Universal M4-30 diesel injector pump spring failure

[Kevin]

Out of the blue my diesel engine was failing to start. The engine is 650 hours old and I acquired it at hour 600. It was due for fuel filters due to how long I've had it. I went through dozens of articles on bleeding / servicing the fuel lines as this is my first diesel engine I've ever owned. I changed the fuel filters and did an oil change. I noticed something peculiar in the bleeding process.

While bleeding the primary and secondary fuel filters, as well as the injector pump inlet bleed, all went according to plan. But, when I went to bleed the injectors, only the first and second cylinder were spurting (the 2 closest to me as i'm viewing the engine). Nothing from 3 and 4. Even if only the 3 or 4 injector were loosened, nothing would come out. This wasn't mentioned in any of the articles I read. I took off the #4 line and was able to blow through it with my mouth so it wasn't clogged. Back to the internet I went looking for info on injector pumps. Most of what I read said not to touch the injector pump and that rebuilds would likely cost hundreds to about $1k. A new pump from westerbeke (who now handles OEM parts for these old universals) runs $1.9k.

I wasn't really happy with that conclusion so my only option was to see if I could find more answers. I dug deeper into kubota tractor land and found 1 video of a guy that pulled a 2 cylinder kubota pump out of his tractor and found a broken spring on one of the pump cylinders.
reference: https://www.youtube.com/watch?v=u7oEC3wJXmg

This made a lot of sense to me in my search for answers. I also noticed that it seems that the pumps are pulled and installed pretty easily, it is just if you want to disassemble the pump itself, then things get REALLY complicated and require professional tools / clean room / test bench etc. I decided to pulll my pump and find out if this was the same situation I was in.

Well, here is what I found when I pulled out my pump:

https://www.youtube.com/watch?v=zf4hecqHCfQ

Cylinders 1,3,4 broken! Only cylinder 2 had a functioning spring. There is only 1 spring element that seems to be for sale on the internet for kubota pumps and that is mentioned in that tractor video I linked.

Kubota part designation is "SPRING,ELEMENT #15841-51280"

I found it for sale at a few online diesel parts stores e.g. https://www.messicks.com/part/15841-51280/spring-element I plan on replacing them all if this spring fits. I'll follow up after they come in. Anyone else ever run into this?

 

[footrope]

Thanks for posting, Kevin. I'll be very interested in how the repair goes for you. If you take that to a repair shop they might encourage you to overhaul the pump completely, unless it has only been 650 hours since new or overhaul.

Did you have any issues with starting or while running before it just wouldn't start? My 5432 sometime starts very hard - 10-15 seconds of cranking. It runs smoothly and I've never had any problems bleeding at the injectors as you mentioned. I just wonder if there are other symptoms you might be able to recall, looking back at your short time with the engine.

Craig

 

[Loren Beach]

Interesting thread and a touch depressing.
I used our prior Universal M25XP, from purchase year (1994) until spring of 2018. It always started with about 10 to 12 seconds of glow plug time. I did have a mechanic bleed it all the way to the individual injectors a couple of times over the years, but I found that I could pretty much always bleed out any air by running the electric lift pump and opening that little valve at the end of the rack, just under the high pressure pump.
My guess is that the HP Pump can digest a very small slug of air, between the valve (that goes to the return line on that model) and still go ahead an run. Our mechanic did say that rebuilding that HP Pump is expensive and would need to be done in a very clean environment.

thanks for the information.
That's wisdom hard-won.
:nerd:

 

[Kevin]

Here are three of the old injector pump springs!



The new springs arrived and have been installed. They were a perfect match. The engine happily running again.

The new springs cost about $25 each (I bought 4), plus another $25 in shipping. In my research I also came across an excellent write up on how to assemble a kubota diesel injector pump. Here is a link to it: http://www.avantmachinery.shop/docu...NL/65136-kubota-d722-injector-pump-repair.pdf

That writeup is for a different engine and pump. But all of the individual components seem identical in size/shape, even though mine is a 4 cylinder.

 

[Christian Williams]

Really good work.

Now we have to remember the thread title so as to find it again for the next guy(It's a good searchable title).