1987 F250 6.9L Diesel question

RonRN18 · 03-25-2008, 12:33 PM

I just purchased a 1987 F250 SuperCab with 6.9L Diesel with an unknown brand turbo system and a U.S. Gear Dual Range system. As I was looking underneath the truck, I noticed something odd. I found that the there are two valves next to each other inside the driver's side "C-channel", just in front of the front tank. One of the valves is obviously the fuel coming from the tanks and presumably switched by the switch inside the cab. The other has one tube going up to the engine compartment and is blue, the other side of the valve has two rubber hoses that have plugs in them and coiled up underneath. I presume they are a fuel bypass or return line to go to each tank. My question is WHY would someone have capped these hoses? Could it have something to do with the turbo system? Is there some other reason? Also, my front fuel tank does not register on the gauge in the dash. The rear tank registers fine, but the front always says empty, despite being full. Is there an easy fix or is it a pain-in-the-rear fix? I presume the wire that goes to this is on the topside of the tank and I can't get to the top of the tank because it is too close to the bed of the truck. I can reach my hand in many places... I just don't know exactly what to feel for and where. Do I need to drain the tank and drop it to work on it? If so, what is the best way to do so? Can I get one of those drill-powered pumps and pump from the front tank to the rear tank, so I don't have to waste any fuel... just wait until the rear is nearly empty?

ajpletcher · 03-26-2008, 07:48 AM

Ok first before anything what is the gauge for the front doing? is it all the way pegged out the the right or something diffrent (it important). Second can you send a picture of the hoses and items in question?

as for the gauge if it is pegged all the way to the right then it's a bad ground. So let us know and we will go from there?

RonRN18 · 03-26-2008, 04:31 PM

When the fuel switch is set to the front tank, the gauge shows it as completely empty. I'll take pictures this weekend.

ajpletcher · 03-26-2008, 06:27 PM

umm then is either a power problem or a sending wire problem. Lets find the wiring diagram and see what the power wire is, and the sender to gague to test those wires.

RonRN18 · 03-28-2008, 11:44 AM

Just an update... I knew I had a full front fuel tank and despite it not showing anything in it, I had it switched to use the front tank. After about 10 minutes or so of driving, the engine started to die. I immediately switched to the rear tank and after a second or so, I got my power back. It got me thinking though that maybe ALL the wires are for some reason disconnected from the tank. Isn't there a low-pressure fuel pump in the tank? It seems to me that it may not have been working and when the pressure in the line started to drop, it started to stall. This also has me wondering how long the fuel has been sitting in the front tank. Should I pump it all out, drop the tank, clean it and check everything out visually and electrically? I'd be happy not to do this, but I'm starting to think that it might be best.

RonRN18 · 03-31-2008, 10:17 PM

Well, I've had a chance to do more with my truck today. I changed the oil for the first time, topped off fluids, added license plate lights and speakers. I also lubricated many spots. In addition to this, I had a chance again to look at the front fuel tank issue. I'd been asked for some pictures and I took a few. I've included three... The first is the devices I believe are valves.

In the picture, if not evident, the front of the vehicle is the right side. I've labeled several hoses in the photo. I think 1a comes from the front tank and 1b comes from the rear tank. They both actually come from a device I'm not exactly sure what it is, which will be my last photo. 2a and 2b are both capped off for some reason. 3a and 3b go to different locations in the engine compartment and difficult to follow all the way.

Above is a photo showing the other end of 2a and 2b.

This is the device that I am not sure what it is. It is located along side the front fuel tank, near the front of it. There is little room and many wires and tubes in this area, making it difficult to trace, but the two hoses coming off of it go to 1a and 1b.