Fuel draining back - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep CJ Forum > Fuel draining back

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineFS: 2007-2013 Jeep Wrangler "HALO" Angel Eye KitFS: Wranger BRIGHT License Plate LED! Just $3! Great value

Reply
Unread 11-20-2012, 05:44 PM   #1
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
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?

__________________
Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
82JeepCJ7 is offline   Reply With Quote
Unread 11-20-2012, 06:03 PM   #2
WhatWasThat
Registered User
1983 CJ7 
 
Join Date: Apr 2011
Location: newnan, georgia
Posts: 35
I have the same problem, any help would be much appreciated.

Philip
WhatWasThat is offline   Reply With Quote
Unread 11-20-2012, 06:11 PM   #3
scottg73
Registered User
1979 CJ5 
 
Join Date: Jun 2012
Location: Danville, Virginia
Posts: 253
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
scottg73 is offline   Reply With Quote
Unread 11-20-2012, 07:19 PM   #4
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
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.
82JeepCJ7 is offline   Reply With Quote
Unread 11-20-2012, 08:21 PM   #5
scottg73
Registered User
1979 CJ5 
 
Join Date: Jun 2012
Location: Danville, Virginia
Posts: 253
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.
scottg73 is offline   Reply With Quote
Unread 11-20-2012, 09:22 PM   #6
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
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.
82JeepCJ7 is offline   Reply With Quote
Unread 11-20-2012, 09:25 PM   #7
wellmax
Registered User
1984 CJ7 
 
Join Date: Nov 2008
Location: Hazel, KY
Posts: 1,046
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!!!!!!
wellmax is offline   Reply With Quote
Unread 11-20-2012, 10:02 PM   #8
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
Well, good thing you ASSUME much...
__________________
Beat it to fit, paint it to match!

Wheel, Wrench, Repeat.
82JeepCJ7 is offline   Reply With Quote
Unread 11-20-2012, 10:08 PM   #9
BuckleshootCJ5
Member
 
BuckleshootCJ5's Avatar
1973 CJ5 
 
Join Date: May 2011
Location: Western, Washington
Posts: 323
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...?
__________________
The world would be a better place if being stupid hurt...
BuckleshootCJ5 is offline   Reply With Quote
Unread 11-20-2012, 10:41 PM   #10
WhatWasThat
Registered User
1983 CJ7 
 
Join Date: Apr 2011
Location: newnan, georgia
Posts: 35
Would putting an electric fuel pump on fix the problem?
WhatWasThat is offline   Reply With Quote
Unread 11-20-2012, 11:42 PM   #11
BagusJeep
Web Wheeler
 
BagusJeep's Avatar
1981 CJ7 
 
Join Date: Jul 2009
Location: Bali, Indonesia
Posts: 4,093
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.
__________________
BagusJeep lives in Bali, the Land of Temples.
With a Jeep every prayer counts.

1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
BagusJeep is offline   Reply With Quote
Unread 11-21-2012, 12:42 AM   #12
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 9,452
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
Matt1981CJ7 is offline   Reply With Quote
Unread 11-21-2012, 07:16 AM   #13
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
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.
82JeepCJ7 is offline   Reply With Quote
Unread 11-21-2012, 07:23 AM   #14
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 9,452
May work.

Let us know.

Matt
Matt1981CJ7 is offline   Reply With Quote
Unread 11-21-2012, 09:05 AM   #15
82JeepCJ7
Registered User
1982 CJ7 
 
Join Date: Jun 2010
Location: Marysville, WA
Posts: 4,660
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.
82JeepCJ7 is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.