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Unread 07-31-2008, 10:13 AM   #1
Waltallshy
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1982 CJ7 
 
Join Date: May 2008
Location: Memphis
Posts: 81
CJ7 Fuel system diagram

I am replacing a previous owner installed 5 gallon fuel cell with an OEM 15 or 21 gallon gas tank. AMC 401 motor.

Currently my fuel cell is direct plumbed to the fuel pump with heater hose. Filter between the pump and carb.

I need a diagram or descriptive outline for the OEM fuel system. Pictures would be great. I can't find anything to go by.

I will be installing new brake at the same time as my fuel lines, another inline fuel filter along the frame, vent canister, etc without pulling my tub if I can help it...

Where does the vent can go? Do I need it or can I just put a hose vent similar to a axle vent on the line and forget about it.

Where did you find the best deals?

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Unread 07-31-2008, 10:22 AM   #2
fuzz401
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Unread 07-31-2008, 10:33 AM   #3
Waltallshy
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Thanks Fuzz.

I am wondering if I need the vapor lines, canister, roll over check valve. Couldn't I just cap those two lines at the tank and run it safely?

The tank will still vent at the filler vent. Would I lose too much fuel due to evaporation or something? Would I vapor lock?
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Unread 07-31-2008, 10:35 AM   #4
Mike Romain
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1986 CJ7 
 
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The 20 gallon poly tanks have the roll over check valve built into the fittings on the top of the tank I believe. Well they held gas just fine when I had to run with the tank on it's side in the back seat after losing it on the trail 200 or so miles from home.

There are two vent line that come together, then you run it up to a charcoal canister which stores the fumes which then get sucked into the PCV system when you are warmed up and at speed. I put my canister up beside the steering column, just under the brake master. This helps keep the mud out of the air filter on it's bottom.

The 'Nutter' threads in this forum go over the plumbing of the canister in detail.

Here is a good link for how all the parts work:
http://home.sprynet.com/~dale02/list.htm
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 07-31-2008, 11:05 AM   #5
Waltallshy
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Where did you run the Manifold Purge Line? I assume you are running headers also. Thank you for the help. Please forgive my ignorance.
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Unread 07-31-2008, 11:16 AM   #6
Mike Romain
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Quote:
Originally Posted by Waltallshy View Post
Where did you run the Manifold Purge Line? I assume you are running headers also. Thank you for the help. Please forgive my ignorance.
I only have the 258, no headers.

The manifold purge line from the 'modern' canister T's into the PCV line so they both go into the PCV fitting on the manifold at the base of the carb.

The purge 'signal' to turn on the canister comes from a 'ported' nipple (distributor advance is usually 'ported') and feeds through a CTO valve. The CTO valve only allows vacuum to flow when the engine is warmed up. If you don't have one, they are cheap and easy to put in.

The only other option is to vent the gas tank to the air. This really stinks, so bad it was getting in our hair and clothes.= when I tried to run mine open.

The stock gas cap will seal the tank and it will vacuum lock causing stalls, there is no vent back there, only a filler vent that is in use when filling the tank. Cap it and it is sealed.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 07-31-2008, 11:28 AM   #7
jfwireless
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1976 CJ7 
 
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There were two different fuel tanks and filler neck/hoses for CJ's. one for 76 and 77, and I believe the diagram posted by fuzz 401 is for the 78 and later fuel tanks. The 76-77 had a larger filler hose inlet and a different filler neck. Also the 76-77 didn't have the roll over check valve, just the liquid check valve. I have no idea what could be the difference between a liquid check valve and a roll over check valve. Both should stop the flow of a liquid and pass the vapors.

Here is a scan of the 76-77 tank for your reference. There are two diagrams here, the top is for the 76 Jeep Truck, the bottom is for the 76-77 CJ-CJ7

Jim
76-77-cj-fuel-tank.jpg  
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Unread 11-26-2010, 09:29 AM   #8
ostavros
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Jfwireless, from what book did you get those diagrams?
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Unread 12-06-2014, 08:06 AM   #9
milemaker01
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What book is this from
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