Long, embarrassing, headache of a story cut short; truck died on the way to work, battery died trying to restart it, realized I couldn't switch to the front tank and I had essentially ran out of fuel but the gage was deceitful. Batteries are reading normal, radios and lights work, but when I try to crank her up, I just hear a rapid clicking. So... First things first, where's the button that makes it go vroom? I put some gas in the rear tank, secondly, I do I switch to my full front tank? I've become very close with the 84 f250 6.9 diesel, we just haven't been seeing eye to eye. Please help ASAP!
Thanks,
Adam

 

The click click sounds like the batteries are dead. These trucks are very very hard to jump off with another vehicle. The best way to get it going is to take the batteries out and charge them at home and then take them back out and install them.

There are several things that can happen to the these trucks that can give fueling problems. The first thing is the sending units have large plastic "shower head "pickups in the tanks, and these like to break off. So it will run out of fuel if you don't keep the tank at least half full.

The second thing is the switching valve on the frame. They like to go bad also. The best thing for you to do in an emergency is to take the lines off the valve and just run one tank till you get time to work on it.

If you have one tank that has a lot of fuel, I would splice those lines into the ones going to the engine(1 supply and 1 return) and then I would go up to the fuel filter and push on the valve that looks like a tire valve. If no fuel squirts out, I would unscrew the fuel filter, and if there is no fuel in it, I would pre-fill it with fuel, and screw it back on. Then with your fresh batteries I would try to get it going.

Everything has to be right on these diesels, or they won't start. The combustion chamber has to be warm(glowplugs) you have to have fuel, and it has to crank at a decent speed(compression) for it to fire. It doesn't have sparkplugs you know.

 

Thank you for your help. I've completely unplugged both batteries and tested them with the multimeter and they both passed with normal numbers. Could it have something to do with starter relay or solenoid? How do I go about accessing the tank selector switch to test if it's faulty. Thanks again.

 

The proper way to test the batteries is with a load tester.

Batteries can read 12V and everything appears just fine until you put a heavy draw on them, the kind of draw a starter motor takes.

If a battery has a shorted cell inside of it, voltage can drop drop drop with power output dropping accordingly with that load attached.

Point being, merely testing a battery's voltage doesn't really tell you much about its condition or ability to deliver power to the starter motor. Charge 'em up and re-install, then see what happens.

A faulty tank selector switch won't cause rapid-fire clicking of starter solenoids, rule that one out.

While you have the batteries out (or disconnected) take the opportunity to clean all the connections as well as the ground connections to the block (and/or frame, as appropriate).

This problem could be the battery, the cables, the solenoid, or the starter motor, there's not really much more to that system.

 

For the tank not switching over.... I replaced the electronic tank switch on the frame..... no fix. I finally got around to checking the darn fuse in the fuse block for the tank switch and low and behold, I had put the good fuse in the wrong space. Got it back in proper spot and everything worked fine....so... check the fuse.

 

hello; I have the same rig and have had the same problem. There is a switch located up
in the frame between the two tanks.When it malfunctions the vehicle reacts the way you have described. Being electrical the switch is one of those works now then does not sort of things. I`ll bet you dollars to doughnuts thats your problem. I have shop manuals for the vehicle and the 6.9