JD750 Fuel Issues? Water contamination?

[rScotty]

Which a bad VR can cause. If the vr is not cycling properly, the battery can indeed fail to charge. Headlights can also be dim and instrument panels can be wonky. The voltage regulator controls the flow of electricity to every working part, including the engine. Bad voltage regulators have been known to cause engine stalling, acceleration issues, irregular engine timing, and misfires.

At this point, i would take off injector fittings and see what I am getting as pump out volume.

I think you are missing something here. We are discussing an old style diesel - the JD750 - which is pre-computer, pre-emissions, and pretty much pre everything electrical. If the starter starts the motor, a failing voltage regulator my not allow the battery to charge, but the but the tractor will run just fine.

A bad voltage regulator on that model tractor - or any similar tractor from that era - will NOT cause engine stalling, acceleration issues, irregular engine timing, or misfires. None of that is electrical. Those are old style very simple diesel tractors. All of those systems are mechanical.
rScotty

 

[dodge man]

A lot of tractors have a lift pump that if it quits it can make the tractor run poorly or not at all. They are electrically powered but in the OP’s case it sounds like it’s all gravity so once it starts running, it’s should keep running. Another exception would be a fuel shutoff solenoid that would require a little juice to operate.

 

[arrow]

I think you are missing something here. We are discussing an old style diesel - the JD750 - which is pre-computer, pre-emissions, and pretty much pre everything electrical. If the starter starts the motor, a failing voltage regulator my not allow the battery to charge, but the but the tractor will run just fine.

A bad voltage regulator on that model tractor - or any similar tractor from that era - will NOT cause engine stalling, acceleration issues, irregular engine timing, or misfires. None of that is electrical. Those are old style very simple diesel tractors. All of those systems are mechanical.
rScotty

This was previously pointed out.
But thank you. I had a JD 750 that I needed to replace 2 VR's in the 28 yrs that I had it. Also had the 950 but for only a short period of time as I sold it when I found out what the 750 could do and also needed money to purchase the 100 acres behind me. Those were the days... hundred bucks an acre cuz it was land locked.
To be honest, I forget the symptoms that told me it needed replacemnt.
Could have been no start-no run.
All I know is when I replaced it, everything was fine.

 

[ctandc]

If you feel it is not a fuel flow issue, then the next thing is an electrical problem.
On the firewall, there is a voltage regulator. These go bad and cause all sorts of problems. See if yours gets hot when tractor dies.
I had to replace mine twice on my JD 750 purchased in 1988 and sold in 2012.

JD 750 voltage regulator...204067476398

Just saw this. Thanks for the heads up. I may just order one for that price. Didn't have time to work on the tractor this past weekend. I had to use the neighbor's tractor to remove 15 mature boxwoods because we're building a front porch. I hate shrubs. With a passion.

I still want to clean the tank - but after a lot of thinking about it - I honestly don't see how it could be the tank. I can see fuel in the filter / sediment bowl when the tractor dies. And it doesn't just cut off - it just slowly idles / stumbles until it finally dies, regardless of throttle position.

 

[ctandc]

It sounds like water in the fuel! It also sounds like the water was induced into the fuel system with the fresh fuel. When you run into things like this, it was running fine then I added fuel because it was low now it won't run, always look at what you did last to find the culprit. A water filter on your fueling system may be in order.

Fuel was from the same fill / same batch / same container that I had used to put fuel in before I ran the tractor for a week or so working it where it ran perfect. Fuel is stored on a rack in my shop.

 

[ctandc]

Get a separate fuel container and connect that up to the feed to your injection pump (with filter or using existing filter).

If it's determined that there isn't fuel blockage from the tank (issue persists after using a separate fuel container) then it still could be a fueling issue. Could be the injection pump is warming up and sucking in air: and any fuel lines should also be held suspect. And or fuel shutoff losing power due to electrical (mechanical?) issue.

Water in the fuel is certainly a cause for concern. And has been mentioned, check the fuel cap: I had this issue on my Kioti (I have a mental note to stuff a can over the top of my fuel tank's filler, but keep forgetting! a replacement cap has been far better but, as it too is a locking style, it's not "water proof" either.)

I know the tank likely needs cleaning - so I hope to get to that this week. I hope it's as simple as something in the tank - but I'm not so sure.

 

[arrow]

I know the tank likely needs cleaning - so I hope to get to that this week. I hope it's as simple as something in the tank - but I'm not so sure.

Easiest way to clean the tank is to suck up the fuel with one of those cheap, battery powered transfer pumps

battery-operated-liquid-transfer-pump-63847.html

 

[arrow]

I know the tank likely needs cleaning - so I hope to get to that this week. I hope it's as simple as something in the tank - but I'm not so sure.

You can test one injector at a time. Unfasten it and put a coffee can under it and see if you're getting flow from the injector.
But I agree, do the simple things first to see if the problem is solved.

 

[rScotty]

I know the tank likely needs cleaning - so I hope to get to that this week. I hope it's as simple as something in the tank - but I'm not so sure.

What worked for me on our little Yanmar might not for you...but here it is anyway. I suspected crud in the fuel tank and thought about taking it off. While looking at how it was mounted I noticed that the tank was black opaque plastic and made in two halves, but that right at the seam midway on the tank there was a joining line where it wasn't so black... in fact the plastic was sort of translucent.

I got to wondering if I could shine a light through that seam and see anything useful. So I took a powerful flashlight, held it against the translucent seam, and looked down the filler neck. Sure enough, diesel fuel has a sort of greenish glow under a strong light. I'd heard that, but never seen it before.

Not only could I see the diesel fuel, but I could also out blobs of a different colored liquid rolling around on bottom of the fuel tank under the diesel. I could even see some pieces of crud on the bottom. And when I shook the little tractor I could make them move around. It had to be water I was seeing.

So I made up a pipette, hooked some clear tubing to a little battery-powered pump and sucked them up. It worked, and I didn't have any more water in the fuel filter.... but really it would have been less work to just take the tank off and clean it the right way.

I also rebuilt the fuel cap and replaced the rubber fuel lines from the tank to the fuel filter & fuel filter to fuel pump. So it could have been any of those things. BTW, for fuel lines recently I've been using some model airplane fuel line. It fits nicely, and so far holds up well.
rScotty

 

[ctandc]

I'm going to pull the tank to give it a proper clean / flush. I want to get in there anyway and fix the tach and go through and clean up some wiring. I also plan on replacing the thermostart hoses from the injectors - as those return lines look to be the originals from 30+ years ago. If that doesn't fix it, the next step is testing injectors and pulling them / cleaning them as needed.