on it when it was in a Chevy truck.

The fuel pump is brand new. I will never run an electric fuel pump other than with fuel injection, so that is out of the question.

The mixture is tuned the best I can get with out an o2 sensor driven meter. It constantly holds 19hg at idle.

The whole fuel system is brand new. New pickup in the tank, new soft line from the pickup to the new hardline on the frame, new line from hardline to pump, new pump, new line to filter, new filter, new line into carb.

I was thinking of installing one of these before the pump.
http://www.summitracing.com/parts/sum-220191b

Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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post #14 of 30 Old 11-21-2012, 07:23 AM
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post #15 of 30 Old 11-21-2012, 09:05 AM Thread Starter
82JeepCJ7
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I just had a thought (I know, it happens sometimes). What if I put a 12v solenoid valve in the line just as the fuel line comes out of the tank and hook it to 12v switched? That way, I can run it though a switch and also act as a theft deterrent device.


Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
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