Stumped on simple Diesel fuel system!!!!

I am working on a Willmar Wrangler loader. It has a JD 4239 four cylinder diesel motor in it with a CAV injection pump. It was low on fuel and there is a barrel of diesel fuel, that was drained out of a larger tractor, that we are just hand pumping into the Wranglers, to use up the fuel. The fellow got the wrong barrel and pumped about five gallons of hydraulic fluid into the diesel fuel. It only ran maybe fifty feet when the filter plugged up and killed it.

So we pulled it back into the shop and drained all the mixed fuel out an flushed the fuel tank out real good. Changed the fuel filter and bleed the system. The engine will run for a few minutes and then the filter starts to fill with small air bubbles. It has the square glass Stanadyne filter on it. It will then die and you have to bleed it all over again.

The bottom of the fuel tank is only 12 inches below the transfer pump. The fuel line is only 16 inches long from the tank to the transfer pump. It is just 5/16 rubber line. So while I was cleaning/flushing the fuel tank I replaced the line with a new one. The transfer pump just did not seem to "feel" right when using it to manually bleed the filter. So I replaced it with a new one. I removed the steel line from the pump to the filter base and cleaned/inspected the entire line for holes/cracks on the flanges/line, it is OK. I even replaced the new filter with another one as I have seen the glass ones leak air around the steel base. This did not help it at all. I removed all the fittings in the inlet side of the filter and cleaned them and reinstalled them with tape AND thread paste. Still getting air.

The total fuel system from the tank to the filter base exit is not 24 inches long and 12 inches in elevation. The tank outlet is in the side of the tank about inch from the bottom of the tank. There is not stand pipe on the inside. The tank has 11 inches of clean fuel in it. So the fuel level is about at the height of the filter inlet.

I can not figure out how I am getting air bubbles into the fuel inlet side of the filter. I am about ready to try a small external fuel tank that would be above the whole system. I am just about out of ideas.

PS The return line goes straight to the tank. It does not join the inlet system. I have seem the ones that tee the return and inlet get air through the return side.

I have seen those square filters not seal well just a speck under the o ring and they will let air in .I have had to change a new filter cause it didn't seal also.

Is there a pencil filter in the tank?? Sounds to me like it's not getting enough fuel to the filter... That is the only thing I can think of right now

Mwj: I have tried two new filters. I have looked at the surface of the filter base with a magnifying glass and it looks clean and smooth. I suspected a crack around the bleeder screw but the housing looks good. This simple little system is kicking my butt. LOL I worked on this thing all day. My fingers are cramping from working the transfer pump to bleed the filters so many times.

The only way you can get air in the fuel system is if it's pulling a vacuum. Which means there's still a blockage somewhere between the tank and transfer pump.

Do you have good fuel flow coming out of tank?

Mark the fuel tank is part of the main frame. It is about 12 inches wide, 18 inches long and 18 inches deep. It just has two pipes welded into the tank. One for the outlet and one for return. These have a hose barb screwed into them for the rubber hoses to connect to. I have removed the bards, replaced the outlet hose and checked for fuel flow out of the tank into a can. It will run the 5/16 line full flow.

I even drained the fresh fuel and replaced it with new fuel again. I drained the fuel and ran it through a screen to see if there was something floating in the tank. I am still wondering if there is something in the tank that will float but sticks to the inside of the tank when I drain it.

I have plugged the tank fill spout with a Brocken tire tube with an air fitting still on.
Hard to make seal but sometimes seals good. Ad some air pressure to tank and found where the fuel was coming out the threads where I was sure it was sealed.
Did this once to find where the fuel rAn back on a 2470 tractor
Had a hair line crack once in the filter housing that you could not see until fuel made it wet.
Was almost like the aluminum casting had become porous.

My suggestion as well. Pressurize the tank about 5 PSI and you will find the suction leak. Jim

My little Super C has never done any work except plow snow since I've had it, always ran like a timex. Started stalling, sometimes it would recover, sometimes not. Looked in the tank several times, nothing, had the carb. apart, looked in the tank again and a little white cap like on a heat bottle was on the outlet, don't know where it was hiding the other times I looked in.

Thanks fellows I had not thought about pressurizing the inlet side of the system. I will try that in the morning and let you know what I find.

As you mentioned about the small external fuel tank I would gravity feed the transfer pump and filter from a fresh clean bucket of diesel with a new piece of 5/16'' hose and see if it ran O.K.

I agree with Mark. It seems as though you are sucking the filter dry. If that is what happens, look in the bends of the fuel line or any fitting up to the pump. I had a mid size JD tractor do that. It ran for 30 seconds or so and died. Filter was sucked dry. I blew out a wasp just before the primer pump. Hard to believe a dead wasp could stop a John Deere tractor.

Had this same problem on my 2550 last year. This all started when we ran it dry feeding cows in the cold.

Did all the same things you did to try to solve the problem - filter, pump, new lines, clamps - nothing seemed to help.

Eventually, by using pressure to watch flow out of the tank, found a lot of junk in the bottom of the fuel tank. It would drain just fine with gravity, but the pressure simulated suction by trying to increase flow out of the tank. Since it holds a lot of fuel, could not see the outlet with a flashlight unless I drained the tank completely. I then saw the crud that was causing the issue. I would have not believed that the tractor could have run prior to running it dry. But now, for sure, the crud was migrating under suction causing a vacuum on the pump and pulling air. Drained the tank twice to get it clean and filled with fresh fuel, then everything started working correctly.

Still don't know why going dry was the catalyst for the issue.

John

I'm going to say that over time that junk settled onto the bottom of the tank, with not enough going into the system to stop/plug it. So it went unnoticed. Then drawing the tank dry changes the whole dynamics of the flow at the bottom of the tank, and the junk starts to pull loose.
I imagine it's something like that, that's JD's problem. As someone below said about a small bottle cap(I think) I had a similar issue with one of those little pieces that comes out of a small bottle cap. It apparently floated/moved around in my tank for a long time, until the fuel got low enough, then it would suck right over the outlet, and kill the engine. BUT, it was a real bugger finding it, because as soon as the engine quit, the draw on the fuel line quit, and that blasted piece would float back off, and I could get the engine running again! It was only because someone gave me the idea of the piece being in there, AND, I was able to look in the tank and eventually see it, that I ever figured it out.

It sounds like its sucking in outside air from somewhere

Had something similar happen on a IH584, there was crud in the tank but also a piece of timothy was stuck in the bolt holding the banjo fitting to the fuel filter. It would idle but with any load it would start sucking air. Removed piece of hay and started over, more crud stuck in the petcock valve on the bottom of tank. Blew lines out back into the tank, would last 2 or 3 tanks before plugging again. Can't remember how we finally got the tank clean but looked like someone put a handful of hay / chaff in the tank.

One of those earwig bugs must have been in the fuel filler nozzle, it got flushed into the fuel tank of my 2355N. It would run grrrreat for a while, then bog down to the point of not even moving the tractor. Finding that little bugger blocking the steel fuel line from the tank to the transfer pump came after a half dozen filters, new transfer pump, tank removal and flush, etc. I was trying to figure out how to attach a temporary tank to the steel line when I saw the end of the bug plugging the line...

We had 2 of these Wranglers where I worked. If you have the rectangular glass filters, compare the mounting face of both your new and the original filter. There are 2 different filters. At the top of the original filter, the face is flat. Most replacement filters from the auto parts stores have a small dimple at the top of the filter and they will not seal. We always had to go to the Deere dealer to get the correct filter. Hope this helps. Jon

I highly doubt the hydraulic oil caused the problem but it could have made an existing problem worse . I'll tell story the anti diesel crowd will probably about lose there mind over but a few years ago I had an old dodge truck run outa fuel I had 2.5 gallon jug of hy tran I dumped in and drove home I was 30 miles from phone service so I had no choice and it got me back to civilization and fuel . Last summer I accidentally put bout 5 gallon gas in my newer dodge didn't have a way to drain the tank so I dumped about 3 gallon 15 40 in for lube and went to hauling hay.