Greetings! It’s been awhile since I’ve been here but I could use some help. Over the years, my 4120 has been invaluable and a steady workhorse. However, it has one repeating problem that I’d like to learn to fix myself. On two separate occasions over the past 16 years, I’ve taken it to a dealer to fix and apparently the return fuel line gets clogged or dirty and needs to be cleaned out. My problem (or one of them) is that I’m not a mechanic and while I do all the routine stuff, I don’t know how to find the return fuel line so that I can clean it. I’ve searched online for a diagram or service manual and have come up empty. Anyone out there who can explain where to find the line and fitting I need to clean? Thanks!
4120 fuel return line location
- Thread starter tinsnip
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Rebeldad1
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you have two fuel lines coming from your fuel tank. the supply line goes to a fuel filter then into the injector pump. the return line would be the line going to the pump without a filter.
maybe you could add a filter to your return line.
you might start adding fuel conditioners to your tank you get your diesel from.
maybe you could add a filter to your return line.
you might start adding fuel conditioners to your tank you get your diesel from.
Thanks for that. I’ll take a look when it stops raining and see if I can make sense of it. As for conditioners, will they help keep the crud from building up? I’ve been told that since I fill my tank using 5 gallon cans, I’m sorta stuck with the dirt thing.
Rebeldad1
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there are funnels that have a filter screen you can use. you might improve on your filter that is inline from your tank to the injector pump. there really shouldnt be anything past that anyway.
beenthere
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See no reason that your using 5 gal cans to re-fuel has any reason to have additional dirt. Been doing that for 40 years, and never been an issue. But then, you may know better how that dirt is getting into the system.
Also, you can buy a service tech manual for your tractor. Sounds like it would be a good investment to help track down and fix your problems that pop up. Cheaper than one visit to the dealer to work on your tractor.
Wish you well getting the system clean again.
Also, you can buy a service tech manual for your tractor. Sounds like it would be a good investment to help track down and fix your problems that pop up. Cheaper than one visit to the dealer to work on your tractor.
Wish you well getting the system clean again.
Tx Jim
New Member
Fuel return to tank hose appears to be item 10. I'm having a difficult time understanding how fuel that's traveled through the tractors fuel filter then through inj lines to injectors gets enough foreign material to clog fuel return line!
Are you positive hose fitting(item 13) that appears it may have a screen isn't getting clogged?
Are you positive hose fitting(item 13) that appears it may have a screen isn't getting clogged?
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If that’s the diagram for the 4120 then thanks! I’ve been searching all over for that. As for your question, the simple answer about “am I sure…” is that NO, I’m not sure of anything. But you’ve given me a place to look and I’ll check that out.
I’m taking advice from a few different people who claim that sludge can build up in that area and inhibit the free flow in the fuel line. The guy who told me that has a lifetime of operating and repairing diesel equipment. So, You could be entirely right. I’m just hoping to get a fix. And yes, service manual would be great. My searches have turned up a bunch of manuals online for prices that are all over the place. I don’t trust a lot of them and so not sure if there’s a legit source. Do you know of one?
Tx Jim
New Member
My knowledge of diesel engines with the type fuel system such as your tractor is limited. You can view JD parts catalog of your tractor at the following link. Yes algae can grow in diesel fuel contaminated with water.
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A follow up. After several attempts to find and clean the return line, I called a friend for help. He's an experienced operator/mechanic for heavy equipment and a willing helper. We played around and determined that we could make fuel exit the bleeder valve over the fuel filter but could not get anything from the fuel pump to the filter when we used the key and cranked it over. Now convinced that we had a bad fuel pump, we proceeded to remove it. After doing so, we pushed the plunger down on the pump by hand and it did push fuel. At that point Darol said, let me look in the opening where the fuel pump sits while you crank it. Ouch. The crankshaft (camshaft?) wasn't turning. Which means the pump wasn't operating, which means (or could mean) some very bad things. Like a broken timing chain (if there is one instead of a belt or gears) or a broken shaft. Ouch, ouch. The local JD dealer is coming to pick it up this coming Tuesday. I might be picking up returnables by the side of the road on Wednesday to pay for it.
beenthere
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Wish you the best, and the cheapest to get it fixed. Thanks for letting us know.
Just got the bad news. The bolt holding the camshaft came loose and backed out. With damage to other parts, replacement parts, outside testing of the head unit, and labor the dealer is estimating around $10K to fix it. This is very unexpected and to be honest, disappointing. I’ve always been so confident in my choice of John Deere and remember feeling that even though the initial cost of the tractor was high, it would last for my lifetime. I have no choice but to fix it and have given the go ahead for the repair. But to put it plainly, it sucks.
oldtimer 66
Platinum Member
A couple of suggestions. How about a new remanufactured engine/ and or a new engine direct from John Deere. The dealer is going to do a lot of inspection work, creating a parts list, ordering materials, follow up when something is missed, etc. extending the repair time. It maybe cheaper and quicker to purchase another engine. Your present engine should have a core value to it. Maybe that cost could cover the replacement labor for another engine. Plus another engine should/ could come with some type of warranty beyond what the dealer is going to supply. Just a thought.
After writing this earlier I thought of the same thing myself. Not sure how feasible it is since JD no longer makes the engine. But I intend to find out. Thanks for suggesting it.
arlen4720
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They still have the complete replacement engines on JD Parts. I just looked it up and they are available at the factory for the dealer to order. 10,000 and some change. I would lean toward a new engine, but total cost would be higher since there would still be quite a bit of labor to install the new engine.
Yes. Engine alone is more than than parts and labor to repair the existing engine. I’m waiting for the test results on the head to make the final decision but I’m leaning towards repair of existing instead of remove and replace. Thanks though.
Tractor is back home again after an engine rebuild. My wallet is gasping. So far so good But haven’t had much opportunity to run it. I know sh#t happens, but the failure of such a key component (the bolt holding the cam in place) has left me with a damaged opinion of Deere’s build quality. I know, there are millions of examples to the contrary. But my experience has left me a little shocked. I figured the tractor would have outlived me. It might now I suppose, but only after some very costly maintenance. Ah well, onward. Time to put the chains on.
