Completely lost

[stephencov]

I have an 89 super cab F-350 2wd 5-spd with the 7.3, and I have been racking my brain trying to chase rabbits with this thing. First it was the over heating, then the alternator, then the glow plug controller, now I think I'm not getting enough fuel.. It cranks up easy, idles like a brand new one, but when I start driving it, the truck starts running really rough, it gets that "hard diesel sound" then it starts shaking really bad then I loose power until it cuts off. When I try to start it again, it acts like its out of fuel for several mins. I have replaced the fuel filter, I have bled the valve on top of the filter, and diesel pours out, never any air. So now I don't know where to look, this truck is all stock no mods at all with 73000 miles on it, if I can get it running 100% then I will start adding fun toys and parts to it but until then... I lost!

[drinkypoo]

test lift pump

remove shrader core from test port on filter head, run a line into a jar
1/3 pint or more after 10 sec. cranking
then hook up a pressure gauge, 4-6 psi within 10 sec. cranking

if either test fails, replace the lift pump

If not, your injection pump could well be going; no start while hot is a common symptom.

[stephencov]

How do I test the injector pump?

[drinkypoo]

you can't without a test bench. only a fuel injection shop can do that. ditto for injectors, although you can build a test rig out of a port-a-power.

[stephencov]

So today I thought to switch from the rear tank to the front, and I babied it up and down the block a few time, no problems, then I picked up the pace until I was driving it like some sort of hotrod... Still no problem, so I think that it may just be a problem that's isolated to the rear tank, any ideas?

[chuckster57]

How much fuel is in the tank(s). The pick-ups breaking off are a known issue and can give you no fuel symptoms at about 1/4 tank. Another possibility is the selector valve not fully seating in one direction.

[stephencov]

I'm not sure as to how much fuel is left in the rear tank, I do know that I have been running off of it for a while... So it sounds like I need to pull the bed and check out the pick-up , and maybe the sending unit...

[stephencov]

Is there a kit to replace the two tank setup with one single (larger) tank? Or has anyone fab'd one?

[chuckster57]

You can just run fuel lines from the tank of your choice, just bypass the selector valve. Make sure you bypass both the delivery side and the return side.

[stephencov]

Not a bad idea, what does the fuel pick up look like, is it just a line run to the bottom of the tank right? Also, how do you tell if the brake booster is going out or if it's the vacuum pump?

[drinkypoo]

the pickup foot is a ridiculous goofy piece of rubber with a bypass valve installed in the side of it that will eventually disintegrate and cause problems, with massive holes in the bottom.