Fuel tank issues

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Mar 28, 2018 | 03:03 PM

Jonathan Lentzkow

Thread Starter

5th Gear

Joined: Mar 2018

Posts: 5

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From: New Sharon, IA

Fuel tank issues

I have a 1989 F150 XLT Lariat, I'm having trouble with the rear fuel tank over flowing/ building up pressure when I run the front tank so ivI' been running on rear tank, problem with that is the gauge doesn't work for the rear but it does for the front and it won't let me put gas in the rear tank but I can fill the front tank. Sorry for the large font don't know how it's so big.

Mar 28, 2018 | 05:01 PM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

You have a bad Dual Function Reservoir. It's mounted on the driver side frame rail. Both tanks feed into it, the other side goes to the engine. Your symptoms are classic failed/stuck DFR. It can be removed and disassembled. Some folks have managed to repair them, but it is rare.

For reference a photo:

courtesy of Steve83

More information on how they work: 1984 to '89 Fuel Reservoirs

Mar 28, 2018 | 05:43 PM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,789

Likes: 1,753

From: Kentucky

Welcome to FTE!

Mar 28, 2018 | 06:39 PM

94ZR580

Tuned

Joined: Dec 2005

Posts: 400

Likes: 57

From: Saskatchewan

The problem you appear to be having is with the valves inside the DFR not responding properly and the fuel return from the engine is all going to the rear tank when you are running off the front tank. If the rear tank is working fine then you maybe able to monitor your usage by using the trip meter to gauge how much fuel you have. I use the trip meter in mine as my gauge is not accurate, except for right near empty. New DFR's can be difficult to come by and are usually fairly expensive. I've disassembled and cleaned mine once, but it appears to be sticking again. One solution is to eliminate one tank and the DFR. Do a search and you'll find a number of threads on this site dealing with this issue.