You CAN repair a leaky fuel injector pump! PICS and a question.

KYKub · Oct 3, 2015

I had a small leak in my fuel injector pump and read that self-repair of these units is impossible, or at least strongly discouraged. Having a brother that is a good mechanic and can bail me out of most of the messes I create, I figured I would give it a shot. My repair was to a 3 cylinder Kubota (D722), but I think the same basic process would work on any Kubota diesel engine. This seems to be a fairly common problem so I hope it saves some time and money for others.

The leak was around the base where the injector lines connect to the pump. Slow leak, but over time builds up oily junk down the side of the engine. The problem is failing O-rings on the shaft of the injector. 2 O-rings on each shaft. Here's what I did:

1. Remove the three fuel lines, disconnecting at the head on one end and the injector pump at the other. 17mm wrench on mine.

2. Remove Torx screws that hold injector shaft into the pump. I suppose the reason for the security Torx is to discourage owners from attempting a repair. Can't think of any other reason. 5 of 6 came out easy with a T30 security Torx bit. Last one, of course, stripped. I used a Dremel cutting blade to cut a slit in the head just large enough to get a good flathead screwdriver into. Borrowed a tool from my brother (told you he was handy) made for just such a case - tap it with a hammer and it impacts and rotates the bit ever so slightly, just enough to break the screw loose.

3. Before going any further, mark the position of the flanges that held the Torx screws. There is a small amount of adjustment possible and it's important that they go back exactly where they were. I used my Dremel blade to etch a small mark on the flange and the housing below it. A marker wouldn't work on the oily surface.

4. After removing Torx screws, use a 17mm wrench to twist the shaft and loosen it.

5. Use pliers to grip the shaft and slowly pull it out of the pump.

***IMPORTANT*** As the injector comes out watch for a really small pin that will fall out of a hole at the bottom end of the injector. I didn't know it was there until I happened to see it fall out of the third injector I pulled. It was a real pain to try to find the other two tiny, tiny pins. Does anybody know what the pin does? See pics.

6. Cover the injector holes with clean cloth so nothing falls into them while you're working.

7. Remove and replace the O-rings, 2 per injector. Here are three part numbers I found for replacement O-rings: KUBOTA 1584151201, SHIBAURA 1312272600,ZEXEL 0165501620. I couldn't find anything in stock in my area so I just pulled out my box of assorted metric O-rings and matched as closely as possible. The ones I used have the following dimensions: ID = 11.8, OD 16.6, Section 2.4

8. Reinsert injector, being careful that the little pin stays in the hole. It's little and slippery so keep an eye on it. Lubricate the O-rings with a bit of oil before inserting. Mine was pretty snug so I used pliers to seat them and line up flange marks ensuring they went back to the position they were originally in.

9. Connect fuel lines, but leave the last one on top, toward the front of the machine, loose to bleed air when you start engine.

10. Start engine and when you see fuel start to spew from the open line, tighten it. I had to crank a couple of times before it started. Cloud of white smoke went away quickly. No leaks, no drips, success!

11. Try not to wonder why a relatively easy repair is discouraged by Kubota. Keep telling yourself that their warnings are nothing more than the opinions of educated men.

/pine · Oct 3, 2015

Nice tutorial...:thumbsup:

gwstang · Oct 3, 2015

That is a good write up. You didn't have to "re-time" the pump to the engine? I don't know anything about an injector pump...but have read about the nightmare of re-timing. Just curious.

KYKub · Oct 3, 2015

Hi, gwstang. No, I didn't re-time anything. I'm far from a mechanic, but between this being a "second" machine and having a brother who knows what he's doing, I'm willing to give most anything a try. I say that because maybe others know more than me and my good outcome might just have been dumb luck.

To be honest, I'm not sure how the timing on these engines is set or adjusted. I've read that there are shims under the injection pump, but I can't see anything on mine. I'm also not exactly sure why it is so important to get the flanges lined back up exactly as they were.

Anybody know what the little pin is or does?

Jeff

skyhook · Oct 4, 2015

My guess would be that timing is done "internally" on the pump. These cylinders appear to be "pumps" to the injector and that little pin ensures the pump is aligned correctly, you can see a slot in your pic where it fits in. I'm sure theres allot more going on "inside" the injection pump, and this is where you should let the pro's handle it. Just a guess.

ehenry · May 11, 2016

I'm about to attempt this repair but I'm having a devil of a time finding the O-rings. Does any one know of any other part number that will work? Even using the dimensions of the rings KyKub gave are proving hard to find.

David_Kb7uns · May 12, 2016

Just for info timing of the pump is done by shims under the mounting flange of the pump.

David

KYKub · May 12, 2016

ehenry - I couldn't find the OEM o-rings locally so I used ones from an o-ring assortment box. Trial and error, lining up old o-ring with the closest I could find from the assortment box.

For what it's worth, the repair seems to have been successful and permanent. Maybe a tad more white smoke on start up, but not bad. Engine runs at all RPMs as always.

Still not sure if I just got lucky with regard to timing. I don't understand how the timing shims work, or even exactly where they are.

ehenry · May 13, 2016

KyKub, I watched a retired diesel mechanic work on a BX22 injection pump which is the same type mentioned here. He lined the engine TDC, removed the 4 allen head screws holding the pump the in housing and lifted the pump out. Under the injection pump is a cam shaft with timing marks on its gear that align with the mark on the pump drive gear. After he removed the pump he then took out the three "plungers" (what you replaced O-rings on) disassembled them and replaced smaller plungers inside them. When he put it back together it was just a matter of bleeding the lines. He did this all on a bench in his barn with normal hand tools. That BX22 is still chugging along. Like you though I dont understand how the shims between the little pump and its housing affects timing.

I didn't find the OEM O-rings by part number so Im going with the ones you gave the dimensions for. I found them today in Jackson $5 for a pack of 25. Wish me luck

KYKub · May 13, 2016

Good luck, ehenry. I wish I had more advice to offer. Remember to watch for the little pins in the end of each "plunger." I look forward to hearing how your repair goes!

ehenry · May 14, 2016

I replaced the orings on each plunger and have put the everything back together, bled fuel lines and cranked the tractor. The tractor cranks fine, runs fine and there does not appear to be a leak at the top of the injector pump any longer. What I do have happening now is there is now diesel fuel leaking from the starter. I removed the starter and the flywheel has diesel on it. The higher the rpm of the engine the fuel from the starter slows down. The lower the rpm the more fuel leaks from there starter. As I said above, the tractor cranks and runs fine. No fuel is getting in to the engine oil either.

If anyone has any idea or clue as to what may be going on I would appreciate it. This was not happening before I replaced the orings on the plungers.

KYKub · May 14, 2016

It might help if you could post some pics.

Are you sure the diesel fuel on the flywheel didn't drip there while you were bleeding the lines?

Can you "follow the path" of the leak to identify the source or area it is coming from?

ehenry · May 14, 2016

I've cleaned the top of the engine with mineral spirits the best I can and can find no fuel leaking from the injectors in the head or from the fuel line. The rubber hose from the injector at the back of the engine that runs back to the fuel tank is not cracked. I guess I'm going let it sit until morning, check the oil to see if fuel is getting in to the oil pan. I'm afraid to run it very long if fuel is getting in oil. The oil level doesn't appear to rising for the short times I've run it to try and determine what is leaking.

gwstang · May 15, 2016

It might help to get a container of baby powder and dust around where you think it is leaking from. The source will show up well in the powder as it tracks downward.

ehenry · May 16, 2016

Here is a video of the lease. You can see the drip below the plastic fuse dripping off the cable holder and the bottom bolt of the starter.

KYKub · May 16, 2016

That is strange (not what you want to hear when you're looking for help). Obviously, the leak doesn't have anything to do with the starter; the fuel is just dripping from a lowest point.

All of the fuel supply, injectors, filters, etc. are on the opposite side of the engine. It seems like it almost has to be leaking at the top or other side and somehow finding it's way to the flywheel/starter.

Not being smart, but are you sure it's diesel fuel that's leaking? Could it be coolant? That would seem more likely to be dripping around the starter area.

If it is diesel fuel, it is probably leaking somewhere on the "fuel side" of the engine and finding it's way to the flywheel. The flywheel is then throwing it on the starter. That's a significant leak so it shouldn't be too hard to trace.

ehenry · May 16, 2016

I popped the instrument cluster off yesterday thinking maybe the fuel tank might be cracked or something leaking on top where the bellhousing and engine bolt together but its dry as a power house underneath the tank. I did loosen all the bolts around the bottom of the bell housing and a cup or more of fuel drained out. I let it drain until it quit and I rocked the tractor by hand and more dripped out. I let it sit for a couple hours then cranked it and the leak was considerably less. I bumped the rpms up to about 2500 and let it run for about 30 minutes and the leak all but stopped. I emptied and cleaned the bucket under the tractor then let the it sit over night last night. THis morning, the bucket was dry with only a drop or three in it.

This afternoon I plan on tightening all the bolts back up and just driving the tractor around my place for a while to see if the leak continues.

My question for this is how did the fuel get in the bell housing when the only thing I did concerning fuel was pull the plungers from the injection pump and replace the orings on the plungers.....WHICH....by the way was a snap and fixed the leaking under the flanges at the top of the injection pump.

LarJea · May 16, 2016

Thanks for the info. If I ever do this, I am going to use Viton O-rings also I believe the O-rings are metric.

arto98607 · Nov 14, 2017

KYKub

I had a small leak in my fuel injector pump and read that self-repair of these units is impossible, or at least strongly discouraged. Having a brother that is a good mechanic and can bail me out of most of the messes I create, I figured I would give it a shot. My repair was to a 3 cylinder Kubota (D722), but I think the same basic process would work on any Kubota diesel engine. This seems to be a fairly common problem so I hope it saves some time and money for others.

The leak was around the base where the injector lines connect to the pump. Slow leak, but over time builds up oily junk down the side of the engine. The problem is failing O-rings on the shaft of the injector. 2 O-rings on each shaft. Here's what I did: ....zip

Thank you thread starter KYKub - your posting is appreciated!

I have exactly the same fuel leak in my Kubota F3060 mower (Kubota V1305 engine), and was able to find the O-rings on the eBay with the dimensions you gave by searching: Viton/FKM O-ring 11.8 x 2.4mm Price for 10 pcs

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