JD750 Fuel Issues? Water contamination?

[ctandc]

Background: FIL gave me his late 80s JD750 tractor w/ 70 series loader. FIL is a GREAT guy -but when it comes to vehicle / equipment maintenance not so much. This tractor was not worked all that hard in the last 30 years. 1400 hours total on it now. He bought it used probably 30 years ago. When I got it, it had no fuel filter in it. Replaced entire bowl assembly / filter with JD parts. Changed the oil / filter (don't get me started how old that might have been in there. It turns over A LOT easier now LOL.

Replaced dry rotted fuel feed hose from tank to filter housing. Same on the line from filter to the injection pump. Fixed a leak at the injection pump bleed screw with new washer / screw. At that point tractor started and ran well. Worked it around our property a good bit. Tractor sat for 3-4 months (lots of other stuff going on). Got it started it up, running fine, one of the hoses on the loader decided to go boom. Found a local place that made a new hose ($45 not bad). Filled hydraulic system, loader works great.

Worked the tractor clearing brush etc for a week or two. No issues. It sat for 4-5 days. Went out to start it up yesterday to work some, it immediately cranked right up and idled fine. Looked at the fuel gauge (mounted in the fuel tank cap). Saw it was low. Cut the tractor off. Put in a few gallons of fresh diesel. Started it back up - runs fine for maybe a minute, then it started stumbling and just died out. Wouldn't start back up. Drained the sediment bowl, cleaned the fuel filter (newer - looked fine). Drained a bit of fuel from the tank into a bucket just in case some water got in the fuel. Hooked it back up, bled fuel filter bowl, bled at injector pump, didn't want to go.

Followed JD procedure - Bled filter bowl>injector bleed screw>loosened delivery holders (1 and 2 only)>loosened all three injector lines. Cranked tractor over. Got what looked like white cloudy mess from top of injector pump and a bit of this from injector lines at engine. Figured water must have gotten in it. Which was odd. Not much rain since I last ran it. Anyway, drained some more fuel from the tank, bled everything.

Fired RIGHT up ran good. Let it idle for a bit. Walked back to my shop to put my tools up. As I got to climb up on the tractor, it starts idling down. Even at higher throttle, it just idled down then slowly died. Cranks RIGHT back up, runs for a bit, then dies out. Bled it again - same deal.

Got a hold of the JD service manual, going to pull the fuel tank (there are a couple of things I want to check out in the electrical anyway - tach cable jumps around something fierce). Figure I'll pull the tank, manual clean / flush it out, then fill it with fresh fuel / bleed and go from there.

Any ideas? Common things on these tractors? I am going to replace the vent hose from the tank to the engine - it's dry rotted / cracking bad.

Any recommendation for additive to deal with condensation / winter etc? (tractor is stored outside for now - no choice - shops are full).

Thanks!

 

[loggin]

Background: FIL gave me his late 80s JD750 tractor w/ 70 series loader. FIL is a GREAT guy -but when it comes to vehicle / equipment maintenance not so much. This tractor was not worked all that hard in the last 30 years. 1400 hours total on it now. He bought it used probably 30 years ago. When I got it, it had no fuel filter in it. Replaced entire bowl assembly / filter with JD parts. Changed the oil / filter (don't get me started how old that might have been in there. It turns over A LOT easier now LOL.

Replaced dry rotted fuel feed hose from tank to filter housing. Same on the line from filter to the injection pump. Fixed a leak at the injection pump bleed screw with new washer / screw. At that point tractor started and ran well. Worked it around our property a good bit. Tractor sat for 3-4 months (lots of other stuff going on). Got it started it up, running fine, one of the hoses on the loader decided to go boom. Found a local place that made a new hose ($45 not bad). Filled hydraulic system, loader works great.

Worked the tractor clearing brush etc for a week or two. No issues. It sat for 4-5 days. Went out to start it up yesterday to work some, it immediately cranked right up and idled fine. Looked at the fuel gauge (mounted in the fuel tank cap). Saw it was low. Cut the tractor off. Put in a few gallons of fresh diesel. Started it back up - runs fine for maybe a minute, then it started stumbling and just died out. Wouldn't start back up. Drained the sediment bowl, cleaned the fuel filter (newer - looked fine). Drained a bit of fuel from the tank into a bucket just in case some water got in the fuel. Hooked it back up, bled fuel filter bowl, bled at injector pump, didn't want to go.

Followed JD procedure - Bled filter bowl>injector bleed screw>loosened delivery holders (1 and 2 only)>loosened all three injector lines. Cranked tractor over. Got what looked like white cloudy mess from top of injector pump and a bit of this from injector lines at engine. Figured water must have gotten in it. Which was odd. Not much rain since I last ran it. Anyway, drained some more fuel from the tank, bled everything.

Fired RIGHT up ran good. Let it idle for a bit. Walked back to my shop to put my tools up. As I got to climb up on the tractor, it starts idling down. Even at higher throttle, it just idled down then slowly died. Cranks RIGHT back up, runs for a bit, then dies out. Bled it again - same deal.

Got a hold of the JD service manual, going to pull the fuel tank (there are a couple of things I want to check out in the electrical anyway - tach cable jumps around something fierce). Figure I'll pull the tank, manual clean / flush it out, then fill it with fresh fuel / bleed and go from there.

Any ideas? Common things on these tractors? I am going to replace the vent hose from the tank to the engine - it's dry rotted / cracking bad.

Any recommendation for additive to deal with condensation / winter etc? (tractor is stored outside for now - no choice - shops are full).

Thanks!

Welcome to tbn! Sounds like you are on the right track. If it is water contamination then I would try and find out how it is getting in otherwise you'll be doing all the work of cleaning the tank and lines all over again, not to mention possible damage to the injector pump. Keep the tank full to prevent condensation and you'll likely get all sorts of opinions and recommendations on additives. I've used Howes diesel treat and Stanadyne.

Hope this helps!!

 

[Tx Jim]

Welcome to TBN
If you operated tractor a good bit after you acquired it from your FIL then it set for a while then tractor operated fine for a week or 2 then you added some "fresh fuel" then you start having engine operating problems then the fuel you added must have been contaminated.

I suggest to check for good fuel flow from tank to inj pump. Also check to be sure fuel tank vent isn't clogged. There is no fuel ""vent hose" from engine to tank but a fuel return line that routes excess fuel that injectors don't utilize back to fuel tank.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/78833/referrer/navigation/pgId/17506081

 

[arrow]

Sometimes a fuel tank will start to delaminate sending bits of plastic into exit orifices. Also what may happen is that "cloudy" stuff you found seeping out of your injectors may solidify within the tank itself. This acts as a shunt to fuel delivery.
I believe your tank may be the culprit here.

When this started happening to me, I took offf the fuel delivery pipe and inserted a tube from one of those oil drain devices and sucked a bunch of crap out of the tank that was mingling within the two inches of fuel I had remaining in the tank.

You aren't supposed to use these devices with volatile fuels such as gasoline but I figured diesel was closer to oil rather than gas so it worked out.

 

[ctandc]

Welcome to TBN
If you operated tractor a good bit after you acquired it from your FIL then it set for a while then tractor operated fine for a week or 2 then you added some "fresh fuel" then you start having engine operating problems then the fuel you added must have been contaminated.

I suggest to check for good fuel flow from tank to inj pump. Also check to be sure fuel tank vent isn't clogged. There is no fuel ""vent hose" from engine to tank but a fuel return line that routes excess fuel that injectors don't utilize back to fuel tank.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/78833/referrer/navigation/pgId/17506081

I guess my timeline wasn't clear. Tractor used very intermittently by FIL. I got it. Did oil / filter and other maintenance. Ran tractor for a few months - fine. Tractor sat over the Winter. Noticed a slight fuel leak from bleed screw at injection pump when I went to get it running when weather warmed up. Drained the tank (did not remove and clean - I plan to this weekend). Replaced fuel hoses from tank to filter housing and from housing to injection pump. Replaced fuel filter and housing. Replaced washer / and injection pump bleed screw. Added fresh fuel from a just filled fuel jug, did not totally fill tractor tank. Bled system per JD. Tractor started up, ran great. Went to lift bucket, hydraulic hose broke. Tractor sat for maybe 1 week while I got a new hose. Replaced hose, filled hydraulic system. Cranked up tractor - ran great. Worked it for a several days. Zero issues.

Sat for 4-5 days. Went out to it to use it, started RIGHT up - no bleeding needed. Noticed fuel gauge showing low (gauge is in the fuel tank cap). Tractor running fine. Added some more fuel from the same jug / same batch of fuel. Tractor still running. Went to pull off, tractor just idles down and dies out.

Right now - starts RIGHT up - no bleeding needed. Runs great for @ 45 second maybe? Then slowly idles down (hand throttle wide open doesn't affect it) and dies. Will then IMMEDIATELY start right back up and die as before. Rinse / repeat.

I'm going to pull and clean the tank this weekend. Add fresh fuel.

As for the tank vent - how do I check this? The tank cap has the gauge built into the cap. Tried running it with cap loose and off - no difference.

Verified good fuel flow from tank to injection pump - removed air bleed screw totally and a decent flow of fuel comes out (it is gravity fed) - but I only let that flow for 45 seconds or so. It doesn't SEEM like it's a 'fuel flow' issue - since the sediment bowl never drops below full when the tractor is running then dies.

Thanks.

 

[arrow]

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

 

[JimRB]

I got a bunch of crud in my 870 tank. I had problems with tractor running. Taking out tank I think involves removing roll cage. A few filter changes of the water separator and maybe some blowing out fixed that problem. My tank was all metal by the way. I did make a new fuel cap gasket from some cork bought from parts store. I may have also changed the fuel line from the tank and water separator to the fuel filter up front by fuel pump/distributor. Maybe even changed out the return line. It has been a few years so my memory is fuzzy. I do have spare filters on the shelf. I will change fuel and oil filters when I get the oil warm and do an oil change this fall.

 

[California]

The fuel caps with a fuel gauge are known to leak water into the tank, and need to be covered if parked outdoors. I doubt that's the problem here but it is a possibility. It does sound like the problem is unwanted material somewhere in the fuel system.

And - if the tach is the same as Yanmar - I quieted a noisy, jumpy one by removing it, turning it face down, and squirting a little lock fluid (graphite in solvent) in around the input part that turns. Left it overnight. Good as new. A kinked tach cable could be a less likely cause for a jumpy tach.

This stalling can't be an electrical problem. Failing to charge is the only possible electrical issue once it is started.

For these Yanmar-built Deeres, you can also find good answers over in the Yanmar (classic) sub-forum.

 

[Wagtail]

G'day Mate and welcome to TBN from Downunder.

If you have access to (or have one yourself) an 'inspection camera', I'd put it down into the fuel tank and have a good look around. Do it with fuel in the tank so that you can see if anything is floating around or if there's a biological growth at the bottom.

Enjoy the site... and please report back to us with your results.

 

[arrow]

Failing to charge is the only possible electrical issue once it is started.

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.