7.3 Fuel system woes

[1994 Turbo]

Alright guys, i'm having a ton of fuel system issues on my 1994 7.3 factory turbo idi. When i first bought the truck back in may of 2014 it ran perfect as it had less than 20K on a reman jasper engine. The previous owner never told me not to use the rear tank and it had some thick black tar like gunk in it from old bio fuel. Well needless to say i never caught it and totaled out an injection pump. Now this is where my story gets interesting. I sent the whole truck to a friend of my father's who works on tractors and injection pumps. He does know what he is doing and i can prove it as he built the pump for our pulling tractor, and when it came back it ran alright for the first few weeks of me putting on 70-100 miles a week. Then i think the tar came out of the injectors because that thing started running like an animal. It would pass our stock 97 PSD auto like it was standing still both of us hauling 450 bu of corn. Fast forward to late November, my brother and i were using it to haul a round bale to the scale at the creamery in town so we could weigh it. It started losing power, i quit daily driving it and let it set because i didn't have time to **** with it. I called the man who rebuilt the pump and he said due to the gunk in the pump he thinks it prematurely wore out the cam ring in the pump. My grandfather then told me he had a rebuilt pump right from navistar or ford that had been sitting on his shelf since his cattle hauling days back in the early 90's. He gave it to me and i installed it myself in my garage this last week. It ran amazing at first, better than it ever had in my ownership, started easy in the 0 degree wisconsin weather. Then i was on my way home from a new years party and it quit. Dad came and towed me home where i pushed it in our shop and began working on it. I installed an electric pump not long after i replaced the first pump and i decided to start with fuel delivery from the tank to the filter housing. it moves a quart every 32 seconds so that shouldnt be the issue, right? Then i checked for fuel at the pump and it has fuel. so i tried starting it and it will start, run flawless for 300 seconds then it's just like i turn the key off. Dead. wait 10 seconds and it does the same thing. So i put a piece of clear line in the line retuning to the top of the pump and it is not returning a drop of fuel. Pulled the line off the pump and it was almost like it had an air compressor blowing on it, sprayed fuel and air everywhere with the pump and engine off. What else can i try? I'm at my wits end with this old girl. Nothing i do seems to work.
Thanks,
Dillan

 

[asmith]

I am not an expert, but it sounds to me like the return is clogged. Probably from that black tar stuff. you could try blowing it out with compressed air, but it might be easier to just replace the lines, that way you know it is all out of there.

 

[79jasper]

And I think it should be more than a quart in that time.

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[1994 Turbo]

The lines from injector to injector?

 

[79jasper]

If you're replying to asmith, yes. And to the tank.
I would disconnect it at the back of the engine where's it the bigger line, then blow through it with a compressor. Take the fuel cap off first.
May try bypassing the tank selector valve also.

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[1994 Turbo]

I might try drawing from a 5 gallon can tomorrow, just let it return to the tank. I'll blow thru the lines as well. Any other things to try?

 

[C_Luft]

I would drop and clean both tanks, replace or blow out fuel lines like asmith said, and just go through everything.

 

[IDIoit]

replacing the tanks and lines sounds like the ticket to me.
youre gonna have a hell of a time getting all that junk out of there.

 

[OLDBULL8]

Once you put Diesel fuel in a contaminated tank (had WVO or WMO in it) it starts washing/loosing all the gunk in the tank. Nothing else to do except clean them out, or it will be forever. There is an orfice in the tee in the line that goes back to tank, could be very well plugged.

 

[icanfixall]

Sadly you have some line pluggage somewhere. A good idea is get some of the crap from the rear tank and see what cuts or clean it. Then use that to clean out the fuel system. Warmed up diesel fuel might be the best cleaner too. You did not say if the fuel filter was ever replaced. If it was not replaced I suggest replacing it.

 

[FarmerFrank]

Whoa whoa whoa. Who missed the part of the story where he is hauling 450 bu of corn!!!!! 55 lb/bu x 450 = 24,750 POUNDS.

That my friend is impressive. I was hauling 250 bu on brothers dodge all fall and I worked the snot out of that truck. But that was also back roads and the gvw was in the 28000 range.

Anyway if your return is plugged then that will indeed shut off your truck. That how the FSS valve works. It stops the return side and the case pressure goes up there for stopping the pump from pushing anymore fuel. If you have a line almost fully plugged and it'll let some fuel pass until the pressure builds up too much therefore stopin the pump.

Hope that helps a little bit

 

[1994 Turbo]

I dropped the front tank and cleaned it. It was spotless so I put it back in and only run the front. Don't bug me cause I have a 150 gallon barrel in the bed. And it actually handles that corn good. I run 4th with 4:10's and she sings along at 60. I haul from the dryer to the ethanol plant. Brother and cousin haul from the field. My brother with his 92 with a sidewinder and cousin with a twisted up 93 12 valve since they're in rougher shape. Could I just run a new line from tank to lift pump and return from injector to tank? Rubber braided fuel line.
Thanks,
Dillan

 

[1994 Turbo]

Well guys, a little late night update. Ran a new return from tank to injector bypassing the selector, did the same with the supply. When I cut the return clear diesel came out which amazed me cause I haven't ran clear diesel in months. Did all this and now it'll start and run for 1-3 seconds and die. Ideas? It is now moving a quart every 20, so it's getting plenty of fuel

 

[asmith]

Do you know what your fuel pressure is? seems to me it should move more fuel than that, but maybe not. You said you dropped your tank, how did the pick up look? was it broken off or corroded at all?